Laser chemistry of dimethylcadmium adsorbed on silicon: 308- versus 222-nm laser excitation

摘要

Abstract: The investigation of UV laser chemistry of dimethylcadmium (DMCd), both adsorbed in UHV on n-type Si(100) with native oxide and in low pressure gas, has been carried out using KrCl and XeCl excimer lasers. The kinetics of the DMCd chemisorption and spontaneous decomposition on silicon as well as the photoprocesses in chemisorbed, physisorbed, and gaseous species induced by the absorption of UV laser radiation by molecules and substrate surface have been studied using mass spectrometry. As the coefficients of the absorption of silicon at the wavelengths of KrCl (222 nm) and XeCl (308 nm) lasers are alike but DMCd only resonantly absorbs the radiation of the KrCl laser, the mechanisms of the action of these lasers on the adlayer are quite different. The KrCl laser induced an efficient DMCd fragmentation and also photoionization of desorbed species, while the photoexcitation of silicon by XeCl laser pulses resulted in desorption of neutral species and some decomposition of the initial molecules. The comparison of DMCd excitation at these wavelengths allows selection of resonance-enhanced effects and determination of the composition of the adlayer as well as the mechanisms of the photoprocesses.!