High mobility tungsten-doped indium oxide (IWO) deposited by room-temperature RF sputtering in pure argon plasma

Transparent conductive oxides (TCOs) are a key element in many applications, such as liquid crystal displays, organic light-emitting diodes and solar cells. In heterojunction solar cells they serve both as antireflective coatings and as conductive layers, so high mobilities along with low electron densities are necessary. Tungstendoped indium oxide (IWO) grown by radio-frequency sputtering is a promising solution to meet all the abovementioned requirements. In this work we show how a simple non-reactive room-temperature radio-frequency sputtering deposition followed by a low-temperature thermal annealing treatment allows producing IWO films with mobilities up to 70.9 cm/V.s and low carrier concentrations of 2-4 x 1020 cm(-3), which result in resistivities as low as 2.5 x 10(-4) Omega.cm. We show that the sputtering damage to passivation can be recovered by a thermal treatment. A work function around 4.2 eV for most IWO films is also evaluated, which is a relevant parameter when applying the IWO as a TCO in solar cells. Possible effects of oxygen depletion in the target during deposition are also discussed.