A new apparatus for crystal growth from the melt under very high vacuum conditions

Abstract

This paper describes new equipment for high purity crystal growth from the melt and presents some experimental results which characterize the quality of the apparatus under operating conditions. Although primarily designed for electron beam float zone growth of metal crystals, the machine provides all necessary mechanical and electrical requirements for crystal growth by pedestal pulling, Czochralski technique or Bridgman method utilizing either electron beam-, r.f.- or resistance-heating. Contamination of the mechanical parts of the equipment by evaporating materials is prevented by a liquid nitrogen cooled cooper baffle which surrounds the energy source-melt assembly. Since this baffle simultaneously acts as a heat shield, outgassing of environmental parts is minimized. Standard conflat flange feedthroughs are used and all parts are bakable which makes the apparatus suitable for UHV operation. In conjunction with a 6 inch diffusion pump vacuum station the system was operated in the very high vacuum range (ultimate pressure 1.5 × 10−8 torr. The linearity of the drive system is better than 1% and the noise amplitude under operating conditions can be kept below two times the background noise level which is ∼ 2 μm rms.