Annealing behaviors of structural, interfacial and optical properties of HfO₂ thin films prepared by plasma assisted reactive pulsed laser deposition

The structure and properties of HfO₂ films deposited by plasma assisted reactive pulsed laser deposition and annealed in N₂ were studied upon thermal annealing as well as the evaluation of thermal stability by Fourier transform infrared spectroscopy, spectroscopic ellipsometry, and optical transmission measurements. The as-deposited HfO₂ films appear predominantly monoclinic with an amorphous matrix which becomes crystallized after high-temperature annealing. No interfacial SiO_x is observed for the as-deposited films on Si. The deposited HfO₂ films exhibit good thermal stability and show excellent transparency in a wide spectral range with optical band gap energies of 5.65-5.73 eV depending on annealing temperature. An improvement in the optical properties by high-temperature annealing is also observed.