Strain relaxation of GeSi alloy with low dislocation density grown on low-temperature Si buffers

We have developed a low-temperature (LT) growth technique. Even with Ge fraction x upto 90%, the total thickness of fully relaxed GexSi1-x buffers can he reduced to 1.7 mu m with dislocation density lower than 5 x 10(6) cm(-2). The surface roughness is no more than 6 nm. The strain relaxation is quite inhomogeneous From the beginning. Stacking faults generate and form the mismatch dislocations in the interface of GeSi/LT-Si. (C) 1999 Elsevier Science B.V. All rights reserved.

First charge collection and position-precision data on the medium-resistivity silicon strip detectors before and after neutron irradiation up to 2x10(14) n/cm(2)

Test strip detectors of 125 mu m, 500 mu m, and 1 mm pitches with about 1 cm(2) areas have been made on medium-resistivity silicon wafers (1.3 and 2.7 k Ohm cm). Detectors of 500 mu m pitch have been tested for charge collection and position precision before and after neutron irradiation (up to 2 x 10(14) n/cm(2)) using 820 and 1030 nm laser lights with different beam-spot sizes. It has been found that for a bias of 250 V a strip detector made of 1.3 k Ohm cm (300 mu m thick) can be fully depleted before and after an irradiation of 2 x 10(14) n/cm(2). For a 500 mu m pitch strip detector made of 2.7 k Ohm cm tested with an 1030 nm laser light with 200 mu m spot size, the position reconstruction error is about 14 mu m before irradiation, and 17 mu m after about 1.7 x 10(13) n/cm(2) irradiation. We demonstrated in this work that medium resistivity silicon strip detectors can work just as well as the traditional high-resistivity ones, but with higher radiation tolerance. We also tested charge sharing and position reconstruction using a 1030 nm wavelength (300 mu m absorption length in Si at RT) laser, which provides a simulation of MIP particles in high-physics experiments in terms of charge collection and position reconstruction, (C) 1999 Elsevier Science B.V. All rights reserved.

The influence of thickness on properties of GaN buffer layer and heavily Si-doped GaN grown by metalorganic vapor-phase epitaxy

The physical properties of low-temperature-deposited GaN buffer layers with different thicknesses grown by metal-organic vapor-phase epitaxy have been studied. A tentative model for the optimum thickness of buffer layer has been proposed. Heavily Si-doped GaN layers have been grown using silane as the dopant. The electron concentration of Si-doped GaN reached 1.7 x 10(20) cm(-3) with mobility 30 cm(2)/V s at room temperature. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

BRCA1在人乳腺癌细胞MCF-7辐射抗性中作用的初步研究

<正>MCF-7细胞是被广泛用以研究乳腺癌的一株模式细胞,该细胞拥有野生型p53基因,但其辐射敏感性与p53基因表达状态无关,这提示可能存在其他基因参与调节其辐

Multiple expansions of C-4 plant biomass in East Asia since 7 Ma coupled with strengthened monsoon circulation

IEECAS SKLLQG

Tectonic uplift in the northern Tibetan Plateau since 13.7 Ma ago inferred from molasse deposits along the Altyn Tagh Fault

IEECAS SKLLQG

28.7MeV/u的~(14,16,18)O+~(7,9)Be反应中的同位素分布研究

用同位旋相关的Boltzmann Langevin方程研究了在入射能量为2 8 7MeV/u下 ,不同弹核 14O ,16 O和 18O轰击不同靶核 7Be和 9Be的反应 ,计算了生成碎片的产生截面 ,发现用丰中子 (缺中子 )炮弹或丰中子 (缺中子 )靶进行反应 ,所得到的产物均有丰中子 (缺中子 )的碎片出现 .同位素分布宽度和峰位与入射体系密切相关 ,产生碎片的电荷数越接近入射弹核的电荷数 ,则同位素分布的宽度越大 ,峰位偏离β稳定线值越远 ,其同位旋效应越明显 .