Journal articles: 'Oxide thin films and heterostructure'

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Golan, G., A. Axelevitch, and Jacob Azoulay. "Properties investigation of thin films photovoltaic hetero-structures." World Journal of Engineering 11, no. 3 (June 1, 2014): 233–38. http://dx.doi.org/10.1260/1708-5284.11.3.233.

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This paper presents an experimental investigation of photovoltaic (PV) properties in heterostructures consisting of indium oxide and amorphous silicon thin films, grown on a single crystalline p-type silicon and polyimide flexible substrates. Both thin films: In2O3 and a-Si were deposited by magnetron sputtering. Such heterostructure thin film systems are attractive because of their ability to convert solar energy into electrical one. Grown Heterostructures films were treated by simultaneous influence of an electron beam and high energetic photons with energy more than 1.5 eV in the so called vacuum photo-thermal processing (VPP).Silicon samples of 100 Ω/sq and 45 Ω/sq were selected as substrates. Thin films deposition was done in argon atmosphere by DC magnetron sputtering.It is shown that:Open circuit voltage of the proposed structure may reach up to ~ 0.35 V,Short circuit current was of no more then 10-7 A,Polyimide materials may be used as substrates for PV thin film deposition structures,VPP dramatically varies the photovoltaic properties of the heterostructure

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Yang, Gene, Wonsang Jung, Sung-Jin Ahn, and Dongkyu Lee. "Controlling the Oxygen Electrocatalysis on Perovskite and Layered Oxide Thin Films for Solid Oxide Fuel Cell Cathodes." Applied Sciences 9, no. 5 (March 12, 2019): 1030. http://dx.doi.org/10.3390/app9051030.

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Achieving the fast oxygen reduction reaction (ORR) kinetics at the cathode of solid oxide fuel cells (SOFCs) is indispensable to enhance the efficiency of SOFCs at intermediate temperatures. Mixed ionic and electronic conducting (MIEC) oxides such as ABO3 perovskites and Ruddlesden-Popper (RP) oxides (A2BO4) have been widely used as promising cathode materials owing to their attractive physicochemical properties. In particular, oxides in forms of thin films and heterostructures have enabled significant enhancement in the ORR activity. Therefore, we aim to give a comprehensive overview on the recent development of thin film cathodes of SOFCs. We discuss important advances in ABO3 and RP oxide thin film cathodes for SOFCs. Our attention is also paid to the influence of oxide heterostructure interfaces on the ORR activity of SOFC cathodes.

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Zhu, Jiaxin, Jung-Woo Lee, Hyungwoo Lee, Lin Xie, Xiaoqing Pan, Roger A. De Souza, Chang-Beom Eom, and Stephen S. Nonnenmann. "Probing vacancy behavior across complex oxide heterointerfaces." Science Advances 5, no. 2 (February 2019): eaau8467. http://dx.doi.org/10.1126/sciadv.aau8467.

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Oxygen vacancies (VO••) play a critical role as defects in complex oxides in establishing functionality in systems including memristors, all-oxide electronics, and electrochemical cells that comprise metal-insulator-metal or complex oxide heterostructure configurations. Improving oxide-oxide interfaces necessitates a direct, spatial understanding of vacancy distributions that define electrochemically active regions. We show vacancies deplete over micrometer-level distances in Nb-doped SrTiO3 (Nb:SrTiO3) substrates due to deposition and post-annealing processes. We convert the surface potential across a strontium titanate/yttria-stabilized zirconia (STO/YSZ) heterostructured film to spatial (<100 nm) vacancy profiles within STO using (T = 500°C) in situ scanning probes and semiconductor analysis. Oxygen scavenging occurring during pulsed laser deposition reduces Nb:STO substantially, which partially reoxidizes in an oxygen-rich environment upon cooling. These results (i) introduce the means to spatially resolve quantitative vacancy distributions across oxide films and (ii) indicate the mechanisms by which oxide thin films enhance and then deplete vacancies within the underlying substrate.

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Zhu, Jiaxin, Jung-Woo Lee, Hyungwoo Lee, Lin Xie, Xiaoqing Pan, Roger A. De Souza, Chang-Beom Eom, and Stephen S. Nonnenmann. "Probing Vacancy Behavior in Complex Oxide Heterostructured Films." ECS Meeting Abstracts MA2018-01, no. 32 (April 13, 2018): 1931. http://dx.doi.org/10.1149/ma2018-01/32/1931.

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Oxygen vacancies (Vo•• ) play a critical role in the transport mechanisms within complex oxides, analogous to electrons and holes within semiconductors. Systems including memristors, all-oxide electronics, and electrochemical cells comprise substrate-supported thin films either in metal-insulator-metal or complex oxide heterostructure configurations. As well-studied defect chemistry dictates mixed electronic/ionic functionality, improving oxide-oxide interfaces necessitates a direct, spatial understanding of vacancy distributions that define electrochemically active regions. Here we show that vacancies deplete over large, micron-level distances within single crystalline perovskite Nb-doped SrTiO3 substrate (Nb:SrTiO3) substrates after typical vacuum film deposition and post-annealing processes. We demonstrate the conversion of the surface potential across a four-layer strontium titanate / yttria-stabilized zirconia (STO/YSZ) heterostructured film to spatially defined (< 100 nm) [Vo•• ] profiles within STO through a unique combination of high temperature (500 °C), in situ scanning probes and classic semiconductor energy band diagram model analysis. Further comparison between room temperature and high temperature potential profiles clearly distinguishes between electronic-dominant and activated, ionic-dominant transport characteristics within the oxide layers. Consequently, we determined that oxygen scavenging by deposited films during pulsed laser deposition significantly reduce the Nb:STO, which is then partially reoxidized in the ambient environment during cooling. The results presented herein i) introduce the means to spatially resolve quantitative vacancy distributions across oxide films, and ii) pose the mechanism by which oxide thin film getters both enhance then deplete vacancies within the underlying substrate.

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Itapu, Srikanth, Kamruzzaman Khan, and Daniel G. Georgiev. "Effect of UV Laser Irradiation on the properties of NiO films and ZnO/NiO Heterostructures." MRS Advances 1, no. 4 (2016): 293–98. http://dx.doi.org/10.1557/adv.2016.99.

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ABSTRACTThe present work accentuates the effect of UV laser irradiation on the conductivity of nickel oxide (NiO) thin films, deposited at various temperatures by radio-frequency reactive sputtering of Ni in oxygen containing atmosphere. The effect of UV irradiation on zinc oxide – nickel oxide heterostructures, obtained by sputtering, was examined as well. It was found that the resistivity of NiO changes from 12 Ω-cm to 0.62 Ω-cm, and the majority carrier concentration from 3.95x1017 holes/cm3 to 4.22x1020 electrons/cm3. The current-voltage (I-V) characteristics of the ZnO/NiO heterostructure shows an improved p-n diode behavior with the forward bias current increasing for the laser-irradiated ZnO/NiO compared to the as-deposited stack. The observed improvement in diode-like behavior suggests that laser irradiation can be an important technique to controllably change the structural, electrical and optical properties of metal oxide thin films.

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Orletskyi, I. G., M. I. Ilashchuk, E. V. Maistruk, M. M. Solovan, P. D. Maryanchuk, and S. V. Nichyi. "Electrical Properties of Sis Heterostructures n-SnS2/CdTeO3/p-CdZnTe." Ukrainian Journal of Physics 64, no. 2 (February 21, 2019): 164. http://dx.doi.org/10.15407/ujpe64.2.164.

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Conditions for the production of rectifying semiconductor-insulator-semiconductor (SIS) heterostructures n-SnS2/CdTeO3/p-Cd1−xZnxTe with the use of the spray-pyrolysis of SnS2 thin films on p-Cd1−xZnxTe crystalline substrates with the formation of an intermediate tunnel-thin CdTeO3 oxide layer have been studied. By analyzing the temperature dependences of the current-voltage characteristics, the dynamics of the heterostructure energy parameters is determined, and the role of energy states at the CdTeO3/p-Cd1−xZnxTe interface in the formation of forward and reverse currents is elucidated. By analyzing the capacity-voltage characteristics, the processes of charge accumulation and inversion in SIS structures is considered. An energy diagram of the examined heterostructure, which well describes experimental electro-physical phenomena, is proposed.

