Photoconductive imaging in a photon scanning tunnelling microscope capable of point‐contact current sensing using a conductive fibre probe

Abstract

SummaryA photoconductive photon scanning tunnelling microscope was developed to investigate the point-contact photoconductive properties of condensed matter. In order to detect the current and the optical signal at a local point on a surface, we coated the edge of a bent type fibre probe with indium tin oxide. Thus it was possible to measure both photocurrent and optical property with subwavelength resolution. The performance of the novel microscope was evaluated by analysing an organic thin film of copper phthalocyanine (CuPc), which is known to be an efficient photoconductive material. Photocurrent and current± voltage characteristics were observed at the local point on the CuPc thin films. Furthermore, photoconductive images were obtained with topography and near-field optical imaging using this system. The photoconductive PSTM shows potential in various areas of future optics and electronics.

High resolution photocurrent imaging by atomic force microscopy on the example of single buried InAs quantum dots

“…This is small compared to the lateral dimension of the current collection region (80 nm), and therefore, the wetting layer signal also contributes to the current at nominally on-dot positions. Note that the collection region on semiconductor samples is different to organic materials, where the limiting length scale for the resolution is given by the tip size or by the lateral diffusion length of charge carriers [19].…”