Dynamics in between Structural and Electrical Properties of as Grown ZnO Thin Films by Thermal ALD

Abstract

The mechanism behind n-type conductivity of undoped ZnO films are not understood well. One and two dimensional defects (grain boundaries, dislocations), and zero dimensional stoichiometric point defects (vacancies, self-interstitials and impurities) play a crucial role in determining the electrical properties of ZnO. All defect mechanisms are strongly controlled by the growth method and conditions. While it is more straightforward examining the one and two dimensional defects, measuring and unveiling the mechanism behind the zero dimensional point defect contribution and their sole effect on the electrical properties are challenging. This is why there has been controversial discussion of results among experimental and computational works relating physical and chemical properties of ZnO to sustainable electrical properties. In this study, to correlate the dynamics in between structural and electrical properties of ZnO grown by thermal ALD; growth temperature, DEZ and DI water precursor pulse times, DEZ/DI water precursor pulse ratio, and N2 purge time were varied. To obtain growth condition specific structural and electrical properties; XRD, AFM, profilometer, ellipsometry, XPS/CasaXPS, UV-VIS spectrometer, Hall-Effect measurements were utilized. Although, there was no strong correlation for oxygen vacancies, the contribution of hydrogen impurities, zinc interstitials and oxygen vacancies to conductivity was observed at different growth conditions. Lowest resistivity and highest average % transmittance were obtained as 6.8x10-3 ohm.cm and 92% in visible spectrum (380-700 nm), respectively.