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Hamlin, Andrew Bradford, Youxiong Ye, Julia Elizabeth Huddy, and William Joseph Scheideler. "Modulation Doped 2D InO_x/GaO_x Heterostructure Tfts Via Liquid Metal Printing." ECS Meeting Abstracts MA2022-01, no. 31 (July 7, 2022): 1326. http://dx.doi.org/10.1149/ma2022-01311326mtgabs.

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Indium gallium zinc oxide (IGZO) and similar wide bandgap metal oxides are among the most widely used channel materials for drive transistors in displays due to their excellent electronic mobility and their ultra-high transparency1. However, industry-standard processing involves expensive vacuum deposition and elevated activation temperatures to produce semiconducting thin films. Liquid metal printing (LMP) is an emerging technique for oxide semiconductor fabrication poised to overcome these drawbacks via scalable vacuum-free transfer of the native oxide layers formed by spontaneous surface oxidation of molten metals2–4. Heterostructures of these 1-4 nm 2D oxide layers provide unprecedented opportunities for engineering electrostatic control of multilayers in thin film transistors, leading to improved mobility, Ion/Ioff ratios, and faster switching capabilities. Likewise, the backchannel is of high importance to these devices, as selection of an appropriate capping layer can enhance performance via remote doping while also mitigating bias stress effects. Herein, we compare the results of heterostructure InOx/GaOx with pure InOx TFTs, which demonstrates the mobility enhancement provided by GaOx modulation doping. Bottom gate thin film transistors (TFTs) (Figures 1a and 1b) were fabricated on Si substrates with 100 nm of thermally grown SiO2. 4 nm thick InOx and GaOx were deposited at 240 ˚C and 180 ˚C, respectively, using a linear printing speed of 8 cm/s. InOx and GaOx were printed in less than 10 s, with no post annealing necessary. Figure 1c illustrates the proposed mechanism for electron donation from GaOx at the heterointerface with InOx. The conduction band offset between these materials results in band bending at the interface and an increased carrier concentration in the InOx layer. The substoichiometric, defective GaOx is expected to further enhance this effect. Figure 1d demonstrates the transfer characteristics of heterostructure InOx/GaOx in comparison with pure InOx. The improved mobility for the heterostructure (7.8 cm2/Vs) vs pure InOx (3.8 cm2/Vs) channels can be attributed to modulation doping provided by GaOx and can be analyzed by extracting the electronic density of states (eDOS). These results illustrate a unique capability of LMP, which is to engineer the electronic structure of highly conductive 2D oxides while maintaining electrostatic control. This work also investigates the material properties of these 2D oxide heterostructures by UV-vis, XRD and XPS characterization. UV-Vis analysis revealed that the GaOx capping layer induces band gap widening and enhanced transparency, which can be explained by the Burstein-Moss effect from modulation doping. Unique to this LMP process is also the low temperature crystallization of the InOx films. XRD showed that even with low deposition temperatures (200 – 240 ˚C), these InOx films are highly crystalline with grain sizes substantially larger than the film thickness. Finally, XPS analysis of the O1s peak was utilized to understand the stoichiometry and interactions between the InOx and GaOx layers. This work demonstrates an effective pathway to enhance electronic transport in semiconducting metal oxides through liquid metal printed 2D heterostructures. The ultrathin films produced by LMP are well suited for thin film devices requiring nm-scale electrostatic control for effective gating. Combining this 2D nature of LMP InOx with a 2D GaOx backchannel capping layer is shown to yield high-performance printed transistors. This approach demonstrates a rapid, open-air compatible and low temperature manufacturing method, elucidating the broad impact of this technology in display fabrication, low-cost and flexible electronics. H. Hosono, Nat Electron, 1, 428–428 (2018). K. A. Messalea et al., ACS Nano, 15, 16067–16075 (2021). R. S. Datta et al., Nat Electron, 3, 51–58 (2020). A. Jannat et al., ACS Nano, 15, 4045–4053 (2021). A. Goff et al., Dalton Transactions, 50, 7513–7526 (2021). C.-H. Choi, Y.-W. Su, L.-Y. Lin, C.-C. Cheng, and C. Chang, RSC Advances, 5, 93779–93785 (2015). Figure 1

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Aivalioti, Chrysa, Alexandros Papadakis, Emmanouil Manidakis, Maria Kayambaki, Maria Androulidaki, Katerina Tsagaraki, Nikolaos T. Pelekanos, et al. "Transparent All-Oxide Hybrid NiO:N/TiO2 Heterostructure for Optoelectronic Applications." Electronics 10, no. 9 (April 21, 2021): 988. http://dx.doi.org/10.3390/electronics10090988.

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Nickel oxide (NiO) is a p-type oxide and nitrogen is one of the dopants used for modifying its properties. Until now, nitrogen-doped NiO has shown inferior optical and electrical properties than those of pure NiO. In this work, we present nitrogen-doped NiO (NiO:N) thin films with enhanced properties compared to those of the undoped NiO thin film. The NiO:N films were grown at room temperature by sputtering using a plasma containing 50% Ar and 50% (O2 + N2) gases. The undoped NiO film was oxygen-rich, single-phase cubic NiO, having a transmittance of less than 20%. Upon doping with nitrogen, the films became more transparent (around 65%), had a wide direct band gap (up to 3.67 eV) and showed clear evidence of indirect band gap, 2.50–2.72 eV, depending on %(O2-N2) in plasma. The changes in the properties of the films such as structural disorder, energy band gap, Urbach states and resistivity were correlated with the incorporation of nitrogen in their structure. The optimum NiO:N film was used to form a diode with spin-coated, mesoporous on top of a compact, TiO2 film. The hybrid NiO:N/TiO2 heterojunction was transparent showing good output characteristics, as deduced using both I-V and Cheung’s methods, which were further improved upon thermal treatment. Transparent NiO:N films can be realized for all-oxide flexible optoelectronic devices.

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Lu, Chengliang, Weijin Hu, Yufeng Tian, and Tom Wu. "Multiferroic oxide thin films and heterostructures." Applied Physics Reviews 2, no. 2 (June 2015): 021304. http://dx.doi.org/10.1063/1.4921545.

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Perret, Edith, Changyong Park, Dillon D. Fong, Kee-Chul Chang, Brian J. Ingram, Jeffrey A. Eastman, Peter M. Baldo, and Paul H. Fuoss. "Resonant X-ray scattering studies of epitaxial complex oxide thin films." Journal of Applied Crystallography 46, no. 1 (January 17, 2013): 76–87. http://dx.doi.org/10.1107/s0021889812047620.

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Resonant anomalous X-ray reflectivity (RAXR) is a powerful technique for measuring element-specific distribution profiles across surfaces and buried interfaces. Here, the RAXR technique is applied to characterize a complex oxide heterostructure, La0.6Sr0.4Co0.2Fe0.8O3−δ, on NdGaO3, and the effects of data sampling and model-dependent fitting procedures on the extracted elemental distribution profile are evaluated. The strontium profile through a 3.5 nm-thick film at 973 K and at an oxygen partial pressure of 150 Torr (1 Torr = 133.32 Pa) was determined from the measured RAXR spectra. The results demonstrate thatin situRAXR measurements can provide key insights into temperature- and environment-dependent elemental segregation processes, relevant, for example, in assessing the cathode performance of solid oxide fuel cells.

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HAO, J. H., and J. GAO. "INTEGRATION OF LASER MBE GROWN OXIDE THIN FILMS OF SrTiO3 WITH YBa2Cu3Oy FOR TUNABLE APPLICATIONS." Surface Review and Letters 14, no. 04 (August 2007): 833–36. http://dx.doi.org/10.1142/s0218625x07010123.

