Dresden 2020 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 37: Focus Session: Functional Metal Oxides for Novel Applications and Devices II (joint session HL/DS)
DS 37.3: Vortrag
Donnerstag, 19. März 2020, 10:15–10:30, POT 81
Surface Stability of β-Ga2O3 at Realistic Temperature and Pressure Conditions from First Principles — •Konstantin Lion1,2, Sergey V. Levchenko3,2, Matthias Scheffler2,1, and Claudia Draxl1,2 — 1Humboldt-Universität zu Berlin, Berlin, DE — 2Fritz-Haber-Institut der MPG, Berlin, DE — 3Skolkovo Institute of Science and Technology, Moscow, RU
The surface properties of a material play a vital role in epitaxial growth and electrical contacts. Depending on the miscut direction on off-oriented (100) β-Ga2O3 substrates, homoepitaxially grown layers show distinct surface morphologies, i.e., the formation of (201) facets [1]. In a first-principles approach, it is important to account for the experimental growth conditions, since they can influence surface stability and thus surface faceting. In this work, we study the stability of all symmetrically inequivalent low-index surfaces of β-Ga2O3 at realistic conditions using ab initio atomistic thermodynamics. In the calculation of the phase diagrams of all surfaces, we include vibrational contributions to the surface free energy. We find that (201) faceting on (100) substrates is thermodynamically favored at T = 825 ∘C and an oxygen partial pressure of 1 mbar, the conditions during homoepitaxial growth. This shows that thermal equilibrium has been reached during growth. Also, we find that the (001) surface is stabilized at higher oxygen chemical potentials, which explains its role as a cleavage plane at ambient conditions.
[1] R. Schewski et al., APL Materials 7, 022515 (2019)