Quantum Well Effects in Ionic Insulators and Metals.

自1986年发现KBr激子带的量子尺寸效应对KCl-KBr交替多层结构吸收光谱的影响后，我们主要研究了几种碱金属卤化物中的量子阱激子，积累了大量的知识。在KCl-KBr或RbCl-xBr多层结构的吸收光谱上，由于量子限制引起的激子动力学的增加和界面混合物的形成引起的阱中带隙的增加，使得出现在最低能量处的由KBr阱引起的激子带发生蓝移。而激子波函数的限制甚至在宽为激子玻尔半径的10倍的阱中也有效地发生，并且似乎使激子带的上升略微陡峭.在未退火的多层膜中，层-层界面混合对蓝移的影响是显著的，在适当的温度下逐层热退火可以减小层-层界面混合的影响，并且在退火的RbCl-KBr多层膜中实现了无界面失配和无界面混合的结构。界面混合物的形成强烈地依赖于退火温度和蒸发速度，目前认为温度180 ℃-200 ℃，蒸发速度小于1A/s是有利的，同时也揭示了，如果层与衬底晶体之间的晶格常数相差较大，在小于100埃的非常薄的膜的情况下，界面失配效应是重要的。3.利用该基金刚刚建成的实验室将用于研究近几年来薄膜的热退火条件和蒸发速度。未来

After discovery of the quantum size effect in the KBr exciton band on the absorption spectra of alternate KCI-KBr multilayer structure in 1986, we have mainly investigated the quantum well excitons in several alkali halides and accumulated lots of knowledges on them. These knowledges are briefly explained as the follows.The exciton band due to the well (KBr) which appears at the lowest energy on the absorption spectra of KCI-KBr or RbCl-xBr multilayer structures exhibits a blueshift in affecting with two effects, namely an increase of the exciton kinetic due to quantum confinement and an increase of band gap in the well due to interface mixture formation. Whereas the confinement of exciton wave function is effectively occurred even in the well with width wider by ten times of exciton Bohr radius and seems to make the rise of exciton band steeper appreciably.The influence of the layer-layer interface mixture to the blueshift which is remarkable in the noannealed multilayer can be decreased by thermal annealing at appropriate temperature for layer by layer, and an interface mismatch free and interface mixture free structure is realized in annealed RbCl-KBr multilayer. The.interface mixture formation strongly depends on annealing temperature and evaporation, speed, and at the present, it is considered that the temperature 180ﾟ-200ﾟ C and the speed less than 1A^^ﾟ/sec are favorable.It is also revealed that, if.there is a large difference of lattice constant between the layer and the substrate crystal, the interface mismatch effect is important in the case of very thin film less than 100A^^ﾟ.The experimental chamber which is just constructed by the grant will be worked to research the conditions of the thermal annealing and the evaporation speed of thin layers in near future.