HREM study on stacking structure of SiGe/Si infrared detector

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B掺杂p型SiGe合金的制备与热电性能表征

以一定化学计量比均匀混合的Si、Ge、B混合粉末为原材料,使用放电等离子烧结(SPS)一步法合金化制备了p型Si₈₀Ge₂₀B_x(x=0.5,1.0,2.0)合金热电材料,并对样品的组成、微观形貌、热电性能进行了表征与分析。结果表明,放电等离子烧结过程实现原位合金化并烧结为块体材料。随着B掺杂量的增加,电导率明显提升,热导率显著下降,当温度为950K时,热导率为1.79W/(m·K)。在1050K时,ZT值达到了0.899。球磨和掺杂的协同作用使得SiGe合金基体内产生不同类型的缺陷特征而散射不同波长的声子,导致硅锗合金热导率的降低。     

快速凝固Gd5Si2Ge2合金的显微组织与相组成

研究了在真空电弧炉和快淬炉2种快速凝固条件下制备的Gd5Si2Ge2合金的显微组织与相组成。结果表明，Gd5Si2Ge2合金亿电弧炉熔炼条件下，具有不同质蟹的样品可以获得不同的显微组织与相组成。不同速度下，快淬甩带实验表明，在小于40m／s的快淬速度下，Gd5Si2Ge2合金为单斜Gd5Si2Ge2-型晶体结构：在50m／s的快淬速度下Gd5Si2Ge2合金包含Gd5Si4-型和Gd5Si2Ge2-型两相。证实了冷却速度对Gd5Si2Ge2合金的相组成有重要影响。     

Growth and dislocation distribution of single Si1-xGex/Si(001) epilayer structures grown by gas source molecular beam epitaxy

The degree of strain relaxation via a formation of misfit dislocation has been calculated in single Si_1-xGe_x/Si (001) epilayers grown at 640°C, by gas-source molecular beam epitaxy. The scale of strain relief via misfit dislocation was below 22% for Ge content x≤0.15. However, in the case of growth temperature of 550°C. the degree of strain relaxation in 270 nra single epilayer structures was 9% via misfit dislocation formation with negligible relaxation by surface undulation. As growth temperature decreased from 640°C to 550°C with higher Ge content (x=0.22), the mode of strain relaxation appears to have changed from one of misfit dislocation and surface undulation mechanism to that of predominant misfit dislocation formation.     

机械合金化制备N型Si80Ge20块体热电材料的微观结构与电性能的研究

本文采用球磨工艺合成了SiGe合金粉末,结合放电等离子烧结制备出了掺杂GaP与P的N型Si<,80>Ge<,20>块体合金.利用XRD、SEM等手段对球磨粉末与烧结体进行了表征,并对烧结体进行了电性能的测试.结果表明:Si、Ge粉末经球磨后可完全形成单相的SiGe合金;通过谢乐公式的计算,机械合金化的合金粉末的平均品粒...     

Structural characteristics of SiGe/Si materials investigated by raman spectroscopy

In this paper, we employ a simple, efficient, and nondestructive Raman scattering analysis method to study the structural features of Si_1−xGe_x/Si film. Markedly, the method can simultaneously determine the Ge fractional composition x, the strain of SiGe films as well as its relaxation degree, the thickness of a SiGe epilayer and the crystallinity of SiGe film. At the same time, Rutherford backscattering spectroscopy/Channeling are also used to characterize SiGe films with the aim of corroborating the validity of the Raman analysis with respect to the Ge content, and the thickness and crystal quality of the SiGe film. It is demonstrated that Raman spectra show significant promise for obtaining a considerable variety of parameters of SiGe film in a nondestructive, highly production-efficient, and cost-effective manner.     

Structure and property of Ge/Si nanomultilayers prepared by magnetron sputtering

Ge/Si nanomultilayers were prepared using magnetron sputtering deposition and adjusting the growth conditions, such as the substrate temperature, sputtering pressure, sputtering power and annealing temperature. The surface topography and microstructure of the nanomultilayers were characterized by X-ray diffraction, Raman spectrometry and AFM. The favorable pressure of working gas was about 0.6 Pa in our experimental conditions. The surface of the as-deposited film is compact and smooth when the sputtering power is 2 W/cm². The as-deposited film is amorphous at room temperature, however, the film is crystalline at the deposition temperature of 300 °C. When the annealing temperature is 500 °C, the Ge/Si nanomultilayers transform into GeSi alloy because the thermal annealing activates Ge/Si atomic interdiffusion. At the annealing temperature of 700 °C, the interdiffusion increases and the amount of Ge in the germanosilicide phase had been decreased compared to that of the sample annealed at 600 °C. In addition, Ge may have segregated from the germanosilicide and lead to the formation of Ge nanocrystals. For the sample annealed beyond 800 °C, the strong agglomeration and the formation of Ge nanocrystals are present.     

