Band gap energy of pure and Al-doped ZnO thin films

Pulsed laser deposition (PLD) technique is used to deposit pure and Al-doped ZnO thin films at different temperatures on glass substrates. From the transmission data from optical spectroscopy the band gap energy Eg of the films is derived. The dependences of Eg on the deposition temperatures of the pure and Al-doped ZnO films are different. The band gap energy of the pure ZnO increases and saturates with temperature. However, Eg of Al-doped ZnO shows an exponential decrease. Refractive indices of 1.9–2.1 in the VIS are determined by the spectroscopic ellipsometry (SE). Photoluminescence (PL) data reveal the strong near band emission by increasing the deposition temperature.