Appararus of Reflection High Energy Electron Diffraction-Physical Proparty Measurments for Grown Surface Atomic Layr at Low temperature

我们构建了一个可以冷却到低温的样品保持器，可以测量表面原子层生长过程中的物理成分。样品保持器与现有的RHEED仪器相结合。利用该仪器测量了RHEED强度振荡、表面元素深度分布和表面电导，发现影响外延生长的重要因素是衬底温度、沉积速率和原子供应方式等，从而系统地改变了在Si(111)表面沉积银和铜的表面温度和沉积速率。结果，我们得到了以下结果。(1)当表面温度降低到160K时，观察到许多RHEED强度振荡(20-46个峰)，与室温下相比；(2)较高的沉积速率为20ml/min。实验结果表明，表面温度和沉积速率的变化会引起扩散长度的变化。考虑到…当Au沉积在Si(111)-Roo&lt；3&gt；*Roo&lt；3&gt；-Ag表面时，我们发现了新的生长模式“替代原子生长模式”和“浮动原子生长模式”。为了研究结构的稳定性，我们将这些表面加热到更高的温度。结果表明，Au-Ag合金的表面结构在300ﾟC左右是稳定的，但在400ﾟC以上是不稳定的，并向合金转变，这与Au-Ag合金原有的相图并不矛盾。因此，我们的结果意味着必须重新考察Au-Ag合金的稳定性，并考虑表面效应。在Si(111)-Roo&lt；3&gt；*Roo&lt；3&gt；-Ag表面沉积银的过程中，我们发现了新的表面结构Roo&lt；21&gt；*Roo&lt；21&gt；-Ag和6*6-Ag。这些结构在外延过程中表现出不同的表面电导及其行为。这意味着表面电导测量为表面结构研究提供了非常重要的信息。较少

We constructed a sample holder which can cool to low temperature and measure physical proparties during growth of surface atomic layrs. The sample holder was combined with an exsisting RHEED apparatus. Using the instrument, we measured RHEED intensity oscillations, depth distributions of surface elements and surface conductance.The important factors to govern epitaxy are substrate temperature, deposition rate and atom supplying methods etc. Thus, we changed systematically surface temperatures and deposition rates, during Ag and Cu deposition on Si (111) surface. As a result, we obtained following results. (1) When surface temeperature was decreased to 160 K,many RHEED intensity oscillations (20-46 peaks) were observed compered with at room temperature, (2) For higher deposition rate of 20ML/min. many RHEED oscillation peaks were observed.(3) These experimental results show that the change of surface temperatures and deposition rates induce the change of diffusion length. Considering th … More e effects, we proposed a new growth modes.When Au was deposited on a Si (111) -ROO<3>*ROO<3>-Ag surface, we found new growth modes "substitution atom growth mode" and "floating atom growth modes". To study the stability of the structures, we heated these surface to higher temperatures. As a result, these surface structures were stable under about 300ﾟC.However, they were unstable and change to an alloy above 400ﾟC.These results are not contradict to the old phase diagram of Au-Ag alloy. Thus, our results implying that the stability of the Au-Ag alloy must be reexamine considering the surface effects. This is a new essential problem on the stability for Au-Ag alloy.During Ag deposition on the Si (111) -ROO<3>*ROO<3>-Ag surface, we found new surface structures, ROO<21>*ROO<21>-Ag and 6*6-Ag. These structures showed diffrent surface conductance and their behaviors during epitaxy. This means that the surface conductance measurements gives very important infomations for surface structure study. Less