A noninvasive laser ultrasonic method has been used to investigate the melt
ing and solidification of a (Cd,Zn)Te alloy during vertical Bridgman growth
. A single zone vertical Bridgman furnace was integrated with a laser ultra
sonic system and used to monitor the time-of-flight of ultrasonic pulses th
at propagate across an ampoule during the melting and solidification of Cd0
.96Zn0.04Te. The measurement approach is based upon the difference in the e
lastic stiffness of the solid and liquid phases of Cd0.96Zn0.04Te (Queheill
alt et al., J. Appl. Phys. 83 (1998) 4124) and its significant dependence u
pon temperature. This results in a reduction of the longitudinal wave ultra
sonic velocity as the temperature was increased (from ambient temperature)
followed by a similar to 45% decrease upon melting. The laser ultrasonic se
nsor provided a robust in-situ method for monitoring the melting and solidi
fication of Cd0.96Zn0.04Te. The data indicated that the melting was slow an
d that solidification was accompanied by a 10-15 degreesC undercooling. (C)
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