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Yang, Jin-Peng, Hai-Tao Chen i Gong-Bin Tang. "Modeling of thickness-dependent energy level alignment at organic and inorganic semiconductor interfaces". Journal of Applied Physics 131, nr 24 (28.06.2022): 245501. http://dx.doi.org/10.1063/5.0096697.
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We identify a universality in the Fermi level change of Van der Waals interacting semiconductor interfaces. We show that the disappearing of quasi-Fermi level pinning at a certain thickness of semiconductor films for both intrinsic (undoped) and extrinsic (doped) semiconductors over a wide range of bulk systems including inorganic, organic, and even organic–inorganic hybridized semiconductors. The Fermi level ( EF) position located in the energy bandgap was dominated by not only the substrate work function (Φsub) but also the thickness of semiconductor films, in which the final EF shall be located at the position reflecting the thermal equilibrium of semiconductors themselves. Such universalities originate from the charge transfer between the substrate and semiconductor films after solving one-dimensional Poisson's equation. Our calculation resolves some of the conflicting results from experimental results determined by using ultraviolet photoelectron spectroscopy (UPS) and unifies the general rule on extracting EF positions in energy bandgaps from (i) inorganic semiconductors to organic semiconductors and (ii) intrinsic (undoped) to extrinsic (doped) semiconductors. Our findings shall provide a simple analytical scaling for obtaining the “quantitative energy diagram” in the real devices, thus paving the way for a fundamental understanding of interface physics and designing functional devices.
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Sacco, Olga, Antonietta Mancuso, Vincenzo Venditto, Stefania Pragliola i Vincenzo Vaiano. "Behavior of N-doped TiO2 and N-doped ZnO in Photocatalytic Azo Dye Degradation under UV and Visible Light Irradiation: A Preliminary Investigation". Catalysts 12, nr 10 (10.10.2022): 1208. http://dx.doi.org/10.3390/catal12101208.
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N-doped TiO2 (N-TiO2) and N-doped ZnO (N-ZnO) were synthesized utilizing ammonia as a dopant source. The chemico-physical characteristics of synthesized samples were studied by Raman spectroscopy, X-ray diffraction, SEM analysis, N2 adsorption–desorption at −196 °C, and diffuse reflectance spectroscopy. Compared to undoped samples, the introduction of nitrogen in the semiconductor lattice resulted in a shift of band-gap energy to a lower value: 3.0 eV for N-ZnO and 2.35 eV for N-TiO2. The photocatalysts were tested for the degradation of Eriochrome Black T (EBT), which was selected as a model azo dye. Both N-doped semiconductors evidenced an improvement in photocatalytic activity under visible light irradiation (62% and 20% EBT discoloration for N-TiO2 and N-ZnO, respectively) in comparison with the undoped samples, which were inactive in the presence of visible light. Different behavior was observed under UV irradiation. Whereas N-TiO2 was more photoactive than commercial undoped TiO2, the introduction of nitrogen in ZnO wurtzite resulted in a drastic reduction in photocatalytic activity, with only 45% EBT discoloration compared to total color removal obtained with the commercial ZnO sample, suggesting intrinsic limitations for doping of this class of semiconductors.
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Abdullahi, Sabiu Said, Garba Shehu Musa Galadanci, Norlaily Mohd Saiden i Josephine Ying Chyi Liew. "Assessment of Magnetic Properties between Fe and Ni Doped ZnO Nanoparticles Synthesized by Microwave Assisted Synthesis Method". Solid State Phenomena 317 (maj 2021): 119–24. http://dx.doi.org/10.4028/www.scientific.net/ssp.317.119.
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The emergence of Dilute Magnetic Semiconductors (DMS) with a potentials for spintronic application have attracted much researches attention, special consideration has been given to ZnO semiconductor material due to its wide band gap of 3.37 eV, large exciting binding energy of 60 meV, moreover, its ferromagnetic behavior at room temperature when doped with transition metals. MxZn1-xO (M = Fe or Ni) nanoparticles were synthesized by microwave assisted synthesis method calcined at 600°C. The structural, morphological and magnetic properties of these nanoparticles were studied using X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Vibrating Sample Magnetometer (VSM) respectively. Single phase Wurtzite hexagonal crystal structure was observed for the undoped and Fe doped ZnO nanoparticles with no any impurity, whereas Ni doped ZnO nanoparticles shows the formation of NiO impurities. The magnetic measurement reveals a diamagnetic behavior for the undoped ZnO meanwhile a clear room temperature ferromagnetism was observed for both Fe and Ni doped ZnO. Fe doped ZnO present a high saturation magnetization compared to Ni doped ZnO. However, Ni doped ZnO present high coercivity. The research was confirmed that Fe doped ZnO material will be good material combination for spintronic applications.
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Sikam, Pornsawan, Ruhan Thirayatorn, Thanayut Kaewmaraya, Prasit Thongbai, Pairot Moontragoon i Zoran Ikonic. "Improved Thermoelectric Properties of SrTiO3 via (La, Dy and N) Co-Doping: DFT Approach". Molecules 27, nr 22 (16.11.2022): 7923. http://dx.doi.org/10.3390/molecules27227923.
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This work considers the enhancement of the thermoelectric figure of merit, ZT, of SrTiO3 (STO) semiconductors by (La, Dy and N) co-doping. We have focused on SrTiO3 because it is a semiconductor with a high Seebeck coefficient compared to that of metals. It is expected that SrTiO3 can provide a high power factor, because the capability of converting heat into electricity is proportional to the Seebeck coefficient squared. This research aims to improve the thermoelectric performance of SrTiO3 by replacing host atoms by La, Dy and N atoms based on a theoretical approach performed with the Vienna Ab Initio Simulation Package (VASP) code. Here, undoped SrTiO3, Sr0.875La0.125TiO3, Sr0.875Dy0.125TiO3, SrTiO2.958N0.042, Sr0.750La0.125Dy0.125TiO3 and Sr0.875La0.125TiO2.958N0.042 are studied to investigate the influence of La, Dy and N doping on the thermoelectric properties of the SrTiO3 semiconductor. The undoped and La-, Dy- and N-doped STO structures are optimized. Next, the density of states (DOS), band structures, Seebeck coefficient, electrical conductivity per relaxation time, thermal conductivity per relaxation time and figure of merit (ZT) of all the doped systems are studied. From first-principles calculations, STO exhibits a high Seebeck coefficient and high figure of merit. However, metal and nonmetal doping, i.e., (La, N) co-doping, can generate a figure of merit higher than that of undoped STO. Interestingly, La, Dy and N doping can significantly shift the Fermi level and change the DOS of SrTiO3 around the Fermi level, leading to very different thermoelectric properties than those of undoped SrTiO3. All doped systems considered here show greater electrical conductivity per relaxation time than undoped STO. In particular, (La, N) co-doped STO exhibits the highest ZT of 0.79 at 300 K, and still a high value of 0.77 at 1000 K, as well as high electrical conductivity per relaxation time. This renders it a viable candidate for high-temperature applications.
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Hüsser, O. E., H. von Käanel i F. Lévy. "Photoelectrochemistry of Doped and Undoped Semiconductors: A Comparison". Journal of The Electrochemical Society 132, nr 4 (1.04.1985): 810–14. http://dx.doi.org/10.1149/1.2113963.
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Heng, Chenglin, Xuan Wang, Chaonan Zhao, Gang Wu, Yanhui Lv, Hanchun Wu, Ming Zhao i Terje G. Finstad. "Ultrathin Rare-Earth-Doped MoS2 Crystalline Films Prepared with Magnetron Sputtering and Ar + H2 Post-Annealing". Crystals 13, nr 2 (13.02.2023): 308. http://dx.doi.org/10.3390/cryst13020308.
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In this work, we propose a method to prepare large-area, crystalline ultrathin rare-earth (RE, i.e., Eu, Yb, Er and Tb)-doped MoS2 thin films, using magnetron sputtering and subsequent Ar + H2 annealing. The film thickness of as-deposited samples varied from 60 to 100 nm, and decreases to be below 10 nm after annealing at 550 °C for 30 min. X-ray diffraction and Raman spectra analysis revealed that the sample films were crystallized after the annealing, which resulted in a MoS2 crystallite size of about 4–5 nm. X-ray photoelectron spectroscopy indicated that most of the RE ions existed in the films in trivalent states. The optical bandgap of the RE-doped MoS2 samples decreased from 1.6 eV (undoped) to 1.3 eV (Eu-doped) in the UV-vis absorption spectra. Electrical measurements showed that the electrical resistance decreased from 9.13 MΩ (undoped) to 0.34 MΩ (Yb-doped), the carrier density increased by one to two orders of magnitude and the carrier mobility decreased from 5.4 cm2/V·s (undoped) to 0.65 cm2/V·s (Yb-doped). The sign of the Hall coefficients indicated that the undoped MoS2 and the Yb-, Tb- and Er-doped MoS2 samples were n-type semiconductors, while the Eu-doped sample showed p-type characteristics. This study may be helpful to broaden the photoelectronic applications of these two-dimensional materials.
