Dual Light Illumination Method in Scanning Tunneling Microscopy for Photoinduced Current Measurements on InAs Wires

Abstract

Statistical considerations have in the past been applied in deriving the optimum thickness for balanced x-ray filters used with fixed-time measurements. Using similar considerations, a criterion has now been formulated which yields the optimum thickness when frxed-count measurements are taken. A double fixed-count method, where separate count totals are used for each filter, is proposed to obtain a near optimum division of counting time. Results quoted include the optimum balanced filter thicknesses for isolating the MoKa and CuKa lines. The construction and performance for the former pair of filters are discussed.

Photoabsorption Properties in InAs Wire Structures Investigated by Dual Light Illumination Method in Scanning Tunneling Microscopy

“…When the sample including the layer with the built-in field near its surface is illuminated by modulated light, the PIC signal should consist of mainly three components: (i) direct contribution of photocarriers to current, (ii) capacitive current, and (iii) surface photovoltaic effect. 4,10) Therefore, it is very important to suppress the latter two components in order to correctly investigate the photoabsorption properties of the InAs wires in our samples, and for such a purpose, the dual light illumination method in STM is very powerful because an additional illumination by continuous-wave (CW) light can flatten the band structure, which was originally bent, and consequently the undesirable components (ii) and (iii) are eliminated from the PIC signal. 10) Our experimental setup of the dual light illumination method is schematically illustrated in Fig.…”

“…4,10) Therefore, it is very important to suppress the latter two components in order to correctly investigate the photoabsorption properties of the InAs wires in our samples, and for such a purpose, the dual light illumination method in STM is very powerful because an additional illumination by continuous-wave (CW) light can flatten the band structure, which was originally bent, and consequently the undesirable components (ii) and (iii) are eliminated from the PIC signal. 10) Our experimental setup of the dual light illumination method is schematically illustrated in Fig. 2.…”

“…[1][2][3][4][5][6][7][8][9] We have already developed a dual light illumination method in STM that allows us to detect photoinduced current (PIC) by excluding the influence of a built-in field in semiconductors and to characterize the photoabsorption properties of nanostructures correctly. 10) A semiconductor nanowire in particular is expected to exhibit unique optical properties resulting from a quantum confinement effect as well as its structural anisotropy. In this study, the InAs wires were examined by means of the dual light illumination method in STM.…”