The Squared optical absorption coefficient versus photon energy for the undoped ZnO and Al-doped ZnO films of different thickness (thickness shown as the number behind AZO-). Bandgap values were determined by a linear extrapolation along the leading edge curve to the background.
VB-XPS of ZnO and the 362 nm thick Al-doped ZnO films are displayed in the region of VB and Zn 3 d. The position (ξ) of the VBM relative to the Fermi level is obtained from the linear extrapolation of the band edge (see the inset).
A fragment of powder x-ray diffraction spectra for the undoped ZnO and Al-doped ZnO films deposited at 500 °C from 5, 10, 20, and 30 ml of precursor solutions, which resulted in films of different thicknesses.
Optical and electronic measurements for the undoped ZnO and Al-doped ZnO films. Film thickness is extracted from the UV-Vis transmittance data. Electron density is measured by Hall effect measurements.
Lattice parameters (a and c), grain size, out-plane strain (δ), and in-plane stress (σ) for the undoped ZnO film, Al-doped ZnO films, and ZnO bulk reference. ZnO bulk reference data adapted from database (JCPDF number: 00-003-0888).
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