Properties of MOCVD Deposits Using Novel Sn(II) Neo-Pentoxide Precursors

Abstract

A family of Sn(II) oxo-alkoxy precursors were investigated for MOCVD applications, which included [Sn(μ-ONep)2]∞ (1, ONep = OCH2CMe3) and its hydrolysis products [Sn5(μ3-O)2(μ-ONep)6] (2) and [Sn6(μ-O)4(ONep)4] (3). Each was found to possess high enough volatility at low temperatures, as indicated by melting point and TGA/DTA data, to warrant investigation as MOCVD precursors to tin oxide thin films. The experimental setup used a lamp-heated cold-wall CVD reactor with direct vaporization of the precursor, without a carrier gas. Compounds 1−3 failed to produce uniform films, but powders and wires of tin oxide and Sn metal were formed under the appropriate conditions. The resultant deposits on Si wafers were investigated using SEM, XRD, and TEM techniques. The nonhydrolyzed species 1 preferentially formed spheres of Sn0 whereas the partially hydrolyzed species 2 formed wires of tin oxide from a proposed vapor−liquid−solid mechanism using Sn0 as the seed. Compound 3 formed an intermediate species possibly due to its more condensed nature limiting its volatility. In general, these compounds are useful for MOCVD, but other conditions or deposition techniques are necessary to form high-quality thin films of tin oxide.