UV Laser-Induced Interaction of C12 with GaAs 110,

We have studied the UV laser-induced interaction of molecular chlorine with a GaAs110 surface under ultra-high vacuum UHV conditions. Unlike previous studies of this system, we concentrated on well-defined surfaces, known coverages and low laser fluences. The experimental setup included a low energy electron diffraction apparatus, an Auger electron spectrometer and a differentially pumped mass spectrometer for thermal desorption spectra TDS and time-of-flight TOF measurements. Without illumination, chlorine was found to adsorb molecularly and dissociatively on n-GaAs110 surfaces at 85 K. The laser experiments were done with a 193- and 351-nm excimer laser, at fluences below 5 mJcm2. Illumination of a molecular chlorine-covered surface at 85 K with 193 nm excimer laser radiation led to the formation of AsCI3, which desorbed at 180 K. Illumination with 351-nm radiation resulted in the formation of smaller amounts of arsenic chloride on the surface.