Blar i NTNU Open på forfatter "Weman, Helge"
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Advanced Micro Photoluminescence Spectroscopy of Single GaAs/AlGaAs Core-Shell Nanowires
Gulla, Stian (Master thesis, 2013)Self-catalyzed (SC) growth is a relatively new approach to growing GaAs nanowires (NWs). It has several advantages to Au-catalyzed growth, such as integration on Si platforms. Many of the growth parameters, including growth ... -
AlGaN Nanowires Grown on SiO2/Si (100) Using Graphene as a Buffer Layer
Wang, Yunyu; Dheeraj, Dasa; Liu, Zhiqiang; Liang, Meng; Li, Yang; Yi, Xiaoyan; Wang, Junxi; Li, Jinmin; Weman, Helge (Peer reviewed; Journal article, 2019)III-Nitride epitaxy is deeply dependent on the substrate and is difficult to grow on amorphous substrates because of the lattice mismatch limits. In this paper, graphene is employed as a buffer layer to assist AlGaN nanowire ... -
Contacts to P-doped GaAs Nanowires by Fabrication of Electrodes using Metals and Graphene
Christoffersen, Ole Morten (Master thesis, 2012)P-type GaAs semiconducting nanowires (NWs) with NW/electrode contacts have been examined by fabricating single NW devices to investigate their electrical properties. Both NWs grown with Au-assisted and Ga-assisted ... -
Cryogenic micro-photoluminescence of silicon solar cell materials
Skarpeteig, Jon (Master thesis, 2010)A literature review of relevant luminescence spectra for silicon solar cell materials has been performed. Three multi crystalline silicon samples in particular has been the focus of attention, one electronic grade sample ... -
Determination of GaAs zinc blende/wurtzite band offsets utilizing GaAs nanowires with an axial GaAsSb insert
Ahtapodov, Lyubomir; Kauko, H; Munshi, A Mazid; Fimland, Bjørn-Ove; Van Helvoort, Antonius; Weman, Helge (Journal article; Peer reviewed, 2017)By applying a correlated micro-photoluminescence spectroscopy and transmission electron microscopy (TEM) approach, we have utilized molecular beam epitaxy grown self-catalysed GaAs nanowires (NWs) with an axial GaAsSb ... -
Direct Growth of AlGaN Nanorod LEDs on Graphene-Covered Si
Ren, Fang; Yin, Yue; Wang, Yunyu; Liu, Zhiqiang; Meng, LIang; Ou, Haiyan; Ao, Jinping; Wei, Tongbo; Yan, Jiancheng; Yuan, Guodong; Yi, Xiaoyan; Wang, Junxi; Li, Jinmin; Dheeraj, Dasa; Weman, Helge (Journal article; Peer reviewed, 2018)High density of defects and stress owing to the lattice and thermal mismatch between nitride materials and heterogeneous substrates have always been important problems and limit the development of nitride materials. In ... -
Effects of substrate annealing on the gold-catalyzed growth of ZnO nanostructures
Weigand, Christian Carl; Skåre, Daniel; Ladam, Cecile; Grepstad, Jostein; Weman, Helge (Journal article; Peer reviewed, 2011)The effects of thermal substrate pretreatment on the growth of Au-catalyzed ZnO nanostructures by pulsed laser deposition are investigated. C-plane sapphire substrates are annealed prior to deposition of a thin Au layer. ... -
Electron Microscopy Based Characterization of Semiconductor Nanowires
Fauske, Vidar Tonaas (Doctoral thesis at NTNU;2016:181, Doctoral thesis, 2016)One-dimensional semiconductor structures have attracted a large research interest, mainly for the purpose of novel or improved opto-electronic properties and applications. In this work, semiconductor nanowires grown using ... -
Electron Microscopy characterization of the Interface between a (111)-Si Substrate and GaAs Nanowires grown by Self-Catalysis by MBE
Fauske, Vidar Tonaas (Master thesis, 2011)The interface between zincblende (ZB) GaAs nanowires (NWs) grown by selfcatalysisin MBE, and a 111-Si substrate was studied. This was done with thepurpose of determining if any defects, stacking fault, twins, different ... -
Epitaxially grown III-arsenide-antimonide nanowires for optoelectronic applications
