Dynamical Observations of MBE Grown Thin Films by Ultrahigh Vacuum In-situ Electron Microscopy

利用超高真空原位透射电子显微镜（UHV in-situ TEM）和UHV原位反射电子显微镜（UHV in-situ reflection electron microscopy，REM）研究了InSb{111}的同质外延生长过程和表面重构。通过对InSb（111）B表面的TEN观察和对重构InSb（111）A和重构InSb（111）B表面的REM观察，得到以下结果：（1）当Sb_4和In_1（1：1）的入射通量照射到InSb（111）B衬底上时，各自的分子形成同质外延生长的InSb膜，留下过量的分子Sb^*，它对InSb膜的形成没有贡献。结果表明，Sb^* 分子的凝聚存在一个临界温度（T_h）.当温度低于T_h时，Sb的表面浓度（n_<sb*>）高于临界浓度（n^c_），从而使（InSb+Sb）两相以多晶状态生长。当n_<sb*>小于n^c_时，InSb薄膜以2 × 2重构面生长。该临界温度被定义为同质外延温度。对T_h的定量解释进行了讨论。(2)通过使用UHV原位REM，首次观察到InSb（111）B和InSb（111）A的表面重构的变化：在420 ℃下，（111）B从2x2-Sb到3xl-In结构，在300 ℃下，（111）A从2x 6-Sb到2x2-In结构。在420 ℃和450 ℃时，在InSb（111）B和（111）A表面上形成的颗粒强烈影响了InSb（111）表面的结构转变。此外，在InSb（111）B-3 × 1-In衬底上形成的颗粒在扩展InSb（111）B的同质外延生长期间出现的（111）B-3 × 3-In区域中起重要作用。

We have studied homoepitaxial growth processes and surface reconstruction of InSb{111} using ultrahigh vacuum in-situ transmission electron microscopy (UHV in-situ TEM) combined with UHV in-situ reflection electron microscopy (REM). From the TEN observations for InSb(111)B and the REM observations for both reconstructed InSb(111)A and reconstructed InSb(111)B surfaces, the following results were obtained:(1) When the incident fluxes(1:1) of Sb_4 and In_1 are impinged onto the InSb(111)B substrate, the respective molecules form homoepitaxially grown InSb films, leaving an excess molecule Sb^* which does not contribute to the formation of the InSb films. As a result, there exists a critical temperature(T_h) for the condensation of Sb^* molecules. Below T_h, the surface concentration of Sb^*(n_<sb*>) becomes higher than a critical concentration for the condensation (n^c_), SO that two phases (InSb+Sb) grow in a polycrystalline state. However, above T_h as n_<sb*> becomes lower than n^c_, InSb films grow with the 2x2 reconstructed surfaces. This critical temperature is defined as a homoepitaxial temperature. Quantitative interpretations of T_h were discussed.(2) By using UHV in-situ REM, changes in the surface reconstructions of InSb(111)B and InSb(111) A were for the first time observed: for (111)B from the 2x2-Sb to the 3xl-In structure at 420ﾟC and for (111)A from the 2x6-Sb to the 2x2-In structure at 300ﾟC. The particles formed on the InSb(111)B and (111)A surface at 420ﾟC and 450ﾟC respectively, intensely affected the structural transformation in the InSb(111) surface. Also, the particle formed on the InSb(111)B-3xl-In substrate played an important role in spreading the (111)B-3x3-In region which appeared during the homoepitaxial growth of InSb(111)B.