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1
Quintero, Miguel A. "Investigation of some chalcopyrite semiconductor alloys." Thesis, University of Ottawa (Canada), 1985. http://hdl.handle.net/10393/4787.
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Unsworth, Paul. "Spectroscopic studies of metal alloys and semiconductor interfaces." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343647.
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Cheng, Siu F. "Metalorganic vapor-phase epitaxy of compound semiconductor Alloys." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1495961311&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Farahmand, Maziar. "Advanced simulation of wide band gap semiconductor devices." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/14777.
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Broomfield, Seth Emlyn. "Picosecond optical studies of solids." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253303.
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Yelgel, Ovgu Ceyda. "Thermoelectric properties of V-VI semiconductor alloys and nanocomposites." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/14110.
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Thermoelectric materials are materials which are capable of converting heat directly into electricity and vice versa. They have long been used in electric power generation and solid-state cooling. The performance of a thermoelectric device determined by the dimensionless figure of merit (ZT) of the material, defined as ZT = (S2 σ/κ)T, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the total thermal conductivity, and T is the absolute temperature. The total thermal conductivity consists of contribution from electrons, electron-hole pairs and phonons. Since the 1960s, the best thermoelectric material has been Bi2Te3 alloys, with a ZT of 1.0 at room temperature. In recent years, the idea of using nanotechnology has opened up the possibility of engineering materials at nanoscale dimensions to achieve higher values of ZT in other words to have more efficient thermoelectric devices. This thesis starts with a broad introduction to thermoelectricity including various thermoelectric effects and their applications. The state-of-the-art thermoelectric materials and the optimisation methods to enhance the value of ZT have also been reviewed. A systematic theoretical modelling of the thermoelectric properties of three dimensional bulk semiconductors has been presented in Chapter 2. Electronic properties (Fermi level, Seebeck coefficient, and electrical resistivity) and thermal conductivity contribution from carriers (donor electrons or acceptor holes) have been derived by using the nearly-free electron approximation and the Fermi-Dirac statistics. Other thermal conductivity contributions originated from electron-hole pairs and phonons have also been described in detail. In Chapter 3, this theoretical study is extended to two dimensional semiconducting quantum well structures bearing in mind that the Fermi level should change with the temperature as well as the quantum well width and additional interface scattering mechanisms (interface mass-mixing and interface dislocation scatterings) should be included for the definition of anharmonic scattering rate. Thermoelectric properties of n-type (Bi2Te3)0.85(Bi2Se3)0.15 single crystals doped with 0.1 wt.% CuBr and 0.2 wt.% SbI3 and p-type (Bi2Te3)x(Sb2Te3)1−x single crystals doped with 3 wt.% Te (0.18 ≤ x ≤ 0.26) have been explored in Chapter 4 and 5, respectively. It has been found that p-type Bi2Te3 based alloys showed higher values of ZT due to their larger power factor (S2σ) and smaller thermal conductivity values. These calculations have concluded that the influence of the composition range of semiconductor alloys together with its type and amount of dopant plays an important role in enhancing the ZT. In Chapter 6, a detailed theoretical investigation and comparision of the thermal conductivities of these single crystals have been reported including frequency dependence of the phonon thermal conductivity for different temperatures. In Chapter 7, based on temperature and well width dependent Fermi level, a full theory of thermoelectric properties has been investigated for n-type 0.1 wt.% CuBr doped Bi2Se3/Bi2Te3/Bi2Se3 and p-type 3 wt.% Te doped Sb2Te3/Bi2Te3/Sb2Te3 quantum well systems. Different values of well thicknesses have been considered for both types of quantum well systems to study the effect of confinement on all thermoelectric transport coefficients. It has been found that reducing the well thickness has a pronounced effect on enhancing the ZT. Compared to bulk single crystals studied in Chapter 4 and 5, significantly higher thermoelectric figure of merits have been estimated theoretically for both n- and p-type semiconducting quantum well systems. For the n-type Bi2Se3/Bi2Te3/Bi2Se3 quantum well system with taking 7 nm well width the maximum value of ZT has been estimated to be 0.97 at 350 K and for the p-type Sb2Te3/Bi2Te3/Sb2Te3 quantum well with well width 10 nm the highest value of the ZT has been found to be 1.945 at 440 K. Chapter 8 briefly recapitulates the results presented in this thesis and outlines possibilities for future work.
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Bulbul, Mahir Mehmet. "Raman spectroscopy of GaN epilayers and InGaAlAs quaternary semiconductor alloys." Thesis, University of Essex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242232.
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Roberts, Victoria. "The growth and characterisation of silicon alloys for heterojunction bipolar transistor applications." Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259846.
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Gateru, Robert Gitumbo. "Memory switching in ion bombarded hydrogenated amorphous silicon alloys." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/842936/.
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Electrical, forming and switching characteristics of metal-semiconductor-metal (MSM) memory switches of ion bombarded hydrogenated amorphous silicon (a-Si:H) and its alloys are presented. MSM devices for memory switching applications are known to be characterised by instabilities as well as non-uniformity and irreproducibility of the forming and switching characteristics. It is believed that the presence of defect states in the semiconductor layer plays a significant role in the observation of memory switching in these MSM devices. Gas-phase doping and current stressing of the semiconductor are some of the techniques that have been used in the past to introduce mid-gap defect states. In this work, we use for the first time, ion bombardment as a novel tool for defect introduction into the semiconductor material of the MSM devices and we compare the electrical, forming and switching characteristics of these devices to those fabricated using the previous techniques mentioned above. A significant observation is that as the density of defects is increased in the semiconductor film with increasing implantation dose, conduction in the devices changes from barrier-controlled thermionic emission to bulk controlled where carriers hop through the defect states in a Poole-Frenkel manner. This transformation eliminates problems associated with Schottky barriers such as quality of contacts, oxidation, etc. In the forming characteristics, not only do we report enhanced uniformity of the forming voltages (VF) but also the magnitude of VF is observed to vary systematically with the implantation dose used. The ON states and switching characteristics in the bombarded devices are also observed to be much more stable presumably as a result of the uniformity of the defects introduced by ion bombardment. We report also an enhanced switching ratio in the ion bombarded devices, especially after partial annealing of the bombardment induced Si dangling bond defects.
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Radulescu, Fabian. "Pd-Ge ohmic contact on to GaAs formed by the solid phase epitaxy of Ge : a microstructure study /." Full text open access at:, 2000. http://content.ohsu.edu/u?/etd,226.
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Wright, Trevor. "A comparison of the metal-insulator transitions amporphous metal-semiconductor alloys." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264356.
