Spatial and Size Distributions of Ti(C₅H₇O₂)₂[(CH₃)₂CHO]₂ Mist Particles in a Tubular Furnace for Conformal and Uniform Deposition of Amorphous TiO₂ Thin Films

Abstract

The spatial and size distributions of titanium diisopropoxide bisacetylacetonate [(C5H7O2)2[(CH3)2CHO]2, also known as Ti(acac)2(OiPr)2] mist, diluted in CH3OH, are investigated in a tubular furnace using atmospheric‐pressure mist chemical vapor deposition (mist CVD). The focus is on the deposition of amorphous (a)‐TiO2 films with tubular furnace temperature and mesh bias as variables. When the furnace temperature reaches 350 °C, the number density of mist particles increases without significant changes in their size distribution, leading to a higher film deposition rate. Further, the deposition rate and average size of the mist particles with lower adhesion coefficient decrease with increasing spatial distance from the furnace inlet. Furthermore, applying a mesh bias results in an increase in the maximum number density of mist particles with a narrower size distribution; however, the overall film deposition rate decreases. These variations are attributed to the chemical reactivity of the mist precursors produced by pyrolysis and mesh bias. The fine mist precursors, which are strongly charged, coordinate with CH3OH and CHO groups through solvation, enhancing their chemical stability and lifetime. This process yields a dense and rigid a‐TiO2 network, improving the junction properties at the a‐TiO2/c‐Si interface.