I(V) Spectroscopy

In I(V) Spectroscopy (or Current Imaging Tunneling Spectroscopy, CITS) a normal topographic image is acquired at fixed I_o and V_o. At each point in the image feedback loop is interrupted and the bias voltage is set to a series of voltages V_i and the tunneling current I_i is recorded. The voltage is then returned to V_o and the feedback loop is turned back on. Each I-V spectra can be acquired in a few milliseconds so there is no appreciable drift in the tip position. This procedure generates a complete current image I_i(x,y) at each voltage V_i in addition to the topographic image z(x,y)|_VoIo.
CITS data can be used to calculate a current difference image
DI_Vi,Vj(x,y) where V_i and V_j bracket a particular surface state, producing an atomic resolved, real space image of a surface state. This technique, for example can be used in UHV to image filled ad-atom states or the dangling bond states for silicon reconstructions.

    References

1. G. Binnig and H. Rohrer: Surf. Sci. 126 (1983) 236. Rep. Prog. Phys. 55, 1165-1240 (1992).

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