High pressure, high temperature scanning tunneling microscopy

The design and performance of a high pressure, high temperature scanning tu nneling microscope (HPHT-STM) system is described. The system combines an u ltrahigh vacuum surface analysis/preparation chamber with a variable pressu re (5 x 10(-10) Torr-1 atm) and temperature (300-675 K) STM. The STM chambe r can be isolated by three gate valves and filled with 1 arm of any gas mix ture. The composition of the gas can be monitored by gas chromatography. A load-lock mechanism allows the transfer of samples and tips into the chambe r without exposing it to air. Heating at high pressure is achieved using a halogen lamp beneath the sample. By switching between tungsten and gold tip s, the microscope can be used in both oxidizing and reducing environments a t room temperature, and reducing environments at elevated temperatures. Thi s instrument allows the exploration of surfaces in a pressure regime that f ew other surface sensitive techniques can work in. (C) 1999 American Vacuum Society. [S0734-211X(99)07403-X].