Atomic layer deposition of SnO2 thin films using tin(IV) acetate as a novel precursor

Tin dioxide (SnO2), with an exceptional combination of high transparency, conductivity, and stability in a harsh chemical environment, has gained enormous attention as a potential material for various optoelectronic applications including transparent electrodes for solar cells, anode materials for batteries, smart windows and displays, gas sensing, and catalysis. Many of these applications require scalable, highly uniform, and conformal thin films with superior quality and performance. Atomic layer deposition (ALD) technique offers a unique combination of scalability, uniformity, and conformality with Ångström level thickness control. In this work, we present a new ALD process for the SnO2 thin film with tin(IV) acetate as a novel precursor. We studied the deposition over a temperature range from 150 to 250 °C and observed that growth per cycle decreases from 0.78 to 0.42 Å as the deposition temperature increased from 150 to 250 °C. The as-deposited films are amorphous, and annealing above 350 °C gives phase-pure crystalline tetragonal SnO2. XPS analysis of the as-deposited SnO2 films confirms the existence of the Sn4+ state at all deposition temperatures. Using time-of-flight elastic recoil detection analysis, small amounts of carbon (∼2.8 at. %) and hydrogen (∼2.2 at. %) impurities were detected, which decrease upon postdeposition annealing in both air and N2 atmospheres.