Relaxation of extrinsic and intrinsic stresses in germanium substrates with silicon films

Si films were deposited on Ge substrates at 400°C by two different Physical Vapor Deposition techniques: (A) ion beam sputtering and (B) magnetron sputtering. The intrinsic stresses in the as-deposited films were measured to be compressive and much greater in samples (A), about −1500 to −2000 MPa than in samples (B), about −300 to −500 MPa. The substrates were subsequently exposed to thermal treatments for varying times at 800°C. In the lower stressed (B) samples, the films had relaxed and reduced the overall curvature of the structure whereas in the high stresses (A) samples, an irreversible large increase in the substrate curvature was found to occur. This indicated that plastic deformation in the Ge substrates itself had occurred.     

Stability and Heat Resistance of Silicide Coatings on Refractory Metals. Part 3. Stability of Silicide Coatings on Niobium Heated in Air at 1500-1800°C

The kinetics of phase redistribution in the (Mo, W)Si₂ Nb system at 1500-1800°C was investigated. The kinetic parameters for growth of the lower silicides (Mo, W, Nb) ₅Si₃ + Nb₅Si₃ and decrease in the layer thickness of the higher silicide (Mo, W)Si₂ as function of the oxidation temperature were determined. It was established that the stability of the multiphase and multicomponent system was more than twice that of the system MoSi₂ Nb, and 15-18 times that of MoSi₂ Mo.     

Photoluminescence enhancement by isolating β-FeSi2 layers from defective layers

We have investigated an optimal annealing process in order to enhance 1.55 μm light emission from semiconducting β-FeSi₂ and found that two steps annealing at 600 °C and 800 °C is effective to its enhancement. Rutherford backscattering spectroscopy and SEM observations revealed that pronounced surface segregation of Fe atoms during annealing at 600 °C caused surface precipitate of β-FeSi₂. The enhancement of light emission is attributed spatial isolation of the surface β-FeSi₂ (light emitting layer) from damaged and defective layers with nonradiative recombination centers.     

Preparation of β-FeSi2 substrates by molten salt method

Large-sized β-FeSi₂ substrates were successfully prepared for the first time from the silicide bulk crystal grown by the molten salt method. The structural, electrical and optical properties of the as-grown β-FeSi₂ bulk crystals were also investigated. The crystal is single phase β-FeSi₂, and polycrystalline with no preferable growth crystallographic orientations. It was also determined that the β-FeSi₂ shows a p-type conduction, and the hole concentration and the Hall mobility at room temperature were about 10¹⁷ cm^− 3 and 10 cm²/Vs, respectively. In addition, the PL emission around 0.8 eV was realized from the β-FeSi₂ bulk crystal. This simple vacuum-free growth technique of β-FeSi₂ and the large-sized substrate preparation procedure encourage us to develop future silicide-based electronics.     

Room-temperature sliding wear properties of laser melt deposited Cr13Ni5Si2/γ alloy

A wear-resistant alloy consisting of Cr₁₃Ni₅Si₂ ternary silicide dendrites and the interdendritic nickel-base solid solution (γ) was designed and fabricated by the laser melting/continuous deposition (LMCD) process. The wear resistance of Cr₁₃Ni₅Si₂/γ alloy was evaluated on an MM-200 block-on-wheel dry sliding wear tester at room temperature. Results indicate that the Cr₁₃Ni₅Si₂/γ alloy has excellent wear resistance and extremely low load-sensitivity of wear under dry sliding wear test conditions due to the high toughness and the high strength, as well as the transferred cover-layer on the worn surface of the alloy. Translated from Acta Metallurgica Sinica, 2006, 42(2): 181–185 [译自: 金属学报]     

