Heat Transfer and Temperature Oscillations in Chemical Vapor Transport Crystal Growth I,
UTAH UNIV SALT LAKE CITY DEPT OF PHYSICS
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It is shown that the temperature profile inside a closed CVT ampoule can deviate greatly from that of its external heat source. This deviation is discussed in terms of the optical and convective properties of the system. Chemical convective instability can result in temperature oscillations of up to plus or minus 25C under typical growth conditions. Depending on the relative molecular weights of the reactants and products involved, CCI can occur in temperature gradients which are either parallel or antiparallel to gravity. This is demonstrated with the transport gases TeCl4 and I2 both of which thermally dissociate and discussed for ReO3 transport with I2, for which temperature instabilities had been observed earlier.