Bulk single crystal growth of SiGe by PMCZ method

A new type of magnetic device was used to replace the conventional electro-magnetic field for CZSi (doped with Ge) growth. The device was composed of three permanent magnetic rings and called PMCZ device. The lines of magnetic force are horizontally distributed at radial 360? Using the ring permanent magnetic field, thermal convection in melt and centrifugal pumping flows due to crystal rotation could be strongly suppressed so that the fluctuations of temperature and micro-growth rate at solid/liquid interface could be restrained effectively. In the PMCZ condition, the growing environment of SiGe bulk single crystal was similar to the crystal growth in space under the condition of micro-gravity. The motion of impurities (Ge, oxygen, etc.) had been controlled by diffusion near the solid/liquid interface. Oxygen concentration became lower and the distribution of composition became more homogeneous along longitudinal direction and across a radial section in the grown SiGe crystal. The mechanism of PMCZ sup     

Determination of Ge content in high concentration Ge-doped Czochralski Si single crystals by FTIR

SiGe single crystals with different Ge concentrations were measured by Fourier transform infrared （FTIR） spectroscopy at room temperature （RT） and 10 K. A new peak appears at the wave number of 710 cm^-1 and the spectroscopy becomes clearer with an increase in Ge content. The absorption strength and wave sharp of the 710 cm^-1 peak are independent of temperature. The relation of the absorption coefficient amax, the band width of half maximum （BWHM） Wit2 of the 710 cm^-1 peak, and the Ge concentration is determined with the Ge content obtained by SEM-EDX. The conversion factor is k = 1.211 at 10 K. Therefore, the Ge content in high concentration Ge doped CZ-Si single crystals can be determined by FTIR.     

INFLUENCE OF Ge ON THE ANTIFERROMAGNETIC TRANSITION AND γ → ε MARTENSITIC TRANSFORMATION OF Fe-24Mn ALLOYS

The aims of the work were to study the effect of Ge (0-6wt. %) on the paramagnetic-antiferromagnetic transition and martensitic transformation of Fe-Mn alloy using the susceptibility, micro structure examination, X-ray diffraction (XRD) and latticeparameter measurement. Ge lowers the Néel temperature, TN, and enhances the magnetic susceptibility x, changing the Pauli paramagnetism above TN to paramagnetismstate obeying the Curie Weiss law, which is essentially similar to that of γ-Fe-Mnalloys containing Al or Si; Ge depresses γ-ε martensitic transformation, whichattribute to Ge increasing the stacking fault energy; Moreover, Ge increases the lattice parameter of γ phase, and low content Ge increases the lattice parameter of γphase more than that of high Ge content. Comparing Ge(4s24p2) with Si(3s23p2) and Al(3s2 3p1), which have the same outer-shell of electron structures, we found that their effects on the martensitic transformation of Fe-Mn alloy are completely different. The result suggests the     

Mn5Ge3-xRx系列合金在低磁场下的磁热效应

在对Mn5Ge3合金研究的基础上,以Si,Sb元素取代Mn5Ge3合金中的部分Ge元素,形成Mn5Ge3-xSix,Mn5Ge3-xSbx系列合金。利用X射线粉末衍射技术确定其结构,并在1．3T的磁场下直接测量其磁热效应。结果表明,随着Sb元素含量的增加,Mn5Ge3-xSbx合金的居里温度升高,少量的Sb元素对合金的磁热效应影响较小;随着Si元素含量的增加,Mn5Ge3-xSix合金的居里温度降低,磁热效应发生明显的衰减。     

Strain relaxation and it’s mechanism of single Si1-xGex/Si epilayer structures grown on Si(00l) substrate

The degree of strain relaxation via a formation of misfit dislocation has been calculated in single Si_1-xGe_x/Si (001) epilayers grown at 640°C, by gas-source molecular beam epitaxy. The scale of strain relief via misfit dislocation was below 22% for Ge content x≤0.15. However, in the case of growth temperature of 550°C. the degree of strain relaxation in 270 nra single epilayer structures was 9% via misfit dislocation formation with negligible relaxation by surface undulation. As growth temperature decreased from 640°C to 550°C with higher Ge content (x=0.22), the mode of strain relaxation appears to have changed from one of misfit dislocation and surface undulation mechanism to that of predominant misfit dislocation formation.     