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Wu, Meirong, Zhiqiang Wei, Wenhua Zhao, Xuan Wang i Jinlong Jiang. "Optical and Magnetic Properties of Ni Doped ZnS Diluted Magnetic Semiconductors Synthesized by Hydrothermal Method". Journal of Nanomaterials 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/1603450.
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Diluted magnetic semiconductors Zn1-xNixS with different consistency ratio (x = 0, 0.01, 0.03, 0.05, and 0.07) were successfully synthesized by hydrothermal method using ethylenediamine as a modifier. The influence of Ni doping concentration on the microstructure, morphology, and optical and magnetic properties of undoped and Ni doped ZnS nanocrystals was characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray energy dispersive spectrometry (XEDS), ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FT-IR), photoluminescence spectra (PL), and the vibrating sample magnetometer (VSM), respectively. The experiment results show the substitution of Ni2+ on Zn2+ sites without changing the hexagonal wurtzite structure of ZnS and generate single-phase Zn1-xNixS with good crystallization. The lattice constant causes distortion and decreases with the increase of Ni2+ doped concentration. The appearance of the samples is one-dimensional well-dispersed nanorods. UV-vis spectra reveal the band gap of all Zn1-xNixS samples greater than that of bulk ZnS (3.67 eV), and blue shift phenomenon occurs. The photoluminescence spectra of undoped and doped samples possess the broad blue emission band in the range of 400–650 nm; the PL intensities of Zn1-xNixS nanorods increase with the increase of Ni content comparing to pure ZnS and reach maximum for x = 0.03. Magnetic measurements indicated that the undoped ZnS samples are superparamagnetic, whereas the doped samples exhibit ferromagnetism.
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Seyidov, MirHasan Yu, Faik A. Mikailzade, Rauf A. Suleymanov, Vafa B. Aliyeva, Tofig G. Mammadov i Galib M. Sharifov. "Polarization switching in undoped and La-doped TlInS2 ferroelectric-semiconductors". Physica B: Condensed Matter 526 (grudzień 2017): 45–53. http://dx.doi.org/10.1016/j.physb.2017.07.003.
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Mittova, Irina Ya, Boris V. Sladkopevtsev i Valentina O. Mittova. "Nanoscale semiconductor and dielectric films and magnetic nanocrystals – new directions of development of the scientific school of Ya. A. Ugai “Solid state chemistry and semiconductors”. Review". Kondensirovannye sredy i mezhfaznye granitsy = Condensed Matter and Interphases 23, nr 3 (17.08.2021): 309–36. http://dx.doi.org/10.17308/kcmf.2021.23/3524.
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New directions of development of the scientific school of Yakov Aleksandrovich Ugai “Solid state chemistry and semiconductors” were considered for the direction “Study of semiconductors and nanostructured functional films based on them”, supervised by I. Ya. Mittova. The study of students and followers of the scientific school of Ya. A. Ugai cover materials science topics in the field of solid-state chemistry and inorganic and physical chemistry. At the present stage of research, the emphasis is being placed precisely on nanoscale objects, since in these objects the main mechanisms of modern solid-state chemistry are most clearly revealed: the methods of synthesis - composition - structure (degree of dispersion) - properties. Under the guidance of Professor I. Ya. Mittova DSc (Chem.), research in two key areas is conducted:“Nanoscale semiconductor and dielectric films” and “Doped and undoped nanocrystalline ferrites”. In the first area, the problem of creating high-quality semiconductor and dielectric nanoscale films on AIIIBV by the effect reasonably selected chemostimulators on the process of thermal oxidation of semiconductors and/or directed modification of the composition and properties of the films. They present the specific results achieved to date, reflecting the positive effect of chemostimulators and modifiers on the rate of formation of dielectric and semiconductor films of the nanoscale thickness range and their functional characteristics, which are promising for practical applications.Nanomaterials based on yttrium and lanthanum orthoferrites with a perovskite structure have unique magnetic, optical, and catalytic properties. The use of various approaches to their synthesis and doping allowing to control the structure and properties in a wide range. In the field of magnetic nanocrystals under the supervision of Prof. I. Ya. Mittova studies of the effect of a doping impurity on the composition, structure, and properties of nanoparticles of yttrium and lanthanum orthoferrites by replacing the Y(La)3+ and Fe3+ cations are carried out. In the Socialist Republic of Vietnam one of the talented students of Prof. I. Ya. Mittova, Nguyen Anh Tien, performs studies in this area. To date, new methods for the synthesis ofnanocrystals of doped and undoped ferrites, including ferrites of neodymium, praseodymium, holmium, etc. have been developed.
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Williams, J. S., Y. Chen, J. Wong-Leung, A. Kerr i M. V. Swain. "Ultra-micro-indentation of silicon and compound semiconductors with spherical indenters". Journal of Materials Research 14, nr 6 (czerwiec 1999): 2338–43. http://dx.doi.org/10.1557/jmr.1999.0310.
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Details of microindentation of silicon, such as the semiconductor-to-metal transformation, which takes place on loading, have been examined using spherical indenters. Various forms of silicon are studied, including heavily boron-doped wafers and silicon damaged and amorphized by ion implantation as well as material containing dislocations. Results indicate that only silicon, which contains high concentrations of point defects or is amorphous, exhibits mechanical properties that differ significantly from undoped, defect-free crystal. Amorphous silicon exhibits plastic flow under low indentation pressures and does not appear to undergo phase transformation on loading and unloading. Indentation of compound semiconductors is also studied and the load/unload behavior at room temperature is quite different from that of silicon. Both gallium arsenide and indium phosphide, for example, undergo slip-induced plasticity above a critical load.
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Hasan, Sayedul, Mohammad Tanvir Ahmed, Abdullah Al Roman, Shariful Islam i Farid Ahmed. "Investigation of Structural, Electronic, and Optical Properties of Chalcogen-Doped ZrS2: A DFT Analysis". Advances in Materials Science and Engineering 2023 (23.02.2023): 1–10. http://dx.doi.org/10.1155/2023/6525507.
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The electrical and optical characteristics of a ZrS2 monolayer doped with chalcogen atoms (O, Se, or Te), where dopants are introduced by substituting the S atom, are examined on the basis of the density functional theory. The semiconductors pristine ZrS2 and O, Se, and Te-doped ZrS2 monolayers possessed indirect band gaps of 1.187 eV, 1.227 eV, 1.146 eV, and 0.922 eV, respectively. According to the formation energy, the O-doped ZrS2 monolayer is more stable compared to Se-doped and Te-doped ZrS2 monolayers. The optical properties are very similar for both the undoped and doped ZrS2 monolayers. The absorption coefficient and optical conductivity are the highest in the ultraviolet energy region. The designed materials are potentially suitable for UV photodetection and UV filtering applications.
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Freitas, Jr., J. A., i W. J. Moore. "Optical Studies of Undoped and Doped Wide Bandgap Carbide and Nitride Semiconductors". Brazilian Journal of Physics 28, nr 1 (marzec 1998): 12–18. http://dx.doi.org/10.1590/s0103-97331998000100002.
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PEARTON, S. J. "HYDROGEN IN CRYSTALLINE SEMICONDUCTORS: PART I—SILICON". International Journal of Modern Physics B 08, nr 09 (20.04.1994): 1093–158. http://dx.doi.org/10.1142/s0217979294000543.
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Hydrogen plays an important role in the properties of Si because of its ability to passivate the electrical activity of shallow dopants and deep level impurities. This passivation can occur during virtually every stage of crystal growth, device fabrication or device operation due to the rapid diffusivity of hydrogen at low temperatures and the fact that it is a component of virtually every gas or liquid that comes in contact with Si. We review the ability of hydrogen to form neutral complexes with dopants and impurities, give examples of hydrogen diffusion profiles in doped and undoped Si, and mention the role of hydrogen during chemical vapor deposition and molecular beam epitaxy of Si.
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Fink, J. "Electronic structure studies of conducting polymers by electron energy-loss spectroscopy". Proceedings, annual meeting, Electron Microscopy Society of America 54 (11.08.1996): 160–61. http://dx.doi.org/10.1017/s0424820100163265.
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Conducting polymers comprises a new class of materials achieving electrical conductivities which rival those of the best metals. The parent compounds (conjugated polymers) are quasi-one-dimensional semiconductors. These polymers can be doped by electron acceptors or electron donors. The prototype of these materials is polyacetylene (PA). There are various other conjugated polymers such as polyparaphenylene, polyphenylenevinylene, polypoyrrole or polythiophene. The doped systems, i.e. the conducting polymers, have intersting potential technological applications such as replacement of conventional metals in electronic shielding and antistatic equipment, rechargable batteries, and flexible light emitting diodes.Although these systems have been investigated almost 20 years, the electronic structure of the doped metallic systems is not clear and even the reason for the gap in undoped semiconducting systems is under discussion.