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Fowler, Daivid Robert. "Non-linear electron dynamics in semiconductor superlattices and dilute nitride alloys." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422744.
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Jia, Roger (Roger Qingfeng). "Properties of thin film III-V/IV semiconductor alloys and nanostructures." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/113928.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 116-121).
A large amount of research and development has been devoted to engineering materials for the next generation of semiconductor devices with high performance, energy efficiency, and economic viability. To this end, significant efforts have been made to grow semiconductor thin films with the desired properties onto lattice constants with viable, cost effective substrates. Comparatively less effort has been made to explore III-V/IV heterovalent nanostructures and alloys, which may exhibit properties not available in existing materials. The investigation of these structures, grown using MOCVD, is the goal of this thesis and is motivated by two factors: one, that III-V/IV nanostructures should be good thermoelectrics based on the "phonon glass electron crystal" concept, and two, that (GaAs)₁-x(Ge₂)x alloys were observed to exhibit near-infrared room temperature luminescence, a result that can have significant implications for low bandgap optical devices. A survey of various growth conditions was conducted for the growth of the model GaAs/Ge system using MOCVD to gain insight in the epitaxy involving heterovalent materials and to identify structures suitable for investigation for their thermoelectric and optical properties. A significant decrease in the thermal conductivities of GaAs/Ge nanostructures and alloys relative to bulk GaAs and bulk Ge was observed. This reduction can be attributed to the presence of the heterovalent interfaces. The electron mobilities of the structures were determined to be comparable to bulk Ge, indicating minimal disruption to electron transport by the interfaces. A further reduction in thermal conductivity was observed in an (In₀.₁Ga₀.₉As)₀.₈₄(Si0₀.₁Ge₀.₉)₀.₁₆ alloy; the alloy had a thermal conductivity of 4.3 W/m-K, comparable to some state-of-the-art thermoelectric materials. Room temperature photoluminescence measurements of various compositions of (GaAs)₁-x(Ge₂)x alloys revealed a maximum energy transition of 0.8 eV. This bandgap narrowing is the result of composition fluctuations; the fluctuations create regions of lower bandgap, resulting in a weak dependence on luminescence as a function of Ge composition as well as lower bandgap than the homogeneous alloy with the same composition. As silicon was added to the (GaAs)₁-x(Ge₂)x alloy, the bandgap increased despite the composition fluctuations. Based on the results from this work III-V/IV nanostructures show promise for thermoelectric and optical applications.
by Roger Jia.
Ph. D.
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White, Stuart. "The properties of amorphous hydrogenated germanium and its alloys." Thesis, The University of Sydney, 1989. https://hdl.handle.net/2123/26241.
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This thesis is concerned with the optical, structural and electrical properties of amorphous hydrogenated semiconductor thin films, in particular germanium and also its alloy with carbon. Interest in the optical properties of these materials is motivated by their potential usefulness as the absorbing component in a solar thermal selective surface. Most of the films studied in this work have been deposited using glow discharge decomposition of semiconductor gases in a cylindrical DC magnetron.
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Goyal, Puneet. "Design and simulation of strained-Si/strained SiGe dual channel hetero-structure MOSFETs /." Online version of thesis, 2007. http://hdl.handle.net/1850/5281.
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Al-Ahmadi, Ahmad Aziz. "COMPLEMENTARY ORTHOGONAL STACKED METAL OXIDE SEMICONDUCTOR: A NOVEL NANOSCALE COMPLEMENTRAY METAL OXIDE SEMICONDUCTOR ARCHTECTURE." Ohio University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1147134449.
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Katulka, Gary L. "Fabrication and characterization of structures and rectifiers based on silicon carbide alloyed with germanium." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 206 p, 2007. http://proquest.umi.com/pqdweb?did=1481670091&sid=15&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Young, Erin Christina. "GaNAs and GaAsBi : structural and electronic properties of two resonant state semiconductor alloys." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/31188.
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Semiconductor alloys that are lattice matched to GaAs but have a smaller energy band gap are of interest for numerous applications, including infrared lasers for telecommunications, high efficiency solar cells, and high electron mobility transistors. For high optoelectronic efficiency, these materials must be highly perfect single crystals with low defect densities. In this thesis, two substitutional GaAs-based alloy families, nitrides and bismides, are investigated experimentally. In the first alloy, GaNAs, the addition of N results in a large band gap reduction, though the small size of the N relative to As introduces tensile strain into the lattice, and the high electronegativity of N attracts electrons. The second alloy, GaAsBi, also has a smaller band gap and is formed by the addition of the very large Bi atom to GaAs, which introduces compressive strain and tends to attract holes. The experimental investigations of these alloys focused on elucidating the relationships between the growth process, atomic structure, and electronic properties. Films were grown by molecular beam epitaxy (MBE) with in-situ process monitoring and subject to post-growth structural and electronic characterization. For GaNAs and a related alloy. InGaNAs, degradation in luminescence efficiency, mobility and structural integrity were observed as the nitrogen content of the alloy was increased. A comprehensive study of strain relaxation in compressively strained InGaNAs and InGaAs quantum wells revealed that the nitrogen alloying did not have an effect on the critical thickness for dislocation formation, or the dislocation density in relaxed films. At large lattice mismatch, InGaNAs quantum wells were observed to relax by means of unusually oriented pure edge-type misfit dislocations aligned with [left angle bracket]100[right angle bracket] directions, likely due to the high stress associated with the large misfit. Use of bismuth as a non-incorporating surfactant during growth was successfully applied to improve the material quality of the nitrides. The Bi surface layer during growth was investigated using in-situ electron diffraction intensity measurements, and was found to improve both the smoothness of nitride films, by promoting a layer-by-layer growth mode, as well as increasing the photoluminescence (PL) intensity by a factor of 2.4. The improvement in PL is attributed to a reduction in nitrogen clusters with the surfactant. In addition, an increase in nitrogen content of up to 50% was observed in films grown with Bi over films grown without the surfactant. The increase in the nitrogen incorporation scales with the Bi flux, and saturates at full Bi coverage. A modified Langmuir model was applied to describe the behaviour of Bi on the surface, as well as the increase in nitrogen incorporation. The bismide alloy family requires atypical MBE growth conditions such as low substrate temperature and low As overpressure in order to achieve Bi incorporation. The conditions are close to those where Ga and Bi droplets form. However, in-situ light scattering was used to identify and avoid growth with droplets, resulting in films with high structural quality as determined by x-ray diffraction, and strong photoluminescence. 1% Bi alloying in GaAs was also found to result in a minimal 15% decrease in electron mobility, as compared with a 94% reduction for 1% N alloying. Finally, a preliminary investigation was made into the concept of co-doping GaAs with both N and Bi. GaNAsBi films showed room temperature PL at long wavelengths commensurate with contributions to band gap reduction from both N and Bi. Since lattice matching to GaAs can be achieved with a Bi/N ratio of 1.7, GaNAsBi and GaAsBi are promising new alloys for the applications described.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Omar, Mustafa Saeed. "Crystal growth and characterization of I-IV2-V3 semiconductor compounds and alloys based thereon." Thesis, University of Bath, 1985. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353400.
