UHV RHEED and Replica Studies of NaCl Films Formed on Mica

Abstract

Thick (1500 to 2500 A) NaCl films were formed under ultra high vacuum (UHV) conditions on aircleaved mica substrates at 25, 100, 150, 200, 250, 300 and 380°C by vacuum deposition. A modified version of a UHV reflection high energy electron diffraction (RHEED) camera, designed and constructed in our laboratory was used for these studies. Typical residual gas pressures after bakeout were in the low 10-10 torr range. The aircleaved muscovite mica substrate was clamped to an OFHC copper block about 10 cm. from the resistance heated vapor source. The substrate was outgassed in UHV at 400 C for a period of at least 12 hours before cooling to the deposition temperature. During deposition the pressure was kept in the 10-9 torr range. The film was examined first in situ by the UHV RHEED technique and then replicated. Finally the system was opened and the Ge-SiO replicas mounted on Cu grids and examined by transmission electron microscopy.