X-ray reflectivity study of solution-deposited ZrO2 thin films on self-assembled monolayers: Growth, interface properties, and thermal densification

Thin films of ZrO2 were deposited from aqueous solution on Si(100) substrat es precovered by functionalized alkyltrichlorosilane self-assembled monolay ers (SAMs), The interface structure, ther mal stability, and densification of these films in the temperature range from room temperature to 750 degree sC in vacuum were measured using in situ x-ray reflectivity. The growth rat e is a nonlinear function of time in solution, with a pronounced nonuniform ity during the first 30 min. The as-deposited films exhibit about 3-nm roug hness and a density below that of bulk ZrO2. Measurements in vacuum reveal decreasing film thickness, increasing film density, and decreasing roughnes s upon annealing up to 750 degreesC. The densification saturates at the hig hest measured temperatures, presumably following evaporation of residual co ntaminants from the aqueous synthesis procedure. Above 200 degreesC the SAM /ZrO2 interface began to deteriorate, possibly due to interdiffusion. The Z rO2 film structure obtained at the highest annealing temperatures persisted upon cooling to room temperature, and there was no visible evidence of str ess-induced microstructural changes, such as peeling or cracking.