Year 2016, Volume 36

Abstract

In this work we present some results of an extensive investigation aimed to find suitable conditions to grow CuZnSnSe (CZTSe) nanostructures through single-step electrodeposition into the channels of polycarbonate membranes. After the optimization of several electrodeposition parameters, we have found that pulsed current deposition, between 0 and -1 mA cm^-2, is the best way to obtain CZTSe nanostructures mechanically attached to the support. An interesting result concerns the effect of supporting electrolyte in the deposition bath. In fact, changing its concentration it is possible to vary morphology of nanostructures from nanotubes to nanowires. In both case uniform arrays of ordered nanostructures were obtained on a Ni current collector that are very stable also after thermal treatment at 550°C.

Abstract

Ni-Co thin films were prepared on glass substrate by RF magnetron sputtering technique. Post-deposition annealing of Ni-Co film in oxygen atmosphere was found to improve film structure and electrical characteristics. The correlation between annealing conditions and the physical structure of the films was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Vis-NIR spectrophotometer. The lowest resistivity was observed after annealing a sputter-deposited Ni-Co film at 600 °C for 5h. The transmittance showed more than 85% in the infrared range. The preferred annealing condition has been found to improve Ni-Co film characteristics for transparent conducting material applications.

Abstract

We report on advances in the fabrication of high quality bipolar heterodiodes with oxide electrodes. The highest rectification above 1010 is obtained for a structure from a-ZCO/ZnO/ZnO:Al on Al₂O₃ (a-ZCO: amorphous ZnCo₂O₄). Rectification better than 10⁶, a value larger than reported for all previous attempts, is obtained for our a-ZCO/a-ZTO (a-ZTO: amorphous zinc tin oxide), a-NiO/ZnO and CuI/ZnO diodes. The ZCO/ZnO has been used as gate in JFETs with ZnO as channel. The bipolar diodes open the field of oxide semiconductor electronics to applications in photovoltaics.

Abstract

Novel tunable p-type thin film transistors (TFTs) were developed by adopting Cu₂O/SnO bilayer channel scheme. Using Cu₂O film produced at a relative oxygen partial pressure O_pp of 10% - as an upper layer - and 3% O_pp SnO films - as lower layers - we built a matrix of bottom gate Cu₂O/SnO bilayer TFTs with different thicknesses. We found that the thickness of the Cu₂O layer plays a major role in the oxidization process exerted onto the SnO layer underneath. The thicker the Cu₂O layer the more the underlying SnO layer is oxidized, and hence, the more the transistor mobility is enhanced at a certain temperature. Both the device performance and the required annealing temperature could then be tuned by controlling the thickness of each layer of the Cu₂O/SnO bilayer TFT.

Abstract

In this communication, the use of gallium nitride doped with beryllium as an efficient converter for white light emitting diode is proposed. Until now beryllium in this material was mostly studied as a potential p-type dopant. Unfortunately, the realization of p-type conductivity in such a way seems impossible. However, due to a very intensive yellow emission, bulk crystals doped with beryllium can be used as light converters. In this communication, it is demonstrated that realisation of such diode is possible and realisation of a colour rendering index is close to that necessary for white light emission.

Abstract

GaN-based InGaN/GaN self-organized quantum dots and InGaN quantum dots (disks) in GaN nanowires are important nanostructures with potential advantages over planar quantum wells, including luminescence at the longer visible wavelengths. We describe the epitaxy and characteristics of red-emitting InGaN/GaN quantum dot edge-emitting lasers and InGaN/GaN nanowire light emitting diodes, which can be used in a host of applications.