Low-temperature ultrahigh-vacuum scanning tunneling microscope

We describe a multipurpose scanning tunneling microscope designed to operate in ultrahigh vacuum as well as in air, over a range extending from room temperature to liquid-nitrogen temperatures. It is a single-tube scanner design with a differential flexing approach mechanism mounted on a vibration isolation stack. The instrument features a novel in situ tip and sample exchange mechanism for extended operation under vacuum. A unique characteristic is that the vacuum chamber and all components with the exception of the gas-cooled sample holder are at room temperature. We present preliminary data taken with this instrument, demonstrating atomic resolution constant current, constant height, and multiple-bias imaging, gap-modulated current-voltage spectroscopy or simultaneous topography, and work function measurements, as well as lithography on the surfaces of graphite, Au(111) on mica, and GaAs(110).