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Qi B.,University of Iceland | Shayestehaminzadeh S.,University of Iceland | Olafsson S.,University of Iceland | Gothelid M.,Materialfysik | Gislason H.P.,University of Iceland
Applied Surface Science | Year: 2014

We demonstrate applying synchrotron radiation based high resolution X-ray photoelectron spectroscopy as a versatile in-situ tool to study the step-wise formation and nitridation of indium gallium (InGa) composite droplets on Si(1 1 1)7 × 7. This includes analysis of initial interactions of Ga and In with Si(1 1 1)7 × 7, and characterization of formation and nitridation of InGa droplets. The results show that after stabilization of Si(1 1 1)7 × 7 structure with Ga and In at 750 °C and formation of Ga nanodroplets as the bases, the InGa composite droplets (In:Ga ≈ 3:1) were formed at RT and 200 °C in a coverage range 3-14 monolayers. The nitridation efficiency and structure of the droplets/Si(1 1 1) with NH3 were temperature dependent. At or below 350 °C, the droplets were hardly nitridated. At 670 °C, the nitridation of InGa was more completed, which however caused an unavoidable nitridation of Si surface. The optimum nitridation occurred around 480 °C and proceed in a 2D mode. Further simultaneous growth and nitridation of the InGa droplets on the 2D nitridated surface at 400 °C resulted in a complex surface composition and structure. An ex-situ atomic force microscopy reveals both the aligned metallic droplet-island assemblies and the fractured nitridated island bases with small droplets on top for the final surface. © 2014 Elsevier B.V.

Agnarsson B.,Materialfysik | Agnarsson B.,University of Iceland | Qi B.,University of Iceland | Gothelid M.,Materialfysik | And 2 more authors.
Thin Solid Films | Year: 2011

We report on an atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) investigation of hard nitridation of sapphire (α-Al2O3) substrate, using an Epi UNI-Bulb RF plasma cell at substrate temperatures ranging from 250 to 600 °C. Our results show that an AlN1-xOx layer forms on sapphire after extended nitridation at all temperatures, following a Stranski-Krastanov growth mode, with less islands forming at higher temperatures. We also observe a layer-dependent charging shift in XPS, separating smooth AlN1- xOx layers from rough AlN1-xO x islands due to their different electronic coupling to the substrate. Although the island growth is suppressed at higher temperatures, the surface roughness increases at higher temperatures as seen by AFM. We also observe sputtering effects with protrusions and pits. © 2011 Elsevier B.V. All rights reseved.

Qi B.,University of Iceland | Olafsson S.,University of Iceland | Zakharov A.A.,Lund University | Gothelid M.,Materialfysik | And 3 more authors.
Applied Surface Science | Year: 2013

We report a study on the spatial homogeneity and nitridation of a nanopattern template using a spectroscopic photoemission and low energy electron microscopy. The template was composed of Al nanodots which were patterned into a SiO2/Si(1 1 1) surface using e-beam lithography and reactive ion etching. The template exhibited a global inhomogeneity in terms of the local topography, Al composition and structure of the individual nanopatterns. After nitridation, the individual nanopatterns were diminished, more corrugated and faceted. The nitridated nanopatterns were structurally ordered but differently orientated. The nitridation effectively removed the fluorine contaminants by decomposition of the fluorocarbon sidewalls, resulting in the AlN nanopatterns and partially nitridated Si substrate surface outside the nanopattern domains. © 2012 Elsevier B.V. All rights reserved.

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