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Influence of initial surface reconstruction on nitridation of Al2O3 (0001) using low pressure ammonia
KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
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2007 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 1, 013519- p.Article in journal (Refereed) Published
Abstract [en]

The purpose of this study is to investigate the effect of initial surface reconstruction on the nitridation process of Al2O3 (0001). This was done by exposing differently reconstructed sapphire substrates at different temperatures to low pressure ammonia (NH3). Structural and chemical analysis were carried out using low-electron energy diffraction and x-ray photoelectron spectroscopy. The experiments revealed that using low pressure ammonia (P-NH3 < 1 X 10(-5) Torr), no nitridation takes place on (1x1) unreconstructed surfaces. However, when the unreconstructed surface starts to change to a (root 31 x root 31) R +/- 9 degrees reconstructed surface, with increasing substrate temperature, the nitridation becomes successful. When using the initially reconstructed surface, the nitridation is successful even from the lowest temperature used. These results suggest that the initial surface reconstruction has a major effect on the nitridation process. This kinetic behavior has not been reported before, with most nitridation studies mainly focusing on the effect of surface temperature on the resulting surface morphology, rather than the actual kinetics of the process itself.

Place, publisher, year, edition, pages
2007. Vol. 101, no 1, 013519- p.
Keyword [en]
molecular-beam epitaxy, sapphire nitridation, alpha-alumina, gan growth, xps, plasma, films, temperature, alpha-al2o3, substrate
National Category
Condensed Matter Physics
URN: urn:nbn:se:kth:diva-16331DOI: 10.1063/1.2384807ISI: 000243585200039ScopusID: 2-s2.0-33846332036OAI: diva2:334373
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-12-10Bibliographically approved
In thesis
1. Surface studies on α–sapphire for potential use in GaN epitaxial growth
Open this publication in new window or tab >>Surface studies on α–sapphire for potential use in GaN epitaxial growth
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This Licentiate thesis summarizes the work carried out by the author the years 2004 to 2008 at the University of Iceland and the Royal Institute of Technology (KTH) in Sweden. The aim of the project was to investigate the structure of sapphire (alpha-Al2O3) surfaces, both for pure scientific reasons and also for potential use as substrate for GaN-growth by molecular beam epitaxy.

More generally the thesis describes some surface science methods used for investigating the substrates; the general physical back ground, the experi- mental implementation and what information they can give. The described techniques are used for surface analysis on sapphire substrates which have been treated variously in order to optimize them for use as templates for epi- taxial growth of GaN or related III-V compounds.

The thesis is based on three published papers.

The first paper focuses on the formation a thin AlN layer on sapphire, which may act as a buffer layer for potential epitaxial growth of GaN or any related III-V materials. Two types of sapphire substrates (reconstructed and non- reconstructed) were exposed to ammonia resulting in the formation of AlN on the surface. The efficiency of the AlN formation (nitridation efficiency) for the two surfaces was then compared as a function of substrate temperature through photoelectron spectroscopy and low electron energy diffraction. The reconstructed surface showed a much higher nitridation efficiency than the non-reconstructed surface.

In the second paper, the affect of different annealing processes on the sapphire morphology, and thus its capability to act as a template for GaN growth, was studied. Atomic force microscopy, X-ray diffraction analysis together with ellipsometry measurements showed that annealing in H2 ambient and subse- quent annealing at 1300 °C in O2 for 11 hours resulted in high quality and atomically flat sapphire surface suitable for III-V epitaxial growth.

The third paper describes the effect of argon sputtering on cleaning GaN surfaces and the possibility of using indium as surfactant for establishing a clean and stoichiometric GaN surface, after such sputtering. Soft sputtering, followed by deposition of 2 ML of indium and subsequent annealing at around 500 °C resulted in a well ordered and clean GaN surface while hard sputtering introduced defects and incorporated both metallic gallium and indium in the surface.

Place, publisher, year, edition, pages
KTH, 2009. xi, 49 p.
Trita-ICT/MAP, 2009:3
National Category
Condensed Matter Physics
urn:nbn:se:kth:diva-10669 (URN)978-91-7415-286-9 (ISBN)
2009-06-05, Sal/Hall C1, KTH-Electrum, Isafjordsgatan 26, Kista, 10:15 (English)
Available from: 2009-06-22 Created: 2009-06-13 Last updated: 2010-11-03Bibliographically approved

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Agnarsson, BjörnGöthelid, MatsKarlsson, Ulf O.
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