| Gold was deposited onto p- and n-type silicon specimens of resistivity about 1000 ohm-cm in a UHV field ion microscope operated at 78 K. Photo-illumination and field induced image-size effects were observed as a function of gold coverage on the specimen shank, with the silicon apex uncovered. For gold shank-overlayers estimated to be in excess of 0.5-1 nm average thickness, all semiconductor effects on the field ion image of the silicon apex and the ion current, due to changes in illumination or applied voltage to the specimen, vanished. Field strengths for imaging p- and n-type silicon in hydrogen or argon were found to be the same as for metals, within our experimental accuracy. |
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