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The existence of various ternary adamantine compounds is discussed. Normal and defect ternary adamantine compounds have been a subject of discussion, particularly from a structural point of view. Rules for the formation of adamantine compounds are explained and related to each other. A home-made DTA apparatus was operated to detect the melting point and phase change from room temperature up to 1300°C for the materials investigated. The group I-IV2-V3 compounds were the main subject of this research. CuGe2Ps and CuSi2P3 were the only compounds found to grow in this family. The first was chosen for study in more detail, mainly because of its lower melting point. CuGe2P3 was compared to other compounds, particularly structural aspects, and solid solutions were tried for twenty-two different materials. This investigation shows similarity with group I2-IV-V3 compounds, such as Cu2GeS3, and new alloys were found with Cu2GeS3. Stoichiometric Cu2GeS3 does not form good material, but alloys containing 10% CuGe2P3 produced good material with a zincblend structure. As well as alloys with ternary compounds, about 33% Ge per mole could be dissolved in CuGe2P3. This result showed similarity with the compounds Cu2GeSe3 and ZnGeAs2, which also dissolve a considerable quantity of Ge. In this investigation, only a maximum of 33% Si per mole in CuSi2P3 was prepared, although it is likely that even more Si can be dissolved. Attention was also given to AqGe2P3. Chemical analysis of single crystals grown from AgGe2P3 composition showed the existence of only the Ag6Ge10P12 compound. Single crystals were grown for all single phase materials. A new modification of the directional freeze technique was employed, which was capable of controlling the pressure and having a steep temperature gradient. This method improved the growth to produce large single crystals of cm dimensions. The CuGe2P3 crystals doped with Zn, S, Sn, Se and ZnIn were prepared. Single crystals of CuGe2P3 were also annealed with Cu-P and CuGe2P3 powder. Room temperature lattice parameters were determined for all the compounds and alloys, while variations of the lattice parameters with temperatures up to the melting point of CuGe2P3 were studied using a high temperature X-ray camera. Measurements of optical properties were not successful in this investigation, although electrical properties were successfully measured. These measurements were carried out for all materials in a single crystal form. Hall mobility and conductivity measurements were carried out from liquid nitrogen to 450 °K. Carrier concentration was very high for phosphide compounds and alloys, whilst it was lower for sulphides. Flash evaporation was used for preparing thin films of compounds CuGe2P3 and Ag6Ge10P12. Single phase films were the result for Ag6Ge10P12, whilst a particular treatment was employed for producing films of CuGe2P3 after evaporation. A final investigation of the compound CuGe2P3 was made into its lattice matching with other compounds. The p-n junctions were produced with n-type GaP, using epitaxial growth, while results were negative with CdS and Si.
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Shantharama, L. G. "The k-p interaction and carrier transport in GaAs, InP and related semiconductor alloys." Thesis, University of Surrey, 1986. http://epubs.surrey.ac.uk/848011/.
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The band structure and transport properties of the technologically important materials GaAs and InP and (GaIn)(AsP)/InP were studied as a function of temperature, pressure and magnetic field. The electron effective mass, m*, was measured as a function of energy gap, E[o], using hydrostatic pressure as a dummy variable to change the band structure. In InP it was found that the three band k-p model was sufficient to explain the energy gap dependence of the effective mass while in GaAs, a small contribution from higher bands was necessary. In Ga[x]In[1-x]As[y]P[1-y] alloys, dm* /dEo was found to be about 50% larger than in compound semiconductors. The variation, dm*/dE[o], as a function of composition follows the variation of alloy disorder. Based on the trends in band gap dependence of the effective mass in various alloy systems and compound semiconductors, a tentative explanation was offered to account for the large dm*/dE[o] value in these alloys. Photoconductivity measurements were made as a function of pressure, to study the variation of the pressure coefficient of the direct band gap with composition. The results indicate that dEo/dP is also influenced by alloy disorder. Measurements of the hole mobility, mu, as a function of pressure show that, while in GaAs and InP dmu/dP is positive, in the alloy dmu/dP is negative. These results were analysed in terms of the transport parameters and their pressure dependence to evaluate the pressure coefficient of the heavy hole effective mass, dm[ch]/dP. It was found that, while in InP and the alloys dm[ch]/dP is positive, in GaAs dm[ch]/dP is negative. Measurements of the activation energy of the Mn acceptor level in (GaIn)(AsP) and its pressure coefficient show that the closer the level is to the valence band the more it is influenced by it, contrary to the arguments that the deep levels are independent of the host material. This is explained on the assumption that the Mn impurity wave functions are somewhat delocalised and are influenced by the valence band. In Mn+Ge co-doped alloys, it was found that when the Mn activation energy is large, even in heavily doped, closely compensated p-type materials the mobility is dominated by phonon scattering. This anamoly is attributed to the formation of Mn+Ge dipoles assosiated with the diffusion of neutral Mn. This hypothesis was supported by the measurements of the diffusion profiles of Mn into various substrates.
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Quinones, Eduardo Jose. "Heterojunction MOSFET devices using column IV alloys grown by UHVCVD /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Yang, Yaxiang. "FP-LMTO modeling of ZnSe and ZnMgSe alloy." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2247.
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Thesis (Ph. D.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains viii, 113 p. : ill. (some col.). Includes abstract. Includes bibliographical references.
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Sirisathitkul, C. "Studies of transport phenomena at ferromagnet/semiconductor interfaces." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325445.
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Norman, A. G. "TEM/TED studies of epitaxial layers of ternary and quaternary III-V compound semiconductor alloys." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233511.
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Yildirim, Asli. "Phase separation and defect formation in stable, metastable, and unstable GaInSaSb alloys for infrared applications." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/1520.