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The frequency tuning can be achieved by integrating SrTiO 3 (STO) thin films into high-temperature superconducting YBa 2 Cu 3 O y (YBCO) devices and tuning the dielectric constant of the STO films by an electrical bias. We have fabricated epitaxial STO thin films on superconducting YBCO. By the combination of various surface characterizations such as scanning probe microscope, structural and dielectric measurements, we attempted to understand the fundamental mechanisms of dielectric properties in STO thin films. Substrate surface and structural properties of the heterostructure were studied. We have measured the temperature dependence of dielectric constant and loss tangent of STO thin films. The system exhibits 41% dielectric constant tuning over a bias of 4 V at low temperature.

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Ghonge, S. G., E. Goo, R. Ramesh, R. Haakenaasen, and D. K. Fork. "Epitaxial ferroelectric thin films." Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994): 572–73. http://dx.doi.org/10.1017/s0424820100170591.

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Microstructure of epitaxial ferroelectric/conductive oxide heterostructures on LaAIO3(LAO) and Si substrates have been studied by conventional and high resolution transmission electron microscopy. The epitaxial films have a wide range of potential applications in areas such as non-volatile memory devices, electro-optic devices and pyroelectric detectors. For applications such as electro-optic devices the films must be single crystal and for applications such as nonvolatile memory devices and pyroelectric devices single crystal films will enhance the performance of the devices. The ferroelectric films studied are Pb(Zr0.2Ti0.8)O3(PLZT), PbTiO3(PT), BiTiO3(BT) and Pb0.9La0.1(Zr0.2Ti0.8)0.975O3(PLZT).Electrical contact to ferroelectric films is commonly made with metals such as Pt. Metals generally have a large difference in work function compared to the work function of the ferroelectric oxides. This results in a Schottky barrier at the interface and the interfacial space charge is believed to responsible for domain pinning and degradation in the ferroelectric properties resulting in phenomenon such as fatigue.

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de Oliveira Machado, Diego Henrique, Emerson Aparecido Floriano, Luis Vicente de Andrade Scalvi, and Margarida Juri Saeki. "Investigation of Photoinduced Electrical Properties in the Heterojunction TiO₂/SnO₂." Advanced Materials Research 975 (July 2014): 201–6. http://dx.doi.org/10.4028/www.scientific.net/amr.975.201.

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TiO2/SnO2 thin films heterostructures are grown by the sol-gel-dip-coating technique. It was found that the crystalline structure of TiO2 depends on the annealing temperature and the substrate type. TiO2 films deposited on glass substrate, submitted to thermal annealing until 550°C, present anatase structure, whereas films deposited on quartz substrate transform to rutile structure when thermally annealed at 1100°C. When structured as rutile, this oxide semiconductor has very close lattice parameters to those of SnO2, making easier the heterostructure assembling. Electrical properties of TiO2/SnO2 heterostructure were evaluated as function of temperature and excitation with different light sources. The temperature dependence of conductivity is dominated by a deep level with energy coincident with the second ionization level of oxygen vacancies in SnO2, suggesting the dominant role of the most external layer material (SnO2) to the electrical transport properties. The fourth harmonic of a Nd:YAG laser line (4.65eV) seems to excite the most external layer whereas a InGaN LED (2.75eV) seems to excite electrons from the ground state of a quantized interfacial channel as well as intrabandgap states of the TiO2 layer.

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Chen, Xiaoyang, Yun Liu, Binbin Huang, and Ping Yu. "High energy storage efficiency and temperature stability realized in the Ba_0.3Sr_0.7Zr_0.18Ti_0.82O₃/LaNiO₃ heterostructure thin films directly deposited on the conductive Si substrate." Applied Physics Letters 121, no. 12 (September 19, 2022): 122901. http://dx.doi.org/10.1063/5.0106263.

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A high-performance energy storage capacitor would not display high energy storage density ( Ue) but high energy storage efficiency ( η). However, during raising the electric field ( E) or temperature ( T), the η in dielectric thin films often shows an obvious degradation process. The degradation process is closely related to the change of the charge carrier transport mechanism as a function of E or T. Compared with the electric breakdown strength, the relationship between η and the charge carrier transport mechanisms in the dielectric thin films was less concerning. In this work, by increasing the trigger E and T of the space charge limited current mechanism, the beginning of the η degradation process was delayed into higher E and T. Consequently, a high Ue (∼56.6 J/cm3) and η (∼93.9%) were achieved simultaneously in Ba0.3Sr0.7Zr0.18Ti0.82O3/LaNiO3 heterostructure thin films directly deposited on low-cost conductive silicon wafers. Moreover, the temperature stability was greatly improved. This result would also offer a promising approach to improve the electrical properties of the dielectric oxide thin films in a harsh environment of high temperatures by redistributing oxygen vacancies through the heterostructure interface.

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Constantinian K. Y., Ovsyannikov G. A., Shadrin A. V., Shmakov V. A., Petrzhik A. M., Kislinskii Yu. V., and Klimov A. A. "Spin magnetoresistance of a strontium iridate/manganite heterostructure." Physics of the Solid State 64, no. 10 (2022): 1410. http://dx.doi.org/10.21883/pss.2022.10.54227.46hh.

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The results of the angular dependences of the magnetoresistance of the SrIrO3/La0.7Sr0.3MnO3 heterostructure made of oxide thin films epitaxially grown on a NdGaO3 substrate are presented and discussed. The resistance of the heterostructure was measured in configuration of planar Hall effect with magnetic field applied in parallel making possible to estimate the spin-Hall angle. The contribution of the anisotropic magnetoresistance and the spin-Hall magnetoresistance occurred due to strong spin-orbit interaction in the SrIrO3 film were evaluated. Keywords: strontium iridate, spin-orbit interaction, spin magnetoresistance, spin-Hall angle.

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Yan, Xi, Hui Cao, Yan Li, Hawoong Hong, David J. Gosztola, Nathan P. Guisinger, Hua Zhou, and Dillon D. Fong. "In situ x-ray studies of growth of complex oxides on graphene by molecular beam epitaxy." APL Materials 10, no. 9 (September 1, 2022): 091114. http://dx.doi.org/10.1063/5.0101416.

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Future technologies are likely to exploit flexible heterostructures exhibiting multifunctional properties constructed from multiple materials. One technique for the synthesis of such systems relies on remote epitaxy, a method employing graphene as a sacrificial layer between a crystalline substrate and an epitaxial film. The technique can be used to create single crystal heterostructures comprised of stacked epitaxial films, their properties optimized by minimizing incompatibilities between the different materials. Details regarding nucleation and growth via remote epitaxy remain unknown, however, due to the many difficulties in studying synthesis in the growth environment with atomic-scale resolution. Here, we describe an in situ synchrotron x-ray investigation of complex oxide thin film growth on graphene by molecular beam epitaxy. Phase retrieval methods were used to reconstruct the electron density profiles from x-ray crystal truncation rods measured under different growth conditions. Our in situ observations combined with post-growth spectroscopy provide a number of key insights regarding graphene in the synthesis environment and the resulting effects on the complex oxide/graphene heterostructure.

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Zhang, Bowen. "Ionically conducting oxide composite thin films and heterostructures." Materials Science and Technology 33, no. 15 (April 23, 2017): 1728–36. http://dx.doi.org/10.1080/02670836.2017.1316581.

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Wu, N. J., A. Ignatiev, and Y. S. Chen. "Perovskite Oxide Thin Film Heterostructures for IR Detector." International Journal of Modern Physics B 12, no. 29n31 (December 20, 1998): 3381–84. http://dx.doi.org/10.1142/s0217979298002696.

