Single and multicomponent mixed layers of silsesquioxane clusters on freshly evaporated gold surfaces have been investigated by X-ray photoelectron spectroscopy and reflection-absorption infrared spectroscopy. Approximately 5-10% of the cluster layers (e.g., H8Si8O12 and H10Si10O15) on gold desorb upon evacuation of the adsorbate from the reaction chamber. These open adsorption sites are an avenue for cluster displacement reactions that yield mixed monolayers (e.g., H8Si8O12/D8Si8O12 and H8Si8O12/C6H13-H7Si8O12) of several compositions on gold. This dynamic behavior is not observed for the C6H13-H7Si8O12 cluster layer on gold. Rather, this molecule acts as a poison to these reported displacement processes at the gold surface.

A cw supersonic Cl2 molecular beam coupled with an angle‐resolved time‐of‐flight (TOF) technique has been used to investigate the laser‐enhanced surface reaction of GaAs(100) with chlorine. The mass and velocity distributions of the major reaction products under 1064 nm laser irradiation have been measured as a function of laser fluence, detection angle, surface temperature and normal component of the translational energy of the incident chlorine molecules. It has been found that increasing both laser fluence and the translational energy of incident chlorine molecules markedly enhance mis surface reaction. The measured flux angular distributions of major reaction products can be fit satisfactorily with a bi‐cosine function. Measurements of the mass and angular distributions of reaction products by a modulated molecular beam mass spectrometry show that the surface temperature effect is obvious for the Cl2/GaAs(100) “dark” thermal reaction. A direct activated dissociative chemisorption is proposed for the mechanism of Cl2 chemisorption on the GaAs(100) surface.

Laser-assisted chemical etching reactions of Cl2 with semiconductor surfaces are investigated using a cw supersonic Cl2 molecular beam coupled with an angle-resolved time-of-flight (TOF) technique. TOF spectra of reaction products are measured as a function of the detection angle. laser fluence and normal component of incident molecules' translational energy. Our results show that the differences in the above etching reactions at 355 and 1064 nm radiations can be explained by the different mechanisms of laser-stimulated desorption process. The flux of the reaction products linearly increases with increasing the nonnal component of the incident translational energy of Cl2 molecules. It implies that the mechanism of Cl2 chemisorption on the surfaces might be a direct translationally activated dissociative chemisorption. SPIE Vol. 2125 /329 / LB Downloaded From: http://proceedings.spiedigitallibrary.org/ on 07/03/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx