Time-Resolved Reflectivity Measurement of the Pressure-Enhanced Crystallization Rate of Amorphous Si in a Diamond Anvil
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TIME-RESOLVED REFLECTIVITY MEASUREMENT OF THE PRESSURE-ENHANCED CRYSTALLIZATION RATE OF AMORPHOUS Si IN A DIAMOND ANVIL CELL. G.Q. LU*, E. NYGREN*, M.J. AZIZ**a), D. TURNBULL*, AND C.W. WHITE** *Division of Applied Sciences, Harvard University, Cambridge MA 02138
**Solid State Division, Oak Ridge National Laboratory, Oak Ridge TN 37831. ABSTRACT We have measured the pressure dependence of the solid phase epitaxial growth (SPEG) rate of self-implanted Si (100) by using the in-situ time-resolved reflectivity technique [1] in a hightemperature and high-pressure diamond anvil cell (DAC). With fluid argon as the pressure transmission medium, a clean and perfectly hydrostatic pressure environment is achieved around the sample. The external heating geometry employed in the DAC provides a uniform temperature across the sample. At temperatures in the range of 530 - 550 °C and pressure up to 50 kbars (5 GPa), the growth rate is enhanced by up to a factor of ten over that at 1 atmosphere pressure. The results are characterized by a negative activation volume of approximately -3.0 cm 3/mole (-27% of the atomic volume). These preliminary results show a significantly weaker pressure dependence than3 does the previous work of Nygren et al. [2], who found an activation volume of -8.7 cm /mole. The implications of these results for the nature of the defect responsible for thermal SPEG and irradiation enhanced SPEG is discussed. INTRODUCTION The solid phase epitaxial growth (SPEG) of amorphous silicon produced by ion implantation has been extensively studied at ambient pressure and its kinetics are fairly well established [1]. In addition, there are two published works on the pressure dependence of SPEG in silicon. Nygren et al. [2] measured the SPEG rate of self-implanted silicon at pressures up to 20 kbars (2 Gpa) in a piston-cylinder pressure apparatus with solid NaCI as a pressure transmission medium. They found a pressure-enhanced SPEG rate, characterized by a negative activation volume of -70% of the atomic volume, similar to the negative activation volume found by Fratello et al. [3] for the growth of quartz from fused silica. Vasin et al. [4] implanted Si (111) with an unreported species and observed SPEG at low pressures (0-300 bars) in a gas apparatus. They reported a very slight retardation in the rate, i.e., a positive activation volume. In both of the high pressure works above, the high-pressure annealing treatment was performed separately from the determination of growth velocity. In the former [2], the growth velocity was measured using Rutherford backscattering and channeling techniques, while in the latter [4], the growth velocity was obtained from sheet resistivity measurements. Recently, Licoppe et al. [5] used the in situ time resolved reflectivity (TRR) technique, developed by Olson et al. [6], to observe a pressure-enhanced SPEG rate of GaAs in a gas apparatus at pressures of up to 5 kbars. The in situ technique has several advantages over the post-mortem measurements performed previously. Instantaneous measur
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