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Mn and Sb-doped PbZrTiO 3 (PMSZT) ferroelectric thin films were integrated to high-T c superconducting YB2Cu3O 7-x (YBCO) thin films on LaAlO 3 (100) and YSZ/Si (100) substrates by the pulsed laser deposition technique. The PZT/YBCO and PM-SZT/YBCO infrared detectors were fabricated and examined as to their photovoltage and photocurrent in response to IR source temperature, and IR wavelength. The detector has relatively high IR sensitivity with a detectivity of ~ 108 cm · Hz 1/2/ W in the wavelength range of 3–16 μm.

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Mazur, M., J. Domaradzki, and D. Wojcieszak. "Optical and electrical properties of (Ti-V)Ox thin film as n-type Transparent Oxide Semiconductor." Bulletin of the Polish Academy of Sciences Technical Sciences 62, no. 3 (September 1, 2014): 583–88. http://dx.doi.org/10.2478/bpasts-2014-0063.

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Abstract In this paper, the influence of vanadium doping on optical and electrical properties of titanium dioxide thin films has been discussed. The (Ti-V)Ox thin films was deposited on silicon and Corning glass substrates using high energy reactive magnetron sputtering process. Measurements performed with the aid of x-ray diffraction revealed, that deposited thin film was composed of nanocrystalline mixture of TiO2-anatase, V2O3 and β-V2O5 phases. The amount of vanadium in the thin film, estimated on the basis of energy dispersive spectroscopy measurement, was equal to 3 at. %. Optical properties were evaluated based on transmission and reflection measurements. (Ti-V)Ox thin film was well transparent and the absorption edge was shifted by only 11 nm towards longer wavelengths in comparison to undoped TiO2. Electrical measurements revealed, that investigated thin film was transparent oxide semiconductors with n-type electrical conduction and resistivity of about 2.7 · 105 Ωcm at room temperature. Additionally, measured I-V characteristics of TOS-Si heterostructure were nonlinear and asymmetrical.

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Curran, Anya, Agnieszka Gocalinska, Andrea Pescaglini, Eleonora Secco, Enrica Mura, Kevin Thomas, Roger E. Nagle, et al. "Structural and Electronic Properties of Polycrystalline InAs Thin Films Deposited on Silicon Dioxide and Glass at Temperatures below 500 °C." Crystals 11, no. 2 (February 5, 2021): 160. http://dx.doi.org/10.3390/cryst11020160.

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Polycrystalline indium arsenide (poly InAs) thin films grown at 475 °C by metal organic vapor phase epitaxy (MOVPE) are explored as possible candidates for low-temperature-grown semiconducting materials. Structural and transport properties of the films are reported, with electron mobilities of ~100 cm2/V·s achieved at room temperature, and values reaching 155 cm2/V·s for a heterostructure including the polycrystalline InAs film. Test structures fabricated with an aluminum oxide (Al2O3) top-gate dielectric show that transistor-type behavior is possible when poly InAs films are implemented as the channel material, with maximum ION/IOFF > 250 achieved at −50 °C and ION/IOFF = 90 at room temperature. Factors limiting the ION/IOFF ratio are investigated and recommendations are made for future implementation of this material.

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Chen, Cheng-Chiang, Lung-Chien Chen, and Yi-Hsuan Lee. "Fabrication and Optoelectrical Properties of IZO/Cu2OHeterostructure Solar Cells by Thermal Oxidation." Advances in Condensed Matter Physics 2012 (2012): 1–5. http://dx.doi.org/10.1155/2012/129139.

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Indium zinc oxide (IZO)/cupper oxide (Cu2O) is a nontoxic nature and an attractive all-oxide candidate for low-cost photovoltaic (PV) applications. The present paper reports on the fabrication of IZO/Cu2O heterostructure solar cells which the Cu2O layers were prepared by oxidation of Cu thin films deposited on glass substrate. The measured parameters of cells were the short-circuit current (Isc), the open-circuit voltage (Voc), the maximum output power (Pm), the fill factor (FF), and the efficiency (η), which had values of 0.11 mA, 0.136 V, 5.05 μW, 0.338, and 0.56%, respectively, under AM 1.5 illumination.

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Marei, Jassim M., Abed A. Khalefa, Qutaiba A. Abduljabbar, and Jamal M. Rzaij. "Nitrogen Dioxide Gas Sensor of In<sub>2</sub>O<sub>3</sub>- ZnO Polyhedron Nanostructures Prepared by Spray Pyrolysis." Journal of Nano Research 70 (October 25, 2021): 41–51. http://dx.doi.org/10.4028/www.scientific.net/jnanor.70.41.

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Heterostructure thin films of indium and zinc oxides (IZO) were prepared by spray pyrolysis from an aqueous solution of the precursors at different substrate temperatures (TS). The polycrystalline structure of bixbyite appeared at a low temperature. The crystallinity was enhanced with the emergence of the zinc oxide phase. By increasing the TS to 623 K, the crystallite size was increased. SEM images reveal that the deposited sample at 523 K is composed of irregularly shaped nanoparticles with a lack of links. Increasing the TS to 573 K increases the average particle diameters, and the particles appeared as polyhedrons well connected with cavities between them, which candidates for gas sensing applications. Increasing TS to 623 K resulted in the particles merging. NO2 gas sensor results confirmed the enhancement of IZO sensitivity performance at 573 K. Keywords: Gas sensor, thin film metal oxide, spray pyrolysis, In2O3– ZnO

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Matsumoto, Kenji, Yutaka Adachi, Takeshi Ohgaki, Isao Sakaguchi, Tsubasa Nakagawa, Naoki Ohashi, and Hajime Haneda. "Zinc Self-Diffusion in Isotopic Heterostructured Zinc Oxide Thin Films." Key Engineering Materials 421-422 (December 2009): 193–96. http://dx.doi.org/10.4028/www.scientific.net/kem.421-422.193.

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Zinc isotopic heterostructured zinc oxide thin films of 64ZnO/68ZnO/64ZnO were synthesized using pulsed laser deposition. The pulsed laser was first irradiated onto a polycrystalline target of 64ZnO to deposit the 64ZnO layer, then onto the 68ZnO target to prepare the 68ZnO layer and finally, the 64ZnO target was used again. The 64ZnO/68ZnO/64ZnO layered thin film was thus obtained. The thin films were annealed at various diffusion annealing temperatures. Diffusion profiles of the zinc isotopes due to the annealing were evaluated using secondary ion mass spectrometry (SIMS). The diffusion coefficients were slightly higher near the interface between the thin film and the substrate (the inner region) compared to the near surface (the outer region).

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Lichtensteiger, Céline. "InteractiveXRDFit: a new tool to simulate and fit X-ray diffractograms of oxide thin films and heterostructures." Journal of Applied Crystallography 51, no. 6 (October 18, 2018): 1745–51. http://dx.doi.org/10.1107/s1600576718012840.

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Fiorenza, P., G. Greco, G. Fisichella, F. Roccaforte, G. Malandrino, and R. Lo Nigro. "High permittivity cerium oxide thin films on AlGaN/GaN heterostructures." Applied Physics Letters 103, no. 11 (September 9, 2013): 112905. http://dx.doi.org/10.1063/1.4820795.

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Zhang, Raymond, Timofey Averianov, and Ekaterina Pomerantseva. "Assembly of Two-Dimensional δ-V₂O₅-Ti₃C₂T_x Heterostructure Electrodes for Li-Ion Batteries." ECS Meeting Abstracts MA2022-02, no. 2 (October 9, 2022): 150. http://dx.doi.org/10.1149/ma2022-022150mtgabs.

