Papers by Author: Tim J. Bullough

Abstract: It is shown that laser-assisted growth of Al films using the CBE method results in remarkable surface composition transformations. The values of the laser reflectivity are slightly correlated with the composition or with the metal thickness. The energy characteristics of the reactions guide the reflectivity changes, together with thickness changes. It was shown that the composition within the laser spot is different from that outside the laser spot due to the destruction of compounds under laser exposure.

Abstract: GaAs surface composition changes occurring during Al film growth using the CBE method with laser assistance were investigated in situ by means of laser reflectivity. The results were compared with data on precise chemical analyses and X-ray microanalyses carried out after film deposition. It was found that the peculiarity of film formation depended upon the laser power. Physicochemical interactions of the Ga atoms from the GaAs surface, with atoms and molecules from the surrounding media, are determinative reactions at a laser power of 2W. At a power of 0.02W, the laser reflectivity changes were mainly due to reactions with Al. The appearance of “free” Ga and As in the region outside of the laser spot indicated the destruction of GaAs islands weakly connected with the GaAs surface.

Abstract: In this work microrelief transformation of the (001) GaAs surface due to thin Al film deposition by means of the CBE method has been observed. The growth process was monitored insitu using laser reflectometry. Investigations of samples formed, carried out using TEM-microscopy, show that one of the basic causes of the microrelief transformation is the laser assistance of metal growth. A laser with a low power is used in this work for Al layer composite control in CBE. It was found that, in spite of using a laser having a low power, it is possible to stimulate and guide the complex physical and chemical reactions between deposited Al atoms and the GaAs near-surface layer. It has been found that metal film growth with laser assistance is a non-equilibrium process. The shapes and dimensions of the grown islands depend upon the laser power.