Observation of HOPG by STM and contact AFM in various gas atmospheres under pressures up to 1.1 MPa

Apparatus comprising a scanning tunneling microscopy (STM) and an atomic force microscopy (AFM) has been developed for use under supra-atmospheres. Observations of highly oriented pyrolytic graphite (HOPG) were carried out by STM and contact AFM operating in air and various gas atmospheres (hydrogen, helium, neon and argon) under pressures up to 1.1 MPa. Atomic resolution images of the HOPG were obtained by STM in all the gas atmospheres studied. However, it was found that the presence of water vapor gave rise to a noise current at increased pressures. Using contact AFM, the atomic resolution in an argon atmosphere decreased with increasing pressure, while atomic images were obtained under the other gas atmospheres at 1.1 MPa.