Phase-controlled SnO2 and SnO growth by atomic layer deposition using Bis (N-ethoxy-2,2-dimethyl propanamido)tin precursor

Abstract

Atomic layer deposition (ALD) of SnO and SnO2 thin films was successfully demonstrated over a wide temperature range of 70300 degrees C using a divalent Sn-precursor, bis(N-ethoxy-2,2-dimethyl propanamido)tin (Sn(edpa)(2)). The regulated growth of the SnO2 and SnO films was realized by employing O-2-plasma and H2O, respectively. Pure SnO2 and SnO films were deposited with negligible C and N contents at all the growth temperatures, and the films exhibited polycrystalline and amorphous structures, respectively. The SnO2 films presented a high transmittance of > 85% in the wavelength range of 400-700 nm and an indirect band gap of 3.6-4.0 eV; meanwhile, the SnO films exhibited a lower transmittance of > 60% and an indirect band gap of 2.9-3.0 eV. The SnO2 films exhibited n-type semiconducting characteristics with carrier concentrations of 8.5 x 10(16)-1.2 x 10(20) cm(-3) and Hall mobilities of 2-26 cm(2)/V s. By employing an alternate ALD growth of SnO and SnO2 films, SnO2/SnO multilayer structures were successfully fabricated at 120 degrees C. The in-situ quadrupole mass spectrometry analysis performed during ALD revealed that the oxidation of chemisorbed Sn-precursor occurs dominantly during the Sn(edpa)(2)/O-2-plasma ALD process, resulting in the production of combustion by-products, whereas the Sn(edpa)(2)/H2O ALD process was governed by a ligand exchange reaction with the maintenance of the original oxidation state of Sn2+.