Thermal vacancy formation in Co-based Heusler-type alloys Co2MnZ (Z = Si, Ge, Sn)

Thermal vacancy formation was studied for the Heusler-type ferromagnetic alloys Co₂MnZ (Z = Si, Ge, Sn) as a function of temperature (773–1273 K) by the density, electrical resistivity and positron annihilation measurements. The vacancy concentration increased with increase in quenching temperature and particularly, a high vacancy concentration exceeding 2% was observed in Co₂MnGe and Co₂MnSn. Estimated vacancy formation and migration energies were comparable with those for B2-type FeAl and CoGa alloys with high vacancy concentration. Further, the vacancy type and the vacancy site were examined for alloys quenched from 773 K. As a result, it was suggested that the mono-vacancies are randomly distributed over the lattice sites.     

Effects of a small amount of Si or Ge addition on stability and hydrogen-induced internal friction of Ti34Zr11Cu47Ni8 glassy alloys

Effects of a small amount of Si or Ge addition on stability and hydrogen-induced internal friction behavior of Ti₃₄Zr₁₁Cu₄₇Ni₈ glassy alloys have been investigated by X-ray diffraction, thermal analysis and temperature dependence of internal friction. It is found that the addition of 1 at.% Si, 2 at.% Si or 1 at.% Ge is effective to stabilize the glassy state and that Si is more effective than Ge. The peak internal friction of the single glassy phase alloy increases with increasing hydrogen content below about 20 at.% H. It is found that (Ti₃₄Zr₁₁Cu₄₇Ni₈)₉₉Si₁ glassy alloys have lower peak internal friction than the Ti₃₄Zr₁₁Cu₄₇Ni₈ glassy alloys, while (Ti₃₄Zr₁₁Cu₄₇Ni₈)₉₈Si₂ and (Ti₃₄Zr₁₁Cu₄₇Ni₈)₉₉Ge₁ glassy alloys have much higher peak internal friction. It should be noted that a (Ti₃₄Zr₁₁Cu₄₇Ni₈)₉₈Si₂ glassy alloy containing 14.4 at.% H shows high internal friction, Q⁻¹ of about 4 × 10⁻². The peak temperature of the single glassy phase alloys decreases with increasing hydrogen content below about 20 at.%. It should be noted that the addition of an extremely small amount of Si is effective to increase the peak temperature of the single glassy phase alloys. The relationship between the tensile strength and specific damping capacity indicates that the hydrogenated (Ti₃₄Zr₁₁Cu₄₇Ni₈)₉₈Si₂ glassy alloys have almost the same potential for a damping material as crystalline Mn–Cu–Al and Cu–Al–Ni alloys and hydrogenated Zr–Cu–Al glassy alloys.     

Growth behaviors of GaN/Si heteroepitaxy with various terrace widths grown by the LEPS method

Epilayers of GaN were grown on patterned Si (111) substrates of various terrace widths by means of metal organic chemical vapor deposition. The technique of lateral epitaxy on a patterned substrate used the growth of GaN epilayers from the periodic and parallel stripes that form as a result of the substrate etching. Silicon substrates were patterned for various terrace widths of 3 μm, 8 μm, and 18 μm. A low temperature AlN was used as a seed layer for the growth of a 1.5 μm thick GaN epilayer. The as-grown samples were characterized by using double-crystal X-ray diffractometry (DCXRD), photoluminescence and atomic force microscopy (AFM). From the DCXRD spectra, the full width at half maximum (FWHM) of the samples was found to decrease as the terrace width decreased. This behavior indicates that there is an improvement in the crystalline quality of the GaN epilayers as the terrace width decreases. The photoluminescence spectra reveal a decrease in the FWHM and an increase in the peak intensity as the terrace width decreases. This behavior indicates that there is an improvement in the optical quality of the GaN epilayer as the terrace width decreases. The atomic force micrographs reveal a dislocation-free homogeneous surface in the trench region compared to the terrace region with defects such as pits and dislocations. The results clearly show that GaN epilayers grown on a patterned Si substrate with a terrace width 3 μm have a good crystalline quality with minimal threading dislocation and excellent band edge emission.     

