Figure 3 | Scientific Reports

Figure 3

From: Critical increase in Na-doping facilitates acceptor band movements that yields ~180 meV shallow hole conduction in ZnO bulk crystals

Figure 3

Fourier transform Infrared spectroscopy (FTIR) measurements (a) IR absorption bands are shown after Na-doping in ZnO crystals. Absorption band movements are seen towards the low energy (valence band) as Na-doping concentration increases, data are moved vertically for the clarity. The intensity of IR absorption peaks increases with Na-acceptor concentration. (b) LVM at 3304 cm−1 is seen in Na-doped (1200 °C) and hydrogenated sample, which vanished after oxygen annealing at 900 °C. Na-acceptors were activated after oxygen annealing which gives rise to Na-acceptor related absorption bands at ~(0.195–0.22) eV.

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