Characterization of metal oxide nanofilm morphologies and composition by terahertz transmission spectroscopy

An all-optical terahertz absorption technique for nondestructive characterization of nanometer-scale metal oxide thin films grown on silicon substrates is described. Example measurements of laser-deposited TiO2 and atomic layer-deposited films of HfO2 are presented to demonstrate applicability to pure Y2O3, Al2O3, and VOx and mixed combinatorial films as a function of deposition conditions and thickness. This technique is also found to be sensitive to HfO2 phonon modes in films with a nominal thickness of 5 nm.