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Kao, Chyuan-Haur, Chia-Shao Liu, Shih-Ming Chan, Chih-Chen Kuo, Shang-Che Tsai, Ming-Ling Lee i Hsiang Chen. "Effects of NH3 Plasma and Mg Doping on InGaZnO pH Sensing Membrane". Membranes 11, nr 12 (20.12.2021): 994. http://dx.doi.org/10.3390/membranes11120994.
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In this study, the effects of magnesium (Mg) doping and Ammonia (NH3) plasma on the pH sensing capabilities of InGaZnO membranes were investigated. Undoped InGaZnO and Mg-doped pH sensing membranes with NH3 plasma were examined with multiple material analyses including X-ray diffraction, X-ray photoelectron spectroscopy, secondary ion mass spectroscopy and transmission electron microscope, and pH sensing behaviors of the membrane in electrolyte-insulator-semiconductors. Results indicate that Mg doping and NH3 plasma treatment could superpositionally enhance crystallization in fine nanostructures, and strengthen chemical bindings. Results indicate these material improvements increased pH sensing capability significantly. Plasma-treated Mg-doped InGaZnO pH sensing membranes show promise for future pH sensing biosensors.
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Debesay, Thomas, Sam-Shajing Sun i Messaoud Bahoura. "Multi-functional organic field effect transistor based on a dual doped P3HT". AIMS Materials Science 8, nr 5 (2021): 823–35. http://dx.doi.org/10.3934/matersci.2021050.
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<abstract> <p>A dual doped regio-regular poly(3-hexylthiophene-2, 5-diyl) (P3HT) was investigated to develop a multi-functional organic field effect transistor (OFET). OFETs based on a pristine P3HT and a dual doped P3HT (P3HT:PCBM:I<sub>2</sub> blend) were fabricated to study the impact of doping on the electrical properties of the samples, and to examine the mechanism through which it amplified the output performance of the doped OFETs. A series of experimental techniques such as device electrical characterization, active layer surface analysis, and photon absorptivity measurements were conducted to quantitatively characterize the principal parameters that are susceptible to change as a result of doping. Topographic mapping revealed the expected doping-induced improvements in surface morphology, which could be associated with the ability of iodine to improve interdigitation between adjacent P3HT chains. Similarly, absorption spectra showed a 3 nm red-shift of the light absorbance spectrum of the doped samples compared to the undoped samples. The electrical conductivity of the samples was also examined at various conditions of temperature and light intensity, and the values obtained from the doped sample were approximately one order of magnitude higher compared to those of the undoped sample at room temperature, which explains the reason behind the higher output current drawn from the doped device compared to that of the undoped OFET. The explanation for this is two-fold, both PCBM and iodine promote the generation of free charge carriers, which increases the electrical conductivity of the active layer; and in addition to that, the improved P3HT main-chain interdigitation brought about by the introduction of iodine results in an increase in charge-carrier mobility, which also results in higher electrical conductivity. The findings of this study offers valuable information that could be instrumental in further advancing the future organic semiconductors based studies.</p> </abstract>
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Lin, Der Yuh, Tung Pai Huang, Fan Lei Wu, Chih Ming Lin, Ying Sheng Huang i Kwong Kau Tiong. "Anisotropy of Photoluminescence in Layered Semiconductors ReS2 and ReS2:Au". Solid State Phenomena 170 (kwiecień 2011): 135–38. http://dx.doi.org/10.4028/www.scientific.net/ssp.170.135.
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The optical anisotropy properties of rhenium disulphide (ReS2) and Au-doped rhenium disulphide (ReS2:Au) have been investigated by polarization-dependent photoluminescence (PL). Because the excitonic transitions show strong polarization dependences in the near-infrared region, we used polarization-dependent PL measurements in the range between 0° and 180° to characterize the unique polarization property of ReS2 and ReS2:Au, and identify the origin of the excitonic transitions. It was observed that the variation in the amplitude of PL excitonic transitions with different polarization characteristics follows the Malus rule. In comparison with the undoped ReS2, the PL spectra of Au-doped sample show not only the main excitonic transitions near the direct band edge but also some extra transitions owing to the doping effects.
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Богацкая, А. В., Н. В. Кленов, П. М. Никифорова, А. М. Попов i А. Е. Щеголев. "Резонансное болометрическое детектирование широкополосных сигналов терагерцевого диапазона частот". Письма в журнал технической физики 47, nr 17 (2021): 50. http://dx.doi.org/10.21883/pjtf.2021.17.51388.18850.
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We discuss the detection of broadband radiation in the terahertz frequency range by a bolometric method using heterostructures consisting of a sequence of conducting and dielectric layers of doped and undoped semiconductors (gallium arsenide, germanium). This structure forms a photonic crystal with allowed and forbidden bands (absorption and transmission ranges). By selecting the thicknesses of the conductive and non-conductive layers and the doping levels, it is possible to form spectral intervals of effective absorption, which allows detecting pulses in the frequency range >10^12 Hz with a spectral width of the order of the carrier frequency.
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Gherras, Hamou, Ahmed Yahiaoui, Aicha Hachemaoui, Abdelkader Belfedal, Abdelkader Dehbi i Andreas Zeinert. "Synthesis and characterization of poly(pyrrole-co-2-nitrocinnamaldehyde) (PPNC), a new copolymer for solar cells applications". Polymers and Polymer Composites 28, nr 4 (9.09.2019): 265–72. http://dx.doi.org/10.1177/0967391119872876.
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The use of conductive polymers as a substitute for metallic conductors and semiconductors has attracted much attention in the literature. In particular, aromatic heterocyclic polymers constitute an important class since they possess chemical and electrical stability in both the oxidized (doped) and neutral (undoped) state. A series of poly(pyrrole- co-2-nitrocinnamaldehyde) were obtained via the condensation of pyrrole and 2-nitrocinnamaldehyde in chloroform using acid exchanged montmorillonite clay called maghnite-H+ as an efficient catalyst. The conjugated copolymer was characterized using proton nuclear magnetic resonance, ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy.
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Appelbaum, Ian. "Introduction to spin-polarized ballistic hot electron injection and detection in silicon". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 369, nr 1951 (28.09.2011): 3554–74. http://dx.doi.org/10.1098/rsta.2011.0137.
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Ballistic hot electron transport overcomes the well-known problems of conductivity and spin lifetime mismatch that plague spin injection attempts in semiconductors using ferromagnetic ohmic contacts. Through the spin dependence of the mean free path in ferromagnetic thin films, it also provides a means for spin detection after transport. Experimental results using these techniques (consisting of spin precession and spin-valve measurements) with silicon-based devices reveals the exceptionally long spin lifetime and high spin coherence induced by drift-dominated transport in the semiconductor. An appropriate quantitative model that accurately simulates the device characteristics for both undoped and doped spin transport channels is described; it can be used to recover the transit-time distribution from precession measurements and determine the spin current velocity, diffusion constant and spin lifetime, constituting a spin ‘Haynes–Shockley’ experiment without time-of-flight techniques. A perspective on the future of these methods is offered as a summary.
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Abdellaziz, I., I. Mellouki, S. Abroug i N. Yacoubi. "Photopyroelectric back detection configuration for thermal diffusivity measurement of undoped and doped GaSb semiconductors". IOP Conference Series: Materials Science and Engineering 28 (7.02.2012): 012001. http://dx.doi.org/10.1088/1757-899x/28/1/012001.
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Batstone, J. L., i J. W. Steeds. "Dislocation Luminescence in ZnSe". Proceedings, annual meeting, Electron Microscopy Society of America 44 (sierpień 1986): 818–19. http://dx.doi.org/10.1017/s0424820100145431.
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Thin film, high purity II-VI semiconductors such as ZnSe are attracting increasing interest as optoelectronic device materials. Recent developments in low temperature epitaxial growth techniques such as organometallic chemical vapour deposition (MOCVD) have enabled growth of single crystal films on a variety of different substrates resulting in blue emission bands at 300K. Characterization of undoped, Al-doped and In-doped MOCVD ZnSe/(100)GaAs layers grown at RSRE, Malvern has been performed using transmission electron microscopy (TEM) and cathodoluminescence (CL). Optically and electrically active stacking faults and dislocations have been observed, revealing correlations with emission bands Y at 2.60eV and S at 2.52eV. Y and S are particularly characteristic of epitaxial growth and radiative emission has been observed from individual dislocations and complex tangles of dislocations commonly found in doped ZnSe. Recent work has concentrated on obtaining an understanding of the mechanism of radiative recombination at dislocations by studying thermal activation energies and excitation dependences.
