Role of Ambient Hydrogen in HiPIMS-ITO Film during Annealing Process in a Large Temperature Range

Indium tin oxide (ITO) thin films were prepared by high power impulse magnetron sputtering (HiPIMS) and annealed in hydrogen-containing forming gas to reduce the film resistivity. The film resistivity reduces by nearly an order of magnitude from 5.6 x 10(-3) omega center dot cm for the as-deposited film to the lowest value of 6.7 x 10(-4) omega center dot cm after annealed at 700 degrees C for 40 min. The role of hydrogen (H) in changing the film properties was explored and discussed in a large temperature range (300-800 degrees C). When annealed at a low temperature of 300-500 degrees C, the incorporated H atoms occupied the oxygen sites (H-o), acting as shallow donors that contribute to the increase of carrier concentration, leading to the decrease of film resistivity. When annealed at an intermediate temperature of 500-700 degrees C, the H-o defects are thermally unstable and decay upon annealing, leading to the reduction of carrier concentration. However, the film resistivity keeps decreasing due to the increase in carrier mobility. Meanwhile, some locally distributed metallic clusters formed due to the reduction effect of H-2. When annealed at a high temperature of 700-800 degrees C, the metal oxide film is severely reduced and transforms to gaseous metal hydride, leading to the dramatic reduction of film thickness and carrier mobility at 750 degrees C and vanish of the film at 800 degrees C.

Automated summary

Indium tin oxide (ITO) thin films were prepared using high power impulse magnetron sputtering (HiPIMS) and were annealed in hydrogen-containing forming gas. The film resistivity decreases significantly after annealing, with the lowest value reached at 700 degrees C for 40 min. The role of hydrogen in changing film properties was studied, and it was found that hydrogen atoms occupied oxygen sites at low temperatures, leading to a decrease in resistivity. At intermediate temperatures, hydrogen defects decayed, resulting in a reduction in carrier concentration but a continued decrease in resistivity due to increased carrier mobility. At high temperatures, the film was severely reduced and transformed into gaseous metal hydride, leading to the disappearance of the film.