Thermal stability of ε-Ga2O3 polymorph

R. Fornari, M. Pavesi, V. Montedoro, D. Klimm, F. Mezzadri, I. Cora, B. Pécz, F. Boschi, A. Parisini, A. Baraldi, C. Ferrari, E. Gombia, M. Bosi

Research output: Contribution to journalArticle

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Abstract

The thermal stability of ε-Ga2O3 polymorph was studied by complementary methods. Epitaxial films of ε-Ga2O3 grown on c-oriented sapphire were annealed at temperatures in the range 700–1000 °C and then investigated by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). In addition, Differential Scanning Calorimetry (DSC) up to 1100 °C was carried out on fragments of pure ε-Ga2O3 taken from a very thick layer. The results clearly indicate that ε-Ga2O3 initiates modifying its crystallographic structure above 650 °C, as demonstrated by a mild endothermic bent of the DSC curves. However, the effective transition to β-phase occurs quite suddenly at 880–920 °C, depending of the DSC heating rate. XRD and TEM results confirm this evidence. TEM investigation in particular shows that after annealing at 1000 °C and rapid cooling the film is completely made of β-Ga2O3 grains, most of them with orientation (310) respect to the sapphire substrate. However, if the cooling rate is substantially reduced, the converted β-Ga2O3 layer assumes the standard orientation (−201) parallel to (00.1) of the Al2O3 substrate. Based on the results of this study we conclude that ε-Ga2O3 may conveniently be used for device fabrication, exploiting its higher crystallographic symmetry and better matching to sapphire. However, all fabrication steps must be carried out at temperatures below 700 °C.

Original languageEnglish
Pages (from-to)411-416
Number of pages6
JournalActa Materialia
Volume140
DOIs
Publication statusPublished - Nov 1 2017

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Aluminum Oxide
Polymorphism
Sapphire
Differential scanning calorimetry
Thermodynamic stability
Transmission electron microscopy
Cooling
Fabrication
X ray diffraction
Epitaxial films
Substrates
Heating rate
Annealing
Temperature

Keywords

  • Gallium oxide
  • Oxide electronics
  • Phase transition
  • Polymorphism
  • Thermal stability

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

Cite this

Fornari, R., Pavesi, M., Montedoro, V., Klimm, D., Mezzadri, F., Cora, I., ... Bosi, M. (2017). Thermal stability of ε-Ga2O3 polymorph. Acta Materialia, 140, 411-416. https://doi.org/10.1016/j.actamat.2017.08.062

Thermal stability of ε-Ga2O3 polymorph. / Fornari, R.; Pavesi, M.; Montedoro, V.; Klimm, D.; Mezzadri, F.; Cora, I.; Pécz, B.; Boschi, F.; Parisini, A.; Baraldi, A.; Ferrari, C.; Gombia, E.; Bosi, M.

In: Acta Materialia, Vol. 140, 01.11.2017, p. 411-416.

Research output: Contribution to journalArticle

Fornari, R, Pavesi, M, Montedoro, V, Klimm, D, Mezzadri, F, Cora, I, Pécz, B, Boschi, F, Parisini, A, Baraldi, A, Ferrari, C, Gombia, E & Bosi, M 2017, 'Thermal stability of ε-Ga2O3 polymorph', Acta Materialia, vol. 140, pp. 411-416. https://doi.org/10.1016/j.actamat.2017.08.062
Fornari R, Pavesi M, Montedoro V, Klimm D, Mezzadri F, Cora I et al. Thermal stability of ε-Ga2O3 polymorph. Acta Materialia. 2017 Nov 1;140:411-416. https://doi.org/10.1016/j.actamat.2017.08.062
Fornari, R. ; Pavesi, M. ; Montedoro, V. ; Klimm, D. ; Mezzadri, F. ; Cora, I. ; Pécz, B. ; Boschi, F. ; Parisini, A. ; Baraldi, A. ; Ferrari, C. ; Gombia, E. ; Bosi, M. / Thermal stability of ε-Ga2O3 polymorph. In: Acta Materialia. 2017 ; Vol. 140. pp. 411-416.
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AU - Pécz, B.

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