以鈀誘發在Mo(111)表面上非晶鉬的皺化(112)面的大小與其厚度之關係

Abstract

摘要

本研究的主要工作是利用低能電子繞射儀(LEED)與掃描式穿隧顯微鏡(STM)等常用之表面科學方法，來研究鈀(Pd)誘發在Mo(111)表面上非晶鉬的{112}皺化面的大小與其厚度的關係。已知鈀(Pd)覆蓋在鉬(Mo)或鎢(W)的bcc(111)表面上時，升溫會使表面能皺化形成各面方向{112}的金字塔狀。在Mo的(111)面上覆蓋大於1ML的鈀原子，經由約800K的加熱退火後，由STM觀察，發現金字塔的分佈大小不均勻。因此，本實驗利用在Mo基底上於90K的低溫下覆蓋不同厚度的Mo，Mo覆蓋層在90K的低溫下為非結晶狀物質，利用不同厚度的非晶鉬其晶粒邊界(grain boundary)的效應，來控制金字塔形成的大小與均勻度。首先，由LEED觀察皺化面的繞射圖形有無變化；接著，作皺化面之繞射點的亮度分析，求其半寬波高(half-width)來估計金字塔形成的最大寬度；最後，由STM觀察實際空間的分佈情況，並且驗證LEED亮度分析的準確度。

Abstract

Pd-induced (112) facet size affected by the thickness of amorphous Mo layers predeposited on Mo(111) has been observed using a scanning tunneling microscope (STM) and a low energy electron diffractometer (LEED). It has been found that the interaction of Pd ultrathin films with a body centered cubic Mo(111) surface, which is atomically rough and open, causes the Mo(111) substrate itself to reconstruct to form microscopic pyramids that expose facets oriented along {112} directions. The distribution of Pd-covered Mo(111) surface is not uniform upon annealing to 800 K. Mo coverage on Mo(111) at low temperature about 90 K is amorphous detected by LEED. To control the size of pyramids we use the effect of grain boundary at different thickness of amorphous. Based on LEED measurements and STM works. We can estimate the diameter of pyramids by measuring the ratio of half-width of spot profile of facets on the LEED pattern and identified by STM measurements.