Ren, Dingding; Ahtapodov, Lyubomir; Van Helvoort, Antonius; Weman, Helge; Fimland, Bjørn-Ove (Journal article; Peer reviewed, 2019)Epitaxially grown ternary III-arsenide-antimonide (III-As–Sb) nanowires (NWs) are increasingly attracting attention due to their feasibility as a platform for the integration of largely lattice-mismatched antimonide-based ... -
Fabricating Si[111] Nanostructures on Graphene by Aluminum-Induced Crystallization for High Yield Vertical III-V Semiconductor Nanowire Growth
Høiaas, Ida Marie (Master thesis, 2014)III-V semiconductor nanowire-graphene photovoltaics is an emerging technology that has the potential of highly efficient, flexible and ultra-thin solar cells. This thesis has explored aluminum-induced crystallization(AIC) ... -
Fabrication and Characterization of GaAs/AlGaAs Core-Shell Photonic Nanowires
Rogstad, Espen (Master thesis, 2009)GaAs/AlGaAs core-shell nanowires (NWs) were grown on GaAs(111)B substrates by Au-assisted molecular beam epitaxy (MBE) to investigate how different Al compositions in the shell influences the structural and optical properties ... -
Fabrication and Characterization of Single Doped GaAs Nanowire Devices
Nordeng, Mikael Johannes (Master thesis, 2011)In the work with this master thesis, electron beam lithography (EBL) and other cleanroom methods was used to develop a reproducible process for making ohmic contactsto nanowires (NWs), with the aim of investigating different ... -
Fabrication and Characterization of Single GaAs Nanowire Devices
Bø, Åsmund Bakke (Master thesis, 2010)In this work, a reproducible fabrication process for contacting single GaAs nanowires (NWs) using electron beam lithography (EBL) has been established. Wurtzite (WZ) GaAs core NWs doped with Te and Be have then been ... -
Fabrication and Electronic Investigation of GaAs nanowire/Graphene Hybrid Devices
Bang, Ambjørn Dahle (Master thesis, 2014)In the present study, a process for fabricating GaAs nanowire/graphene hybrid devices using electron beam lithography processing techniques is presented and demonstrated. Fabricated devices were investigated electronically ... -
Fabrication and Measurements of GaAs Nanowire Array Solar Cell Devices
Sandell, Susanne (Master thesis, 2013)Radial junction p-i-n GaAs nanowire array solar cell (NWASC) devices have been fabricated and optoelectrically measured. Substrates for nanowire (NW) growth were fabricated by electron beam lithography or nanoimprint ... -
Fabrication of Si(111) crystalline thin film on graphene by aluminum-induced crystallization
Høiaas, Ida Marie; KIM, DONG CHUL; Weman, Helge (Journal article; Peer reviewed, 2016)We report the fabrication of a Si(111) crystalline thin film on graphene by the aluminum-induced crystallization (AIC) process. The AIC process of Si(111) on graphene is shown to be enhanced compared to that on an amorphous ... -
Focused ion beam lithography for position-controlled nanowire growth
Mosberg, Aleksander Buseth; Ren, Dingding; Ahtapodov, Lyubomir; Weman, Helge; Fimland, Bjørn Ove Myking; Van Helvoort, Antonius (Peer reviewed; Journal article, 2023) -
GaAs/AlGaAs Nanowire Array Solar Cell Grown on Si with Ultrahigh Power-per-Weight Ratio
Mukherjee, Anjan; Ren, Dingding; Vullum, Per Erik; Huh, Junghwan; Fimland, Bjørn-Ove; Weman, Helge (Peer reviewed; Journal article, 2021)Here we demonstrate a more effective use of III–V photoconversion material to achieve an ultrahigh power-per-weight ratio from a solar cell utilizing an axial p-i-n junction GaAs/AlGaAs nanowire (NW) array grown by molecular ... -
GaN/AlGaN nanocolumn ultraviolet light-emitting diode using double-Layer graphene as substrate and transparent electrode
Høiaas, Ida Marie; Liudi Mulyo, Andreas; Vullum, Per Erik; Kim, Dong Chul; Ahtapodov, Lyubomir; Fimland, Bjørn-Ove; Kishino, Katsumi; Weman, Helge (Journal article, 2019)The many outstanding properties of graphene have impressed and intrigued scientists for the last few decades. Its transparency to light of all wavelengths combined with a low sheet resistance makes it a promising electrode ...