Abstract
We report on the deposition and characterization of hafnium silicate and aluminium silicate thin films for different applications in optics and electronics. Pulsed laser deposition in a controllable oxygen atmosphere was used as a processing technique, with optimized parameters in terms of laser wavelength, laser fluence and oxygen pressure. The thin films were investigated using atomic force microscopy, spectroscopic ellipsometry, UV–VIS spectroscopy and X-ray photoelectron spectroscopy. The morphological investigations evidenced uniform layers with low roughness (in the order of nanometres). The optical investigations revealed that aluminium silicate layers with low roughness and low absorption in the infrared (IR) range can be obtained at high substrate temperatures (600 °C). The behaviour of the silicate thin films with respect to the nanosecond IR laser irradiation revealed that aluminium silicate layers have higher laser-induced damage threshold values in comparison with hafnium silicate.
Highlights
Introduction of Hafnium and Aluminium SilicatesHafnia and alumina are high-κ dielectrics with remarkable properties, such as high abrasion resistance and high thermal and chemical stability, which make them useful in a wide area of applications: dielectric gate in various types of transistors [1,2], mirrors or antireflective coatings
The fact that such a low roughness was measured proves that these films can be used for optical coatings, where a slight increase in roughness would alter the spectral properties of the films
The morphological and optical investigations revealed that uniform layers based on aluminium silicates with low roughness and low absorption in the IR range can be obtained by pulsed laser deposition (PLD) at high temperatures
Summary
Hafnia and alumina are high-κ dielectrics with remarkable properties, such as high abrasion resistance and high thermal and chemical stability, which make them useful in a wide area of applications: dielectric gate in various types of transistors [1,2], mirrors or antireflective coatings. The reflective/antireflective properties of multi-layer dielectric coatings can be tuned by adjusting the thickness of the layers to suit a specific wavelength [7] Such heterostructures based on Al2 O3 and HfO2 have already been studied for mirrors with high laser damage threshold [8]. Most of these materials have a low crystallization temperature and produce grain boundaries [14]
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