(a) Typical (0002) 2θ/ω scan curves of Zn1− x Co x O (x = 0, 0.01, 0.05, 0.10, 0.16, 0.19, and 0.24) layers. (b) Dependence of a- and c-axis lattice lengths on Co content (x). Closed and empty circles indicate a- and c-axis lattice lengths, respectively. (c) Dependence of cell volume on Co content (x).
(a) Dependence of the ratio (a/c) of a- and c-axis lattice lengths on Co concentration (x). (b) Dependence of the u parameter on Co concentration (x). Inset figure shows typical tetrahedral coordination in a wurtzite-type structure (P63 mc) consisting of A (cation) and X (anion) atoms. The value of u indicates the deformed ration from a regular tetrahedron and is calculated using the following equation: u = 1/3(a/c) + 1/4. (c) ΔP sp versus x in Zn1− x Co x O obtained with a combination of (a) and (b).
(a) MCD spectra at 10 K measured at Co2+-related 3d intra-transitions in Zn1− x Co x O layers with x = 0.01 (orange), 0.05 (pink), 0.10 (black), 0.16 (green), 0.19 (red), and 0.24 (blue). (b) MCD intensity and (c) peak energy at the 3d intra-transition from 4 A 2(F) to 2 E 1(G) as a function of Co concentration (x). Inset shows PL spectra at 10 K of Zn1− x Co x O with x = 0.01 and 0.05.
MCD spectra at 10 K measured in photon energies from ultra-violet to visible regions in Zn1− x Co x O layers with x = 0.01 (a)–0.24 (f). The dotted lines represent non-polarized absorption spectra at 10 K in Zn1− x Co x O layers with x = 0.01–0.24. (g) A line-width (Γ FWHM) of MCD peak at 10 K as a function of Co concentration.
(a) Peak energies derived from the MCD and absorption spectra at the band edge, which essentially indicates the band gap of Zn1− x Co x O layers. (b) Valence band XPS spectra of Zn1− x Co x O with x = 0, 0.16, and 0.24. (c) The difference spectra (closed and empty circles) between ZnO and Zn1− x Co x O (x = 0.16 and 0.24) layers are related to the Co 3d states.
(a) Zeeman splitting energy (ΔEsp-d ) due to the sp-d exchange interaction as a function of Co concentration (x). Red and green lines indicate probabilities of Co singles and open triples calculated by Beheringer's equations. (b) Probabilities of Co pairs and closed triples calculated by Beheringer's equations.
(a) Temperature dependence of the Zeeman splitting energy of Zn1− x Co x O layers with x = 0.01, 0.10, and 0.24. The inset shows the magnetic field dependence of the MCD signal intensity at x = 0.10. (b) The parameter values of C and g eff (10 K) as a function of Co concentration (x).
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