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ARTICLE This journal isChlorine doping in a ZnO matrix to a concentration of 0.65±0.05 at.% was accomplished via atomic layer deposition using a home-made chlorine source at a low deposition temperature of 140 o C. Structural and morphological properties were investigated using X-ray diffraction, field emission scanning electron microscopy, and grazing incidence wide-angle X-ray diffraction. The introduction of chlorine into the ZnO matrix resulted in significant grain growth reorientation due to chlorine doping in the oxygen sites of ZnO. Cl − ions preferentially occupied the substitutional O − ion site and O vacancies, and preferential growth in the {100} planes changing to {002} planes along the longitudinal direction of the hexagonal wurtzite structure as a function of Cl doping levels. This important phenomenon was explained by a passivation effect resulting from the chlorine doping mechanism, which was elucidated using transmission electron microscopy. The optical transmittance of undoped ZnO and ZnO:Cl films was approximately the same (88 %), but the optical band gap was increased by the introduction of the Cl dopant in ZnO due to a Burstein-Moss effect. The lowest resistivity of ZnO:Cl was 1.215×10 -2 Ω cm, and the corresponding carrier concentration and mobility were 5.715×10 19 cm -3 and 31.81 cm 2 V -1 s -1 . Finally, the calculated doping efficiency of chlorine in ZnO was as high as 10.8 % when compared with aluminum-doped ZnO, even though the deposition temperature was very low when applied to plastic substrates due to the non-laminated growth of ZnO:Cl films.

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