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A theoretical study of laser-induced chemical vapor deposition
A574 Surface Science 257 (1991) 389-401 North-Holland
389
Computation of the time dependence of dynamic and kinematic RHEED intensities for growing surfaces M.G. Knibb Department of Physics, University of Leicester, University Road, Leicester, LE1 7RH, UK Received 28 February 1991; accepted for publication 17 May 1991 The time dependence of the dynamic (i.e., multiple scattering) and kinematic (i.e., single scattering) RHEED intensities is computed for a model of a growing GaAs(001) surface. The surface was constructed using Monte Carlo simulation on a 7 × 7 lattice. Two incident beam angles were used. one corresponding to an out of phase condition for monolayers and the other corresponding to an out-of-phase condition for bilayers. For the dynamic intensities for these two angles completion of bilayers occurs at peaks of the specular beam intensity. To calculate kinematic intensities a model is developed to include the effects of refraction and damping in the 0th order wavefunctions. It is shown that kinematic intensities for the specular and a few other beams at the out-of-phase condition for bitayers agree with the dynamic results. For the remaining beams the kinematic results are very different from the dynamic results. At the monolayer out-of-phase condition kinematic intensities do not agree with the dynamic intensities for any beam. Some comments are made about the procedure used to include refraction and damping and the implications of the results are briefly discussed.
Surface Science 257 (1991) 402-416 North-Holland
A theoretical study of laser-induced chemical vapor deposition Joseph Bloch, Yehuda Zeiri Department of Physics, Nuclear Research Center - Negec, P.O. Box 9001. Beer-Sheva, Israel
Robert R. Lucchese Department of Chemistry, Texas A & M University, College Station, TX 77843, USA Received 19 November 1990; accepted for publication 3 May 1991 The laser-induced chemical vapor deposition process has been studied using a Monte Carlo procedure. First the action of the laser beam is assumed to induce the gas-phase decomposition of a parent organometallic molecule. It was then assumed that pyrolytic decomposition of adsorbed species can be neglected. The goal of the simulations was to establish the relationship between the morphology of the deposited layer as well as the deposition rate and various characteristics of the system. In particular the dependence on buffer gas pressure, beam intensity and nature (continuous and pulsed) and beam shape were examined. It was found that when a CW beam is used "volcano"-shape deposited layers are obtained due to a competition between the diffusion of parent organometallic molecules back into the irradiated zone and the rate of photodissoeiation fragments production. In contrast, Gaussian-shape deposited layers were obtained for a pulsed beam. In addition, the deposition rate was found to exhibit a strong dependence on the total pressure in the system.
Surface Science 257 (1991) 417-426 North-Holland
417
Kinetic lattice gas model: a systematic closure approximation A. Wierzbicki and H.J. Kreuzer Department of Physics, Dalhousie University, Halifax, NS, Canada B3H 3J5 Received 5 February 1991; accepted for publication 8 May 1991 A systematic closure approximation for the kinetic lattice gas model is formulated that allows one to truncate the hierarchy of equations of motion for correlation functions at any level. In equilibrium, the quasi-chemical approximation and an improved version of Hill's approximation are recovered at the two lowest levels. Implications for thermal desorption in systems with slow and fast diffusion are studied for a square lattice with nearest-neighbor repulsive interactions.
389
Computation of the time dependence of dynamic and kinematic RHEED intensities for growing surfaces M.G. Knibb Department of Physics, University of Leicester, University Road, Leicester, LE1 7RH, UK Received 28 February 1991; accepted for publication 17 May 1991 The time dependence of the dynamic (i.e., multiple scattering) and kinematic (i.e., single scattering) RHEED intensities is computed for a model of a growing GaAs(001) surface. The surface was constructed using Monte Carlo simulation on a 7 × 7 lattice. Two incident beam angles were used. one corresponding to an out of phase condition for monolayers and the other corresponding to an out-of-phase condition for bilayers. For the dynamic intensities for these two angles completion of bilayers occurs at peaks of the specular beam intensity. To calculate kinematic intensities a model is developed to include the effects of refraction and damping in the 0th order wavefunctions. It is shown that kinematic intensities for the specular and a few other beams at the out-of-phase condition for bitayers agree with the dynamic results. For the remaining beams the kinematic results are very different from the dynamic results. At the monolayer out-of-phase condition kinematic intensities do not agree with the dynamic intensities for any beam. Some comments are made about the procedure used to include refraction and damping and the implications of the results are briefly discussed.
Surface Science 257 (1991) 402-416 North-Holland
A theoretical study of laser-induced chemical vapor deposition Joseph Bloch, Yehuda Zeiri Department of Physics, Nuclear Research Center - Negec, P.O. Box 9001. Beer-Sheva, Israel
Robert R. Lucchese Department of Chemistry, Texas A & M University, College Station, TX 77843, USA Received 19 November 1990; accepted for publication 3 May 1991 The laser-induced chemical vapor deposition process has been studied using a Monte Carlo procedure. First the action of the laser beam is assumed to induce the gas-phase decomposition of a parent organometallic molecule. It was then assumed that pyrolytic decomposition of adsorbed species can be neglected. The goal of the simulations was to establish the relationship between the morphology of the deposited layer as well as the deposition rate and various characteristics of the system. In particular the dependence on buffer gas pressure, beam intensity and nature (continuous and pulsed) and beam shape were examined. It was found that when a CW beam is used "volcano"-shape deposited layers are obtained due to a competition between the diffusion of parent organometallic molecules back into the irradiated zone and the rate of photodissoeiation fragments production. In contrast, Gaussian-shape deposited layers were obtained for a pulsed beam. In addition, the deposition rate was found to exhibit a strong dependence on the total pressure in the system.
Surface Science 257 (1991) 417-426 North-Holland
417
Kinetic lattice gas model: a systematic closure approximation A. Wierzbicki and H.J. Kreuzer Department of Physics, Dalhousie University, Halifax, NS, Canada B3H 3J5 Received 5 February 1991; accepted for publication 8 May 1991 A systematic closure approximation for the kinetic lattice gas model is formulated that allows one to truncate the hierarchy of equations of motion for correlation functions at any level. In equilibrium, the quasi-chemical approximation and an improved version of Hill's approximation are recovered at the two lowest levels. Implications for thermal desorption in systems with slow and fast diffusion are studied for a square lattice with nearest-neighbor repulsive interactions.