Origin ofp-type conduction in single-crystalCuAlO2

Abstract

We report measurements of the structural, optical, transport, and magnetic properties of single crystals of the anisotropic p-type transparent semiconductor CuAlO 2. The indirect and direct band gaps are 2.97 and 3.47 eV, respectively. Temperature-dependent Hall measurements yield a positive Hall coefficient in the measured range and an activated carrier temperature dependence. The resistivity is anisotropic, with the ab-plane resistivity about 25 times smaller than the c-axis resistivity at room temperature. Both are activated with similar activation energies. The room-temperature ab-plane mobility is relatively large at 3 cm 2 V −1 s −1 , and we infer a c-axis mobility of 0.12 cm 2 V −1 s −1. The Seebeck coefficient is positive at all measured temperatures, and has a T −1 dependence over most of the measured range. The low-temperature paramagnetic moment is consistent with a spin-1/2 defect with a density of 3.4ϫ 10 20 cm −3. These results suggest that the conduction mechanism for p-type carriers in CuAlO 2 is charge transport in the valence band and that the holes are thermally activated from copper-vacancy acceptor states located about 700 meV above the valence-band maximum.

Dellafossite CuAlO2 film growth and conversion to Cu–Al2O3 metal ceramic composite via control of annealing atmospheres

“…CuO has previously been used as a flux to grow 30 CuAlO 2 single crystals. [18][19] In this case we speculate that the excess CuO may be contributing to the enlarged crystal by acting as a flux, however a number or other explanations are also possible such as the formation of a eutectic or peritectic. …”

“…The relative intensity of the CuAlO 2 diffraction peaks vary substantially as compared to the reference powder spectra shown in figure 1 (a) (11)(12)(13)(14)(15)(16)(17)(18)(19)(20). 25 In this work, the polycrystalline Al 2 O 3 substrates used have x-ray 15 reflections corresponding to both the (0001) and (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) planes and these are used in conjunction with CuO thereby satisfying conditions identified in previous work for both CuAl 2 O 4 and CuAlO 2 formation. However, our results in figure 4 below show that, post annealing, only a very small fraction of the films are in 20 the spinel phase.…”

Understanding doping anomalies in degenerate p-type semiconductor LaCuOSe

“…It has become increasingly clear, however, that all of these materials are limited by poor conductivities caused by deep acceptor levels, [29][30][31] and that the majority of Cu I based oxides …”

The luminescent properties of CuAlO2

“…4 The theoretical analysis of Scanlon et al indicate that the dominant defects are Cu Al and V Cu ; with V Cu forming an acceptor level at 680 meV. 34 Given that the optical bandgap determined in this work is $3.68 eV, then a transition from the zero vibrational level excited state to the acceptor level may then be expected around 2.98 eV, close to the peak emission of the blue band at (2.88 eV).…”

“…It has been prepared by both relatively low temperature hydrothermal processing and high temperature reactions using either solid state reactions or sol-gel processing. [2][3][4][5][6][7][8] Thin lms have also been prepared by sputtering, using pulsed laser deposition from CuAlO 2 targets made by high temperature methods, and by interfacial reactions. [7][8][9][10][11] Additionally, more exotic methods such as polymer assisted deposition and fungus assisted synthesis have also been demonstrated.…”