Optical properties and structure of HfO2 thin films grown by high pressure reactive sputtering



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Mártil de la Plaza, Ignacio (2007) Optical properties and structure of HfO2 thin films grown by high pressure reactive sputtering. Journal of Physics D-Applied Physics, 40 (17). pp. 5256-5265. ISSN 0022-3727

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Official URL: http://dx.doi.org/10.1088/0022-3727/40/17/037


Thin films of hafnium oxide ( HfO2) have been grown by high pressure reactive sputtering on transparent quartz substrates ( UV- grade silica) and silicon wafers. Deposition conditions were adjusted to obtain polycrystalline as well as amorphous films. Optical properties of the films deposited on the silica substrates were investigated by transmittance and reflectance spectroscopy in the ultraviolet, visible and near infrared range. A numerical analysis method that takes into account the different surface roughness of the polycrystalline and amorphous films was applied to calculate the optical constants ( refractive index and absorption coefficient). Amorphous films were found to have a higher refractive index and a lower transparency than polycrystalline films. This is attributed to a higher density of the amorphous samples, which was confirmed by atomic density measurements performed by heavy- ion elastic recoil detection analysis. The absorption coefficient gave an excellent fit to the Tauc law ( indirect gap), which allowed a band gap value of 5.54 eV to be obtained. The structure of the films ( amorphous or polycrystalline) was found to have no significant influence on the nature of the band gap. The Tauc plots also give information about the structure of the films, because the slope of the plot ( the Tauc parameter) is related to the degree of order in the bond network. The amorphous samples had a larger value of the Tauc parameter, i. e. more order than the polycrystalline samples. This is indicative of a uniform bond network with percolation of the bond chains, in contrast to the randomly oriented polycrystalline grains separated by grain boundaries.

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© 2007 IOP Publishing Ltd. Parts of this work were done during a research stay of one of the authors (FLM) at the ISL of the HMI with support of a mobility grant (PR2004-0426) of the Spanish Ministry of Education and Science. It was also supported by the research project TEC2004/1237 and the research grant (AP2003-4434) of the same Ministry. Special thanks are given to the ISL and to the CAI-‘Tecnologías Físicas for a long trajectory of fruitful collaboration.

Uncontrolled Keywords:Electron-Cyclotron-Resonance, Chemical-Vapor-Deposition, Hafnium Oxide, Spectroscopic Ellipsometry, Compositional Analysis, Amorphous-Silicon, Gate Dielectrics, Sioxnyhz Flms, Sin(X)-H Films, Plasma Method.
Subjects:Sciences > Physics > Electricity
Sciences > Physics > Electronics
ID Code:25982
Deposited On:09 Jul 2014 07:10
Last Modified:31 Dec 2020 00:03

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