Controlled planar interface synthesis by ultrahigh vacuum diffusion bonding/deposition

An ultrahigh vacuum (UHV) diffusion bonding/deposition instrument was desig ned and constructed, which can produce homophase and heterophase planar int erfaces from a wide array of materials. The interfaces are synthesized in s itu by diffusion bonding of two substrates with or without various interfac ial layers, at temperatures up to about 1500 degrees C. Substrate surfaces can be heat treated, ion-beam sputter cleaned, and chemically characterized in situ by Auger electron spectroscopy prior to deposition and/or bonding. Bicrystals can be synthesized by bonding two single-crystal substrates at a specified orientation. Interfacial layers can be deposited by electron be am evaporation and/or sputter deposition in any layered or alloyed combinat ion on the substrates before bonding. The instrument can accommodate cylind rical and/or wafer type specimens whose sizes are sufficient for fracture m echanical testing to measure interface bond strength. A variety of planar i nterfaces of metals, semiconductors, and ceramics were synthesized. Example s of bonded stainless steel/Ti/stainless steel, Si/Si, and sapphire/sapphir e interfaces are presented.