Local structures and roles of Fe³⁺ and Cr³⁺ in p‐type semiconductor CuAlO₂

Abstract

Single crystals of the p‐type semiconductor CuAlO2, synthesized from the CuO flux method, have been investigated by electron paramagnetic resonance (EPR) spectroscopy at temperatures from 3.5 to 294 K. EPR spectra reveal an axial Cr3+ center and an axial Fe3+ center, presumably arising from impurities in the starting materials. The Cr3+ center at 294 K is characterized by g = 1.979(1) and D = − 7803(3) × 10−4 cm−1. The Fe3+ center at 294 K has g// = 1.9942(1), g⟂ = 1.9964(1), D = 261.9(3) × 10−4 cm−1, $B_{4}^{0} = 4.533(3) \times 10^{- 4} \,{\rm cm}^{- 1} $, and $B_{4}^{3} = 104.23(3) \times 10^{- 4} \,{\rm cm}^{- 1} $. These spin‐Hamiltonian parameters, evaluated by superposition model analyses and periodic density functional theory (DFT) calculations, suggest that both Cr3+ and Fe3+ occupy the Al3+ site but the latter involves distortion related to perturbation from a substitutional Cu+ ion at the nearest Al site. This difference in the local structure between Fe3+ and Cr3+ explains their contrasting effects on the p‐type conductivity in CuAlO2.

Oxygen Vacancy Defects Boosted High Performance p-Type Delafossite CuCrO2 Gas Sensors

“…The oxygen vacancies were further resolved by electron spin resonance spectroscopy, as shown in Figure . Both samples exhibit symmetrical ESR signals at g = 1.946, which is different from the ESR signal of Cr 3+ with a g -value of 1.97–1.99, and free electron trapped in V o with a g -value of 2.002–2.003 . The measured g -value is close to the reported g -value of V o • in ZnO ( g = 1.95), , suggesting the presence of V o • in the ternary CCO nanoparticles with a specific defect configuration. , Moreover, the ESR intensity of g-CCO is higher than that of h-CCO, indicating abundance of V o • in g-CCO prepared by glycine nitrate combustion method.…”

“…The oxygen vacancies were further resolved by electron spin resonance spectroscopy, as shown in Figure 4. Both samples exhibit symmetrical ESR signals at g = 1.946, which is different from the ESR signal of Cr 3+ with a g-value of 1.97−1.99, 34 and free electron trapped in V o with a g-value of 2.002−2.003. 31 The measured g-value is close to the reported g-value of V o • in ZnO (g = 1.95), 35,36 suggesting the presence of V o…”

Multistate Traffic Flow Headway Fitting

“…As is shown in reference [5], finite mixture Erlang distribution is dense in all distribution functions on interval[0, ) +∞ . When the shape parameter ( 1, 2, , )…”

Electronic and magnetic properties of second main-group and second sub-group metals substitution for Al in delafossite CuAlO2

“…Among them, most of the commercial and practical applications are n-type [6,7], whose monopolarity somewhat limits their use as oxide semiconductors [8]. Moreover, most devices need p-type TCOs to develop functional p-n junctions [6,9,10], which induces considerable attention to discover available p-type TCOs [11,12]. However, the conductivity of p-type TCOs is obviously lower than that of common n-type TCOs [13,14].…”