skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in Mg{sub x}Zn{sub 1−x}O

Abstract

The self-assembled formation of ordered, vertically stacked rocksalt/wurtzite Mg{sub x}Zn{sub 1−x}O heterostructures by planar phase separation is shown. These heterostructures form quasi “natural” two-dimensional hetero-interfaces between the different phases upon annealing of MgO-oversaturated wurtzite Mg{sub x}Zn{sub 1−x}O layers grown by plasma-assisted molecular beam epitaxy on c-plane sapphire substrates. The optical absorption spectra show a red shift simultaneous with the appearance of a cubic phase upon annealing at temperatures between 900 °C and 1000 °C. Transmission electron microscopy reveals that these effects are caused by phase separation leading to the formation of a vertically ordered rock salt/wurtzite heterostructures. To explain these observations, we suggest a phase separation epitaxy model that considers this process being initiated by the formation of a cubic (Mg,Zn)Al{sub 2}O{sub 4} spinel layer at the interface to the sapphire substrate, acting as a planar seed for the epitaxial precipitation of rock salt Mg{sub x}Zn{sub 1−x}O. The equilibrium fraction x of magnesium in the resulting wurtzite (rock salt) layers is approximately 0.15 (0.85), independent of the MgO content of the as-grown layer and determined by the annealing temperature. This model is confirmed by photoluminescence analysis of the resulting layer systems after different annealing temperatures. In addition, we show that the thermalmore » annealing process results in a significant reduction in the density of edge- and screw-type dislocations, providing the possibility to fabricate high quality templates for quasi-homoepitaxial growth.« less

Authors:
; ; ; ; ; ;  [1]; ;  [2];  [3];  [2]; ; ;  [4];  [5]
  1. Faculty of Physics and Materials Sciences Center, Philipps-Universität Marburg, Hans-Meerwein-Straße 6 and Renthof 5, 35032 Marburg (Germany)
  2. Walter Schottky Institut, Technische Universität München, Am Coulombwall 4, 85748 Garching (Germany)
  3. Institut für Physik, Humboldt-Universität zu Berlin, Newtonstraße 15, 12489 Berlin (Germany)
  4. I. Physikalisches Institut and Laboratorium für Materialforschung (LaMa), Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen (Germany)
  5. Institute for Physical Chemistry and Laboratorium für Materialforschung (LaMa), Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 58, 35392 Gießen (Germany)
Publication Date:
OSTI Identifier:
22494676
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 118; Journal Issue: 4; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTRA; ANNEALING; DISLOCATIONS; MAGNESIUM; MAGNESIUM OXIDES; MOLECULAR BEAM EPITAXY; PHOTOLUMINESCENCE; PLASMA; PRECIPITATION; RED SHIFT; SALT DEPOSITS; SAPPHIRE; SPINELS; TRANSMISSION ELECTRON MICROSCOPY; TWO-DIMENSIONAL SYSTEMS

Citation Formats

Gries, K. I., Vogel, S., Straubinger, R., Beyer, A., Chernikov, A., Chatterjee, S., Volz, K., Wassner, T. A., Bruckbauer, J., Häusler, I., Laumer, B., I. Physikalisches Institut and Laboratorium für Materialforschung, Kracht, M., Heiliger, C., Eickhoff, M., and Janek, J. Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in Mg{sub x}Zn{sub 1−x}O. United States: N. p., 2015. Web. doi:10.1063/1.4926776.
Gries, K. I., Vogel, S., Straubinger, R., Beyer, A., Chernikov, A., Chatterjee, S., Volz, K., Wassner, T. A., Bruckbauer, J., Häusler, I., Laumer, B., I. Physikalisches Institut and Laboratorium für Materialforschung, Kracht, M., Heiliger, C., Eickhoff, M., & Janek, J. Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in Mg{sub x}Zn{sub 1−x}O. United States. https://doi.org/10.1063/1.4926776
Gries, K. I., Vogel, S., Straubinger, R., Beyer, A., Chernikov, A., Chatterjee, S., Volz, K., Wassner, T. A., Bruckbauer, J., Häusler, I., Laumer, B., I. Physikalisches Institut and Laboratorium für Materialforschung, Kracht, M., Heiliger, C., Eickhoff, M., and Janek, J. 2015. "Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in Mg{sub x}Zn{sub 1−x}O". United States. https://doi.org/10.1063/1.4926776.
@article{osti_22494676,
title = {Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in Mg{sub x}Zn{sub 1−x}O},
author = {Gries, K. I. and Vogel, S. and Straubinger, R. and Beyer, A. and Chernikov, A. and Chatterjee, S. and Volz, K. and Wassner, T. A. and Bruckbauer, J. and Häusler, I. and Laumer, B. and I. Physikalisches Institut and Laboratorium für Materialforschung and Kracht, M. and Heiliger, C. and Eickhoff, M. and Janek, J.},
abstractNote = {The self-assembled formation of ordered, vertically stacked rocksalt/wurtzite Mg{sub x}Zn{sub 1−x}O heterostructures by planar phase separation is shown. These heterostructures form quasi “natural” two-dimensional hetero-interfaces between the different phases upon annealing of MgO-oversaturated wurtzite Mg{sub x}Zn{sub 1−x}O layers grown by plasma-assisted molecular beam epitaxy on c-plane sapphire substrates. The optical absorption spectra show a red shift simultaneous with the appearance of a cubic phase upon annealing at temperatures between 900 °C and 1000 °C. Transmission electron microscopy reveals that these effects are caused by phase separation leading to the formation of a vertically ordered rock salt/wurtzite heterostructures. To explain these observations, we suggest a phase separation epitaxy model that considers this process being initiated by the formation of a cubic (Mg,Zn)Al{sub 2}O{sub 4} spinel layer at the interface to the sapphire substrate, acting as a planar seed for the epitaxial precipitation of rock salt Mg{sub x}Zn{sub 1−x}O. The equilibrium fraction x of magnesium in the resulting wurtzite (rock salt) layers is approximately 0.15 (0.85), independent of the MgO content of the as-grown layer and determined by the annealing temperature. This model is confirmed by photoluminescence analysis of the resulting layer systems after different annealing temperatures. In addition, we show that the thermal annealing process results in a significant reduction in the density of edge- and screw-type dislocations, providing the possibility to fabricate high quality templates for quasi-homoepitaxial growth.},
doi = {10.1063/1.4926776},
url = {https://www.osti.gov/biblio/22494676}, journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 4,
volume = 118,
place = {United States},
year = {Tue Jul 28 00:00:00 EDT 2015},
month = {Tue Jul 28 00:00:00 EDT 2015}
}