Direct Evidence of Mg Incorporation Pathway in Vapor-Liquid-Solid Grown p-type Nonpolar GaN Nanowires

Doping of III-nitride based compound semiconductor nanowires is still a challenging issue to have a control over the dopant distribution in precise locations of the nanowire optoelectronic devices. Knowledge of the dopant incorporation and its pathways in nanowires for such devices is limited by the growth methods. We report the direct evidence of incorporation pathway for Mg dopants in p-type nonpolar GaN nanowires grown via vapour-liquid-solid (VLS) method in a chemical vapour deposition technique for the first time. Mg incorporation is confirmed using X-ray photoelectron (XPS) and electron energy loss spectroscopic (EELS) measurements. Energy filtered transmission electron microscopic (EFTEM) studies are used for finding the Mg incorporation pathway in the GaN nanowire. Photoluminescence studies on Mg doped GaN nanowires along with the electrical characterization on heterojunction formed between nanowires and n-Si confirm the activation of Mg atoms as p-type dopants in nonpolar GaN nanowires.Comment: 29 pages, 6 figures, journa

Polarity-dependent reversible resistance switching in Ge–Sb–Te phase-change thin films

In this paper, we demonstrate reversible resistance switching in a capacitorlike cell using a Ge–Sb–Te film that does not rely on amorphous-crystalline phase change. The polarity of the applied electric field switches the cell resistance between lower- and higher-resistance states, as was observed in current-voltage characteristics. Moreover, voltage pulses less than 1.25 V showed this switching within time scales of microseconds with more than 40% contrast between the resistance states. The latter are found to be nonvolatile for months. The switching could also be achieved at nanoscales with atomic force microscopy with a better resistance contrast of three orders of magnitude.

Alignment, morphology and defect control of vertically aligned ZnO Nanorod array: competition between ‘surfactant’ and ‘stabilizer’ roles of the amine species and its photocatalytic properties

We demonstrate effective control of the morphology, defect content and vertical alignment of ZnO nanorod (NR) arrays grown by a solution method by simply varying the hexamine concentration during growth. We show that the amine acts both as a growth ‘stabilizer’ and ‘surfactant’ and controls both Zn release for ZnO formation and caps non-polar planes, respectively. Competition between these ‘stabilizer’ and ‘surfactant’ roles facilitates morphology, alignment and defect content control of 1D ZnO NR arrays. Well aligned, prismatic, defect (Zn interstitial) controlled ZnO NR arrays grown with a 1M amine concentration show higher photocatalytic degradation of Methylene Blue dye solutions under UV irradiation. Shallow donor zinc interstitials readily supply electrons which may increase the space charge near the nano-catalyst surface. The increased band bending associated with the interfacial electric field in the space charge region may then better facilitate the separation of photogenerated carriers and thus enhance the photocatalytic performance. Understanding the role of amine in the solution growth of 1D ZnO NR arrays holds great promise for tailoring ZnO NR functionalities for various potential applications

Spectroscopically forbidden infra-red emission in Au-vertical graphene hybrid nanostructures

Implementation of Au nanoparticles (NPs) is a subject for frontier plasmonic research due to its fascinating optical properties. Herein, the present study deals with plasmonic assisted emission properties of Au NPs-vertical graphene (VG) hybrid nanostructures. The influence of effective polarizability of Au NPs on the surface enhanced Raman scattering and luminescence properties is investigated. In addition, a remarkable infra-red (IR) emission in the hybrid nanostructures is observed and interpreted on the basis of intra-band transitions in Au NPs. The flake-like nanoporous VG structure is invoked for the generation of additional confined photons to impart additional momentum and a gradient of confined excitation energy towards initiating the intra-band transitions of Au NPs. Integrating Au plasmonic materials in three-dimensional VG nanostructures enhances the light-matter interactions. The present study provides a new adaptable plasmonic assisted pathway for optoelectronic and sensing applications.Comment: 5 figure