Douglas W. Akers

In situ characterization of crystal growth and heat treatment in semiconductor materials

In situ characterization methods are being developed at the Idaho National Laboratory that can be used to characterize the atomic lattice structure of materials used for semiconductor and scintillation detectors during the crystal growth and heat treatment processes, which have been shown to be critical for the development of optimized semiconductor and scintillation radiation detectors. Multiple methods for implanting positrons into the material have been developed and integrated with measurement techniques including Doppler broadening, coincidence Doppler broadening and positron lifetime measurement. The INL developed induced positron technique allows positron measurements to be performed at depth up to 10 cm inside crystal boules. Also, a portable measurement system suitable for field use has been developed that is suitable for assessing heat treatments at depths up to 1 cm inside a material in an industrial environment. Results of measurements that address the effects of composition and heatup/melting/cool down on material lattice structures are discussed along with plans for the in situ crystal studies.