Atomic Layer Deposition of Tungsten Oxide for Solar Cell Application

Tungsten oxide is deposited by atomic layer deposition (ALD) using tungsten hexacarbonyl [W(CO)6] and ozone [O3]. Growth characteristic is studied in detail by in-situ quartz crystal microbalance (QCM). A narrow temperature window is observed with a saturated growth rate of 0.21 Å per ALD cycle. In-situ Fourier transform infrared (FTIR) vibration spectroscopy investigation is performed to determine the surface chemistry during each ALD half cycle under linear growth regime. X-ray photo electron spectroscopy confirms the deposit presence and chemical nature of tungsten and oxygen in the as-deposited WO3 film. The as deposited films are found amorphous which crystalized to monoclinic WO3 upon annealing.