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GaInAsSb is a promising material for mid-infrared devices such as lasers and detectors because it is a direct band gap material with large radiative coefficient and a cut-off wavelength that can be varied across the mid-infrared (from 1.7 to 4.9 μm) while remaining lattice matched to GaSb. On the other hand, the potential of the alloy is hampered by predicted ranges of concentration where the constituents of the alloy become immiscible when the crystal is grown near thermodynamic equilibrium at typical growth temperatures. There have been efforts to extend the wavelength of GaInAsSb alloys through such techniques as digital alloy growth and non-equilibrium growth, but most of the compositional range has for a long time been inaccessible due to immiscibility challenges. Theoretical studies also supported the existence of thermodynamic immiscibility gaps for non-equilibrium growth conditions.
Lower growth temperatures lead to shorther adatom diffusion length. While a shorter adatom diffusion length suppresses phase separation, too short an adatom length is associated with increased defect formation and eventually loss of crystallinity. On the other hand, hotter growth temperatures move epitaxial growth closer to thermodynamic equilib- rium conditions, and will eventually cause phase separation to occur. In this study thick 2 μm; bulk GaInAsSb layers lattice-matched to GaSb substrates were grown across the entire (lattice-matched) compositional range at low growth temperatures (450°C), including the immiscibility region, when grown under non-equilibrium conditions with MBE. High quality epitaxial layers were grown for all compositions, as evidenced by smooth morphology (atomic force microscopy), high structural quality (X-ray diffraction), low alloy fluctuactions (electron dispersive spectroscopy in cross sectioned samples), and bright room temperature photoluminescence.
Because initial theoretical efforts have suggessted that lattice strain can influence layer stability, we have studied effects of strain on alloy stability. Unstable and metastable alloys were grown hot enough for the onset of phase separation, then progressively strained and characterized. We show that strain is effective in suppressing phase separation.
Finally, we performed time-resolved carrier lifetime measurements for InAsSb alloy with low concentrations of Ga to investigate the role of Ga in influencing nonradiative carrier recombination. There have been studies on non-Ga containing antimonide structures (InAsSb, InAs/InAsSb) that show long carrier lifetimes, which suggest that Ga plays a role in reducing carrier lifetime, because Ga-containing structures such as InAs/GaSb superlattices have much shorter carrier lifetimes. Ga may reduce carrier lifetime through native defects that increase background carrier concentration, or that create mid-gap electronic states. Here, a series of GaInAsSb alloys were grown with low to zero Ga concentration. No difference in carrier lifetime was observed between Ga and Ga-free structures, and minority carrier lifetimes > 600 ns were observed. Additional work remains to be done to obtain background carrier densities in the samples with Hall measurements.
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Wang, Cai Johnson R. Wayne. "High temperature high power SiC devices packaging processes and materials development." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Spring/doctoral/WANG_CAI_24.pdf.
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Portz, Verena [Verfasser], Philipp [Akademischer Betreuer] Ebert, and Thomas Günter [Akademischer Betreuer] Taubner. "Investigation of ternary nitride semiconductor alloys by scanning tunneling microscopy / Verena Portz ; Philipp Ebert, Thomas Günter Taubner." Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1158599617/34.
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Anteney, Iain M. "An investigation of group IV alloys and their applications in bipolar transistors." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326641.
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Eckner, Stefanie [Verfasser], Claudia Sarah [Gutachter] Schnohr, Dirk [Gutachter] Lützenkirchen-Hecht, and Olivier [Gutachter] Pagès. "Vibrational dynamics in semiconductor compounds and alloys / Stefanie Eckner ; Gutachter: Claudia Sarah Schnohr, Dirk Lützenkirchen-Hecht, Olivier Pagès." Jena : Friedrich-Schiller-Universität Jena, 2019. http://d-nb.info/1205884254/34.
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Brun, del Re Riccardo. "A comparative study of some manganese- and iron-based chalcopyrite semiconductor alloys: Basic properties and the effects of ordering." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7775.
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Dilute magnetic semiconductor alloys based on I-III-VI$\sb2$ chalcopyrite structure compounds and containing either iron or manganese as the magnetic component, were investigated in the context of a comparative study. The implications and effects of crystallographic ordering were of particular interest to this research. As a result of these experimental investigations, the phase diagram of the CuIn$\sb{\rm 1-x}$Fe$\sb{\rm x}$S$\sb2$ system was proposed, and certain modifications to the previously accepted phase diagrams of the systems containing manganese were given. For the iron containing system, the magnetic behaviour was interpreted in terms of a Curie-Weiss law, and the applicability of ligand field theory was investigated as a theoretical basis for understanding the results so obtained. It was determined that a transition similar to the $\sp6$A$\sb1$-$\sp4$T$\sb1$ crossover of crystal field theory may occur as a function of iron concentration in this material. Various computer fits and simulations were carried out in order to analyze the diffraction, and magnetic susceptibility measurements made on the alloys containing manganese. Besides displaying the usual non-magnetic-ion type of cationic ordering as in the transition from zincblende to chalcopyrite structure, these systems have been shown to exhibit behaviour characteristic of magnetic-ion crystallographic ordering (Mn-ordering). These ordering properties have been shown to be highly sensitive to sample heat treatment. The diffraction techniques were found to be insensitive to the types of Mn- ordering suspected to occur, however these alloys yielded direct evidence for the Mn-ordering in the form of their static, low field magnetic susceptibility behaviour. Of particular interest, some of the low temperature annealed, high concentration magnetic ion materials were found not to display the low temperature spin-glass cusp characteristic of the rapidly cooled samples, and this was interpreted to be the clearest signature of the Mn-ordering. The manganese systems may deviate from the chalcopyrite structure in the low temperature region of the phase diagram. The magnetic behaviour of these alloys was shown to be consistent with a long-range exchange, mean-field analysis of the planar ordering model. (Abstract shortened by UMI.)
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Lloyd, Neil Stuart. "Interactions between molecules and surfaces : part 1- plasma etching of Si, Ge and Siâ†1â†-â†xGeâ†x alloys; part 2 - adsorption and desorption of methyl salicylate on various wall coverings." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241949.
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Essary, Chad Robert. "Ultraviolet-assisted oxidation and nitridation of hafnium and hafnium aluminum alloys as potential gate dielectrics for metal oxide semiconductor applications." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0006612.
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Wei, Shuai, Garrett J. Coleman, Pierre Lucas, and C. Austen Angell. "Glass Transitions, Semiconductor-Metal Transitions, and Fragilities in Ge-V-Te (V = As, Sb) Liquid Alloys: The Difference One Element Can Make." AMER PHYSICAL SOC, 2017. http://hdl.handle.net/10150/624356.