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The bilayered phase of vanadium oxide (δ-V2O5∙nH2O or BVO) synthesized via sol-gel synthesis method is an attractive candidate to be used as a cathode material for Li-ion batteries (LIBs) due to its expanded interlayer spacing, and high theoretical capacity. However, poor electrical conductivity and rapid capacity fade present challenges for achieving high-rate performance and good cycle life during cycling in LIBs. A viable solution to mitigating these drawbacks is to fabricate two-dimensional (2D) heterostructures comprised of vanadium oxide and an additional selected 2D material. Titanium carbide (Ti3C2Tx) MXenes are particularly of interest for their high electronic conductivity (103 S cm-1) and well developed delamination protocols. Herein, we present a wet-based approach for assembling BVO and MXene nanoflakes into 2D heterostructures in suspension. In this study, we first demonstrate a simple liquid phase exfoliation technique utilizing probe ultrasonication to exfoliate bulk -LixV2O5·nH2O (LVO). Previous experiments from our group showed the exfoliation technique in n-methyl-2-pyrrolidone, an organic solvent that is toxic, flammable, and resulted in low yield during exfoliation. Here, for the first time, we have successfully performed exfoliation of LVO in aqueous media and obtained few layered nanoflakes with high yield after centrifugation. Despite the partial solubility of vanadium oxide in water, these nanoflakes suspended in aqueous media maintained chemical stability and readily assembled into a free-standing film using vacuum filtration. The LVO nanoflake films have a two-dimensional (2D) layered morphology as confirmed by SEM and maintain the bilayered structure as confirmed by XRD. Due to the hydrated nature of LVO, we also highlight the importance of controlling interlayer water content with vacuum drying for achieving better cycling stability. The comparison of a 105°C and 200°C vacuum drying temperature and corresponding interlayer water content was carried out using XRD, TGA, and Raman spectroscopy characterization methods. The 200°C vacuum dried LVO nanoflake cathode achieved an initial ion storage capacity of 212 mAh g-1 which was 32.5% higher than the sample dried at 105°C. In addition, galvanostatic cycling experiments conducted for the 200°C vacuum dried LVO nanoflake cathode show there were significant improvements in capacity retention by ~35%, compared to the 105°C dried sample, after 100 cycles at a current density of 20 mA g-1. Subsequently, dispersions of LVO and Ti3C2Tx flakes in water were combined in different weight ratios of 9:1, 4:1, and 1:1 LVO to Ti3C2Tx. The heterostructure electrostatic assembly was facilitated by the introduction of a cationic species into the mixed suspensions. Resistivity measurements showed that heterostructure films achieved electronic conductivities as high as ~105 higher than pristine LVO. Through electrochemical testing, the 9:1 heterostructure cathodes delivered the highest ion storage capacity of 167 mAh g-1. At the cost of lower capacity (125.3 mAh g-1), the 4:1 heterostructures maintain a superior capacity retention of ~96% after 10 cycles. Furthermore, rate capability experiments for the 9:1 heterostructure cathodes demonstrate that the addition of 10 wt % Ti3C2Tx to LVO enables greater tolerance to high current densities with a capacity retention of ~90% after cycling through increasing current densities. In this work we also show that increased capacities can be acquired upon the extension of the potential window below 2V covering where Ti3C2Tx exhibits redox activity. These results demonstrate an environmentally friendly and safe approach to obtaining 2D LVO nanoflakes and offers pathways to constructing novel vanadium oxide based 2D heterostructures for improving electrochemical performance in energy storage devices.

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SALIM, EVAN T., MARWA S. AL WAZNY, and MAKRAM A. FAKHRY. "GLANCING ANGLE REACTIVE PULSED LASER DEPOSITION (GRPLD) FOR Bi2O3/Si HETEROSTRUCTURE." Modern Physics Letters B 27, no. 16 (June 6, 2013): 1350122. http://dx.doi.org/10.1142/s0217984913501224.

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Thin films of micro bismuth oxide particles were successfully prepared by in situ oxidation of the laser ablated bismuth metal. (111) oriented p-type crystalline silicon substrates were used. The effects of substrate tiled angle on the characteristics of the prepared film were studied. Also, the performance of n- Bi 2 O 3/p- Si heterojunction device was investigated. The obtained current–voltage characteristics in dark and under illumination insure the dependence of the fabricated device characteristic on the deposition angle. The I–V characteristics show that all prepared devices are of abrupt type.

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Endo, Kazuhiro, Noriaki Ikenaga, and P. Badica. "Multi-Component Oxide Thin Films and Heterostructures for Electronics: Growth Principles." Advances in Science and Technology 77 (September 2012): 209–14. http://dx.doi.org/10.4028/www.scientific.net/ast.77.209.

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In the last years oxide materials for electronics show significant progress. However, many details regarding technology control of the properties have to be solved. For electronics, thin films and heterestructures are important taking advantage of integration and synergetic concepts leading to new types of devices and functionalities. It is notable that, while fabrication of new devices and materials showing new phenomena are booming, the growth principles and concepts are somehow developing slowly within this general trend. This is because in many cases, growth of materials is very personalized. Understanding of the bi-directional relationship between the general and particular principles deserves attention. The immediate benefit is that knowledge on growth for one material can be transferred to another one. In our work we have analyzed such relationships for some oxide multicomponent perovskites. Materials used in our examples are Bi-Sr-Ca-Cu-O and YBa2Cu3O7, (Ca, Sr)CuO2, (Ca, Ba)CuO2and Bi4Ti3O12. Presented thin films or heterostructures are with c-axis and non-c-axis orientations and based on these examples we discuss some of the growth principles.

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Heo, Seungyang, Daseob Yoon, Sangbae Yu, Junwoo Son, and Hyun Myung Jang. "Non-volatile ferroelectric control of room-temperature electrical transport in perovskite oxide semiconductor La:BaSnO3." Journal of Materials Chemistry C 5, no. 45 (2017): 11763–68. http://dx.doi.org/10.1039/c7tc03730a.

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Complex oxide heterostructures composed of oxide semiconductor thin films and ferroelectric single crystals have attracted substantial interest due to the electrically switchable channel resistance by the polarization reversal of ferroelectrics.

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30

Schaper, Nicholas, Dheyaa Alameri, Yoosuk Kim, Brian Thomas, Keith McCormack, Mathew Chan, Ralu Divan, David J. Gosztola, Yuzi Liu, and Irma Kuljanishvili. "Controlled Fabrication of Quality ZnO NWs/CNTs and ZnO NWs/Gr Heterostructures via Direct Two-Step CVD Method." Nanomaterials 11, no. 7 (July 15, 2021): 1836. http://dx.doi.org/10.3390/nano11071836.

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A novel and advanced approach of growing zinc oxide nanowires (ZnO NWs) directly on single-walled carbon nanotubes (SWCNTs) and graphene (Gr) surfaces has been demonstrated through the successful formation of 1D–1D and 1D–2D heterostructure interfaces. The direct two-step chemical vapor deposition (CVD) method was utilized to ensure high-quality materials’ synthesis and scalable production of different architectures. Iron-based universal compound molecular ink was used as a catalyst in both processes (a) to form a monolayer of horizontally defined networks of SWCNTs interfaced with vertically oriented ZnO NWs and (b) to grow densely packed ZnO NWs directly on a graphene surface. We show here that our universal compound molecular ink is efficient and selective in the direct synthesis of ZnO NWs/CNTs and ZnO NWs/Gr heterostructures. Heterostructures were also selectively patterned through different fabrication techniques and grown in predefined locations, demonstrating an ability to control materials’ placement and morphology. Several characterization tools were employed to interrogate the prepared heterostructures. ZnO NWs were shown to grow uniformly over the network of SWCNTs, and much denser packed vertically oriented ZnO NWs were produced on graphene thin films. Such heterostructures can be used widely in many potential applications, such as photocatalysts, supercapacitors, solar cells, piezoelectric or thermal actuators, as well as chemical or biological sensors.

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Baiutti, Federico, Georg Christiani, and Gennady Logvenov. "Towards precise defect control in layered oxide structures by using oxide molecular beam epitaxy." Beilstein Journal of Nanotechnology 5 (May 8, 2014): 596–602. http://dx.doi.org/10.3762/bjnano.5.70.

