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XRD data of undoped and ZnO:Cu films for different Cu concentrations (0.1% and 1%). The 2θ (002) and (004) peaks at around 34° and 72°, respectively, show the pronounced c-axis orientation in the thin film. In undoped ZnO thin films, smaller peaks corresponding to (100), (101), (102), (110), and (103) orientations are also seen at 31.7°, 36.2°, 47.6°, 56.55°, and 68.11°, respectively, due to deviation from c-axis orientation. Non c-axis oriented peaks are absent in ZnO:Cu films. Arrows indicate the possible positions of CuO XRD peak.
X-ray photoelectron spectroscopic data of Cu 2p 3/2 (∼933 eV) peak of 1% Cu doped ZnO thin film. Empty circles represent the experimental data. The thick solid line which is the sum of two peaks modeled as Gaussian due to +1 (Cu+) and +2 (Cu++) charge states is fit to the experimental data.
PL spectra (left panel) of (a) undoped ZnO, (b) doped ZnO:Cu (0.1%), (c) doped ZnO:Cu (0.5%), and (d) doped ZnO:Cu (1%) thin films. Strong green luminescence band can be observed in ZnO:Cu (0.1%) and ZnO:Cu (0.5%) samples. Right panel: Corresponding magnetization data as a function of applied field at 300 K of (e) undoped ZnO, (f) doped ZnO:Cu (0.1%), (g) doped ZnO:Cu (0.5%), and (h) doped ZnO:Cu (1%) thin films. PL spectra were taken at 10 K and magnetization data were taken at 300 K. Undoped ZnO shows diamagnetic behavior and all Cu doped ZnO thin films show room temperature ferromagnetic behavior.
Magnetic moment per Cu atom (empty circles) and ratio (empty squares) between the PL intensities of green luminescence band (IGLB) and excitonic (IEX) transitions plotted against Cu content in ZnO:Cu thin films.
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