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Glass-transition temperatures (T-g) and liquid fragilities are measured along a line of constant Ge content in the system Ge-As-Te, and contrasted with the lack of glass-forming ability in the twin system Ge-Sb-Te at the same Ge content. The one composition established as free of crystal contamination in the latter system shows a behavior opposite to that of a more covalent system. The comparison of T-g vs bond density in the three systems Ge-As-chalcogen differing in chalcogen, i.e., S, Se, or Te, shows that as the chalcogen becomes more metallic, i.e.,in the order S < Se < Te, the bond-density effect on T-g becomes systematically weaker, with a crossover at < r > = 2.3. When the more metallic Sb replaces As at < r > greater than 2.3, incipient metallicity rather than directional bond covalency apparently gains control of the physics. This observation leads us to an examination of the electronic conductivity and then semiconductor-to-metal (SC-M) transitions, with their associated thermodynamic manifestations in relevant liquid alloys. The thermodynamic components, as seen previously, control liquid fragility and cause fragile-to-strong transitions during cooling. We tentatively conclude that liquid-state behavior in phase-change materials is controlled by liquid-liquid (LL) and SC-M transitions that have become submerged below the liquidus surface. In the case of the Ge-Te binary, a crude extrapolation toGeTe stoichiometry indicates that the SC-Mtransition lies about20% belowthe melting point, suggesting a parallel with the intensely researched "hidden liquid-liquid transition" in supercooled water. In the water case, superfast crystallization initiates in the high-fragility domain some 4% above the LL transition temperature (T-LL) which is located at approximately 15% below the (ambient pressure) melting point.
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Gaucher, Samuel. "Growth of lattice-matched hybrid semiconductor-ferromagnetic trilayers using solid-phase epitaxy." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22599.
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Diese Arbeit befasst sich mit dem Wachstum von Dünnschichtstrukturen, die zur Herstellung eines Spin-selektiven Schottky-Barrier-Tunneltransistors (SS-SBTT) erforderlich sind. Das Bauelement basiert auf dem Transport von Ladungsträgern durch eine dünne halbleitende (SC) Schicht, die zwei ferromagnetische (FM) Kontakte trennt. Daher müssen hochqualitative und gitterangepasste vertikale FM/SC/FM-Trilayer gezüchtet werden, was aufgrund der inkompatiblen Kristallisationsenergien zwischen SC und Metallen eine experimentelle Herausforderung darstellt. Das Problem wurde mit einem Festphasenepitaxie-Ansatz gelöst, bei dem eine dünne amorphe Ge-Schicht (4-8 nm) durch Ausglühen über Fe3Si auf GaAs(001)-Substraten kristallisiert wird. Langsame Glühgeschwindigkeiten bis zu einer Temperatur von 260°C konnten ein neues gitterangepasstes Polymorph von FeGe2 erzeugen, über das ein zweites Fe3Si mittels Molekularstrahlepitaxie gezüchtet werden könnte. SQUID-Magnetometermessungen zeigen, dass die dreischichtigen Proben in antiparallele Magnetisierungszustände versetzt werden können. Vertikale Spin-Ventil-Bauelemente, die mit verschiedenen Trilayern hergestellt wurden, wurden verwendet, um zu demonstrieren, dass der Ladungstransport über die Heteroübergänge spinselektiv ist und bei Raumtemperatur einen Magnetowiderstand von höchstens 0,3% aufweist. Der Effekt nimmt bei niedrigen Temperaturen ab, was mit einem ferromagnetischen Übergang in der FeGe2-Schicht korreliert. Durch TEM- und XRD-Experimente konnte festgestellt werden, dass das neue FeGe2-Polymorph die Raumgruppe P4mm aufweist und bis zu 17% Si-Atome als Ersatz für Ge-Stellen enthält. Die Isolierung von FeGe2 war möglich, indem das Verhältnis von Fe-, Si- und Ge-Atomen so eingestellt wurde, dass die richtige Stöchiometrie bei vollständiger Durchmischung erreicht wurde. Anhand von FeGe2-Dünnschichten wurde ein zunehmender spezifischer Widerstand bei niedriger Temperatur und ein semi-metallischer Charakter beobachtet.This thesis discusses the growth of thin film structures required to fabricate a Spin-Selective Schottky Barrier Tunnel transistor (SS-SBTT). The device relies on charge carriers being transported through a thin semiconducting (SC) layer separating two ferromagnetic (FM) contacts. Thus, high quality and lattice-matched FM/SC/FM vertical trilayers must be grown, which is experimentally challenging due to incompatible crystallization energies between SC and metals. The problem was solved using a solid-phase epitaxy approach, whereby a thin amorphous layer of Ge (4-8 nm) is crystallized by annealing over Fe3Si on GaAs(001) substrates. Slow annealing rates up to a temperature of 260°C could produce a lattice-matched Ge-rich compound, over which a second Fe3Si could be grown my molecular-beam epitaxy. The compound obtained during annealing is a new layered polymorph of FeGe2. SQUID magnetometry measurements indicate that the trilayer samples can be placed in states of antiparallel magnetization. Vertical spin valve devices created using various trilayers were used to demonstrate that charge transport is spin-selective across the heterojunctions, showing a magnetoresistance of at most 0.3% at room temperature. The effect decreases at low temperature, correlating with a ferromagnetic transition in the FeGe2 layer. TEM and XRD experiments could determine that the new FeGe2 polymorph has a space group P4mm, containing up to 17% Si atoms substituting Ge sites. Isolating FeGe2 was possible by tuning the proportion Fe, Si and Ge atoms required to obtain the right stoichiometry upon full intermixing. Hall bars fabricated on FeGe2 thin films were used to observe an increasing resistivity at low temperature and semimetallic character.
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Turcu, Mircea Cassian. "Defect energies, band alignments, and charge carrier recombination in polycrystalline Cu(In,Ga)(Se,S)2 alloys." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1086247686828-95497.
