Enhancement of the hall mobility in hydrogen-ion-irradiated ZnO films

RF-sputtered ZnO films were irradiated with hydrogen ions by using an ion accelerator at 110 keV. The physical and the electrical characteristics of the irradiated ZnO films were studied as functions of the hydrogen-ion irradiation dose. The Hall measurement indicated that the carrier concentration had small changes regardless of irradiated hydrogen amount, but the mobility was dramatically enhanced after irradiation of 10 ¹⁵ atoms/cm ². Even when the irradiated hydrogen dose was increased, the crystalline structure had no transformation and the composition was preserved. On the other hand, the electronic structure, measured by using X-ray absorption spectroscopy, exhibited a modification of the molecular orbital structure in the ZnO films irradiated at doses above 10 ¹⁵ atoms/cm ². These distortions of the molecular orbital in the conduction band could lead to a mobility enhancement without a structural transformation.