Atomic layer deposition of in ₂O ₃ using cyclopentadienyl indium: A new synthetic route to transparent conducting oxide films

Indium oxide (In ₂O ₃) forms the basis for an important class of transparent conducting oxides that see wide use in optoelectronic devices, flat-panel displays, and photovoltaics. Here we present a new method for depositing In ₂O ₃ thin films by atomic layer deposition (ALD) using alternating exposures to cyclopentadienyl indium and ozone. Using a precursor vaporization temperature of 40°C and deposition temperatures of 200-450°C, we measure growth rates of 1.3-2.0 Å/cycle. A significant advantage of this synthesis route over previous techniques is the ability to conformally coat porous materials such as anodic aluminum oxide membranes. The deposited films are nanocrystalline, cubic phase In ₂O ₃ and are highly transparent and conducting. In situ quadrupole mass spectrometry and quartz crystal microbalance measurements elucidate the details of the In ₂O ₃ growth mechanism.