Effect of Doped Boron on the Properties of ZnO Thin Films Prepared by Sol-gel Spin Coating

Transparent conductive boron-doped ZnO thin films were prepared by sol-gel spin coating method. The effect of doped boron concentration on the properties of the films was systematically discussed. The films were characterized by X-ray diffraction, atomic force microscopy, spectrophotometry, and Hall effect measurement system. All the doped and undoped ZnO films were of a single hexagonal structure, and showed a preferred orientation of (002). The particle size and surface roughness of the films decreased with increased doped boron concentration. All the films exhibited an average transmittance of approximate 90% in visible-light region and an energy gap of about 3.3 eV. The maximum carrier concentration, the highest carrier mobility and the lowest resistivity were observed at a doped boron concentration of 0.5%(molar fraction). Based on these results, we suggested that the saturation concentration of doped boron in ZnO film is 0.5%(molar fraction).