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In this paper we present the atomic-layer-by-layer oxide molecular beam epitaxy (ALL-oxide MBE) which has been recently installed in the Max-Planck Institute for Solid State Research and we report on its present status, providing some examples that demonstrate its successful application in the synthesis of different layered oxides, with particular reference to superconducting La2CuO4 and insulator-to-metal La2− x Sr x NiO4. We briefly review the ALL-oxide MBE technique and its unique capabilities in the deposition of atomically smooth single-crystal thin films of various complex oxides, artificial compounds and heterostructures, introducing our goal of pursuing a deep investigation of such systems with particular emphasis on structural defects, with the aim of tailoring their functional properties by precise defects control.

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32

Endo, Kazuhiro, Petre Badica, Shunichi Arisawa, Hiroshi Kezuka, Hidehito Nanto, Noriaki Ikenaga, Masahiro Seto, Hiroshi Saito, and Tamio Endo. "Thin Film Composite Heterostructures of Oxide Multicomponent Perovskites for Electronics." MRS Proceedings 1454 (2012): 175–81. http://dx.doi.org/10.1557/opl.2012.1345.

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ABSTRACTOxide materials for electronics show recently significant progress. Among the most interesting are oxide composite heterostructures made of thin films. They are taking advantage of integration, anisotropy and synergetic concepts leading to new types of devices and functionalities. Remarkable is that, in the last few years, new devices and artificial materials showing new phenomena were demonstrated. At the same time, their synthesis, processing or fabrication is very often by complex, sophisticated, and, hence, by expensive methods. For further industrial implementation, deep understanding of the growth principles and concepts is required. On a higher level, understanding of the bi-directional relationship between the general and particular principles becomes important and deserves much attention. The immediate benefit is that knowledge on growth for one material can be transferred to another one. This may lead for search of less expensive but optimum technological approaches and can also lead to generation of new materials and devices. In our work we have analyzed the relationship between the particular and general growth principles for some oxide multicomponent perovskites. Materials used in our examples are Bi-Sr-Ca-Cu-O and YBa2Cu3O7, (Ca, Sr)CuO2, (Ca, Ba)CuO2 and Bi4Ti3O12. Presented thin films or heterostructures are with c-axis and non-c-axis orientations. We discuss and we review based on our results film-substrate lattice relationships, principles to control the growth mechanism, the morphology/roughness, the uniformity, and the stability domain and inter diffusion aspects.

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Moumen, Abderrahim, Gayan C. W. Kumarage, and Elisabetta Comini. "P-Type Metal Oxide Semiconductor Thin Films: Synthesis and Chemical Sensor Applications." Sensors 22, no. 4 (February 10, 2022): 1359. http://dx.doi.org/10.3390/s22041359.

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This review focuses on the synthesis of p-type metal-oxide (p-type MOX) semiconductor thin films, such as CuO, NiO, Co3O4, and Cr2O3, used for chemical-sensing applications. P-type MOX thin films exhibit several advantages over n-type MOX, including a higher catalytic effect, low humidity dependence, and improved recovery speed. However, the sensing performance of CuO, NiO, Co3O4, and Cr2O3 thin films is strongly related to the intrinsic physicochemical properties of the material and the thickness of these MOX thin films. The latter is heavily dependent on synthesis techniques. Many techniques used for growing p-MOX thin films are reviewed herein. Physical vapor-deposition techniques (PVD), such as magnetron sputtering, thermal evaporation, thermal oxidation, and molecular-beam epitaxial (MBE) growth were investigated, along with chemical vapor deposition (CVD). Liquid-phase routes, including sol–gel-assisted dip-and-spin coating, spray pyrolysis, and electrodeposition, are also discussed. A review of each technique, as well as factors that affect the physicochemical properties of p-type MOX thin films, such as morphology, crystallinity, defects, and grain size, is presented. The sensing mechanism describing the surface reaction of gases with MOX is also discussed. The sensing characteristics of CuO, NiO, Co3O4, and Cr2O3 thin films, including their response, sensor kinetics, stability, selectivity, and repeatability are reviewed. Different chemical compounds, including reducing gases (such as volatile organic compounds (VOCs), H2, and NH3) and oxidizing gases, such as CO2, NO2, and O3, were analyzed. Bulk doping, surface decoration, and heterostructures are some of the strategies for improving the sensing capabilities of the suggested pristine p-type MOX thin films. Future trends to overcome the challenges of p-type MOX thin-film chemical sensors are also presented.

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Abliz, Ablat, Patigul Nurmamat, and Da Wan. "Rational design of oxide heterostructure InGaZnO/TiO2 for high-performance thin-film transistors." Applied Surface Science 609 (January 2023): 155257. http://dx.doi.org/10.1016/j.apsusc.2022.155257.

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35

Nagarajan, V., C. S. Ganpule, A. Stanishevsky, B. T. Liu, and R. Ramesh. "Nanoscale Phenomena in Synthetic Functional Oxide Heterostructures." Microscopy and Microanalysis 8, no. 4 (August 2002): 333–49. http://dx.doi.org/10.1017/s1431927602020287.

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This paper reviews nanoscale phenomena such as polarization relaxation dynamics and piezoelectric characterization in model ferroelectric thin films and nanostructures using voltage-modulated scanning force microscopy. Using this technique we show the three-dimensional reconstruction of the polarization vector in lead zirconate titanate (PZT) thin films. Second, the time-dependent relaxation of remanent polarization in epitaxial PZT ferroelectric thin films, containing a uniform two-dimensional grid of 90° domains (c-axis in the plane of the film), has been investigated extensively. The 90° domain walls preferentially nucleate the 180° reverse domains during relaxation. Relaxation occurs through the nucleation and growth of reverse 180° domains, which subsequently coalesce and consume the entire region as a function of relaxation time. In addition we also present results on investigation of the relaxation phenomenon on a very local scale, where pinning and bowing of domain walls has been observed. We also show how this technique is used for obtaining quantitative information on piezoelectric constants and by engineering special structures, and how we realize ultrahigh values of piezoconstants. Last, we also show direct hysteresis measurements on nanoscale capacitors, where there is no observable loss of polarization in capacitors as small as 0.16 μm2 in area.

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36

Tileli, Vasiliki, Martial Duchamp, Anna-Karin Axelsson, Matjaz Valant, Rafal E. Dunin-Borkowski, and Neil McN Alford. "On stoichiometry and intermixing at the spinel/perovskite interface in CoFe2O4/BaTiO3 thin films." Nanoscale 7, no. 1 (2015): 218–24. http://dx.doi.org/10.1039/c4nr04339a.

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The performance of complex oxide heterostructures depends primarily on the interfacial coupling of the two component structures. Here, we report on the chemical complexity of the heteroepitaxy between CoFe₂O₄ and BaTiO₃ on the atomic level.

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37

Harada, T., T. Nagai, M. Oishi, and Y. Masahiro. "Sputter-grown c-axis-oriented PdCoO₂ thin films." Journal of Applied Physics 133, no. 8 (February 28, 2023): 085302. http://dx.doi.org/10.1063/5.0136749.

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Metallic delafossites, ABO2 ( A = Pd or Pt), are layered oxides that are as conductive as elemental metals. The high conductivity and surface polarity make metallic delafossites fascinating electrode materials for heterostructure devices. Here, we report the successful growth of c-axis-oriented PdCoO2 thin films on Al2O3 (001) substrates by magnetron sputtering that is widely used in industries. The observation of the PdCoO2 thin films through scanning transmission electron microscopy revealed layered crystal structures. A sharp interface exhibiting a layer stacking sequence of Pd/CoO2/Al2O3 was observed clearly, similar to the interfaces obtained with other growth methods such as pulsed laser deposition and molecular beam epitaxy. This layer stacking is particularly interesting because it can induce a high work function at the interface. The in-plane resistivity of the as-grown PdCoO2 thin film was 73 μΩ cm at room temperature, which decreased to 11 μΩ cm after post-annealing. The residual resistivity ratio of the annealed thin films was approximately 2.9. The impurity phases of PdO x were observed using x-ray diffraction and scanning transmission electron microscopy. The sputtering deposition of c-axis-oriented thin films could lead to the practical application of the polar surface of PdCoO2 in semiconductor devices.

