Work function of doped zinc oxide films deposited by ALD
Al-doped ZnO (AZO) is a promising earth-abundant alternative to Sn-doped In2O3 (ITO) as an n-type transparent conductor for electronic and photovoltaic devices. We have deposited AZO films with resistivities as low as 1.1 × 10-3 ω·cm by atomic layer deposition (ALD) using trimethylaluminum (TMA), diethylzinc (DEZ), and water at 200 °C. The work functions of the films were measured using a scanning Kelvin probe (sKP) to investigate the role of aluminum concentration. The work function of AZO films prepared by two different ALD recipes were compared: a "Al-terminated" recipe and a "ZnO-terminated" recipe. As aluminum doping increases, the Al-terminated recipe produces films with a consistently higher work function than the ZnO-terminated recipe. The resistivity of the Al-terminated recipe films shows a minimum at a 1:16 Al:Zn atomic ratio and using a ZnO-terminated recipe, minimum resistivity was seen at 1:19. The film thicknesses were characterized by ellipsometry, chemical composition by EDX, and resistivity by a four-point probe.
|Keywords||atomic layer deposition, scanning probe microscopy, transparent conductor|
|Journal||Journal of Materials Research|
Gordon, P.G, Bačić, G. (Goran), Lopinski, G.P. (Gregory P.), & Barry, S.T. (2020). Work function of doped zinc oxide films deposited by ALD. Journal of Materials Research, 756–761. doi:10.1557/jmr.2019.334