Techniques for routine UHV in situ electron microscopy of growth processes of epitaxial thin films

Abstract

Techniques for routine UHV in situ electron microscopy of epitaxial growth processes of thin films are described for a wide variety of deposit-substrate combinations. The column vacuum of a commercial electron microscope is improved to 10^-5 Pa simply by scrupulous reassembly. The top-entry specimen chamber of the microscope, into which the evaporator system is inserted, is differentially evacuated to 4-7 mu Pa by a sublimation pump and an orbital ion pump. The substrate crystal set on the side-entry specimen stage is surrounded by a cryogenic tip which can be cooled by liquid nitrogen or helium so that the residual vapours (except He, Ne and H₂) around the substrate are reduced to 10^-6-10^-8 Pa. The improvement in the vacuum is made without serious loss of electron optical performance or of operational amenities of the microscope. The substrate crystal and/or the material to be deposited can be changed within minutes. Details are given of in situ deposition; the nature of substrate crystals prepared in situ is discussed.