|M.Sc Student||Lyadov Yury|
|Subject||Investigation of Native Oxides Reduction from the InAs(100)|
Surface by Thermal Annealing, Molecular Hydrogen
Cleaning and Effect of Applied
Electrical Bias to the InAs Su
|Department||Department of Chemistry||Supervisors||PROF. Alon Hoffman|
|DR. Eliezer Weiss|
In the present work three methods for reduction of native oxides and carbon based compounds from the InAs(100) surface were studied: 1) Thermal Oxide Desorption (TOD); 2) Molecular Hydrogen Cleaning (MHC); 3) Bias Enhanced Molecular Hydrogen Cleaning (BEMHC). Main accent was done on the research of correlation between threshold temperature for reduction of native oxides and magnitude and polarity of the applied electrical bias. The effect of listed methods on the stoichiometry and morphology of the InAs(100) surface was investigated by X-ray photoelectron microscopy (XPS), X-ray induced Auger electron spectroscopy (AES), and atomic force microscopy (AFM).
During TOD experiment the InAs(100) surface was annealed at temperatures between 150˚C and 450˚C in the ultra high vacuum ambient (chamber base pressure 1?10-9 torr). This experiment revealed that surface temperatures above 400˚C are needed in order to initiate reduction of native oxides.
The effect of MHC on reduction of native oxides was studied by annealing of the InAs(100) surface at temperatures up to 260˚C under molecular hydrogen flux with dynamic pressure of 5?10-6 torr. The onset of native oxides reduction from the InAs(100) surface by MHC was detected at surface temperature of 260˚C.
An enhancement of MHC, in terms of decrease in the threshold temperature, was done by application of positive electrical bias to InAs substrate. The BEMHC experiment was carried out on the InAs(100) surface under molecular hydrogen flux with dynamic pressure of 5?10-6 torr and surface temperatures between the room temperature and 180˚C. It has been shown, that threshold temperature decreases proportionally to the square root of magnitude of the applied positive bias. In addition, a retention in the rate of native oxides removal from the InAs(100) surface was achieved by application of negative electrical bias to InAs substrate.
Complementary study of electrical bias effect on reduction of native oxides from the InAs(100) surface was done by application of positive bias to InAs substrate during TOD at temperatures between 160˚C and 450˚C. It was found that biasing of InAs substrate during TOD has no effect on threshold temperature.
Stoichiometric changes in the InAs(100) surface, which were induced by the applied procedures, revealed that arsenic oxides are removed at lower temperatures before indium oxides. Morphological measurements of the treated InAs(100) surfaces have shown slight increase in the surface roughness as a result of applied treatments.