Electrical and optical properties of Al-doped ZnO films deposited by atomic layer deposition

Al-doped ZnO(AZO) thin films were synthesized using atomid layer deposition(ALD), which acurately controlledthe uniform film thickness of the AZO thin films. To investigate the electrical and optical properites of the AZO thin films, AZO films using ALD was controlled to be three different thicknesses (50 nm, 100 nm, and 150 nm). The structural, chemical, electrical, and optical properties of the AZO thin films were analyzed by X-ray diffraction, X-ray photoelectron spectroscopyfield-emssion scanning electron microscopy, atomic force microscopy, Hall measurement system, and UV-Visspectrophotometry. As the thickness of the AZO thin films increased, the crystallinity of the AZO thin films gradually increased, and the surface morphology of the AZO thin films were transformed from a porous structure to a dense structure. The averagesurface roughnesses of the samples using atomic force microscopy were ~3.01 nm, ~2.89 nm, and ~2.44 nm, respectively. Asthe thickness of the AZO filmsincreased, the surface roughness decreased gradually. These results affect the electrical and opticalproperties of AZO thin films. Therefore, the thickest AZO thin films with 150 nm exhibited excellent resistivity (~7.00 × 10^-4Ωcm), high transmittance (~83.2 %), and the best FOM (5.71 × 10^-3Ω^-1). AZO thin films fabricated using ALD may be used as a promising cadidate of TCO materials for optoelectronic applications.