SSL Seminar Series 2003 No.4

Combined talks (two speakers)

Date: November 27 (Thursday), 2003
Time: 5:00-6:00pm
Venue: Physics Resource Room (Blk S13 # 02-16)

Speaker I: Mr. Md. Abdul Kader Zilani (PhD Candidate)
Title: STM study of C60 molecules on Co/Si(111)
Molecular devices with novel quantum properties are potentially the building blocks of future nanoscale electronic devices.
Fullerenes represent a unique structure of cage molecules with a wide range of sizes, shapes and molecular weights.
Since C60 has a unique icosahedral symmetry, these molecules provide a prototype system for spectroscopy, optics, and other basic science investigations.
A number of experiments have been done using UHV-STM to investigate the properties of fullerene molecules deposited on Si(111) and Si(100) surfaces.
In this paper we will present an STM, LEED and XPS study of the dynamic behavior of C60 molecular on cobalt-silicide
surface formed by deposed Co on clean Si (111) STM shows alignment of C60 molecules along a specific direction
on this surface for sub monolayer coverage of C60 on the ultrathin cobalt-silicide surface. It was indicated that the interaction of C60 on CoSi surface
depending on the annealing temperatures and CoSi film thickness. On contrary to Si(111)7¡Á7 surface, C60 does not self-assemble due to strong covalent bonds formed, and we can conclude that the interaction of C60 with cobalt-silicide is weak compared to Si(111) 7¡Á7.

Speaker II: Mr. Mayandi Jeyanthinath (MSc student)
Title: Evolution and ordering of multi-layer Ge quantum dots on Si(001)
Scanning tunneling microscope has been used to study multi-layer Ge/Si(001) islands grown by physical vapor deposition at about 550 ¡ãC.
It is well-known that the first-layer Ge islands are huts- and pyramidal-like, bounded by {105} facets.
Their sizes range from 10 to 15 nm while its heights are in the order of 2 nm in average.
We observed that the huts and pyramids begin to merge or break during the deposition of Si buffer layer.
From the qualitative analysis, we suggest a mechanism for occurrence of such growth process, which could lead to the ordering and uniformity of dots.
The merging and breaking (splitting) of dots can be explained as a consequence of strain due to lattice mismatch,
intermixing of Si and Ge to form solid solution. Apart from the mechanism of splitting and merging,
the surface corrugation of Si spacer layer has significant role for the nucleation in the growth of subsequent quantum dot layers.