9:45 AM - 10:00 AM
▼ [19a-H113-4] Scanning Tunneling Microscopic Analysis of Highly Phosphorus-Doped Si(111)-(7x7) Surface
Keywords:Scanning Tunneling Microscopy,Si(111)-(7x7) surface modification
The structure and the applications of Si(111)-(7x7) surface have being investigated extensively due to its notable high stability and large unit cell size. Si(111)-(7x7) surface acts as a natural template to obtain desired self-assembled nanostructures under controlled environment. Highly doped n-type Si has metal like properties which can affect the self-assembled nanostructures on the surface of Si wafer. Highly phosphorus-doped Si(111)-(7x7) surfaces have been investigated by scanning tunneling microscopic techniques (STM). Diffusion doping process was carried out to prepare heavily doped n-type Si(111) wafers and STM measurements were carried out on the doped Si (111)-(7x7) under UHV conditions (~ 1 x 10-8 Pa). Obtained STM image after the reconstruction of highly P-doped Si(111)-(7x7) surface demonstrates that P atoms are favored to occupy faulted half atom positions of the unit cell. Filled-state STM images shows bright maximum spots which indicates the presence of P atoms or effect of those on other Si adatoms in unit cells. Another interesting fact is that these bright spots often appears as triplets on the images. P atoms can occupy rest-atom positions in the faulted half of the unit cell, affecting the electronic states of nearby Si adatoms giving bright triplets. The preferential selection of P atoms in the faulted half of the unit cell may be due to its electronegativity and chemical concept of local softness.