AVS 45th International Symposium
    Surface Science Division Monday Sessions
       Session SS-MoP

Paper SS-MoP17
Reaction of Atomic Hydrogen and Activated Methane with Si(111) as Precursor for Diamond Nucleation Studied with High Temperature STM

Monday, November 2, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: F. Schaefer, Ruhr-Universitaet Bochum, Germany
Authors: F. Schaefer, Ruhr-Universitaet Bochum, Germany
H. Bethge, Ruhr-Universitaet Bochum, Germany
A. Bianco, Ruhr-Universitaet Bochum, Germany
U.K. Koehler, Ruhr-Universitaet Bochum, Germany
Correspondent: Click to Email
An STM has been designed especially for studies under the extreme conditions of hot-filament-CVD diamond growth. As a first step the etch-attack of atomic hydrogen and the reaction of activated methane with Si(111) has been investigated by in-situ, time resolved STM in the temperature range between 500°C and 800°C. Gas activation was done by the iongetter pump of the UHV system or by hot filaments. The etch-attack of atomic hydrogen on Si(111) starts at step edges and preferential etching along crystallographic directions is found. The etch-rate has been investigated in dependence on hydrogen flux and substrate temperature. Etching is found to be an activated process with an acitvation energy (E=0.8eV) close to the diffusion energy of Si-atoms on Si(111). Activated methane does not react with Si(111) at temperatures below 500°C. At higher temperatures a layer-by-layer consumption of substrate material and the formation of disordered clusters up to 60 Å height can be seen. Two different contributions to the consumption of Si are discussed: formation of SiC and etching due to the hydrogen supplied by the activated methane. The ratio of consumed substrate material to Si incorporated in the clusters is about 1:1, indicating a consumption of Si due to the formation of amorphous SiC clusters. A quantitative analysis of the nucleation behavior has been carried out. Although the clusters are amorphous their density evolution with growth-rate and temperature can be described according to classical rate equation theories. Different activation energies for nucleation for the two activation methods are found and can be assigned to different species responsible for the growth. As a further step to real hot-filament-CVD diamond growth conditions the reaction of activated methane diluted with hydrogen (1%CH@sub 4@/H@sub 2@) has been investigated for pressures up to 1 mbar.