Abstract
The aim of this work is to determine the influence of medium frequency magnetron sputtering powers on the various properties of hafnium dioxide (HfO2) thin films. Microstructure observations show that an increase in the sputtering power has a significant influence on HfO2 films’ microstructure. As-deposited hafnia thin films exhibit nanocrystalline structure with a monoclinic phase, however the rise of the sputtering power results in an increase of crystallite sizes. Atomic force microscopy investigations show that the surface of the deposited films is smooth, crack-free, and composed of visible grains. The surface roughness and the value of the water contact angle increase with the increase of the sputtering power. Measurements of the optical properties show that HfO2 coatings are transparent in the visible wavelength range. A higher sputtering power causes a decrease of an average transmittance level and a simultaneous increase of the real part of the refractive index. Nanoindentation measurements reveal that the thin film hardness and Young’s elastic modulus increase with an increase in the sputtering power. Moreover, the results of plasticity index H/E and plastic resistance parameter H3/E2 are discussed. Based on the obtained results, a correlation between the sputtering power and the structural, surface, and optical properties, as well as the hardness and Young’s elastic modulus, were determined.
Highlights
In the last decade, hafnium dioxide (HfO2 ) has been widely studied because of its attractive properties and potential technological applications [1,2,3,4,5,6,7,8,9]
As a result of the high transparency, hafnia thin films can be used as antireflective coatings for night vision devices, IR optical devices, and in cameras used for space applications [3,4,5,6,13,14]
Pulsed magnetron sputtering can be achieved by applying an impulse (medium frequency (MF) or pulsed-DC) waveform of the electrical signal supplying the cathode of the magnetron, or an impulse dosing of the gas to the deposition chamber
Summary
Hafnium dioxide (HfO2 ) has been widely studied because of its attractive properties and potential technological applications [1,2,3,4,5,6,7,8,9]. Various optical applications of HfO2 thin films have been pursued such as, for example, chirped mirrors and band pass filters, UV mirrors with a high damage threshold, and heat mirrors for energy efficient windows. HfO2 is considered to be one of the most promising candidates to replace SiO2 in Si-based gate electronic devices, because of their high dielectric constant and thermodynamic stability [1,16]. Its hydrophobic nature along with its suitable optical properties open
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