LASER-INDUCED EMISSION OF ATOMS AND ELECTRONS FROM DEPOSITED SI ATOMSON THE SI(100) 2X1 SURFACE

We have measured the emissions of electrons and Si atoms induced by la ser irradiation on a Si(100) 2x1 surface with Si atoms deposited in a coverage range between 4.6x10(-4) and 1.67x10(-1) monolayers (ML) at r oom temperature. Two types of configurations, referred to as configura tion R and S, of deposited atoms are differentiated. The atom emission from configuration R occurs above a laser fluence of 310 mJ/cm(2) for 28-ns laser pulses with a photon energy of 2.48 eV, while that from c onfiguration S occurs only above a fluence of 540 mJ/cm(2). The electr on emission from configuration R gives rise to a peak at a binding ene rgy of 5.0 eV, while that from configuration S gives rise to a peak at 4.85 eV. Component R grows in proportion to the Si coverage in a cove rage range below 4.0x10(-2) ML and then saturates, while component S g rows in proportion to the square of the coverage at the initial stage before saturation occurs. The yield of atom emitted from configuration R is reduced by continued irradiation with laser pulses, while that f rom configuration S is reduced only for small coverages. Based on the number of atoms emitted by laser irradiation, the concentrations of co nfiguration R and S after saturation were estimated to be 1.2x10(-4) M L and 1.94x10(-3) ML, respectively. It is suggested that configuration R is an adatom weakly bonded by the step edge or a defect and configu ration S is an ad-dimer.