Local photoconductivity of microcrystalline silicon thin films excited by 442 nm HeCd laser measured by conductive atomic force microscopy

Microcrystalline silicon (μc-Si:H) thin films were studied by photo-conductive atomic force microscopy (PC-AFM) under top side illumination by HeCd 442 nm laser and/or by scattered light of AFM detection diode. In order to make the top side illumination possible, so called “nose” type cantilevers, with the tip at the end of cantilever, were used for local photo-current map measurements. Local current intensity under different illumination is discussed mainly from a point of view of the absorption depth of the used light. Diffusion length of charge carriers ~ 300 nm was estimated from comparison of the current levels under different illumination.

► Photoconductive atomic force microscopy (PC-AFM) on μc-Si:H was used ► Nose type cantilevers were used for top side illuminated PC-AFM set-up ► Photocurrent induced by HeCd 442 nm laser was measured by PC-AFM ► Diffusion length ~ 300 nm was estimated from local photo-currents ► Approach for single defect detection in silicon thin films was suggested