Laser-Induced Charge Separation in CdSe Nanowires

Abstract

A combination of electrostatic force microscopy and optical microscopy was used to investigate the charge state of individual CdSe nanowires upon local illumination with a focused laser beam. The nanowires were found to be positively charged at the excitation spot and negatively charged at the distant end(s). For high laser powers, the amount of accumulated charges increases logarithmically with the laser power. These effects are described by a diffusion-based model where the results are in good agreement with the experimentally observed effects. On the basis of this model the charge imbalance along the nanowire should establish in the course of nanoseconds. The net charge separation within homogeneous nanowires upon local illumination is of importance for several electronic devices.

Doping profile of InP nanowires directly imaged by photoemission electron microscopy

“…4,5 Other methods, such as electron beam induced current 6 or scanning photocurrent microscopy 7 also need a device setup. Kelvin probe force microscopy or electrostatic force microscopy can also be used, 8,9 however, the relatively large probe could disturb the device potentials. As a result, new and complementary imaging and spectroscopy methods capable of revealing doping levels on the nanoscale would be desirable.…”

Layer‐by‐Layer Fabrication of Nanowire Sensitized Solar Cells: Geometry‐Independent Integration

“…Since the IQE is a product of charge injection and charge collection effi ciencies, our results indicate that charge injection and/or charge collection are about a factor of two more effi cient in NW composites than in QD composites. We attribute this to a high exciton and/or charge mobility along the length of NWs, [ 18 ] which allows carriers to effectively diffuse to the optimal sites for NW-to-TiO 2 electron injection as well as hole collection by the electrolyte. This interpretation is also consistent with our observation of decreasing EQEs for thick fi lms.…”

“…Importantly, we show that this fi nding is due to the better light-harvesting properties of NWs compared to QDs (NW absorption cross-sections are ∼1 order-of-magnitude higher than QDs on a volumenormalized basis) [ 17 ] as well as better charge-collection in NW devices, which may be related to the tendency of NWs to exhibit very effi cient light-induced charge separation. [ 18 ] As we show herein, these dual opportunities for performance enhancement coupled with a new approach for NCSSC fabrication point the way to a low-cost, low-processing-temperature photovoltaic technology that uniquely permits use of the most effi cient nanomaterial irrespective of particle geometry.…”

Morphology of CD4+T Lymphocytes Bound on Nano-Patterened Substrates for Sensing the Size of Nanoholes

“…In last decades, the application of nanotechnology in the fields of electronic and optical engineering was well established [1][2][3]. Furthermore, nanostructures have been increasingly used for studies on cell interaction with solid nanostructures because unique properties of nanostructured surfaces enable a variety of novel functions of immobilized cells on the nanostructured surfaces [4,5].…”