The magnetic ordering in the Ho5Si3 and Ho5Ge3 compounds

A neutron diffraction investigation has been performed on the Ho₅Si₃ and Ho₅Ge₃ compounds (hexagonal Mn₅Si₃-type, hP16, P6₃/mcm) to study their magnetic structure. The results prove that these intermetallic phases show a complex sine-modulated type magnetic ordering, both presenting on cooling two subsequent antiferromagnetic orderings (T_N1 and T_N2).Between T_N1 = 24(2) and T_N2 = 16(4) K Ho₅Si₃ shows a first antiferromagnetic ordering of the sine-modulated type with a propagation vector K₁ = [0, 0, ±0.284(1)]; then, below T_N2 the sine-modulated type ordering is conserved, but by the two propagation vectors K₁ = [0, 0, ±0.2773(7)] and K₂ = [±1/5, ±1/5, 0].For Ho₅Ge₃, between T_N1 = 27(2) and T_N2 = 18(4) K, the sine-modulated ordering is realized through the propagation vectors K₁ = [0, 0, ±3/10] and K₂ = [0, 1/2, 0], whilst below T_N2 the ordering takes place with propagation vectors K₁ = [0, 0, ±3/10], K₂ = [0, 1/2, 0], K₃ = [0, 0, ±2/5] and K₄ = [±1/5, ±1/5, 0]. For both the Ho₅Si₃ and Ho₅Ge₃ compounds, the dimensions of the magnetic unit cell are 5a × 5a × 10c times the crystal unit cell of Mn₅Si₃-type.     

微处理器芯片技术的发展及展望

作为计算机核心的微处理器芯片问世至今三十多年以来，式样不断翻新，产品性能突飞猛进，有力的带动了信息产业发展，本文回顾了三十年以来从4004微处理器到当今Pentium4的技术发展历程，从芯片所用材料的变更，封装技术及光布线技术发展的角度进一步探讨，展望了微处理器芯片未来的发展趋势。     

难熔金属硅化物的喇曼散射

用电子束蒸发方法在10~(-7)托真空中使单晶硅上蒸上一层Ti膜后,于N_2中进行从500-1000℃10秒钟的快速热退火,由激光喇曼光谱结合薄层电阻测量和转靶X射线衍射研究分析了TiSi_2的形成.退火温度高于680℃时,观察到207和244cm~(-1)波数处的两个TiSi_2的特征喇曼峰,当退火温度为580℃时,只有270,297和3ncm~(-1)的三个喇曼峰,这些可能是钛的氧化物和不包括TiSi的钛硅化物.     

离子束混合诱导稀土金属Ce与Si的界面反应及硅化物的形成

本文详细讨论了离子束混合下,Ce/Si〈100〉双层膜体系界面反应的动力学过程以及硅化物的形成规律.样品经150KeV Ar离子注入,辐照温度从LNT到300℃,剂量从5×X10~(14)到8.1×10~(16)Ar/cm~2.界面反应形成的硅化物为CeSi_2,其结构为体心正交结构.硅化物是分层生长的,厚度与注入剂量的平方根成线性关系,这说明界面反应是扩散控制的.与近贵金属/硅体系和难熔金属/硅体系相比较可以看出,稀土金属Ce/Si体系的相变过程与难熔金属/硅体系的相似;而混合的动力学行为与近贵金属/硅体系的相似.本文还讨论了化学驱动力和辐射增强扩散对混合的贡献.     

Degradation of semiconducting polymers by concentrated sunlight

A lens based sunlight concentration setup was used to accelerate the degradation of semiconducting polymers. Sunlight was collected outdoor and focused into an optical fiber bundle allowing for indoor experimental work. Photo-degradation of several polymers was studied by UV-vis absorbance spectroscopy and infra-red spectroscopy. This showed that the degradation rate is significantly increased by increasing illumination intensity. Acceleration factors exceeding 100 compared to standard 1 sun illumination were observed for solar concentration of 200 suns in the case of P3HT. A comparison between infra-red spectra of MEH-PPV degraded at 1 sun intensity and at high solar concentration only showed minor deviations in degradation mechanisms. The acceleration factor was found to vary linearly with the solar concentration. Finally, a comparison of the degradation rates at 1 sun and 100 suns was carried out in a materials study employing five different conjugated polymers relevant to polymer solar cells for which acceleration factors in the range 19-55 were obtained.