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Re-amorphization of GeSbTe alloys not through a melt-quenching process
摘要： Ge–Sb–Te (GST) alloys are one of the most successful chalcogenides used in rewritable optical discs and electric non-volatile memories. In these materials the structural phase transition between amorphous and crystalline states is used for recording. Here, we report that a melt-quenching method is not necessarily the only way to form a high-resistance phase. We found that amorphous-like grains with high resistance are formed in the GST crystal film by holding it at above the crystallization temperature under an external magnetic field, followed by cooling accompanied with pulse current injection. The treatment may open new route for ultra-low current switching phase change memory.
关键词： pulse current injection,Ge–Sb–Te alloys,phase change memory,re-amorphization,magnetic field
更新于2025-09-09 09:28:46
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Synthesis and photoluminescence properties of hexagonal BGaN alloys and quantum wells
摘要： Hexagonal boron nitride (h-BN) has emerged as an important extreme bandgap semiconductor as well as a two-dimensional material. Achieving the ability for tuning the optoelectronic properties through alloying and heterojunction will further expand the applications of h-BN. By utilizing h-BN epilayer as a template, the synthesis of BN-rich B1?xGaxN alloys and quantum wells crystalized in the hexagonal phase has been demonstrated for the first time by metal organic chemical vapor deposition. The incorporation of Ga tends to enhance the conductivity. A blue shift in the band-edge emission upon the formation of h-BN/BGaN/BN QW has been observed, indicating the feasibility for heterojunction formation.
关键词： hexagonal boron nitride,MOCVD,photoluminescence,BGaN alloys,quantum wells
更新于2025-09-09 09:28:46
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Empirical expressions for the spectral dependence of the refractive index for the case of thin-film silicon and some of its common alloys
摘要： We aim to model the spectral dependence of the refractive index associated with thin-film silicon, and some of its common alloys, using a series of elementary polynomial fits. For the purposes of this particular analysis, experimental data sets for the refractive index as a function of the photon energy corresponding to samples of thin-film silicon, and its alloy with germanium and carbon, prepared through evaporation, plasma enhanced chemical vapor deposition, and dc sputtering, are considered, this range of results providing a reasonably representative sampling over the thin-film silicon genome. The results of this analysis, i.e., the polynomials that arise from these fits, are explicitly tabulated. We believe that such models will offer the thin-film silicon community a number of advantages, including the ease with which such a result can be replicated, manipulated, and employed by fellow thin-film silicon researchers in their analyzes of this material system.
关键词： spectral dependence,alloys,refractive index,polynomial fits,thin-film silicon
更新于2025-09-09 09:28:46
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Epitaxial Ge-rich silicon layers after dry oxidation of Ge implanted silicon
摘要： We report on formation of epi-layer of SixGe1-x by taking standard procedure in CMOS technology. The competitive process of solid solubility of Ge dopant into Si and SiO2 is the key to engineer atomically sharp, low defect very thin epitaxial layer at the interface of oxide-Si. Oxidation time process was used to control the distribution of the doped Ge ions at the interface of Si with oxide and in the oxide layer. Implanted samples (35 keV and 1 × 1016 Ge+/cm2) were oxidized at 1050 °C for 30–90 min. RBS-Channeling analysis shows two separate peaks of Ge corresponds to different depths after oxidation. Corroborate with high resolution microscopy and elemental analysis, we determined the first peak as enriched layer of SixGe1-x at the interface of SiO2eSi. Less than 10 nm epitaxially grown interfacial layer is very low in defects, and Ge ions are fully substituted into the host lattice. The second peak originated from diffusion of Ge into SiO2 resulted in a segregated layer containing Ge in oxide film. Technological demand on forming SixGe1-x layer for CMOS application through standard routes is what we address in this research.