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Mușat, Viorica, Mariana Ibănescu, Dana Tutunaru i Florentina Potecaşu. "Fe-Doped ZnO Nanoparticles: Structural, Morphological, Antimicrobial and Photocatalytic Characterization". Advanced Materials Research 1143 (luty 2017): 233–39. http://dx.doi.org/10.4028/www.scientific.net/amr.1143.233.
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Oxide semiconductors have attracted increasing interest due to their potential in solving environmental problems. ZnO-based nanoparticles (NPs) are among the most investigated for efficient disinfection and microbial control.Iron-doped zinc oxide nanoparticles (Fe:ZnO NPs) were successfully fabricated through precipitation method at low temperature followed by thermal treatment. The obtained Fe:ZnO NPs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet-visible (UV–Vis) spectroscopy. The effect of iron content on structural, morphological, antimicrobial and photocatalytic properties was investigated and discussed.The photocatalytic activity of the nanoparticles was tested by degradation of methylene blue (MB) solution under UV light for 60 min irradiation. The antibacterial activity was determined by paper disc method on Mueller-Hinton agar against the Gram-negative bacteria Escherichia coli (E. coli) and the Gram-positive bacteria Staphylococcus aureus (S. aureus) and compared to that of the undoped ZnO NPs. Consistent improvement on the photocatalytic and antimicrobial activity of Fe-doped ZnO nanoparticles was noticed.
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Perovic, D. D., i J. H. Paterson. "High-angle annular dark-field STEM imaging of doped semiconductor layers". Proceedings, annual meeting, Electron Microscopy Society of America 49 (sierpień 1991): 704–5. http://dx.doi.org/10.1017/s0424820100087835.
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With the development of crystal growth techniques such as molecular beam epitaxy (MBE), it is now possible to fabricate modulation-doped superlattices consisting of alternating ultrathin layers of n-and/or p-type material abruptly separated by undoped material. At sufficiently high dopant concentrations these abrupt layers may be imaged in cross section by electron microscopy. Pennycook et al. and Treacy et al. have used high angle annular dark-field (HAAD) imaging in the scanning transmission electron microscope (STEM) to image low levels of dopants (∼1 at. %) in semiconductors. This work is concerned with imaging boron and arsenic doped layers in silicon at levels « 1 at.%.Fig. 1 shows a HAAD image of a B-Si superlattice at the <110> zone-axis orientation taken at 100 kV using a VG HB501UX STEM. The bright vertical layers are the B-doped regions, containing ∼4 x 1020 B/cm3. The horizontal lines are due to beam instability while the image was recorded. Fig.2 shows a line scan across the same superlattice, recorded by scanning the beam across the specimen in a direction perpendicular to the layers.
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Gaied, Imen, Salima Lassoued, Fredéric Genty i Noureddine Yacoubi. "New Photothermal Deflection Method to Determine Thermal Properties of Bulk Semiconductors". Defect and Diffusion Forum 297-301 (kwiecień 2010): 525–30. http://dx.doi.org/10.4028/www.scientific.net/ddf.297-301.525.
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In this paper, we present a new Photothermal Deflection Technique (PTD) to determine thermal properties of bulk doped or undoped semiconductor such as GaAs, GaSb, InAs, etc. The method proposed here consists in covering the sample with a thin graphite layer in order to increase the photothermal signal and to ovoid any reflection on the sample surface. This method deals with the analysis of the logarithm of amplitude and phase variation of the photothermal signal versus square root modulation frequency where the sample placed in air is heated by a modulated light beam coming from a halogen lamp. So the best coincidence between experimental curves and corresponding theoretical ones gives simultaneously the best values of thermal conductivity and thermal diffusivity of the sample. These obtained values are in good agreement with those found in literature. The advantage of applying this method in this way lies in its simplicity and its sensibility to both thermal conductivity and thermal diffusivity.
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Phung, Tram Ngoc, Yue Feng, Timothée Petitjean, Catherine Henry-de-Villeneuve, Michel Rosso i François Ozanam. "Boron-Doped Methylated Amorphous Silicon for Negative Electrodes in Li-Ion Batteries". ECS Meeting Abstracts MA2022-02, nr 3 (9.10.2022): 241. http://dx.doi.org/10.1149/ma2022-023241mtgabs.
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In spite of its outstanding capacity for alloying with lithium, silicon cannot be practically used as a negative electrode for Li-ion batteries: its large volume expansion upon lithiation leads to a poor capacity retention [1]. Promising results have been obtained by incorporating methyl groups in amorphous silicon (methylated amorphous silicon). This material exhibits an improved stability upon electrochemical cycling while keeping a capacity close to that of pure silicon [2]. However, the conductivity of methylated amorphous silicon may be a strong limitation, especially at high methyl content: for example, 10% methylated amorphous silicon is 10000 more resistive than pure amorphous silicon. Doping is a well-known method to enhance the electronic conductivity of semiconductors, even if the dopant activity is lower in amorphous semiconductors than in crystalline ones. 2% boron doping increases the conductivity of 10% methylated amorphous silicon by five orders of magnitude compared to the undoped material. Boron doped methylated silicon thin films (100nm thick) with various methyl content were cycled in the range 0.025V – 1V at C/2 rate (electrolyte: LP30 with 5%FEC). 10% methylated amorphous silicon with 2% boron doping exhibits a capacity retention of 70% after 500 cycles of full lithiation/delithiation, an improved performance as compared to the undoped material (see Figure 1a). Interestingly, boron doping allows for using higher methyl content without demanding pre-conditioning procedures for the electrochemical cycling of the material. The stability upon cycling is found to be further increased for 15% and 20% methylated electrodes, with a capacity retention exceeding 80% over 1000 cycles of full lithiation/delithiation (Figure 1b). This figure comes at the expense of a decreased total capacity (which remains 3 to 4 times larger than that of the current carbon electrodes). The SEI evolution and structural changes are currently investigated using operando ATR FTIR and ex-situ Raman spectroscopies, in order to rationalize the factors limiting the Coulombic efficiency to 99.7%. References [1] M. N. Obrovac, L. Christensen, D. B. Le and J. R. Dahn, J. Electrochem.Soc, 154, A849-A855 (2007). [2] L. Touahir, A. Cheriet, D. Alves. Dalla Corte, J.-N. Chazalviel, C. Henry-de-Villeneuve, F. Ozanam, I. Solomon, A. Keffous, N. Gabouze and M. Rosso, J. Power Sources, 240, 551-557 (2013). Figure 1
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Makarova, Marina V., Andrey Prokhorov, Alexander Stupakov, Jaromir Kopeček, Jan Drahokoupil, Vladimir Trepakov i Alexander Dejneka. "Synthesis and Magnetic Properties of Carbon Doped and Reduced SrTiO3 Nanoparticles". Crystals 12, nr 9 (8.09.2022): 1275. http://dx.doi.org/10.3390/cryst12091275.
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We report on the studies of the synthesis, structural, and magnetic properties of undoped SrTiO3 (STO), carbon-doped STO:C, and reduced STO STO:R nanoparticles. Fine (~20–30 nm) and coarse (~100 nm) nanoparticles with a single phase of cubic perovskite-type structure were sintered by thermal decomposition of SrTiO(C2O4)2. Magnetization loops of fine STO:C and STO:R nanoparticles at low temperatures and an almost linear decrease in magnetization with temperature indicate the realization of a soft, ferromagnetic state in them, with a pronounced disorder effect characteristic of doped dilute magnetic semiconductors. Oxidation and particle size increase suppress the magnetic manifestations, demonstrating the importance of surface-related defects and oxygen deficiency in the emergence of magnetism. It was found that oxygen vacancies and doping with carbon make similar contributions to the magnetization, while complementary electron paramagnetic resonance, together with magnetization measurement studies, show that the most probable state of oxygen vacancies, which determine the appearance of magnetic properties, are charged F+ oxygen vacancies and C-impurity centers, which tend to segregate on the surface of nanoparticles.
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Huang, Menglin, Zhengneng Zheng, Zhenxing Dai, Xinjing Guo, Shanshan Wang, Lilai Jiang, Jinchen Wei i Shiyou Chen. "DASP: Defect and Dopant ab-initio Simulation Package". Journal of Semiconductors 43, nr 4 (1.04.2022): 042101. http://dx.doi.org/10.1088/1674-4926/43/4/042101.
