Investigation on heteroepitaxy of I-VII compounds and their surface propeties

对目前的研究成果进行了总结。(1)卤化亚铜的异质外延及其表面性质卤化亚铜CuX （Ib-VII化合物）属于具有闪锌矿晶体结构的四面体配位二元化合物，通过IV、III-V、II-VI和I-VII化合物形成等电子序列的端点。从这个意义上说，CuX位于共价材料和离子材料之间。我们研究了CuCl、cur和CuI在不同晶面的GaAs和Si衬底上的生长，并阐明了其生长性质。晶体表面的原子结构就像Si和GaAs一样不同。然而，CuX表面的悬空键的活性低于Si和GaAs。(2)极性NaCl（111）表面的生长岩盐晶体的a（111）表面是由阳离子或阴离子组成的极性表面，预计会表现出非常特殊的表面性质。到目前为止，这种表面只能通过氧化金属表面来获得，并且对于具有…多层的薄膜是稳定的。利用分子束外延技术，生长出NaCl/CuCl/CuBr/GaAs（111）等复杂的纳米结构，稳定了平坦的NaCl（111）表面。（111）表面存在约半层铜原子，这可能抵消了偶极子层沿[111]方向积聚所产生的宏观电场。本研究结果为金属氧化物等其他材料的极性表面的形成开辟了一条道路，这可能在催化、低维物理等领域实现一种新的表面。(3)卤化物超薄膜的原位光学测量我们前期的实验将卤化物（Ia-VII化合物）在国外卤化物衬底上的生长方式分为三种。这些信息是通过精确的RHEED测量获得的。我们设计了一种新的实验装置，由一个生长室和一个光学室组成，可以在特高压条件下对生长膜进行光吸收测量，而不破坏真空。使用该系统可以测量纳米厚度的超薄薄膜。我们研究了在外源卤化物衬底上异质外延生长的卤化物薄膜的激子能。根据峰值能量位移，我们可以计算出界面处的应变，这与RHEED测量值吻合得很好。少

The results of the present research are summarized.(1)Heteroepitaxy of cuprous halide and their surface propertiesCuprous halide CuX (Ib-VII compounds) belongs to tetrahedrally coordinated binary compounds with zinc blende crystal structure and forms the end points of isoelectronic sequences through IV,III-V,II-VI and I-VII compounds. In this sense CuX is positioned between covalent and ionic materials. We have examined the growth of CuCl, CuBr and CuI on GaAs and Si substrates with various crystal faces and clarified the growth nature. The surface atomic structure differs between crystal faces just like Si and GaAs. However, the dangling bond on CuX surfaces is less active than that of Si and GaAs.(2)Growth of a polar NaCl (111) surfaceA (111) surface of rocksalt crystals is a polar surface consisting of either cations or anions and is expected to show very peculiar surface properties. Up to now such a surface was obtained only by oxidizing a metal surface and was stable for films wit … More h several layrs. We have stabilized a flat NaCl (111) surface by growing such complicated haterostructure as NaCl/CuCl/CuBr/GaAs (111) with use of molecular beam epitaxy. There exist about half layr copper atoms on the (111) surface, which might cancel the macroscopic electric field arising from accumulation of dipole layrs along the [111] direction. The present result opens a way to form a polar surface of another materials such as metal oxides, which might achieve a novel surface in the field of catalysis, low dimensional physics and so on.(3)In-situ optical measurement of alkali halide ultrathin filmsGrowth mode of alkali halide (Ia-VII compounds) on foreign alkali halide substrates has been classified to three types by our previous experiments. That information was obtained by presise RHEED measurement. We have devised a new experimental apparatus consisting of a growth chamber and an optics chamber, where optical absorption measurement could be done in UHV condition for the grown film without breaking vacuum. Use of this system enables the measurement of an ultrathin film with nm thickness. We have investigated the exciton energy for alkali halide thin films, which were grown heteroepitaxially on foreign alkali halide substrates. From the peak energy shift, we could calculate the strain at the interface, which agrees well with the value estimated from the RHEED measurement. Less