Characterization of GaN Nanorods Fabricated Using Ni Nanomasking and Reactive Ion Etching: A Top-Down Approach

Large thermal mismatch between GaN surface and sapphire results in compressive stress in Gallium Nitride (GaN) layer which degrades the device performance. Nanostructuring the GaN can reduce this stress leading to reduction in Quantum Confined Stark Effect. Aligned GaN nanorods based nanodevices have potential applications in electronics and optoelectronics. This paper describes the fabrication of GaN nanorods using Ni nanomasking and reactive ion etching. The morphology of GaN nanorods was studied by field emission scanning electron microscopy. The optical properties of GaN nanorods were studied by Cathodoluminescence (CL) spectroscopy. CL results revealed the existence of characteristic band-edge luminescence and yellow band luminescence. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3099

Carrier induced refractive index change observed by a whispering gallery mode shift in GaN microrods

Vertical oriented GaNmicrorods were grown by metal organic vapor phase epitaxy with four different n type carrier concentration sections above 1019 cm amp; 8722;3 along the c axis. In cathodoluminescence investigations carried out on each section of the microrod, whispering gallery modes can be observed due to the hexagonal symmetry. Comparisons of the spectral positions of the modes from each section show the presence of an energy dependent mode shift, which suggest a carrier induced refractive index change. The shift of the high energy edge of the near band edge emission points out that the band gap parameter in the analytical expression of the refractive index has to be modified. A proper adjustment of the band gap parameter explains the observed whispering gallery mode shif

Pancreatectomy for metastasis to the pancreas from colorectal cancer and reconstruction of superior mesenteric vein: a case report

<p>Abstract</p> <p>Introduction</p> <p>Tumors of the pancreatic head can infiltrate the superior mesenteric vein. In such cases, the deep veins of the lower limbs can serve as suitable autologous conduits for superior mesenteric vein reconstruction after its resection. Few data exist, however, describing the technique and the immediate patency of such reconstruction.</p> <p>Case report</p> <p>We present the case of a 70-year-old Caucasian man with a metachronous metastasis of colon cancer and infiltration of the uncinate pancreatic process, on the anterior surface of which the tumor was located. <it>En bloc </it>resection of the tumor was performed with resection of the superior mesenteric vein and reconstruction. A 10 cm segment of the superficial femoral vein was harvested for the reconstruction. The superficial femoral vein segment was inter-positioned in an end-to-end fashion. The post-operative conduit patency was documented ultrasonographically immediately post-operatively and after a six-month period. The vein donor limb presented subtle signs of post-operative venous hypertension with edema, which was managed with compression stockings and led to significant improvement after six months.</p> <p>Conclusion</p> <p>In cases of exploratory laparotomies with high clinical suspicion of pancreatic involvement, the potential need for vascular reconstruction dictates the preparation for leg vein harvest in advance. The superficial femoral vein provides a suitable conduit for the reconstruction of the superior mesenteric vein. This report supports the uncomplicated nature of this technique, since few data exist about this type of reconstruction.</p

Self-catalyzed, vertically aligned GaN rod-structures by metal-organic vapor phase epitaxy

This paper will discuss the influence of parameters such as temperature, V/III ratio, atmosphere and pressure on the vertical growth of GaN rod-structures on sapphire by metalorganic vapor phase epitaxy. For all growth experiments a simple two step method is applied consisting of a nitridation step on the sapphire substrate and the growth of GaN. Vertically aligned rod-like structures were achieved with this mask-free and catalyst-free approach. The influence of the nitridation step on the formation process of the vertically rodstructures will be discussed. The results will give an insight into the formation of vertically aligned GaN structures which is an important step towards the understanding and control of self-assembled GaN rods and nanorods in metal-organic vapor phase epitaxy. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Colour and multicolour tuning of InGaN quantum dot based light-emitting diodes

InGaN quantum dots (QDs) formed via spinodal and binodal decomposition are used as an optically active region for light-emitting diodes (LEDs). It is shown that the emission wavelength of the electroluminescence (EL) can be shifted from blue to green by adjusting the deposition time of the InGaN QD layer. A first approach towards a monolithic multicolour emitting diode is presented. Strong difference of the EL on the InGaN QD stacking sequence is observed and is attributed to both low hole concentration and mobility

Whispering gallery modes in GaN microdisks, microrods and nanorods grown by MOVPE

Self-assembled GaN microdisks, micro-and nanorods were grown by a mask-free and self-catalyzed metal-organic vapor phase epitaxy method. The morphology of the structures is analyzed by scanning electron microscopy. All rods have a hexagonal shape with smooth sidewall facets and sharp edges. Depending on the deposition of a GaN nucleation layer prior to growth of GaN rod structures the diameter of the rods can be adjusted. Nanorods with diameters down to 400 nm as well as microrods and disks with diameters up to 5 mu m can be achieved. The optical properties of the rods are investigated utilizing a combined scanning electron microscopy and cathodoluminescence system. Electron beam excitiation of GaN rods leads to a typical GaN spectrum showing GaN near band edge emission at 369 nm and broad yellow defect luminescence at 560 nm. Enhanced emission is located at the top of the rod. By fixing the focussed electron beam at a sidewall position of a single GaN rod, whispering gallery modes are observed in the cathodoluminescence spectrum. Depending on the diameter of the micro-/nanorods the spectral position of the modes as well as the spectral distance between the modes can be adjusted. Quality factors up to 475 are measured. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Growth of GaN Nanorods and Wires and Spectral Tuning of Whispering Gallery Modes in Tapered GaN Wires

This paper reports on the growth of GaN nanorods and wires by metal-organic vapor phase epitaxy. Density, height and diameter are strongly influenced by the growth time. A deposition time of a few minutes leads to the formation of GaN nanorods. Increasing the deposition time up to 1 h yields wires with heights exceeding 47 mu m. Transmission electron microscopy and convergent beam electron diffraction measurements are showing the presence of N- and Ga-polar GaN in a single nanorod. Cathodoluminescence measurements are performed showing the appearance of whispering gallery modes. Due to slight tapering of the wires the whispering gallery modes can be spectrally tuned by changing the position of the exposing electron beam at the sidewall facet of the rod. (C) 2013 The Japan Society of Applied Physic

A comparative study of beta-Ga2O3 nanowires grown on different substrates using CVD technique

A comparative study of beta gallium oxide (beta-Ga2O3) nanowires (NWs) grown on different substrates such as silicon (Si), sapphire, and GaN/sapphire has been reported. Field emission scanning electron microscopy (FESEM) results revealed that the beta-Ga2O3 NWs grown on GaN/sapphire substrate were comparatively more aligned than grown on other substrates. The diameter of the NWs varied from 150 to 400 nm, and their length ranging up to tens of micrometers. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) showed the single crystalline monoclinic nature of NWs. The Raman spectra acquired from three samples revealed similar features consisting of two active modes such as mid and high frequency. However, low frequency mode was absent in our results. The cathodoluminescence (CL) spectra of beta-Ga2O3 NWs on different substrates showed a strong broad UV-blue emission band and a weak red emission band in all the samples. Hence, the morphologies and structural properties of the beta-Ga2O3 NWs grown on three substrates showed some observable changes, while their optical properties were quite similar. (C) 2013 Elsevier B. V. All rights reserved