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“Background One-dimensional Captisol cost silicon nanostructures, such as Si nanowires (NWs), nanorods (NRs), or nanopillar (NPs) have gained particular interests due to their special properties and potential applications

in electronic and optoelectronic devices [1–4]. Theoretical and experimental studies have reported that when arranged in a highly ordered fashion, Si NRs or NWs can improve light absorption and charge collection, making it possible to achieve high efficiency in solar cells TPCA-1 [5–8]. Therefore, periodic Si NRs (or NWs) arrays have attracted considerable attentions in the fields of solar cells. However, despite the huge efforts to control and understand the growth mechanisms underlying the formation of these nanostructures [9, 10], some fundamental properties and inside mechanisms are

still not well understood. To reveal their properties, the investigation on single NRs is preferred. Recently conductive scanning probe microscopy techniques have been attempted to investigate the electrical properties of single NWs/NRs. Among them, electrostatic force microscopy (EFM) can provide direct information of trapped carriers in single nanostructures and has been applied to investigate the charge trapping in single nanostructures, such as carbon nanotubes [11], pentacene monolayer islands [12], CdSe quantum dots (QDs) [13, 14], and etc. More recently, photoionization of QDs [15, 16] and photo-induced charging of photovoltaic films [17–19] have been studied by EFM combined with laser irradiation. But the photogenerated charging effects have not been concerned on Si NRs or NWs yet. In this letter, EFM measurements combined with laser Interleukin-3 receptor selleck screening library irradiation are applied to investigate the photogenerated charging properties on single vertically aligned Si NRs in periodic arrays. Methods Periodic arrays of Si NRs are fabricated by nanosphere lithography and metal-assisted chemical etching. Three samples (labeled as NR1, NR2, NR3) which contain periodic NR arrays with the same diameter of about 300 nm and different length or constructions are prepared. NR1 and NR2 are n-type Si (approximately 1,000 Ω cm) NRs with the length of about 0.5 and 1.0 μm, respectively, while NR3 is Si/SiGe/Si hetero-structural NRs with the length of 1.