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This work investigates the defect energies, band alignments, and charge carrier recombination in polycrystalline Cu(In1-xGax)(Se1-ySy)2 chalcopyrite thin films and the interrelationship with the alloy composition. Photoluminescence spectroscopy of investigated Cu-poor Cu(In,Ga)(Se,S)2 layers generally shows broad emission lines with the corresponding maxima shifting towards higher energies under decreasing temperature or under increasing excitation power. Admittance spectroscopy of Cu-poor ZnO/CdS/Cu(In,Ga)(Se,S)2 chalcopyrite devices shows that the activation energies of the dominant defect distributions involving donors at the CdS/absorber interface and deep acceptors in the chalcopyrite bulk, increase upon alloying CuInSe2 with S. The band alignments within the Cu(In1-xGax)(Se1-ySy)2 system are determined using the energy position of the bulk acceptor state as a reference. The band gap enlargement under Ga alloying is accommodated almost exclusively in the rise of the conduction band edge, whereas the increase of band gap upon alloying with S is shared between comparable valence and conduction band offsets. The extrapolated band discontinuities [delta]EV(CuInSe2/CuInS2) = -0.23 eV, [delta]EC(CuInSe2/CuInS2) = 0.21 eV, [delta]EV(CuInSe2/CuGaSe2) = 0.036 eV, and [delta]EC(CuInSe2/CuGaSe2) = 0.7 eV are in good agreement with theoretical predictions. Current-voltage analysis of Cu-poor ZnO/CdS/Cu(In,Ga)(Se,S)2 devices reveals recombination barriers which follow the band gap energy of the absorber irrespective of alloy composition, as expected for dominant recombination in the chalcopyrite bulk. In turn, the recombination at the active junction interface prevails in Cu-rich devices which display substantially smaller barriers when compared to the band gap energy of the absorber. The result indicates that the Cu-stoichiometry is the driving compositional parameter for the charge carrier recombination in the chalcopyrite heterojunctions under investigations.
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Valakh, M. Ya, A. P. Litvinchuk, V. M. Dzhagan, V. O. Yukhymchuk, Ye O. Havryliuk, M. Guc, I. V. Bodnar, V. Izquierdo-Roca, A. Pérez-Rodríguez, and D. R. T. Zahn. "Optical properties of quaternary kesterite-type Cu2Zn(Sn1−xGex)S4 crystalline alloys: Raman scattering, photoluminescence and first-principle calculations." Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-219947.
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The transformation of the vibrational spectrum of Cu2Zn(Sn1−xGex)S4 single crystals over the entire composition range (0 ≤ x ≤ 1) is studied experimentally by low-temperature Raman scattering and photoluminescence spectroscopies, as well as theoretically in the framework of density functional theory (DFT). It is shown that unlike “classic” mixed binary II–VI and III–V compounds, which are characterized by either one- or two-mode behavior of spectra transformation upon composition variation, the vibrational modes of the quaternary semiconductor Cu2Zn(Sn1−xGex)S4 exhibit both types of behavior within the same alloy system. DFT calculations reveal that the two-mode transformation is in fact observed for the vibrational modes, which possess a very small dispersion across the Brillouin zone, that is typical for a molecular crystal. These modes are due to the “breathing” motion of sulfur within GeS4 and SnS4 tetrahedra. The effects of structural (positional) disorder of mixed crystals are analyzed based on Raman scattering as well as photoluminescence resultsDieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Turcu, Mircea Cassian. "Defect energies, band alignments, and charge carrier recombination in polycrystalline Cu(In,Ga)(Se,S)2 alloys." Doctoral thesis, Technische Universität Dresden, 2003. https://tud.qucosa.de/id/qucosa%3A24342.
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This work investigates the defect energies, band alignments, and charge carrier recombination in polycrystalline Cu(In1-xGax)(Se1-ySy)2 chalcopyrite thin films and the interrelationship with the alloy composition. Photoluminescence spectroscopy of investigated Cu-poor Cu(In,Ga)(Se,S)2 layers generally shows broad emission lines with the corresponding maxima shifting towards higher energies under decreasing temperature or under increasing excitation power. Admittance spectroscopy of Cu-poor ZnO/CdS/Cu(In,Ga)(Se,S)2 chalcopyrite devices shows that the activation energies of the dominant defect distributions involving donors at the CdS/absorber interface and deep acceptors in the chalcopyrite bulk, increase upon alloying CuInSe2 with S. The band alignments within the Cu(In1-xGax)(Se1-ySy)2 system are determined using the energy position of the bulk acceptor state as a reference. The band gap enlargement under Ga alloying is accommodated almost exclusively in the rise of the conduction band edge, whereas the increase of band gap upon alloying with S is shared between comparable valence and conduction band offsets. The extrapolated band discontinuities [delta]EV(CuInSe2/CuInS2) = -0.23 eV, [delta]EC(CuInSe2/CuInS2) = 0.21 eV, [delta]EV(CuInSe2/CuGaSe2) = 0.036 eV, and [delta]EC(CuInSe2/CuGaSe2) = 0.7 eV are in good agreement with theoretical predictions. Current-voltage analysis of Cu-poor ZnO/CdS/Cu(In,Ga)(Se,S)2 devices reveals recombination barriers which follow the band gap energy of the absorber irrespective of alloy composition, as expected for dominant recombination in the chalcopyrite bulk. In turn, the recombination at the active junction interface prevails in Cu-rich devices which display substantially smaller barriers when compared to the band gap energy of the absorber. The result indicates that the Cu-stoichiometry is the driving compositional parameter for the charge carrier recombination in the chalcopyrite heterojunctions under investigations.
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Palinginis, Kimon Christoph. "Electronic properties and metastability of hydrogenated amorphous silicon-germanium alloys with low germanium content /." view abstract or download file of text, 2000. http://wwwlib.umi.com/cr/uoregon/fullcit?p9986749.
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Thesis (Ph. D.)--University of Oregon, 2000.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 168-174). Also available for download via the World Wide Web; free to University of Oregon users.
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Souza, Junior Helio Oliveira. "Síntese e caracterização de nanocristais ternários de MgCdS e nanocompósito de MgCdS e derivados de grafeno." Pós-Graduação em Química, 2017. https://ri.ufs.br/handle/riufs/7073.
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Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPqIn this work the synthesis of MgCdS ternary semiconductor nanocrystal alloys has been carried out by aqueous route through a bottom-up approach, using conventional hydrothermal heating as well as in situ onto graphene matrices. In the synthesis of MgCdS nanocrystals, the effect of each reaction parameter on the spectroscopic properties was studied aiming to understand the possibilities to control the optical properties. Emission spectra of MgCdS samples obtained in the experiments designed to optimize reaction parameters exhibited a single emission band reflecting nanocrystal growth, with quantum yields as high as 85%. Based on the presence of two bands in absorption spectra as well as atomic absorption spectrometry (AAS) data it was possible to propose that nanocrystals are composed of Cd and Mg. Concerning the structural architecture, it has been proposed that nanocrystals show a core-shell structure with a diffuse interface. Data from AAS also showed that the final composition of nanocrystals is generally different from the initial reaction Cd:Mg proportion, as the metal precursors have distinct reactivities. Morphological analyses by transmission electron microscopy (TEM) of nanocrystals evidenced the predominance of spherical shapes and sizes below 4 nm. Studies of the formation of nanocrystal alloys with Mg1-xCdxS and Cd1-xMgxS composition, by ion exchange from the binary components MgS and CdS helped the discussion of spectroscopic behavior of the ternary system MgCdS. It was possible to confirm that the introduction of a second cation (Cd2+ or Mg2+) into each binary structure (MgS or CdS) is consistent with the observation of two absorption bands and only one emission band. The addition of graphene derivatives during the synthesis of MgCdS nanocrystals was carried out aiming to improve the properties of the materials, as well as providing a physical support to the nanocrystals, favoring future applications. The presence of graphene induced shifts in the emission bands to larger wavelengths concomitant with intensity reduction, which can be taken as evidence of interactions between the materials. The morphologies of composites were characterized by typical graphene sheets decorated with spherical nanocrystals.
