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Hydrogen desorption kinetics from the Si(1-x)Gex(100)-(2x1) surface
E S Tok1, S W Ong, H Chuan Kang
1Department of Materials Science, National University of Singapore, 10 Science Drive 4, Singapore 117543.
The Journal of Chemical Physics
|July 23, 2004
Summary
Germanium atoms influence molecular hydrogen desorption from silicon-germanium surfaces. A low barrier desorption channel from mixed dimers is key, resolving discrepancies in surface coverage measurements.
Area of Science:
- Surface Science
- Materials Science
- Computational Chemistry
Background:
- Understanding hydrogen desorption from semiconductor surfaces is crucial for microelectronics fabrication.
- Silicon-germanium alloys are vital in modern semiconductor devices.
- Accurate modeling of surface reactions is needed to explain experimental observations.
Purpose of the Study:
- To investigate the effect of germanium on hydrogen desorption energetics from Si(1-x)Ge(x) surfaces.
- To elucidate the role of mixed silicon-germanium dimers in desorption processes.
- To reconcile discrepancies between theoretical and experimental surface composition data.
Main Methods:
- Density functional cluster calculations were employed.
- A three-dimer model simulated the Si(1-x)Ge(x)(100)-(2x1) surface.
- Energetics of surface configurations and desorption barriers were computed.
Main Results:
- Two desorption channels exist for mixed dimers, with barriers similar to pure Ge or Si dimers.
- Mixed dimers form preferentially on the surface.
- Germanium in the second layer significantly impacts desorption barriers, while dimers in the first layer have minimal influence.
Conclusions:
- The low barrier desorption channel from mixed dimers is critical for hydrogen desorption from SiGe surfaces.
- This finding helps resolve discrepancies in surface germanium coverage determination.
- The study provides insights into the surface chemistry of SiGe alloys relevant to semiconductor manufacturing.