Portal de Periódicos da CAPES

Scanning Tunnelling Microscopy

1992; Springer Nature; Linguagem: Inglês

10.1007/978-3-662-02767-7_10

2198-4743

B.A. Sexton,

Mechanical and Optical Resonators

The scanning tunnelling microscope, or STM, has emerged over the last few years as a fascinating new technique for examining conducting solid surfaces with high resolution [10.1–5]. A sharpened metal wire is brought close enough to the surface so that the electrons “tunnel” across the narrow gap (0.5–1.5 nm). A small bias potential (2 mV-2 V) provides the necessary potential difference for tunnelling to occur. As a result of the exponential dependence of tunnelling current on separation, the tip height above the surface can be kept constant by using a feedback controller. The tunnel current is monitored and applied to a “PI” controller which in turn drives a piezoelectric arm attached to the tip. By scanning another set of piezoelectric arms, the tip can be rastered in an XY plane whilst simultaneously following the surface corrugations. In this way, a three-dimensional image of the surface can be formed by plotting z(x, y). The imaging is non-destructive since the tip does not normally touch the surface during the scans.