• Atomic resolution imaging of beryl: an investigation of the nano-channel occupation 

      Van Helvoort, Antonius; Holst, Bodil; Schmitz, F.D.; Arivazhagan, V.; Vullum, Per Erik (Journal article; Peer reviewed, 2016)
      Beryl in different varieties (emerald, aquamarine, heliodor etc.) displays a wide range of colours that have fascinated humans throughout history. Beryl is a hexagonal cyclo-silicate (ring-silicate) with channels going ...
    • Conductivity control via minimally invasive anti-Frenkel defects in a functional oxide 

      Evans, Donald; Holstad, Theodor Secanell; Mosberg, Aleksander Buseth; Småbråten, Didrik Rene; Vullum, Per Erik; Dadlani, Anup; Shapovalov, Konstantin; Yan, Zewu; Bourret, Edith; Gao, David Zhe; Akola, Jaakko; Torgersen, Jan; Van Helvoort, Antonius; Selbach, Sverre Magnus; Meier, Dennis (Peer reviewed; Journal article, 2020)
      Utilizing quantum effects in complex oxides, such as magnetism, multiferroicity and superconductivity, requires atomic-level control of the material’s structure and composition. In contrast, the continuous conductivity ...
    • Contact-free reversible switching of improper ferroelectric domains by electron and ion irradiation 

      Roede, Erik Dobloug; Mosberg, Aleksander Buseth; Evans, Donald; Bourret, Edith; Yan, Zewu; Van Helvoort, Antonius; Meier, Dennis (Peer reviewed; Journal article, 2021)
      Focused ion beam (FIB) and scanning electron microscopy (SEM) are used to reversibly switch improper ferroelectric domains in the hexagonal manganite ErMnO3. Surface charging is achieved by local ion (positive charging) ...
    • Crystal Phase Mapping by Scanning Precession Electron Diffraction and Machine Learning Decomposition 

      Ånes, Håkon Wiik; Andersen, Ingrid Marie; Van Helvoort, Antonius (Journal article; Peer reviewed, 2018)
      Analyzing the distribution of crystal phases is required to understand nanostructures. Conventional analysis in the transmission electron microscope (TEM) include acquiring dark-field (DF) images for each expected crystal ...
    • Crystallographic relationships of T-/S-phase aggregates in an Al–Cu–Mg–Ag alloy 

      Sunde, Jonas Kristoffer; Johnstone, D.N.; Wenner, Sigurd; Van Helvoort, Antonius; Midgley, Paul A.; Holmestad, Randi (Journal article; Peer reviewed, 2018)
      T-(Al20Cu2Mn3) phase dispersoids are important for limiting recovery and controlling grain growth in Al-Cu alloys. However, these dispersoids can also reduce precipitation hardening by acting as heterogeneous nucleation ...
    • 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 ...
    • 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 ...
    • FIB lift-out of conducting ferroelectric domain walls in hexagonal manganites 

      Mosberg, Aleksander Buseth; Roede, Erik Dobloug; Evans, Donald; Holstad, Theodor S.; Bourret, Edith; Yan, Zewu; Van Helvoort, Antonius; Meier, Dennis (Journal article; Peer reviewed, 2019)
      A focused ion beam (FIB) methodology is developed to lift out suitable specimens containing charged domain walls in improper ferroelectric ErMnO3. The FIB procedure allows for extracting domain wall sections with well-defined ...
    • FIB lift-out of conducting ferroelectric domain walls in hexagonal manganites 

      Evans, Donald; Meier, Dennis; Mosberg, Aleksander Buseth; Roede, Erik Dobloug; Holstad, Theodor S.; Bourret, Edith; Yan, Zewu; Van Helvoort, Antonius (Journal article; Peer reviewed, 2019)
      A focused ion beam (FIB) methodology is developed to lift out suitable specimens containing charged domain walls in improper ferroelectric ErMnO3. The FIB procedure allows for extracting domain wall sections with well-defined ...
    • Growth study of self-assembled GaN nanocolumns on silica glass by plasma assisted molecular beam epitaxy 

      Liudi Mulyo, Andreas; Konno, Yuta; Nilsen, Julie Stene; Van Helvoort, Antonius; Fimland, Bjørn-Ove; Weman, Helge; Kishino, Katsumi (Journal article; Peer reviewed, 2017)
      We demonstrate GaN nanocolumn growth on fused silica glass by plasma-assisted molecular beam epitaxy. The effect of the substrate temperature, Ga flux and N2 flow rate on the structural and optical properties are studied. ...
    • In-situ observations of dislocation recovery and low angle boundary formation in deformed aluminium 

      Ånes, Håkon Wiik; Van Helvoort, Antonius; Marthinsen, Knut (Journal article; Peer reviewed, 2019)
      An experimental study of the recovery of dislocations and low angle boundary formation in aluminium is presented. By combining in-situ annealing with orientation mapping in the transmission electron microscope, maps of ...
    • Nanocrystal segmentation in scanning precession electron diffraction data 

