Inspection of free energy functions in gradient crystal plasticity

The dislocation density tensor computed as the cud of plastic distortion is regarded as a new constitutive variable in crystal plasticity. The dependence of the free energy function on the dislocation density tensor is explored starting from a quadratic ansatz. Rank one and logarithmic dependencies are then envisaged based on considerations from the statistical theory of dislocations. The rele- vance of the presented free energy potentials is evaluated from the corresponding analytical solutions of the periodic two-phase laminate problem under shear where one layer is a single crystal material undergoing single slip and the second one remains purely elastic.

Transition Gibbs free energy level cross section and formulation of carrier SRH recombination rate

The transition among multiple charging states of a semiconductor＇s localized intrinsic/impurity defects is considered as phase transitions, and the concept of transition Gibbs free energy level （TGFEL） is proposed. Dependence of the cross section of TGFEL on its charge state is discussed. Introduction of TGFEL to replace acti- vation energy has fundamentally important consequences for semiconductor physics and devices. TGFEL involves entropy. What is to be included and not included in the entropy term consistently for all defect levels is an unre- solved open question, related to correct interpretation of various experimental data associated with various defect levels. This work is a first step towards resolving this question.

室温核辐射CdZnTe像素探测器的研制

采用布里奇曼法生长的CdZnTe（CZT）单晶,制成室温核辐射像素探测器。首先通过红外透过显微（IRTM）成像、电阻率测量以及单元探测器能谱响应测试等手段,综合评定了探测器用CZT晶体的质量,结果表明,晶片富Te相密度为28.43 mm-2且尺寸分布较均匀,电阻率为1010Ω.cm;电子迁移率寿命积为1.07×10-3cm2/V,晶片质量完全达到像素探测器的制作要求。采用光刻及双层胶剥离技术在CZT晶片表面制备出4×4像素Au电极,制备出金属-半导体-金属（MSM）结构像素阵列探测器,并研究了像素探测器的H2O2溶液湿法钝化和低能氧离子轰击干法钝化工艺,钝化后16个像素在100 V偏压下的漏电流为0.79~1.2 nA。室温下测试像素探测器对未经准直的241Am@59.5 keVγ射线的能谱响应,结合Shockley-Ramo理论,分析了不同像素能谱响应的影响规律。