In-Ga-Zn-O thin films with tunable optical and electrical properties prepared by high-power impulse magnetron sputtering

Reactive high-power impulse magnetron sputtering (HiPIMS) was used for deposition of amorphous In-Ga-Zn-O films at low substrate temperature (<70 °C). The depositions were performed using a strongly unbalanced magnetron equipped with a ceramic In2Ga2ZnO7 target (100 mm in diameter). Films were prepared at a constant argon pressure of 1 Pa on standard soda-lime glass at a target-to-substrate distance of 100 mm. The effect of pulse-averaged target power density (in the range 100-1020 W cm−2 at a constant average target power density of 5 W cm−2) is discussed for two series of films: with and without admixed O2 into the discharge. Obtained results show that the value of the pulse-averaged target power density is an effective parameter for tuning of electrical and optical properties of the films. The films prepared without admixed O2 exhibit increasing optical transparency and Hall mobility with an increasing value of the pulse-averaged target power density whereas the electrical resistivity is in the range ~10−1-101 Ω cm as a result of an increasing oxygen film concentration. The admixed O2 into the plasma discharge strongly influenced the chemical composition of the films which is in this case invariant to value of the pulse-averaged target power density. However, in this case, there is a rapid increase of the film resistivity (from ~100 to 106 Ω cm) with an increasing pulse-averaged target power density whereas all films are highly optically transparent (extinction coefficient at the wavelength of 550 nm ≤ 9 × 10−3). Various mechanisms responsible for the different behaviors of these two series are also discussed.