      Bergh, Tina; Johnstone, D.N.; Crout, P; Høgås, Simon; Midgley, Paul A.; Holmestad, Randi; Vullum, Per Erik; Van Helvoort, Antonius (Journal article; Peer reviewed, 2019)
      Scanning precession electron diffraction (SPED) enables the local crystallography of materials to be probed on the nanoscale by recording a two‐dimensional precession electron diffraction (PED) pattern at every probe ...
    • Processing and indexing of electron backscatter patterns using open-source software 

      Ånes, Håkon Wiik; Hjelen, Jarle; Sørensen, Bjørn Eske; Van Helvoort, Antonius; Marthinsen, Knut (Peer reviewed; Journal article, 2020)
      A new method to increase the signal-to-noise ratio S/N of electron backscatter patterns (EBSPs) based upon principal component analysis (PCA) is presented. The PCA denoising method is applied to ten scans of EBSPs from the ...
    • Scanning Precession Electron Diffraction Study of Hybrid Precipitates in a 6xxx Series Aluminium Alloy 

      Sunde, Jonas Kristoffer; Johnstone, Duncan; Marioara, Calin Daniel; Van Helvoort, Antonius; Midgley, Paul A.; Holmestad, Randi (Journal article; Peer reviewed, 2017)
      Obtaining reliable and statistical assessment of nanoscale precipitates to link the microstructure with material properties is a primary objective of transmission electron microscopy (TEM) studies of agehardenable aluminium ...
    • Scanning Precession Electron Diffraction to aid Aluminum Alloy Development 

      Sunde, Jonas Kristoffer; Christiansen, Emil; Thronsen, Elisabeth; Wenner, Sigurd; Marioara, Calin Daniel; Van Helvoort, Antonius; Holmestad, Randi (Peer reviewed; Journal article, 2019)
    • Selective area grown ZnTe nanowires as the basis for quasi-one-dimensional CdTe-HgTe multishell heterostructures 

      Hajer, Jan; Mantei, Willi; Kessel, Maximilian; Brüne, Christoph; Wenner, Sigurd; Van Helvoort, Antonius; Buhmann, Hartmut; Molenkamp, Laurens W. (Peer reviewed; Journal article, 2020)
      Selective area growth is employed in the vapor-liquid-solid molecular beam epitaxy of ZnTe nanowire arrays. Full control over the location of the individual nanowires is achieved by defined positioning of the growth catalyst. ...
    • Selective area growth of AlGaN nanopyramid arrays on graphene by metal-organic vapor phase epitaxy 

      Munshi, A Mazid; Kim, Dong-Chul; Heimdal, Carl Philip J; Heilmann, Martin; Christiansen, Silke; Vullum, Per Erik; Van Helvoort, Antonius; Weman, Helge (Journal article; Peer reviewed, 2018)
      Wide-bandgap group III-nitride semiconductors are of special interest for applications in ultraviolet light emitting diodes, photodetectors, and lasers. However, epitaxial growth of high-quality III-nitride semiconductors ...
    • SiC crystalline micro bullets on bio-carbon based charcoal substrate 

      Jayakumari, Sethulakshmy; Vullum, Per Erik; Van Helvoort, Antonius; Tangstad, Merete (Peer reviewed; Journal article, 2020)
      Silicon carbide (SiC) micro bullets were grown on a bio-carbon based charcoal substrate, the morphology and crystal structure were analyzed. In order to collect the crystallographic details scanning electron microscopy ...
    • Single-Mode Near-Infrared Lasing in a GaAsSb-Based Nanowire Superlattice at Room Temperature 

      Ren, Dingding; Ahtapodov, Lyubomir; Nilsen, Julie Stene; Yang, Jianfeng; Gustafsson, Anders; Huh, Junghwan; Conibeer, G; Van Helvoort, Antonius; Fimland, Bjørn-Ove; Weman, Helge (Journal article; Peer reviewed, 2018)
      Semiconductor nanowire lasers can produce guided coherent light emission with miniaturized geometry, bringing about new possibilities for a variety of applications including nanophotonic circuits, optical sensing, and ...
    • Stabilisation of amorphous calcium phosphate in polyethylene glycol hydrogels 

      Schweikle, Manuel; Bjørnøy, Sindre Hove; Van Helvoort, Antonius; Haugen, Håvard Jostein; Sikorski, Pawel; Tiainen, Hanna (Journal article; Peer reviewed, 2019)
      Acellular polymer-calcium phosphate composites are promising bone graft materials. Hydrogels are suitable for providing a temporary matrix, while calcium phosphate minerals serve as ion depots for calcium and phosphate ...