Effect of in situ hydrogen plasma treatment on zinc oxide grown using low temperature atomic layer deposition

Zinc oxide (ZnO) films under in situ hydrogen plasma were deposited via atomic layer deposition (ALD) at an extremely low temperature (100 °C). Diethyl zinc ((C2H5)2Zn) and deionized water were used as the zinc and oxygen source, respectively. The growth rate of the ZnO films decreased to 1.26 and 1.06 Å/cycle due to changes in the hydrogen plasma treatment power and exposure time, respectively. The resistivity of the ZnO films decreased to 7.6 × 10−4 Ω cm, even at 100 °C, with a very high carrier concentration (1.4 × 1021 cm−3) due to the increasing oxygen deficiencies in the ZnO films. The carrier mobility was decreased slightly to 8.6 cm2/Vs via grain boundary scattering due to the enhanced polycrystallization. Based on the x-ray diffraction and x-ray photoelectron spectroscopy, the carrier concentration and mobility were strongly correlated to the oxygen deficiency and crystallinity, respectively. In addition, the in situ hydrogen plasma in the ZnO ALD had an important role in sequentially generating oxygen deficiencies and enhancing polycrystal growth.