关键词： High resolution electron microscopy,Point defects,Germanium silicon alloys,Ion implantation,Solid phase epitaxy
更新于2025-09-09 09:28:46
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The structural and elastic properties of InSb1-xBix alloys
摘要： Based on density functional theory, the structural and elastic properties of InSb1-xBix alloys have been studied using first principle calculations. The generalized gradient approximation in the presence of spin-orbit coupling is utilized to perform the calculations presented in this paper. The calculated lattice constants of InSb1-xBix alloys are in good agreement with the available experimental data. The mechanical stability of these alloys is demonstrated using elastic constants. The ductility and brittleness of these alloys are investigated using both Poisson’s ratio and Pugh’s ratio. Moreover, the anisotropy of InSb1-xBix alloys is studied using the universal index and the 3D representation of Young's modulus. According to the obtained values of Poisson’s ratio, the InSb0.5Bi0.5 and InBi alloys are auxetic materials.
关键词： InSb1-xBix alloys,structural properties,Density functional theory,elastic properties
更新于2025-09-04 15:30:14
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Reference Module in Materials Science and Materials Engineering || SixGe1-x Bulk Crystals
摘要： Germanium–silicon (Ge1(cid:1)xSix) or silicon–germanium (SixGe1(cid:1)x) alloy, where x indicates the mole fraction of silicon, is a complete solid-solution semiconductor having the diamond cubic structure. The lattice parameters of the two elements differ by 4% and those of the solid solution closely follow Vegard's law from 0.564 (pure germanium) to 0.534 nm (pure silicon), while the bandgap changes from 0.72 (germanium) to 1.2 eV (silicon) according to composition. GeSi alloys are important for both microelectronic and optoelectronic devices and various functional materials because of the potential for bandgap and lattice parameter engineering they offer. The phase diagram of GeSi alloy is shown in Figure 1. The solidus and liquidus curves are widely separated. The equilibrium distribution coef?cient, k0 ? xs/xl (xs and xl being the solidus and liquidus concentration of silicon), is as large as 6 for germanium-rich solutions and about 2.2 at the average melting-point temperature of each element. Such a large gap between the liquidus and the solidus and the difference in the physical properties of the constituent elements, such as density, lattice parameter, and melting temperature, make the crystal growth of GeSi alloys very dif?cult. This article provides an outline of the applications and reviews the growth of bulk GeSi, discussing relevant problems, residual defects, impurities and dopants, and covers the structural properties of the alloys. The study of such alloys is also of interest from the fundamental view point of solidi?cation.
关键词： solid-solution semiconductor,crystal growth,microelectronic devices,optoelectronic devices,GeSi alloys
更新于2025-09-04 15:30:14
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Photopolymerization of electroactive film applied to full polymer electrochromic device
摘要： Electroactive films of thiophene-acrylate polymers were simultaneously photopolymerized by means of ultraviolet (UV) irradiation using diphenyliodonium hexafluorophosphate and acrylate special photoinitiators (PIs) as a mixed photoinitiator. Free radicals from PIs can promote cationic polymerization of thiophenes. Electrical conductivity and transmittance of the electroactive film are high to 10–2 S·cm–1 and >90%. Electroactivity of the photopolymerized polymer film was confirmed by electro-polymerization of aniline on this film in aqueous solution and employed to assemble a full polymer electrochromic device having a superior optical contrast of 36.6%.
关键词： electrochromic device,polymer blends and alloys,thiophene-acrylate polymer composites,photopolymerization,electroactive film
更新于2025-09-04 15:30:14
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Atomic layer deposited TiO <sub/>2</sub> -IrO <sub/>x</sub> alloys enable corrosion resistant water oxidation on silicon at high photovoltage.
