光生物传感技术与癌症易感性的检出

介绍了检测肿瘤易感个体的新方法-光生物传感技术。由此可作出细胞癌变的易感个体的预警,并给出针对性的预防措施。

一种纳米分辨率近场光学显微镜-光子扫描隧道显微镜

报导了一台光子扫描隧道显微镜。论述了原理，结构，光纤探针制造，信号放大以及调试中解决的几个技术问题等。图像的横向分辨率优于10nm,纵向分辨率约1nm，扫描范围10μm×10μm。还观察了云母、高密度乙烯HDPE高取向薄膜等透明材料及铌酸锂(LiNbO_3+T_i)波导的电光效应等。

Type I-type II transition of self-assembled In0.55Al0.45As/Al0.5Ga0.5As quantum dots

The photoluminescence (PL) of In0.55Al0.45As/Al0.5Ga0.5As self-assembled quantum dots has been measured at 15 and 80 K under hydrostatic pressure. The lateral size of the dots ranges from 7 to 62 nm. The emissions from the dots with 26, 52 and 62 nm size have a blue shift under pressure, indicating that these quantum dots have the normal type-I structure with lowest conduction band at the Gamma -valley. However, the PL peak of dots with 7 nm diameter moves to lower energy with increasing pressure. It is a typical character for the X-related transition. Then these small dots have a type-II structure with the X-valley as the lowest conduction level. An envelope-function calculation confirms that the Gamma -like exciton transition energy will rise above the X-like transition energy in the In0.55Al0.45As/Al0.5Ga0.5As structure if the dot size is small enough.

Self-sustained oscillations caused by magnetic field in a weakly-coupled GaAs/AlAs superlattice

We have investigated the influence of transverse magnetic field B up to 14 T at 1.6 K on the tunneling processes of electric field domains in doped weakly coupled GaAs/AlAs superlattices. Three regimes, i.e, stable field domains, current self-sustained oscillations and averaged field distribution are successively observed with increasing B. The mechanisms of switching-over among these regimes are due to B-induced modification of the dependence of the effective electron drift velocity on electric field. The simulated calculation gives a good agreement with the observed experimental results. (C) 2000 Published by Elsevier Science B.V. All rights reserved.