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(a) The XRD spectra of (0 ≤ x ≤ 0.03) films. The symbol “*” denotes the peak from Si (200). The inset shows the c-axis parameter c film of films with different x. (b) The O K-edge XAS spectra of ZnO, films and reference sample of taken in TEY mode. The dashed lines are guide for eyes.
(a) The Cr L 3-edge XAS spectra of (0 ≤ x ≤ 0.03) films and reference sample of taken in TEY mode. (b) Experimental Cr L 3-edge XAS spectrum (circles) of (x = 0.01) film and weighted sum (solid line) of theoretical XAS spectra (dashed lines) of Cr1+, Cr2+, Cr3+, and Cr5+ calculated using the CTM4XAS5.5 program. The dashed line is guide for eyes.
(a) Room-temperature M-H curves of (0 ≤ x ≤ 0.03) films after subtracting the diamagnetic background. (b) Relative concentrations of Cr1+, Cr2+, Cr3+, and Cr5+ in films and corresponding calculated average spin magnetic moment per Cr based on the results of theoretically calculated XAS spectra and spin magnetic moment per Cr obtained from M-H curves.
The Lnρ vs T−1/4 curves of (0.01 ≤ x ≤ 0.03) films. The inset shows the dependence of resistivity on the measured temperature. The solid lines are guide to eyes.
The schematic diagram of carrier hopping between two defects in (a)low and (b) high Ga concentration films. r BMP is the radius of BMPs (solid line circles). ξ is the localization radius of VRH spheres (dashed line circles). The defects are represented by rectangles. The low and high valence state Cr ions are represented by big and small circles with arrow, respectively.
Parameters of (0 ≤ x ≤ 0.03) films obtained from Hall effect measurement [resistivity (ρ), electron concentration (n), kFl, and mean free path (l) calculated using Drude formula ( ) (Ref. 6 )] and standard four probe measurement [characteristic hopping temperature (T 0) and localization radius (ξ)].
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