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Abstract In order to perform automated calculations of defect and dopant properties in semiconductors and insulators, we developed a software package, the Defect and Dopant ab-initio Simulation Package (DASP), which is composed of four modules for calculating: (i) elemental chemical potentials, (ii) defect (dopant) formation energies and charge-state transition levels, (iii) defect and carrier densities and (iv) carrier dynamics properties of high-density defects. DASP uses the materials genome database for quick determination of competing secondary phases when calculating the elemental chemical potential that stabilizes compound semiconductors. DASP calls the ab-initio software to perform the total energy, structural relaxation and electronic structure calculations of the defect supercells with different charge states, based on which the defect formation energies and charge-state transition levels are calculated. Then DASP can calculate the equilibrium densities of defects and electron and hole carriers as well as the Fermi level in semiconductors under different chemical potential conditions and growth/working temperature. For high-density defects, DASP can calculate the carrier dynamics properties such as the photoluminescence (PL) spectrum and carrier capture cross sections which can interpret the deep level transient spectroscopy (DLTS). Here we will show three application examples of DASP in studying the undoped GaN, C-doped GaN and quasi-one-dimensional SbSeI.
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Siyar, Muhammad, Jun-Young Cho, Woo-Chan Jin, Euy Heon Hwang, Miyoung Kim i Chan Park. "Thermoelectric Properties of Cu2SnSe3-SnS Composite". Materials 12, nr 13 (26.06.2019): 2040. http://dx.doi.org/10.3390/ma12132040.
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Heavily doped degenerate semiconductors such as Cu2SnSe3 (CTSe) attracted attention in thermoelectric (TE) and optoelectronic fields, due to their high electrical conductivity and small band gap. The small Seebeck coefficient of undoped CTSe, however, is the major issue in achieving high TE performance (figure of merit, ZT). Here, we report that the Seebeck coefficient of CTSe can be controlled by adding SnS within a CTSe matrix. CTSe-SnS composite has not only high Seebeck coefficient in the range of 300–500 µVolt/K but thermal conductivity which is lower than that of pristine CTSe due to the scattering at the interface between the matrix and the SnS particles. A reasonable ZT of 0.18 is achieved at 570 K by adding a small amount (3 wt.%) of SnS to the CTSe matrix.
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Mathur, Arpit Swarup, Praveen Kumar i B. P. Singh. "Comparative study of absorption band edge tailoring by cationic and anionic doping in TiO2". Materials Science-Poland 36, nr 3 (1.09.2018): 435–38. http://dx.doi.org/10.2478/msp-2018-0060.
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AbstractTitanium dioxide (TiO2) is one of the most favored metal oxide semiconductors for the use as photoanode in photoelectrochemical cells (PEC) splitting the water into hydrogen and oxygen. However, the major impediment is its large bandgap that limits its utilization as photoanode. Doping has evolved as an effective strategy for tailoring optical and electronic properties of TiO2. This paper describes the synthesis of undoped as well as iron (Fe, cationic) and nitrogen (N, anionic) doped nanocrystalline titanium dioxide by sol-gel spin coating method for solar energy absorption in the visible region. All the prepared thin films were characterized by X-ray diffraction and UV-Vis spectroscopy. Doping of both Fe and N into TiO2 resulted in a shift of absorption band edge towards the visible region of solar spectrum.
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Qin, Juan, Niu Yi Sun, Guo Hua Wang, Min Zhang, Wei Min Shi i Lin Jun Wang. "The Fabrication of Fe-Doped TiCoSb Thin Films by Magnetron Sputtering and Rapid Thermal Annealing". Applied Mechanics and Materials 341-342 (lipiec 2013): 129–33. http://dx.doi.org/10.4028/www.scientific.net/amm.341-342.129.
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TiCoSb-based half-Heusler compounds, which are narrow band gap semiconductors with a high Seebeck coefficient, have been intensively studied in bulk form but rarely in thin films. In this article TiFexCo1-xSb (x=0, 0.17) thin films were synthesized on n-type single crystal Si (100) and MgO (100) substrates by DC magnetron sputtering followed by rapid thermal annealing. The X-ray diffraction patterns show that Fe doping does not affect the crystallization temperature of TiCoSb phase, but seem to induce the formation of binary phases like TiSb. Hall measurements reveal that the undoped TiCoSb thin films are n-type semiconducting, while TiFe0.2Co0.8Sb turns to p-type with half-order higher carrier concentration of 1.5×1021cm-3. The vibrating sample magnetometer spectrum indicate that the TiCoSb thin film is non-magnetic and TiFexCo1-xSb (x=0.17) is weak magnetic.
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Wang, Yanping, Qian Duan, Qingcheng Liang, Gongzheng Yan, Dezhi Yang i Dongge Ma. "A comparative investigation of electron transport properties in Li2CO3 doped and undoped organic semiconductors by admittance spectroscopy". Organic Electronics 66 (marzec 2019): 58–62. http://dx.doi.org/10.1016/j.orgel.2018.12.019.
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Lan, Linfeng, Chunchun Ding, Penghui He, Huimin Su, Bo Huang, Jintao Xu, Shuguang Zhang i Junbiao Peng. "The Mechanism of the Photostability Enhancement of Thin-Film Transistors Based on Solution-Processed Oxide Semiconductors Doped with Tetravalent Lanthanides". Nanomaterials 12, nr 21 (4.11.2022): 3902. http://dx.doi.org/10.3390/nano12213902.
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The applications of thin-film transistors (TFTs) based on oxide semiconductors are limited due to instability under negative bias illumination stress (NBIS). Here, we report TFTs based on solution-processed In2O3 semiconductors doped with Pr4+ or Tb4+, which can effectively improve the NBIS stability. The differences between the Pr4+-doped In2O3 (Pr:In2O3) and Tb4+-doped In2O3 (Tb:In2O3) are investigated in detail. The undoped In2O3 TFTs with different annealing temperatures exhibit poor NBIS stability with serious turn-on voltage shift (ΔVon). After doping with Pr4+/Tb4+, the TFTs show greatly improved NBIS stability. As the annealing temperature increases, the Pr:In2O3 TFTs have poorer NBIS stability (ΔVon are −3.2, −4.8, and −4.8 V for annealing temperature of 300, 350, and 400 °C, respectively), while the Tb:In2O3 TFTs have better NBIS stability (ΔVon are −3.6, −3.6, and −1.2 V for annealing temperature of 300, 350, and 400 ℃, respectively). Further studies reveal that the improvement of the NBIS stability of the Pr4+/Tb4+:In2O3 TFTs is attributed to the absorption of the illuminated light by the Pr/Tb4fn—O2p6 to Pr/Tb 4fn+1—O2p5 charge transfer (CT) transition and downconversion of the light to nonradiative transition with a relatively short relaxation time compared to the ionization process of the oxygen vacancies. The higher NBIS stability of Tb:In2O3 TFTs compared to Pr:In2O3 TFTs is ascribed to the smaller ion radius of Tb4+ and the lower energy level of Tb 4f7 with a isotropic half-full configuration compared to that of Pr 4f1, which would make it easier for the Tb4+ to absorb the visible light than the Pr4+.
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Ikenoue, Takumi, Satoshi Yoneya, Masao Miyake i Tetsuji Hirato. "Epitaxial Growth and Bandgap Control of Ni1-xMgxO Thin Film Grown by Mist Chemical Vapor Deposition Method". MRS Advances 5, nr 31-32 (2020): 1705–12. http://dx.doi.org/10.1557/adv.2020.219.
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ABSTRACTWide-bandgap oxide semiconductors have received significant attention as they can produce devices with high output and breakdown voltage. p-Type conductivity control is essential to realize bipolar devices. Therefore, as a rare wide-bandgap p-type oxide semiconductor, NiO (3.7 eV) has garnered considerable attention. In view of the heterojunction device with Ga2O3 (4.5–5.0 eV), a p-type material with a large bandgap is desired. Herein, we report the growth of a Ni1-xMgxO thin film, which has a larger bandgap than NiO, on α-Al2O3 (0001) substrates that was developed using the mist chemical vapor deposition method. The Ni1-xMgxO thin films epitaxially grown on α-Al2O3 substrates showed crystallographic orientation relationships identical to those of NiO thin films. The Mg composition of Ni1-xMgxO was easily controlled by the Mg concentration of the precursor solution. The Ni1-xMgxO thin film with a higher Mg composition had a larger bandgap, and the bandgap reached 3.9 eV with a Ni1-xMgxO thin film with x = 0.28. In contrast to an undoped Ni1-xMgxO thin film showing insulating properties, the Li-doped Ni1-xMgxO thin film had resistivities of 101–105 Ω∙cm depending on the Li precursor concentration, suggesting that Li effectively acts as an acceptor.
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Kim, Sung-Yoon, Go-Eun Lee i Il-Ho Kim. "Charge Transport and Thermoelectric Properties of Mn-Doped Tetrahedrites Cu12-xMnxSb4S13". Korean Journal of Metals and Materials 59, nr 5 (5.05.2021): 329–35. http://dx.doi.org/10.3365/kjmm.2021.59.5.329.
