Ultrathin Al-doped transparent conducting zinc oxide films fabricated by pulsed laser deposition

Al-doped transparent conducting zinc oxide (AZO) films, approximately 20-110 nm-thick, were deposited on glass substrates at substrate temperatures between 200 and 300 degrees C by pulsed laser deposition (PLD) using an ArF excimer laser (lambda = 193 nm). When fabricated at a substrate temperature of 260 degrees C, a 40-nm-thick AZO film showed a low resistivity of 2.61 X 10(-4) Omega(.)cm. carrier concentration of 8.64 x 10(20) cm(-3), and Hall mobility of 27.7 cm(2)/V.s. Furthermore, for an ultrathin 20-nm-thick film, a resistivity of 3.91 x 10(-4) Omega(.)cm, carrier concentration of 7.14-10(20) cm(-3), and Hall mobility of 22.4 cm(2)/V(.)S were obtained. X-ray diffraction (XRD) spectra, obtained by the theta-2 theta method, of the AZO films grown at a substrate temperature of 260 degrees C showed that the diffraction peak of the ZnO (0002) plane increased as the film thickness increased from 20 to 110 nm. The full-width-at-half-maximum (FWHM) values were 0.5500 degrees, 0.3845 degrees, and 0.2979 degrees for film thicknesses of 20, 40, and 110 nm, respectively. For these films, the values of the average transmittance in visible light wavelengths (400-700 nm) were 95.1%, 94.2%, and 96.6%, respectively. Field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) observations showed that even the 20-nm-thick films did not show island structures. In addition, exfoliated areas or vacant and void spaces were not observed for any of the films. (c) 2008 Elsevier B.V. All rights reserved.