The growth and conductivity of nanostructured ZnO films grown on Al-doped ZnO precursor layers by pulsed laser deposition

The structure and electrical properties of nanostructured Al-doped ZnO (AZO)/ZnO bilayers grown as potential solar cell electrodes by pulsed laser deposition on (0001) sapphire substrates are investigated. Transmission and scanning electron microscopy and X-ray diffraction show a narrow temperature window around 350–450 °C where nanostructures are formed. 2-D mapping of electrical conductivity by tunnelling atomic force microscopy showed that these nanostructures provided low resistance pathways, but that the overall film resistivity increased for substrate temperatures above 350 °C. The reasons for this are discussed.