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38

GE, CHEN, KUI-JUAN JIN, HUI-BIN LU, and CONG WANG. "NOVEL PROPERTIES IN OXIDE HETEROSTRUCTURES." Modern Physics Letters B 23, no. 09 (April 10, 2009): 1129–45. http://dx.doi.org/10.1142/s0217984909019594.

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A brief review of recent investigations in oxide heterostructures is presented. First, experimental results are shown. Positive colossal magnetoresistance with high sensitivities are obtained at low magnetic field (<1000 Oe) nearly at room temperature. Picoseconds photoelectric effects of the rise time ~ 210 ps and the half-maximum ~ 650 ps are also found in some oxide heterostructures. Furthermore, resistance switching characteristic and electric displacement-voltage hysteresis loops have been observed in BaTiO 3-δ/ Si p–n heterostructures. Second, theoretical descriptions are also shown here. A model for the mechanism causing the positive colossal magnetoresistance has been established. Moreover, the transport properties and the important role played by oxygen vacancies are theoretically investigated in oxide heterostructures. In addition, an extended percolation model is well developed, with which the transport characteristic in oxide thin films can be well simulated based on the phase separation scenario. Notably, the interface effects play a crucial role in the multifunctional properties of the oxide heterostructures.

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Mackevičiūtė, Rūta, Šarūnas Bagdzevičius, Maksim Ivanov, Barbara Fraygola, Robertas Grigalaitis, Nava Setter, and Jūras Banys. "Strain engineering of electrical conductivity in epitaxial thin Ba0.7Sr0.3TiO3 film heterostructures." Lithuanian Journal of Physics 56, no. 3 (October 17, 2016): 173–81. http://dx.doi.org/10.3952/physics.v56i3.3366.

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Thin epitaxial films have a great potential to be used in real life applications, such as oxide-on-silicon. However, they often contain a large amount of defects, leading to an enhanced electrical conductivity. This could be desirable in some applications (i. e. memristors), but the mechanism is not fully understood. Here we report on the investigation of epitaxial barium strontium titanate thin films deposited on strontium titanate single crystal substrates (Ba0.7Sr0.3TiO3/SrRuO3//SrTiO3 heterostructures) with a controlled epitaxial strain. The impedance analysis allowed us to propose a model, which explains changes in the temperature dependence of the conductivity based on the strain-dependent anisotropic change of electron/hole mobility.

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Eom, C. B., R. J. Cava, Julia M. Phillips, and D. J. Werder. "Epitaxial thin films and heterostructures of a copper‐oxide‐based isotropic metallic oxide (La8−xSrxCu8O20)." Journal of Applied Physics 77, no. 10 (May 15, 1995): 5449–51. http://dx.doi.org/10.1063/1.359240.

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Sanctis, Shawn, Jan Krausmann, Conrad Guhl, and Jörg J. Schneider. "Stacked indium oxide/zinc oxide heterostructures as semiconductors in thin film transistor devices: a case study using atomic layer deposition." Journal of Materials Chemistry C 6, no. 3 (2018): 464–72. http://dx.doi.org/10.1039/c7tc03724d.

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Kaul, Andrey R., Roy R. Nygaard, Vadim Yu Ratovskiy, and Alexander L. Vasiliev. "TSF-MOCVD – a novel technique for chemical vapour deposition on oxide thin films and layered heterostructures." Kondensirovannye sredy i mezhfaznye granitsy = Condensed Matter and Interphases 23, no. 3 (August 17, 2021): 396–405. http://dx.doi.org/10.17308/kcmf.2021.23/3531.

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A new principle for supplying volatile precursors to MOCVD gas-phase chemical deposition systems is proposed, based on a two-stage evaporation of an organic solution of precursors from a soaked cotton thread, which passes sequentially through the zones of evaporation of the solvent and precursors. The technological capabilities of TSF-MOCVD (Thread-Solution Feed MOCVD) are demonstrated based on examples of obtaining thin epitaxial films of СеО2, h-LuFeO3 and thin-film heterostructures β-Fe2O3/h-LuFeO3. The results of studying the obtained films by X-ray diffraction, energy dispersive X-rayanalysis, and high- and low-resolution transmission microscopy are presented. Using the TSF module, one can finely vary the crystallisation conditions, obtaining coatings of the required degree of crystallinity, as evidenced by the obtained dependences of the integral width of the h-LuFeO3 reflection on the film growth rate. Based on the TEM and XRD data, it was concluded that β-Fe2O3 grows epitaxially over the h-LuFeO3 layer. Thus, using TSF-MOCVD, one can flexibly change the composition of layered heterostructures and obtain highly crystalline epitaxial films with a clear interface in a continuous deposition process

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Strkalj, Nives, Elzbieta Gradauskaite, Johanna Nordlander, and Morgan Trassin. "Design and Manipulation of Ferroic Domains in Complex Oxide Heterostructures." Materials 12, no. 19 (September 24, 2019): 3108. http://dx.doi.org/10.3390/ma12193108.

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The current burst of device concepts based on nanoscale domain-control in magnetically and electrically ordered systems motivates us to review the recent development in the design of domain engineered oxide heterostructures. The improved ability to design and control advanced ferroic domain architectures came hand in hand with major advances in investigation capacity of nanoscale ferroic states. The new avenues offered by prototypical multiferroic materials, in which electric and magnetic orders coexist, are expanding beyond the canonical low-energy-consuming electrical control of a net magnetization. Domain pattern inversion, for instance, holds promises of increased functionalities. In this review, we first describe the recent development in the creation of controlled ferroelectric and multiferroic domain architectures in thin films and multilayers. We then present techniques for probing the domain state with a particular focus on non-invasive tools allowing the determination of buried ferroic states. Finally, we discuss the switching events and their domain analysis, providing critical insight into the evolution of device concepts involving multiferroic thin films and heterostructures.

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Ahn, C. H. "Ferroelectricity at the Nanoscale: Local Polarization in Oxide Thin Films and Heterostructures." Science 303, no. 5657 (January 23, 2004): 488–91. http://dx.doi.org/10.1126/science.1092508.

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Liao, Zhaoliang, and Jiandi Zhang. "Metal-to-Insulator Transition in Ultrathin Manganite Heterostructures." Applied Sciences 9, no. 1 (January 3, 2019): 144. http://dx.doi.org/10.3390/app9010144.

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Thickness-driven phase transitions have been widely observed in many correlated transition metal oxides materials. One of the important topics is the thickness-driven metal to insulator transition in half-metal La2/3Sr1/3MnO3 (LSMO) thin films, which has attracted great attention in the past few decades. In this article, we review research on the nature of the metal-to-insulator (MIT) transition in LSMO ultrathin films. We discuss in detail the proposed mechanisms, the progress made up to date, and the key issues existing in understanding the related MIT. We also discuss MIT in other correlated oxide materials as a comparison that also has some implications for understanding the origin of MIT.

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Nagata, Takahiro, Somu Kumaragurubaran, Kenichiro Takahashi, Sung-Gi Ri, and Toyohiro Chikyow. "(Invited) Combinatorial Synthesis and Interface Analysis for Development of High Dielectric Constant Thin Films." ECS Meeting Abstracts MA2022-01, no. 19 (July 7, 2022): 1070. http://dx.doi.org/10.1149/ma2022-01191070mtgabs.