Neste trabalho foram realizadas as sínteses de nanocristais (NCs) semicondutores ternários de MgCdS via síntese aquosa através da metodologia bottom-up, assistida por tratamento térmico hidrotermal convencional, além da síntese in situ de nanocompósitos de MgCdS em matrizes de grafeno. A síntese do nanocristal de MgCdS foi avaliada através do efeito da variação de cada parâmetro de síntese sobre as propriedades espectroscópicas do material, a fim de se compreender as possibilidades de controle das propriedades ópticas. Os espectros de emissão dos NCs de MgCdS, referente ao estudo de otimização dos parâmetros de síntese, apresentaram uma única banda de emissão intensa que reflete o crescimento do nanocristal, com rendimentos quânticos de fotoluminescência elevados, chegando a 85%. Com base na presença de duas bandas de absorção no espectro de UV-visível, bem como de dados de espectrofotometria de absorção atômica (AAS), pode-se inferir que os nanocristais são compostos pelos metais de Cd e Mg, propondo-se a hipótese de uma arquitetura caroço-casca com interface difusa. Os dados obtidos através de AAS mostraram também que, como os precursores tem reatividades distintas, a composição dos materiais formados tende a diferir da proporção Cd2+:Mg2+ utilizada na reação. As análises morfológicas realizadas por microscopia eletrônica de transmissão (TEM) permitiram verificar o contorno esférico e uniforme das nanoesferas e estimar o tamanho dos nanocristais, sendo abaixo de 4 nm. Estudos de formação de ligas do tipo Mg1-xCdxS e Cd1-xMgxS, por troca iônica a partir dos componentes binários MgS e CdS permitiram compreender melhor os dados espectroscópicos dos nanocristais formados introduzindo ambos precursores simultaneamente. Confirmou-se que a introdução do segundo cátion (Cd2+ ou Mg2+) em cada estrutura binária (MgS ou CdS) de fato causa a formação de duas bandas de absorção e somente uma de emissão. A implementação de derivados de grafeno na síntese do MgCdS foi realizada a fim de aprimorar as propriedades gerais do material, bem como de propiciar um suporte físico aos nanocristais de MgCdS, favorecendo aplicações. A presença do grafeno na síntese do nanocristal proporcionou deslocamento da banda de emissão para maiores comprimentos de onda com redução da intensidade luminescente, evidenciando interações entre os materiais. As morfologias dos compósitos apresentam folhas de grafeno decoradas com nanocristais esféricos.
São Cristóvão, SE
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Wee, Siew Fong. "Interdiffusion of semiconductor alloy heterostructures." Thesis, University of Surrey, 1998. http://epubs.surrey.ac.uk/844156/.
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This thesis is concerned with a quantitative study of intermixing in GaAs/AlGaAs and ZnSe/ZnCdSe single quantum well semiconductor structures. In this study, a method of iterative isothermal anneals and photoluminescence used to characterize this phenomenon has enabled the evolution of the diffusion coefficients for the interdiffusion process with anneal time to be followed. The blue-shift emissions arising from this method are predicted by a model based on Fick's law of diffusion. This model is developed in an attempt to relate the energy shift that is observed experimentally to the diffusion length. The mixing is modelled using an error function expression to solve the diffusion equation so as to describe the variation in well shape which is attributed to compositional disordering induced during thermal processing. Using this approach, where evidence of intermixing was monitored, the emission would be expected to shift measurably. Data has been taken to cover a wide temperature range to establish values for the activation energy EA. From this data, it has been found that the diffusion coefficients at various temperatures are thermally activated with an energy of 3.6 +/- 0.2 eV in GaAs/AlGaAs. The data is compared with the available literature data taken under a wide range of experimental conditions. We show that despite the range of activation energies quoted in the literature all the data appears to be consistent with a single activation energy. Departures from the 'mean' value are ascribed to experimental uncertainties in determining the diffusion coefficients for example, to fluctuations in the composition of the material, to techniques used, or to a wide range of perturbations. Photoluminescence observations on ZnSe/ZnCdSe show that an improvement in the optical quality of these quantum well structures was found for anneals at temperatures (~500°C). A value of EA = 2.9 +/- 0.3 eV was derived from the experiments for the interdiffusion process over a 250 K temperature range and four decades of interdiffusion coefficient. The interdiffusion process of both these systems was inferred to be Fickian with no dependence on alloy composition or strain.
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Theys, Bertrand. "Photoelectrochimie du seleniure d'indium." Paris 7, 1987. http://www.theses.fr/1987PA077165.
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Mikeš, David. "Svařování hliníkových slitin pomocí vysokovýkonového polovodičového laseru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231108.
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Thesis deals with the optimization of process parameters during laser welding of aluminum alloys 5000 series. The theoretical part describes the types of lasers and their applications in industry, further discusses the properties of aluminum alloys, laser welding theory and principles of monitoring and diagnostics of laser process. In the experimental part the samples were welded using a semiconductor laser. For those samples were evaluated mechanical properties, welded defects and structure depending on the process parameters. Using the photodetector was observed stability of laser process by sensing the plasma plume. The link between stability and the formation of structural defects in the weld joint was observed from the measurement results.
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Cottle, Rand Duprez. "Isotropic copper-invar alloys for microelectronics packaging /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Kumta, Prashant Nagesh 1960. "RAPID SOLIDIFICATION PROCESSING OF INDIUM GALLIUM ANTIMONIDE ALLOYS." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276468.
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Solidification from the melt is an essential step in nearly all conventional processes to produce bulk materials for industrial applications. Rapid quenching from the liquid state at cooling rates of 102 to 106K/s or higher has developed into a new technology for processing novel materials. InxGa1 - xSb a ternary III-V compound semiconductor was synthesized by using the rapid spinning cup (RSC) technique. Several compositions of these alloys were batched and cast into ingots in evacuated sealed quartz tubes. These ingots were then melted and ejected onto a rapidly rotating copper disk. This resulted in the generation of flakes or powders depending on the rpm of the disk. Microstructural characterization of the flakes and powders was performed using XRD, SEM and TEM. Efforts were also made to measure the bulk resistivity of the annealed flakes to see the effect of annealing on ordering of the phases.
