Functional Metal Oxide Thin Films Grown by Pulsed Laser Deposition

Abstract

The aim of this work is to show that material processing by laser-based technologies can lead to the growth of multifunctional thin films with potential in a large area of applications. The synthesis of Hf, Ta, Si, and Al metal oxides described here relies on the use of pulsed laser deposition (PLD), or radiofrequency (RF) assisted PLD. The morphology and structure of the as-grown thin films are investigated by atomic force microscopy, X-ray diffraction, and transmission electron microscopy, whilst the optical properties are determined by spectroellipsometry. The dielectric behaviour of the deposited layers is investigated by electrical measurements. It is shown that by tuning the deposition parameters, the materials of interest can be synthesized as compact and dense oxide layers. Parameters such as substrate temperature , oxygen pressure, or laser wavelength have a critical impact on the crystallinity of the films, as well as on the characteristic functional properties. For example, hafnium dioxide, tantalum oxide, and aluminium oxide layers grown by RF-PLD at room temperature have low leakage currents, which make them useful for dielectric gates. When high substrate temperatures are involved in the PLD process, these oxide layers have a crystalline structure and smooth surfaces, with potential in antireflective coatings.