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Compound semiconductor-based power devices such as SiC and GaN require high-temperature operational passive devices such as a capacitor. SiC based active devices are capable of operating over 250°C. For module and system level advancement, the high-temperature operational passive should be developed urgently. In the case of capacitors, current available capacitors can efficiently function up to 175°C only. Therefore, a thin film capacitor that can be operated at high-temperatures and integrated monolithically in the proximity of active device should be developed. In this talk, I will introduce our achievements of development of high temperature operational dielectric film materials and its interface control of metal/oxide stacking structure mainly. By employing combinatorial method and the thermal diffusion theory, we found some candidates for the dielectric materials based on ferroelectric materials. The BaTiO3 based relaxor ferroelectrics with a high dielectric constant (> 200) and free of hazardous elements are promising candidates. Among the BaTiO3 based relaxor ferroelectrics, we have chosen x[BaTiO3]-(1-x)[Bi(Mg2/3Nb1/3)O3] (BT-BMN). The permittivity of 400 and the stability <8% from room temperature to 400°C has been obtained, which are promising as a high-temperature dielectric medium. For the practical device application, a thermal stable electrode on the dielectrics is also required. To control the interface stability of the electrode/BT-BMN interfaces, several electrodes were investigated by photoelectron spectroscopy (PES). From the viewpoints of the oxidization energy, cost, and Bi thermal diffusion energy, RuO2, TiC, and TaC were selected as the electrode candidates to compare with the Pt electrode. To probe the interface structure and the band alignment non-destructively, we employed a combination of conventional x-ray PES using Al Kα light source (SXPES: hν= 1486.6 eV) and hard x-ray PES (HAXPES, hν= 5.95 keV). HAXPES is a powerful tool for investigating heterostructure interfaces due to its longer inelastic mean free path (IMFP) than that of SXPES. The IMFP of Pt 4f7/2, which was the heaviest element with the shortest IMFP in our measurement, was 4.68 nm, and HAXPES probed approximately 15 nm (probing depth: 3×IMFP) below the surface. For the Pt electrode, which is usually used as an electrode for Bi-contained oxides, the Bi diffusion into the electrode layer and the change of band alignment were clearly observed after annealing at 400°C. In contrast, the TiC electrode inhibited the Bi diffusion and did not show any change of the band alignment after annealing, meaning that the TiC electrode is a potential candidate for the electrode of Bi-contained oxide for high temperature operational devices. In the presentation, we also introduce the development of new high-k gate materials for GaN and Ge channels by combining the combinatorial method and HAXPES analysis. For a Ge channel, which has been attracting a lot of attention as a replacement for the Si channel used in current Si-based metal-oxide-semiconductor (CMOS) devices. This is because the Ge channel has high electron and hole mobility, which lead to a higher drive current, and Ge has a narrower band gap than Si thus allowing supply voltage scaling. However, Ge has the same issue as Si, namely an unintentionally oxidized layer with a low dielectric constant (~5.6) can form at an oxide/Ge interface. Furthermore, in contrast with SiO2, which is a good insulating layer for MOS devices, GeOx is thermodynamically unstable and water soluble. These properties cause high defect densities at the interface between high-k and Ge and a large hysteresis in the capacitance-voltage characteristic. To overcome these issues, we have proposed the direct growth of (110) rutile TiO2 or non-oxide materials on (100) Ge substrates.

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Ravichandran, Jayakanth. "Thermoelectric and thermal transport properties of complex oxide thin films, heterostructures and superlattices." Journal of Materials Research 32, no. 1 (November 14, 2016): 183–203. http://dx.doi.org/10.1557/jmr.2016.419.

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Molinari, Alan, Saleh Gorji, Jan Michalička, Christian Kübel, Horst Hahn, and Robert Kruk. "Tailoring interface epitaxy and magnetism in La_1−xSr_xMnO₃/SrTiO₃ heterostructures via temperature-driven defect engineering." Journal of Applied Physics 132, no. 10 (September 14, 2022): 105304. http://dx.doi.org/10.1063/5.0095406.

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Defect engineering of La1− xSr xMnO3 (LSMO)—a strongly correlated oxide displaying half metallicity and ferromagnetism above room temperature—has been the focus of a long-standing quest aimed at the exploitation of this material as a functional building block for memory storage and spintronic applications. Here, we discuss the correlation between structural defects and magnetism in La0.74Sr0.26MnO3/SrTiO3 (LSMO/STO) epitaxial heterostructures as a function of growth temperature and post-deposition annealing. Upon increasing the growth temperature from 500 to 700 °C at a fixed oxygen partial pressure of 0.007 mbar, the sputter-deposited epitaxial LSMO films experience a progressive increase in Curie temperature Tc from 110 to 270 K and saturation magnetization Ms from 1.4 to 3.3 μB/u.c. owing to a reduction in oxygen deficiencies. Concurrently, however, growth temperatures above 600 °C trigger the formation of off-stoichiometric, dendritic-like SrMoO x islands at the film/substrate interface as a possible aftermath of temperature-driven diffusion of impurities from the STO substrate. Notably, although the interfacial spurious islands cause an increase in sample surface roughness, the heterostructure still preserves high-quality epitaxy. In general, the best compromise in terms of both structural and magnetic properties, comprising high-quality epitaxy, atomically flat surface, and robust ferromagnetism above room temperature, is obtained for LSMO films grown at a relatively low temperature of about 500–540 °C followed by a post-deposition annealing treatment at 900 °C for 1 h in air. Our study compares effective routes based on temperature-controlled defect engineering to finely tailor the complex interplay between microstructure and magnetism in LSMO thin films.

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Ye, Lianxu, Di Zhang, Juanjuan Lu, Sicheng Xu, Ruixing Xu, Jiyu Fan, Rujun Tang, et al. "Epitaxial (110)-oriented La_0.7Sr_0.3MnO₃ film directly on flexible mica substrate." Journal of Physics D: Applied Physics 55, no. 22 (March 4, 2022): 224002. http://dx.doi.org/10.1088/1361-6463/ac570d.

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Abstract Manufacture and characterizations of perovskite-mica van der Waals epitaxy heterostructures are a critical step to realize the application of flexible devices. However, the fabrication and investigation of the van der Waals epitaxy architectures grown on mica substrates are mainly limited to (111)-oriented perovskite functional oxide thin films up to now and buffer layers are highly needed. In this work, we directly grew La0.7Sr0.3MnO3 (LSMO) thin films on mica substrates without using any buffer layer. By the characterizations of x-ray diffractometer and scanning transmission electron microscopy, we demonstrate the epitaxial growth of the (110)-oriented LSMO thin film on the mica substrate. The LSMO thin film grown on the mica substrate via van der Waals epitaxy adopts domain matching epitaxy instead of conventional lattice matching epitaxy. Two kinds of domain matching relationships between the LSMO thin film and mica substrate are sketched by Visualization for Electronic and STructural Analysis software and discussed. A decent ferromagnetism retains in the (110)-oriented LSMO thin film. Our work demonstrates a new pathway to fabricate (110)-oriented functional oxide thin films on flexible mica substrates directly.

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He, Xi, Xiaotao Xu, Xiaoyan Shi, and Ivan Božović. "Optimization of La2−xSrxCuO4 Single Crystal Film Growth via Molecular Beam Epitaxy." Condensed Matter 8, no. 1 (January 20, 2023): 13. http://dx.doi.org/10.3390/condmat8010013.

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Atomic layer-by-layer molecular beam epitaxy (ALL-MBE) combined with ozone is one of the best methods to fabricate single-crystal thin films of complex oxides. Cuprate such as La2−xSrxCuO4 (LSCO) is a representative complex-oxide high-temperature superconductor (HTS) material. Our group utilizes this method to produce high-quality single-crystal HTS films with atomically smooth surfaces and interfaces. In addition, ALL-MBE enables us to engineer multilayer heterostructures with atomic precision. This allows the fabrication of tunnel junctions, various nanostructures, and other HTS devices of interest for superconducting electronics. We have synthesized over three thousand LSCO thin films in the past two decades. These films’ structural and electronic properties have been studied and characterized by various methods. Here, we distill the extensive experience we accumulated into a step-by-step protocol to fabricate atomically perfect LSCO films. The recipe includes substrate preparation, ozone generation and distillation, source calibration, the in situ monitoring of the film synthesis, post-growth annealing, and ex situ characterization. It discloses a reproducible way to fabricate single-crystal LSCO films for basic research and HTS electronic applications.

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Journal articles on the topic 'Oxide thin films and heterostructure'

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