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Freitas, Felipe Lopes de. "Semiconductors for optoelectronic applications : algaInn alloys for ultraviolet and gesn alloys for infrared photoemission." Instituto Tecnológico de Aeronáutica, 2015. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=3388.
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A cluster expansion method combined with Density Functional Theory is used to derive structural properties of quaternary AlGaInN and binary GeSn alloys. The energy gaps for both systems are calculated including quasiparticle effects within the framework of the computationally inexpensive and parameter free DFT-1/2 method. The model developed is able to treat the complexity of semiconductor alloys, which have important application in heterostructures, band gap engineering and lattice constant matching. The transition energy of the effective electronic bands is calculated including statistical disored and compared to spectroscopic measurements. The range of the tunable energy gap of cubic and hexagonal AlGaInN alloys lattice matched to GaN is calculated, together with the direct-indirect gap transition region in the cubic alloy. We also discuss trends for phase separation of GeSn alloys and do not observe any significant indication of decomposition in the binodal-spinodal composition range. It is shown that the oscillator strength of the optical transition in the alloy is considerably higher than that of pure Ge. Results are contextualized in light of applications of AlGaInN alloys for ultraviolet and GeSn alloys for mid-infrared photoemission. Differences and similarities between our model and other calculations in the existing literature are also elucidated.
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Jing-Ping, Zhang. "Oxidation of relaxed Si0.5 Ge0.5 alloy." Thesis, University of Surrey, 1994. http://epubs.surrey.ac.uk/844611/.
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Oxidation is a fundamental process in the fabrication of microelectronic devices and in order to promote the incorporation of SiGe into Si technology we have investigated the thermal oxidation of Si1-yGey alloy (y≈0.5) at high temperatures (mainly 900°C and 1000°C) using Rutherford backscattering spectroscopy, infrared transmission spectroscopy and X-ray photoelectron spectroscopy. It has been observed that three distinct regions form during oxidation of Si0.5Ge0.5 alloy, which are (I) a mixed oxide layer Si0.5Geg0.5O2, (II) a pure SiO2 layer and (III) a Si1-yGey (y≠0.5) alloy layer. These are formed during both wet and dry oxidation when the sample is not preheated, whilst only two regions (II) and (III) form when the sample is preheated in a non oxygen ambient up to the oxidation temperature prior to oxidation. Enhancement of the rate of wet oxidation of SiGe compared with bulk Si and the accumulation of Ge in region III just below SiO2 layer (region II) has also been observed. This behaviour is in good agreement with other results, however, some abnormal behaviour during wet and dry oxidation has been observed. The rate of oxidation during short wet oxidations (15 minutes) of Si0.5 Ge0.5 decreases as the oxidation temperature increases from 800°C to 1000°C for 15 minutes, which has not been previously reported, A reduced rate of oxidation of Si1-yGey (y≈0.5) in a dry environment has been observed and is discussed. In order to investigate the thermodynamics of the oxidation process new experiments have been carried out which involve the synthesis of a buried oxide layer, by O+ implantation followed by a high temperature anneal. The implanted oxygen atoms preferentially bond to silicon atoms and the oxygen atoms are found to bond to germanium atoms only after all of the silicon atoms are fully oxidised. Germanium tends to be rejected from the growing oxide during a subsequent higher temperature ( > 900°C) anneal. The different behaviour of the Si and Ge atoms during both thermal and internal oxidations is described in terms of the thermodynamics and kinetics of the SiGe alloy system. There are three important conclusions which emerge from these analyses: (i) in order to adequately control the composition of thermal oxides (T > 800°C) grown on Si0.5Ge0.5 material it is necessary to preheat the samples in a non oxidising atmosphere prior to oxidation. By so doing the entrapment of Ge in the near surface layer (region I) is inhibited; (ii) during the initial stage of dry oxidation the process is described by the reaction Si+O2?Si2 and we suggest that the rate is controlled by the availability of oxygen atoms and is numerically the same as for bulk Si; (iii) in contrast, during the initial stage of wet oxidation, the process is described by the reaction Si+2OH→SiO2+H2 and the rate is controlled by the areal density of Si atoms, which we propose is high due to the weak Si-Ge binding energy and thus an enhanced oxidation rate occurs.
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David, Dugdale. "Electronic structure calculations on nitride semiconductors and their alloys." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4324/.
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Calculations of the electronic properties of AIN, GaN, InN and their alloys are presented. Initial calculations are performed using the first principles pseudopotenial method to obtain accurate lattice constants. Further calculations then investigate bonding in the nitrides through population analysis and density of state calculations, the empirical pseudopotential method is also used in this work. Pseudopotentials 'or each of the nitrides are constructed using a functional form that allows strained material and alloys to be studied. The conventional k,p valence band parameters for both zincblende and wurtzite are obtained from the empirical band structure using two different methods. A Monte-Carlo fitting of the k.p band structure to the pseudopotential data (or an effective mass method for the zincblende structure) is used to produce one set. Another set is obtained directly from the momentum matrix elements and energy eigenvalues at the centre of the Brillouin zone. Both methods of calculating k.p parameters produce band structure in excellent agreement with the original empirical band calculations near the centre of the Brillouin zone. The advantage of the direct method is that it produces consistent sets of parameters, and can be used in studies involving a series of alloy compositions. Further empirical pseudopotential method calculations are then performed for alloys of the nitrides. In particular, the variation of the band gap with alloy composition is investigated, and good agreement with theory and experiment is found. The direct method is used to obtain k.p parameters for the alloys, and is contrasted with the fitting approach. The behaviour of the nitrides under strain is also studied. In particular, valence band offsets for nitride heterojunctions are calculated, and a strong forward-backward asymmetry in the band offset is found, in good agreement with other results in the literature.
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Butler, Barry R. "Atmospheric pressure metal-organic vapour phase epitaxy of InP, (GaIn)As and (GaIn)(AsP) alloys." Thesis, Durham University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386374.
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Lang, Matthias. "The fabrication and characterization of ion-implanted germanium-incorporated silicon-carbide diodes and transistors." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 1.35 Mb., 102 p, 2006. http://wwwlib.umi.com/dissertations/fullcit/1436218.
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Craig, Duncan Wilson. "Optical nonlinearities in CdHgTe." Thesis, Heriot-Watt University, 1987. http://hdl.handle.net/10399/1015.
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