On nanometer ordering in thin amorphous hydrogenated silicon

We investigated thin films of amorphous hydrogenated silicon (a-Si:H) deposited by PECVD under increasing dilutions of silane plasma by hydrogen. We found out that under increasing additional hydrogen at the depositions, thin films obtain less hydrogen bonded to silicon. The optical band gap energies determined from UV Vis transmittance and reflectance spectra were found to be increasing function of the dilution. We deduce that optical band gaps expanse due to the decreasing dimensions of silicon nanocrystals. They were calculated to be of 2 – 4 nm which proves the medium-range order in a-Si:H

ZnO nanostructures prepared by RF sputtering

ZnO is shortly reviewed as significant material for nanotechnology. Sputtered ZnO thin films showed colummar polycrystalline structure with preffered orientation in direction, resistivity ~ 1 Wcm and optical bandgap Eg = 3,33 eV. Nanoclusters of Au and ZnO were formed by use of RF sputtering

Structural and optical properties of individual GaP/ZnO core–shell nanowires

Structural and optical properties of ZnOeGaP coreeshell nanowires were studied by means of electron microscopy and microphotoluminescence. A thin ZnO shell layer was deposited by RF sputtering on GaP nanowires, which were grown on GaP (111)B substrates under vapoureliquidesolid mode by MOVPE. The SEM and TEM characterization showed that the ZnO shells fully covered the surface of the NWs from top to bottom. Each GaP NW core is composed of many well-defined twinned segments with the planes of twinning oriented in perpendicular to the growth direction. This was contradicted in kinked GaP NWs: their growth direction was initially perpendicular to the twinning planes, but once the NW had kinked, it changed to lie within the twinning planes. The ZnO shell deposited on the GaP core has a columnar morphology. The columns are inclined at a positive angle close to 70 with respect to the GaP growth axis. All observed columns were tilted at this angle to the growth direction. Micro-photoluminescence study showed that thermal annealing improved the quality of the ZnO crystallographic structure; the annealing made observable the photoluminescence peak related to the band-to-band transition in ZnO

Plasmonic behaviour of sputtered Au nano island arrays

Je demonstrována specifikace formování naprášených Au nano-ostrůvkových polí (NOP) na skleněných substrátech, anebo na tenkých vrstvách ZnO dopovaných galiem. Statistická analýza morfologie zobrazení SEM a AFM ukázala normální rozdělení velikosti nano-částic na dlouhou vzdálenost - jejich modus AM se měnil z 8 na 328 nm2 v závislosti na hustotě výkonu naprašování, který definoval nominální tloušťku vrstvy v rozpětí 2-8 nm. Přednostní orientace krystalitů Au NOP ve směru [111] kolmém k podložce se zvyšuje s vyšší hustotou výkonu naprašování a po tepelném zpracování vrstev. Příčně lokalizovaná povrchová plazmonická rezonance (LPPR vyhodnocená pomocí transmisní UV-Vis spektrofotometrie) ukázala „rudý“ posun extinkčního maxima (l ≤ 100 nm) se zvýšením nominální tloušťky a „modrý“ posun (≤ -65 nm) po žíhání Au NOP. Plazmonické vlastnosti Au NOP byly popsány modifikací velikostně škálovacího univerzálního modelu použitím nominální tloušťky vrstvy jako technologického škálovacího parametru. Naprášením mezilehlé ultra-tenké vrstvy titanu mezi sklo a zlato se zlepší adheze zlatých nano-ostrůvků, jakož i podpora formování lépe definované struktury Au NOP menší dimenze.The specificity of the formation of Au sputtered nanoisland arrays (NIA) on a glass substrate or on a ZnO thin film doped by Ga is demonstrated. Statistical analysis of morphology images (SEM, AFM) exhibited the Log-normal distribution of the size (area) of nanoislands—their modus AM varied from 8 to 328 nm2 depending on the sputtering power density, which determined the nominal thicknesses in the range of 2–8 nm. Preferential polycrystalline texture (111) of Au NIA increased with the power density and after annealing. Transverse localised surface plasmonic resonance (LSPR; evaluated by transmission UV–vis spectroscopy) showed the red shift of the extinction peaks (l ≤ 100 nm) with an increase of the nominal thickness, and the blue shift( ≤ −65 nm) after annealing of Au NIA. The plasmonic behaviour of Au NIA was described by modification of a size-scaling universal model using the nominal thin film thickness as a technological scaling parameter. Sputtering of a Ti intermediate adhesive ultrathin film between the glass substrate and gold improves the adhesion of Au nanoislands as well as supporting the formation of more defined Au NIA structures of smaller dimensions