Structure and magnetic properties of intermetallic compounds Gd5Si2-xGe2-xM2x

1 Introduction Nowadays, there is much interest in magnetic refrigeration materials, as they offer the prospect of an energy-efficient and environment friendly alternative for the traditional vapour cycle refrigeration technique. Magnetic refrigeration is…     

Effects of Nb and Si on high temperature oxidation of TiAl

The isothermal oxidation behavior of TiAl based alloys at 900℃ in air with a combination of Nb (5%-10%, mole fraction) and Si (1%-5%, mole fraction) was investigated. The microstructure and the composition of the oxidation scale were studied by using XRD, TEM and EPMA. The results show that the combination of Nb and Si can improve the oxidation resistance of the alloys significantly. The element Si can change the typical microstructure of oxidation scale on TiAl based alloys. In alloys with Si addition, the compact Al2O3 forms in the interior side of oxidation scale. When x (Si)3%, the Ti5Si3 phase forms and the coarse crystal TiO2 forms on Ti5Si3 phase after oxidation. The increase of Nb content in the TiAl based alloys impedes the growth of Ti5Si3 phase, and the formation of TiO2 on surface and on Ti5Si3 phase is also impeded.     

MOCVD生长GaN力学性能研究

采用MOCVD技术在蓝宝石衬底（0001）面上生长了GaN外延膜，利用原子力显微镜AFM、扫描电镜SEM分析了薄膜表面形貌，利用纳米压痕仪和UMT试验机考察了GaN膜的硬度、临界载荷以及摩擦学性能等。结果表明，薄膜以二维模式均匀生长，表面平整，硬度达22．1MPa，弹性模量为299．5GPa，与衬底结合紧密，临界载荷达1．6N，与GCr15钢球对磨时摩擦系数仅为0．13，与Si3N4陶瓷球摩擦时膜很快就磨穿。     

Growth kinetics and pesting resistance of MoSi2 and germanium-doped MoSi2 diffusion coatings grown by the pack cementation method

The rapid, destructive low-temperature oxidation (pesting) of MoSi₂ is an important limitation to its practical use. The growth of molybdenum silicide diffusion coatings by a halide-activated pack cementation method results in an adherent superficial, salt by-product, whose composition depends on the halide activator used to grow the coating. As a consequence of the residual salt deposit, coatings grown by a NaF-activated pack did not pest after 2500 hours of isothermal oxidation or after cyclic oxidation for 600 1 hour cycles in air at 500°C. An additional minor improvement in the pesting resistance was observed for the germanium-doped MoSi₂ Coatings. The growth kinetics for a three-layer Ge-doped Mo(Si, Ge)₂/Mo₅(Si, Ge)₃/Mo₃(Si, Ge) coating are compared with rates calculated for the diffusion-controlled growth of an undoped three-layer silicide and for three-layer germanide coatings. The activation energy for the solid-state diffusional growth of MoSi₂ is the same as that for Mo(Si, Ge)₂, but the growth rates for Mo(Si, Ge)₂ are faster. The activation energies for the solid state diffusional growth of the inner Mo₅(Si, Ge)₃ and Mo₃(Si, Ge) layers are similar to Mo₅Ge₃ and Mo₃Ge, but the rates are slower. The chemical demixing of Mo(Si, Ge)₂ under a chemical potential gradient creates a maximum in the Ge concentration at the Mo(Si, Ge)₂/Mo₅(Si, Ge)₃ interface, which produces unusual growth kinetics for the Mo₅(Si, Ge)₃ and Mo₃(Si, Ge) layers.     

增强调制掺杂Si80Ge20基热电材料功率因子的研究

采用成熟工艺制备了N型、P型调制掺杂型Si80Ge20基固溶体合金及等化学计量比的均匀掺杂型Si80Ge20基固溶体合金,重点研究了两类固溶体合金的热电性能。结果表明：温度为773 K时,N型系列、P型系列,调制掺杂型固溶体合金较均匀掺杂型的功率因子分别提高了13.6%和49.2%,热电优值ZT分别提高了7.9%和12.9%