Nucleation and Epitaxial Growth of Cu on W

Abstract

Nucleation and growth of Cu on W from the vapor phase has been studied by field emission microscopy in the temperature range from −195° to 750°C for a limited range of impingement rates. Nucleation occurs in patches rather than homogeneously, the nucleation sites varying with substrate temperature, becoming very specific above ∼300°C. Cu crystals can readily be grown having surface areas comparable in size with the W field‐emitter surface.Epitaxial relationships are determined from the field‐emission micrographs. The crystal plane initially formed is {111} Cu superposed on an {011} W plane with either a Cu 〈112〉 direction parallel to a W 〈011〉 direction or a Cu 〈112〉 direction parallel to a W 〈112〉 direction. The crystal growth technique is proposed as a general means of obtaining clean surfaces for field emission microscope studies.