摘要： We synthesized by atomic layer deposition (ALD) TiO2-IrOx alloys that enable high photovoltages and catalyze water oxidation on silicon metal-insulator-semiconductor (MIS) photoanodes. The ratio of TiO2 to IrOx was precisely controlled by varying the number of ALD cycles for each precursor. Silicon with a 2 nm surface SiO2 layer was coated with TiO2-IrOx alloys ranging in composition from 18-35% iridium relative to the sum of titanium and iridium concentrations. IrOx catalyzed oxygen evolution and imparted a high work function to the TiO2-IrOx alloys, enabling photovoltages during water oxidation that exceeded 600 mV. TiO2 imparted stability and inhibited corrosion of the underlying silicon light absorber. After annealing in forming gas (5% H2 / 95% N2), TiO2-IrOx alloys were stable for 12 hours of continuous water oxidation in 1 M H2SO4. Key properties of the MIS junction affecting electrochemical operation were also extracted by electrochemical impedance spectroscopy. This work demonstrates that alloying by ALD is a promising approach for designing corrosion resistant Schottky contacts with optimized electronic and materials properties for catalyzed, solar driven water oxidation.
关键词： photovoltage,water oxidation,TiO2-IrOx alloys,Atomic layer deposition,corrosion resistance,silicon photoanodes
更新于2025-09-04 15:30:14
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Metamorphic InAs(Sb)/InGaAs/InAlAs nanoheterostructures grown on GaAs for efficient mid-IR emitters
摘要： High-efficiency semiconductor lasers and light-emitting diodes operating in the 3–5 μm mid-infrared (mid-IR) spectral range are currently of great demand for a wide variety of applications, in particular, gas sensing, noninvasive medical tests, IR spectroscopy etc. III-V compounds with a lattice constant of about 6.1 ? are traditionally used for this spectral range. The attractive idea to fabricate such emitters on GaAs substrates by using In(Ga,Al)As compounds is restricted by either the minimum operating wavelength of ～8 μm in case of pseudomorphic AlGaAs-based quantum cascade lasers or requires utilization of thick metamorphic InxAl1-xAs buffer layers (MBLs) playing a key role in reducing the density of threading dislocations (TDs) in an active region, which otherwise result in a strong decay of the quantum efficiency of such mid-IR emitters. In this review we present the results of careful investigations of employing the convex-graded InxAl1-xAs MBLs for fabrication by molecular beam epitaxy on GaAs (001) substrates of In(Ga,Al)As heterostructures with a combined type-II/type-I InSb/InAs/InGaAs quantum well (QW) for efficient mid-IR emitters (3–3.6 μm). The issues of strain relaxation, elastic stress balance, efficiency of radiative and non-radiative recombination at T = 10–300 K are discussed in relation to molecular beam epitaxy (MBE) growth conditions and designs of the structures. A wide complex of techniques including in-situ reflection high-energy electron diffraction, atomic force microscopy (AFM), scanning and transmission electron microscopies, X-ray diffractometry, reciprocal space mapping, selective area electron diffraction, as well as photoluminescence (PL) and Fourier-transformed infrared spectroscopy was used to study in detail structural and optical properties of the metamorphic QW structures. Optimization of the growth conditions (the substrate temperature, the As4/III ratio) and elastic strain profiles governed by variation of an inverse step in the In content profile between the MBL and the InAlAs virtual substrate results in decrease in the TD density (down to 3 × 107 cm?2), increase of the thickness of the low-TD-density near-surface MBL region to 250–300 nm, the extremely low surface roughness with the RMS value of 1.6–2.4 nm, measured by AFM, as well as rather high 3.5 μm-PL intensity at temperatures up to 300 K in such structures. The obtained results indicate that the metamorphic InSb/In(Ga,Al)As QW heterostructures of proper design, grown under the optimum MBE conditions, are very promising for fabricating the efficient mid-IR emitters on a GaAs platform.
关键词： Buffer layer,Non-radiative recombination,Mid-infrared emitters,Photoluminescence,Metamorphic heterostructures,InSb,InAs,Structural properties,Molecular beam epitaxy,Nanostructures,In(Ga,Al)As ternary alloys,Threading dislocations,Quantum well
更新于2025-09-04 15:30:14