Scanning tunneling microscopy operating under a plasma environment

Apparatus comprising a scanning tunneling microscope (STM) has been develop ed for the first time for use under a plasma environment. It consists of an STM system and a radio-frequency (r.f.) (430 MHz) plasma generation system housed in a vacuum chamber with a rotary pump. A special amplifier with a resolution of 10 fA. up to 1 kV is employed for tunneling current measureme nts. To prevent noise current from the plasmal the Pt-Ir probe tip is coate d with epoxy grease and insulated glass except around its apex of about 3 m u m using the sol-gel method. Under the conventional glow-plasma condition, the noise current from the plasma was deduced to be less than 0.1 nA durin g plasma exposure for 1800 s. Using this apparatus, the step structure and atomic image of highly oriented pyrolytic graphite (HOPG) were obtained und er r.f. low-pressure (0.3 Torr) air glow plasma. (C) 1999 Elsevier Science S.A. All rights reserved.