A study on influences of hydrogen on growth mechanisms of thin films by electron energy loss spectroscopy

我们利用高分辨电子能量损失谱和反射高能电子衍射研究了薄膜的生长过程，如外延和氧化。尤其是氢，因为它在生长过程中起着重要的作用而受到人们的关注。因此，我们研究了氢对Si_2 H_6外延生长Ge/Si的影响，得到的主要结果如下：（1）在Si（100）面上生长时，生长速率的活化能与氢从Si（100）面脱附的活化能一致。这一结果表明，硅的生长受到氢的脱附的限制。已经发现，单独添加的过量氢原子增加了Si表面上的氢覆盖率并降低了生长速率，这表明使用氢控制膜生长的可能性。2）在Ge 2. 5 ML/Si（100）衬底上生长Si时，观察到Ge原子的表面偏聚现象。从Ge偏析的衰减长度的评估，过量的氢是有效的，阻碍偏析。然而，过量的氢原子加速了岛状生长。这些事实表明，氢原子严重影响硅的生长机制。

We have investigated growth processes of thin films, such as epitaxy and oxidation, by high-resolution electron energy loss spectroscopy and reflection high-energy electron diffraction. Especially, hydrogen has been focused on our attention because it plays an important role of the growth processes. Therefore, we have studied influences of hydrogen on Ge/Si epitaxial growth using Si_2H_6 and obtained the main results as follows :1) In the case of Si growth on Si(100) surfaces at temperatures below 550ﾟC、the activation energy of growth rate is in agreement with that of desorption of hydrogen from Si(100) surfaces. This result indicates that the Si growth is limited by the desorption of hydrogen. It has been found that excess hydrogen atoms added separately increase the hydrogen coverage on the Si surface and lower the growth rate, which suggests the possibility of a control of film growth using hydrogen. Moreover, it has been clarified that the adsorbed hydrogen atoms hinder the surface migration of precursors such as Si atoms and Si hydride species.2) In the case of Si growth on Ge2.5ML/Si(100) substrates, the surface segregation of Ge atoms is observed. From the evaluation of the decay length for Ge segregation, excess hydrogen is effective for hindering the segregation. However, the excess hydrogen atoms accelerate the islanding growth. These facts indicate that hydrogen atoms seriously influence the mechanism of Si growth.