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 degrees C). The depositions were performed using a strongly unbalanced magnetron equipped with a ceramic In2Ga2ZnO7 target (100mm 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 Wcm(-2) at a constant average target power density of 5 Wcm(-2)) is discussed for two series of films: with and without admixed O-2 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 O-2 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 similar to 10(-1)-10(1) Omega cm as a result of an increasing oxygen film concentration. The admixed O-2 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 similar to 10(0) to 10(6) Omega 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 x 10(-3)). Various mechanisms responsible for the different behaviors of these two series are also discussed.