Effects of convection during the physical vapor transport process: application of laser Doppler velocimetry

Abstract

Experimental studies have been conducted on the effects of convection in the physical vapor transport (PVT) process of Hg 2Cl 2 using a laser Doppler velocimetry (LDV) technique to make in situ velocity measurements of the vapor phase in closed ampoules. The experiments are performed in closed cylindrical ampoules with an aspect ratio (diameter-to-height) of 0.12 in a two-zone furnace. The experimental data obtained indicate that the local velocity profiles of Hg 2Cl 2 vapor measured at a fixed location are asymmetrical and have a cellular flow pattern, which provides evidence of convection. The magnitude of the axial velocity is 0–4 cm/s.