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Mn-doped tetrahedrites Cu12-xMnxSb4S13 (0.1 ≤ x ≤ 0.4) were synthesized by mechanical alloying (MA) and sintered by hot pressing (HP). A single tetrahedrite phase was synthesized by MA without post-annealing, and it was stable without any phase changes after HP. The hot-pressed specimens had a relative density higher than 98.6%. The lattice constant of the Mn-doped samples increased compared to that of undoped Cu12Sb4S13, but no significant change in the lattice constant was observed with a change in Mn content. All Mn-doped tetrahedrites acted as p-type semiconductors, as confirmed from positive Hall and Seebeck coefficient values. The Seebeck coefficient increased with increasing temperature but decreased with increasing Mn content; maximum Seebeck coefficient values of 200−219 μVK-1 were obtained at 323−723 K for x = 0.1. Electrical conductivity increased with increasing temperature and Mn content; the highest electrical conductivity values of (1.76−2.45) × 104 Sm-1 were obtained at 323−723 K for x = 0.4. As a result, Cu11.6Mn0.4Sb4S13 exhibited a maximum power factor of 0.80 mWm-1K-2 at 723 K. As the Mn content increased, both the electronic and lattice thermal conductivities increased, and thus, the total thermal conductivity was the lowest at 0.48–0.63Wm-1K-1 at 323–723 K for x = 0.1. A maximum dimensionless figure of merit of 0.75 was obtained at 723 K for Cu11.7Mn0.3Sb4S13. The MA-HP process is suitable for preparing doped tetrahedrites exhibiting excellent thermoelectric performance.
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Warren, Ross, Paul W. M. Blom i Norbert Koch. "Molecular p-doping induced dielectric constant increase of polythiophene films determined by impedance spectroscopy". Applied Physics Letters 122, nr 15 (10.04.2023): 152108. http://dx.doi.org/10.1063/5.0146194.
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The dielectric constant ( εr) is a fundamental material parameter that governs charge transfer processes in organic semiconductors, yet its value is often assumed rather than measured. Here, we use impedance spectroscopy to determine εr in regioregular poly(3-hexylthiophen-2,5-diyl) (P3HT) thin films p-doped with the molecular dopants hexafluoro-tetracyanonaphthoquinodimethane and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). We fit the impedance spectra using a single RC circuit model to determine the frequency-dependent capacitance and extract εr. The value of the dielectric constant increases by around two-thirds from 2.9 ± 0.1 (undoped polymer) to 4.9 ± 0.6 on the addition of one F4TCNQ molecule per 500 P3HT monomer units. In contrast, the addition of the weak dopant 7,7,8,8-tetracyanoquinodimethane (TCNQ), which does not undergo ground state charge transfer with P3HT, has no effect on the dielectric constant. Our results support the hypothesis that molecular doping has a considerable impact on the materials dielectric constant via polarizable host-dopant complexes.
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Ïçelli, Orhan. "Measurement of efffective atomic numbers of holmium doped and undoped layered semiconductors via transmission method around the absorption edge". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 600, nr 3 (marzec 2009): 635–39. http://dx.doi.org/10.1016/j.nima.2008.12.144.
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Ramelan, A. H., H. Harjana i P. Arifin. "Growth of AlGaSb Compound Semiconductors on GaAs Substrate by Metalorganic Chemical Vapour Deposition". Advances in Materials Science and Engineering 2010 (2010): 1–8. http://dx.doi.org/10.1155/2010/923409.
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EpitaxialAlxGa1-xSb layers on GaAs substrate have been grown by atmospheric pressure metalorganic chemical vapour deposition using TMAl, TMGa, and TMSb. We report the effect of V/III flux ratio and growth temperature on growth rate, surface morphology, electrical properties, and composition analysis. A growth rate activation energy of 0.73 eV was found. For layers grown on GaAs at 580∘C and 600∘C with a V/III ratio of 3 a high quality surface morphology is typical, with a mirror-like surface and good composition control. It was found that a suitable growth temperature and V/III flux ratio was beneficial for producing good AlGaSb layers. Undoped AlGaSb grown at 580∘C with a V/III flux ratio of 3 at the rate of 3.5 μm/hour shows p-type conductivity with smooth surface morphology and its hole mobility and carrier concentration are equal to 237 cm2/V.s and 4.6 × 1017 cm-3, respectively, at 77 K. The net hole concentration of unintentionally doped AlGaSb was found to be significantly decreased with the increased of aluminium concentration. All samples investigated show oxide layers (Al2O3,Sb2O3, andGa2O5) on their surfaces. In particular the percentage of aluminium-oxide was very high compared with a small percentage of AlSb. Carbon content on the surface was also very high.
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Raship, Nur Amaliyana, Siti Nooraya Mohd Tawil, Nafarizal Nayan, Khadijah Ismail, Anis Suhaili Bakri, Zulkifli Azman i Faezahana Mohkhter. "Magnetic Domain Characterization and Physical Properties of Gd-Doped and (Gd, Al) Co-Doped ZnO Thin Films". Materials 15, nr 22 (14.11.2022): 8025. http://dx.doi.org/10.3390/ma15228025.
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Undoped ZnO, Gd-doped ZnO with various doping concentration (1, 3, 5, and 7 at%), and 3 at% (Gd, Al) co-doped ZnO films were prepared on a glass substrate using the co-reactive sputtering method. The influence of the doping and co-doping process on the films was characterized using X-ray diffraction, FESEM, EDX, MFM, VSM, UV–VIS spectroscopy, and the Hall Effect measurement at room temperature. XRD study confirmed that the Gd and Al ions are incorporated into a ZnO lattice. EDX analysis confirmed the existence of Zn, O, Al, and Gd elements in the prepared Gd-doped ZnO and (Gd, Al) co-doped ZnO films, which suggests the successful doping procedure. All the deposited films obtained maximum optical transmittance above 80%, showing a high transparency of the films in the visible region. The optical band gap was found red-shifted from 3.11 to 3.21 eV with the increase in Gd doping concentration. The increase in band gap energy from 3.14 eV to 3.16 eV was obtained for 3 at% Gd and 3 at% (Gd, Al) co-doped ZnO films. The MFM measurement proved the existence of room-temperature ferromagnetism and spin polarization in Gd and (Gd, Al) co-doped ZnO films. By co-doping with Al, the result obtained from MFM shows the enhancement of magnetic properties, as it exhibited a smaller domain size with a shorter magnetic correlation length L, a larger phase shift Φrms, and the highest value of δfrms compared to the sample with 3 at% Gd incorporated into ZnO. The carrier concentration and electrical conductivity increased with the increase in Gd concentration, whereas the electrical resistivity and hall mobility showed a reverse trend. The similar trend of results obtained for 3 at% (Gd, Al) co-doped ZnO as compared to 3 at% Gd-doped ZnO also indicates greater electrical properties after a shallow donor such as aluminum was incorporated into Gd-doped ZnO thin films. In conclusion, for future applications, one should consider the possible influence of other types of shallow donor incorporation in an attempt to enhance the properties of new types of diluted magnetic semiconductors (DMSs).
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Ramrakhiani, Meera, Nitendra Kumar Gautam, Kamal Kushwaha, Sakshi Sahare i Pranav Singh. "Electroluminescence in Chalcogenide Nanocrystals and Nanocomposites". Defect and Diffusion Forum 357 (lipiec 2014): 127–69. http://dx.doi.org/10.4028/www.scientific.net/ddf.357.127.
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Several research groups have reported that nanocrystalline II-VI semiconductors show enhanced luminescence, increased oscillator strength and shorter response time. Nanocrystalline powder samples of CdS, CdSe, ZnS and ZnSe nanocrystals and their composites with PVA and PVK have been prepared by chemical route. SEM. TEM and AFM images indicate agglomeration of particles. XRD reveal the crystal structure and size in nanometer range and absorption spectra show increased band gap due to quantum confinement.The EL studies on nanocrystalline powder samples and nanocrystal/polymer composites have shown that the light emission starts at certain threshold voltage, different for different specimens and then increases with increasing voltage. It is found that smaller nanocrystals have lower threshold voltage and higher EL brightness. It is observed that nanocomposite give much higher electroluminescence starting at lower voltage and increasing very fast with the voltage as compared to nanocrystalline powder. The emission spectra are found to depend on the material, crystalline size and doping. Electroluminescence in undoped and doped chalcogenide nanocrystals and nanocomposites is reviewed in this paper. In nanosize regime, electroluminescence (EL) is governed by the size quantization effect. Contents of Paper
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Pozina, Galia, Chih-Wei Hsu, Natalia Abrikossova i Carl Hemmingsson. "Plasma-Assisted Halide Vapor Phase Epitaxy for Low Temperature Growth of III-Nitrides". Crystals 13, nr 3 (22.02.2023): 373. http://dx.doi.org/10.3390/cryst13030373.
