Simple monoclinic 20 atom cell of β–Ga2O3 (twice the primitive cell) showing distorted octahedral and approximately tetrahedral gallium sites. There are three non-equivalent oxygen sites.
Optical Absorption spectra for undoped, Mn-doped, and Cr-doped β–Ga2O3 single crystals. Black vertical lines mark the optical gap for each linear polarization.(inset) The same data plotted with a log scale on the vertical axis.
K-edge XANES for (a) Cr-doped Ga2O3 and various Cr-containing compounds with varying Cr valence, and (b) Mn-doped Ga2O3 and several reference compounds (MnO, Mn3O4, Mn2O3, MnO2) with various Mn valence (2+ thru 4+).
Magnetic moment in μb /TM ion from SQuID at 5 K vs applied field for (a) Mn (red squares) and Cr (blue triangles) from 1000 Oe to −1000 Oe to 1000 Oe (loop), and (b) Mn samples from beginning, middle, and end of the crystal (increasing Mn) from 1000 Oe to 50,000 Oe (5 T). The curves in (b) are almost exactly overlapping. A linear diamagnetic contribution has been subtracted.
DFT:GGA band structure plot for relaxed, neutral, 40-atom cell of (a) undefected β–Ga2O3 (b) β–Ga2O3 with one Mn replacing an octahedral Ga and (c) one Cr atom replacing an octahedral Ga. Filled states are shown in red dots (darker) and unfilled states in green dots (lighter).
Schematic diagram showing mid-gap Fermi level near the Mn2 +/Mn3+ transition level.
Transition metal concentrations from PIXE and crystal quality parameter from RBS (χ min ) for undoped crystal, Cr-doped crystal, and Mn-doped crystal at three points along color gradient. Mn concentration correlates inversely with crystal quality, but Cr does not.
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