Effects from adsorption of organic species on the surface of nanomaterials have been investigated. Exposure to organic contaminants during material processing, handling and environmental exposure is unavoidable during the manufacturing process of nanoscale materials. In addition, at the nanoscale, surface area to volume ratios increase and surface effects will have an increasing influence on the material properties. Experimentally measured electrical properties of gold nanowires and composition will be presented. The results indicated that C, C—O—C and C=O are adsorbed at the surface of the gold nanowires. These surface contaminants are believed to cause the increase in measured resistivity. A theoretical study was performed to investigate diffusion of these contaminants into the first surface layer, which may act as scattering mechanisms for current flow.
Magnetic properties of Fe nanowire arrays (NWs) electrodeposited in anodic alumina membranes have been studied. The influence of nanowire geometry (length, pore diameter) and an external magnetic field applied during electrodeposition process on the magnetic properties of nanowire arrays was investigated. With the use of the X-ray diffraction analysis the structure of iron wires was determined. The iron wires have the regular Body Centered Cubic structure. Magnetic measurements show that shape anisotropy aligns the preferential magnetization axis along the wire axis. It was found that the application of an external magnetic field in a parallel direction to the sample surface induces magnetic anisotropy with an easy axis of magnetization following the nanowire axis. The dependence of the height of Fe wires on the electrodeposition time was determined.
In our studies the absorption, transmittance and reflectance spectra for periodic nanostructures with different parameters were calculated by the FDTD (Finite-Difference Time-Domain) method. It is shown that the proportion of reflected light in periodic structures is smaller than in case of thin films. The experimental results showed the light reflectance in the spectral range of 400–900 nm lower than 1% and it was significantly lower in comparison with surface texturing by pyramids or porous silicon.
Silicon nanowires on p-type Si substrate were formed by the Metal-Assisted Chemical Etching method (MacEtch). At solar cells with radial p-n junction formation the thermal diffusion of phosphorus has been used at 790°C. Such low temperature ensures the formation of an ultra-shallow p-n junction. Investigation of the photoelectrical properties of solar cells was carried out under light illumination with an intensity of 100 mW/cm2. The obtained parameters of NWs' solar cell were Isc = 22 mA/cm2, Uoc = 0.62 V, FF = 0.51 for an overall efficiency η = 7%. The relatively low efficiency of obtained SiNWs solar cells is attributed to the excessive surface recombination at high surface areas of SiNWs and high series resistance.
In this paper, a low power highly sensitive Triple Metal Surrounding Gate (TM-SG) Nanowire MOSFET photosensor is proposed which uses triple metal gates for controlling short channel effects and III–V compound as the channel material for effective photonic absorption. Most of the conventional FET based photosensors that are available use threshold voltage as the parameter for sensitivity comparison but in this proposed sensor on being exposed to light there is a substantial increase in conductance of the GaAs channel underneath and, thereby change in the subthreshold current under exposure is used as a sensitivity parameter (i.e., Iillumination/IDark). In order to further enhance the device performance it is coated with a shell of AlxGa1-xAs which effectively passivates the GaAs surface and provides a better carrier confinement at the interface results in an increased photoabsorption. At last performance parameters of TM-SG Bare GaAs Nanowire MOSFET are compared with TM-SG core-shell GaAs/AlGaAs Nanowire MOSFET and the results show that Core-Shell structures can be a better choice for photodetection in visible region.