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Developing growth techniques for the manufacture of wide band gap III-nitrides semiconductors is important for the further improvement of optoelectronic applications. A plasma-assisted halide phase vapor epitaxy (PA-HVPE) approach is demonstrated for the manufacture of undoped and In-doped GaN layers at ~600 °C. A dielectric barrier discharge (DBD) plasma source is utilized for the low-temperature activation of ammonia. The use of the plasma source at a growth temperature of ~600 °C increases the growth rate from ~1.2 to ~4–5 µm/h. Furthermore, the possibility for the growth of InGaN at ~600 °C has been studied. Precursors of GaCl and InCl/InCl3 are formed in situ in the reactor by flowing HCl gas over a melt of metallic Ga and In, respectively. The In concentration was low, in the order of a few percent, as the incorporation of In is reduced by plasma due to the activation of chlorine-containing species that etch the relatively poorly bonded In atoms. Nevertheless, the approach of using plasma for ammonia activation is a very promising approach to growing epitaxial III-nitrides at low temperatures.
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Güler, Ömer. "The effect of an excessive amount of carbon nanotubes on the properties of zinc oxide-carbon nanotube nanocomposites". Science and Engineering of Composite Materials 23, nr 4 (1.07.2016): 389–94. http://dx.doi.org/10.1515/secm-2014-0197.
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AbstractThe effect of the amount of carbon nanotubes on the electrical and optical properties of carbon nanotube (CNT)-zinc oxide nanocomposites was investigated. In this study, carbon nanotubes were prepared by chemical vapor deposition in a fluidized reactor. The diameters and lengths of the carbon nanotubes that were synthesized were determined by high-resolution transmission electron microscopy to be 20–30 nm and a few micrometers, respectively. Then, CNTs were added to commercial zinc oxide powder to prepare the nanocomposite. The structural, optical, and electrical properties of the samples were characterized by various techniques, such as scanning electron microscopy (SEM), UV-vis absorption, and electrical transport measurements. The room temperature conductivity σ25 values of the undoped ZnO and ZnO doped with 0.1% CNTs, 0.2% CNTs, and 5% CNTs were found to be 6.55×10-5, 5.46×10-4, 1.23×10-3, and 2.83×10-2 S/cm, respectively. The optical band gaps of the composites were determined by the Kubelka-Munk theory based on the analysis of diffuse reflectance. The results that were obtained indicated that the electrical and optical properties of ZnO semiconductors can be improved by the incorporation of CNTs. However, the ZnO lost some of its distinctive properties when excess amounts of CNTs were used in the ZnO-CNT composites.
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Kim, Y., i A. Ourmazd. "Diffusion in multilayers, studied by quantitative chemical mapping at the atomic level". Proceedings, annual meeting, Electron Microscopy Society of America 48, nr 4 (sierpień 1990): 354–55. http://dx.doi.org/10.1017/s0424820100174904.
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Using chemical lattice imaging in combination with vector pattern recognition, we study diffusion and interdiffusion at single interfaces in mulilayered semiconductors quantitatively with atomic plane resolution. 20 periods of 50Å C-doped GaAs/50Å undoped GaAs/50Å Al0.4Ga0.6As grown by Molecular Beam Epitaxy(MBE) at 600C was examined to study interdiffusiuori across single GaAs/AlGaAs interfaces as a function of temperature (650C to 750C), depth of interface beneath the surface, and doping . After annealing in bulk form, cross-sectional TEM samples were prepared chemically. Chemical lattice images in the <100> zone axis obtained at an accelerating voltage of 400KV with a JEOL 4000-EX high resolution transmission electron microscope were analyzed by a digital pattern recognition method to obtain composition profiles at each interface before and after annealing.Figure 1 is a chemical lattice image of a C:GaAs/AlGaAs interface. The compositional information in the sample is contained in the local patterns that make up such images. The analysis of such chemical images by the pattern recognition yields quantitative composition profiles across single interfaces. The composition profiles shown in Figure 2 refer to a single interface at a depth of 300Å, before and after annealing at 700C for one hr.
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Furuta, Mamoru, i Yusaku Magari. "(Invited, Digital Presentation) Nondegenerate Hydrogen-Doped Polycrystalline Indium Oxide (InOx:H) Thin Films for High-Mobility Thin Film Transistors". ECS Meeting Abstracts MA2022-02, nr 35 (9.10.2022): 1266. http://dx.doi.org/10.1149/ma2022-02351266mtgabs.
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Transparent metal oxide semiconductors (OSs) have been extensively investigated for use as the active channel layer of thin film transistors (TFTs) for next-generation flat-panel displays, nonvolatile memories, image sensors, and pH sensors, to name a few. Among OSs, the amorphous In–Ga–Zn–O (IGZO) has attracted particular attention for TFT applications owing to its high field effect mobility (μFE) of more than 10 cm2V−1s−1, steep subthreshold swing (S.S.), extremely low off-state current, large-area uniformity, and good bias stress stability. Although the μFE of an IGZO TFT is approximately one order of magnitude higher than that of an amorphous Si TFT, further improvement of the μFE of OS TFTs is required to expand their range of applications as an alternative to polycrystalline Si TFT. Single-crystalline In2O3 has a Hall mobility as high as 160 cm2V−1s−1, which makes amorphous (a-) or polycrystalline (poly-) InOx a potential material for enhancing the μFE of OS TFTs. However, undoped InOx thin films is known as a degenerate semiconductor with high background electron density of over 1020 cm-3, which is attributed to the presence of native defects, such as oxygen vacancies, making them unsuitable for a channel material of OS TFTs. In this presentation, nondegenerate hydrogen-doped polycrystalline InOx (poly-InOx:H) thin films were successfully prepared by low-temperature solid phase crystallization (SPC). A degenerate amorphous InOx:H thin film was deposited by sputtering in Ar, O2, and H2 gases, and an amorphous to polycrystalline phase transition (SPC) of the film was achieved after PDA at more than 175 °C. By PDA at 250 °C in air, a nondegenerate poly-InOx:H film could be obtained with a carrier density as low as 2.4 × 1017 cm−3, which is approximately three orders of magnitude lower than that of the initial a-InOx:H film. The TFTs with a 50 nm thick nondegenerate poly-InOx:H channel could be fully depleted by a gate electric field. A maximum μFE of 125.7 cm2V−1s−1 was exhibited by the TFT with the poly-InOx:H channel. The use of a nondegenerate poly-InOx:H film is a promising approach to boost the μFE of OS TFTs.
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Kourkoutas, C. D., G. J. Papaioannou, P. C. Euthymiou i G. E. Zardas. "Determination of the scattering mechanisms in p-type semiconductors of the III–V group: The case of Zn-doped GaP and natural (undoped) GaSb". Solid State Communications 67, nr 6 (sierpień 1988): 651–55. http://dx.doi.org/10.1016/0038-1098(88)90185-8.
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Abdelfatah, Mahmoud, Nourhan Darwesh, Mohamed A. Habib, Omar K. Alduaij, Abdelhamid El-Shaer i Walid Ismail. "Enhancement of Structural, Optical and Photoelectrochemical Properties of n−Cu2O Thin Films with K Ions Doping toward Biosensor and Solar Cell Applications". Nanomaterials 13, nr 7 (4.04.2023): 1272. http://dx.doi.org/10.3390/nano13071272.
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n-type Cu2O thin films were grown on conductive FTO substrates using a low-cost electrodeposition method. The doping of the n−Cu2O thin films with K ions was well identified using XRD, Raman, SEM, EDX, UV-vis, PL, photocurrent, Mott–Schottky, and EIS measurements. The results of the XRD show the creation of cubic Cu2O polycrystalline and monoclinic CuO, with the crystallite sizes ranging from 55 to 25.2 nm. The Raman analysis confirmed the presence of functional groups corresponding to the Cu2O and CuO in the fabricated samples. Moreover, the samples’ crystallinity and morphology change with the doping concentrations which was confirmed by SEM. The PL results show two characteristic emission peaks at 520 and 690 nm which are due to the interband transitions in the Cu2O as well as the oxygen vacancies in the CuO, respectively. Moreover, the PL strength was quenched at higher doping concentrations which reveals that the dopant K limits e−/h+ pairs recombination by trapped electrons and holes. The optical results show that the absorption edge is positioned between 425 and 460 nm. The computed Eg for the undoped and K−doped n−Cu2O was observed to be between 2.39 and 2.21 eV. The photocurrent measurements displayed that the grown thin films have the characteristic behavior of n-type semiconductors. Furthermore, the photocurrent is enhanced by raising the doped concentration, where the maximum value was achieved with 0.1 M of K ions. The Mott–Schottky measurements revealed that the flat band potential and donor density vary with a doping concentration from −0.87 to −0.71 V and 1.3 × 1017 to 3.2 × 1017 cm−3, respectively. EIS shows that the lowest resistivity to charge transfer (Rct) was attained at a 0.1 M concentration of K ions. The outcomes indicate that doping n−Cu2O thin films are an excellent candidate for biosensor and photovoltaic applications.
