Scanning semiconductor electrodes

According to Sec. 3, the characterization of interface states at semiconductor electrodes is a key question since these states influence the behavior of the interface [76, 77]. The many different techniques of characterization have been reviewed [35, 76, 77] for the solid/liquid interface. True STS has not been applied until now. In first attempts to derive energy information the sample voltage was scanned to avoid problems with the electrochemical current at the tip extremity. The possibility of scanning the tip bias is discussed later. 

Scanning Tunneling Microscopy of Semiconductor Electrodes With Feedback Loop Active (Pseudospectroscopy)... 

Current-potential measurements, in the dark and under illumination of the semiconductor working electrode, are extremely useful for first defining the charge-transfer behavior across the interface before more sophisticated experiments are undertaken. The irradiation can be either continuous or intermittent (chopped) the latter mode has the distinct advantage that both the dark and light behavior can be examined in the same scan [55, 58]. Even some dynamic information can thus be extracted under the nominally steady-state conditions typical of a cyclic or linear potential sweep experiment. Another useful steady-state experiment is photocurrent spectroscopy (performed at a fixed DC potential) [55], although this can also be dynamically performed via IMPS (see below). Such measurements not only yield the so-called photoaction spectrum of the semiconductor electrode, but also afford information on surface recombination and surface state activity at the interface as discussed below. 

Area-selective irradiation of the semiconductor electrode requires irradiation through a mask or irradiation with a scanned laser beam. Considering the nature of light and the present... 

P. Allongue, in Scanning Tunneling Microscopy of Semiconductor Electrodes. Advances in Electrochemical Science and Engineering, H. Gerisher and C. Tobias (ed.), VCH, Weinheim, New York (1995), vol 4, p. 62. 

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