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Schwarz, Daniel, Johannes Ziegler, Hannes Simon Funk, Joerg Schulze i Michael Oehme. "Hydrogen-Assisted Molecular Beam Epitaxy of SiGeSn ". ECS Meeting Abstracts MA2022-02, nr 32 (9.10.2022): 1164. http://dx.doi.org/10.1149/ma2022-02321164mtgabs.
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Since its first synthesis in 2003 [1], the ternary alloy semiconductor SiGeSn has seen an increasing interest due to its unique properties in the field of Group-IV semiconductors [2–6]. SiGeSn not only allows the decoupling of its bandgap and lattice-constant by what it is predestined for the epitaxy of strain-reduced heterostructures on the Si platform. Furthermore, SiGeSn becomes a direct bandgap semiconductor at high Sn concentrations. Considering these properties, SiGeSn is an attractive material system for optoelectronic applications. An exemplary heterojunction optoelectronic device is the single confinement heterostructure laser diode, the still missing key component for the monolithic integration of the optical on-chip communication on Si. However, one of the greatest challenges faced by many Group-IV researchers is the epitaxy of SiGeSn bulk alloys with high crystal quality. The temperature induced segregation of Sn results in interstitial Sn atoms and subsequently in acceptor-like defect states, as it was already reported for GeSn [7]. In this work, we show the molecular beam epitaxy (MBE) of SiGeSn structures under Hydrogen ambient. First of all, we determined the concentration of the acceptor-like defect states of undoped SiGeSn NA,defect on the basis of capacitance-voltage (C-V) measurements of SiGeSn pin diodes. Furthermore, we investigated Hydrogen-assisted epitaxy as an approach for the reduction of the acceptor-like defect states. All epitaxy experiments were performed in a 6” MBE system, where Si, Ge and Sn are used as matrix materials and B and Sb as dopants respectively. In particular, we investigated the influence of molecular (H2) as well as atomic (H) Hydrogen on the epitaxy process and therefore the quality of the grown structures. For this purpose, the MBE system was upgraded with a Hydrogen atom beam source for the generation of an atomic Hydrogen flux. Since the Sn segregation is affected mostly by the substrate temperature, this critical growth parameter is measured in-situ using an infrared pyrometer, which allows the observation of the dynamic processes on the sample surface [8] and the precise control of the substrate temperature at TSub = 200 °C during the SiGeSn epitaxy. All SiGeSn structures are based on Ge virtual substrates (Ge-VS) on Si(001) [9], followed by a 400 nm thick additional Ge buffer layer. In order to fulfil lattice matching of SiGeSn on Ge, a constant ratio of Si and Sn of Si/Sn = 3.67 was kept for all structures. The Sn concentration was varied in the range of 5 % < cSn < 10 %. For material characterization, 300 nm thick undoped SiGeSn layers were grown on this substrate layer stack (see Fig. 1a). A detailed characterization of the crystallinity and the surface roughness was performed using X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. The comparison of AFM micrographs of SiGeSn layers, grown with and without Hydrogen assistance (see Fig. 1b) show a clear reduction of the surface roughness due to Hydrogen assisted epitaxy. In order to determine NA,defect, C-V measurements on SiGeSn pin diodes (see Fig. 1c) were performed. The diode layer structure, also based on the previously described substrate layer stack, starts with a 400 nm thick p-doped SiGeSn bottom layer with an acceptor concentration of NA = 5x1019 cm-3, followed by an 300 nm thick undoped SiGeSn layer and a closing 200 nm thick n-doped SiGeSn top layer with a donor concentration of ND = 5x1019 cm-3. Subsequently, pin diodes were fabricated using a single mesa process consisting of four basic steps: Mesa structuring using inductive coupled plasma reactive ion etching (ICP-RIE) with HBr, mesa passivation with plasma enhanced chemical vapor deposition (PECVD) grown SiO2, oxide window opening using RIE with CHF3 and metallization using sputtered Al. An exemplary device can be seen in the scanning electron microscopy (SEM) image in Fig. 1d. The SiGeSn pin diodes were electrically characterised by means of C-V measurements using a Keithley 4200 semiconductor characterisation system. For further evaluation, the C-V characteristics of the pin diodes show linear behaviour when plotted on a C-2-V-scaled diagram (Fig. 1e). Under the assumption of a strongly asymmetric pn junction, (ND >> NA,defect), the slope m of the C-2-V characteristics is proportional to NA,defect. In this manner, we determined NA,defect for several SiGeSn pin diodes in dependence of the alloy composition. The results, as shown in Fig. 1f, show an acceptor-like defect concentration between 1017 cm-3 < NA,defect < 1018 cm-3, which is comparable with results reported by other groups for GeSn [7]. In our presentation, we will discuss Hydrogen-assisted epitaxy as a promising approach for improving the SiGeSn crystal quality. Figure 1
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Epstein, Arthur J., i Yang Yang. "Polymeric and Organic Electronic Materials: From Scientific Curiosity to Applications". MRS Bulletin 22, nr 6 (czerwiec 1997): 13–15. http://dx.doi.org/10.1557/s0883769400033571.
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While polymers and organic materials have been known and utilized broadly for many decades, finding such materials with the intrinsic properties of semiconductors and metals is a relatively recent phenomenon. The report in 1977 about doping polyacetylene to achieve relatively high conductivity opened up important new vistas for chemistry and physics, and for technology in general. This report recognized that a key feature of the electronic polymers and organic materials was a backbone consisting of alternating single and double bonds resulting in a “π-conjugated network.” This in turn led to a relatively small energy gap, enabling the appearance of both semiconducting and metallic properties.Initially these polymers were unstable in air and not readily processed. Over the past decade, major advances have occurred in the synthesis of new forms of conducting and semiconducting polymers that enable processing under a broad range of conditions including organic solvents, inorganic solvents, and aqueous media. There are even meltprocessable versions of some of the electronic polymers.A prime focus of the field has been the determination of the mechanisms for charge conduction and the intrinsic conductivity of these fascinating materials, especially doped polymers. In the past decade, interest has increased in the semiconducting (generally undoped) forms of these polymers and organic materials, including their photophysics and their use in a wide variety of devices. The reports of light-emitting devices fabricated from molecular and oligomeric constituents in the mid-1980s and from polymeric constituents in 1990 stimulated interest in this area of research.
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Erzeneoğlu, S., O. İçelli, B. Gürbulak i A. Ateş. "Measurement of mass attenuation coefficients for holmium doped and undoped layered semiconductors InSe at different energies and the validity of mixture rule for crystals around the absorption edge". Journal of Quantitative Spectroscopy and Radiative Transfer 102, nr 3 (grudzień 2006): 343–47. http://dx.doi.org/10.1016/j.jqsrt.2005.06.001.
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Epstein, Arthur J. "Electrically Conducting Polymers: Science and Technology". MRS Bulletin 22, nr 6 (czerwiec 1997): 16–23. http://dx.doi.org/10.1557/s0883769400033583.
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For the past 50 years, conventional insulating-polymer systems have increasingly been used as substitutes for structural materials such as wood, ceramics, and metals because of their high strength, light weight, ease of chemical modification/customization, and processability at low temperatures. In 1977 the first intrinsic electrically conducting organic polymer—doped polyacetylene—was reported, spurring interest in “conducting polymers.” Intrinsically conducting polymers are completely different from conducting polymers that are merely a physical mixture of a nonconductive polymer with a conducting material such as metal or carbon powder. Although initially these intrinsically conducting polymers were neither processable nor air-stable, new generations of these materials now are processable into powders, films, and fibers from a wide variety of solvents, and also are airstable. Some forms of these intrinsically conducting polymers can be blended into traditional polymers to form electrically conductive blends. The electrical conductivities of the intrinsically conductingpolymer systems now range from those typical of insulators (<10−10 S/cm (10−10 Ω−1 cm1)) to those typical of semiconductors such as silicon (~10 5 S/cm) to those greater than 10+4 S/cm (nearly that of a good metal such as copper, 5 × 105 S/cm). Applications of these polymers, especially polyanilines, have begun to emerge. These include coatings and blends for electrostatic dissipation and electromagnetic-interference (EMI) shielding, electromagnetic-radiation absorbers for welding (joining) of plastics, conductive layers for light-emitting polymer devices, and anticorrosion coatings for iron and steel.The common electronic feature of pris tine (undoped) conducting polymers is the π-conjugated system, which is formed by the overlap of carbon pz orbitals and alternating carbon-carbon bond lengths.