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  4. Nanocrystalline Low-Refractive Magnesium Fluoride Films Deposited by Reactive Magnetron Sputtering: Optical and Structural Properties
 
research article

Nanocrystalline Low-Refractive Magnesium Fluoride Films Deposited by Reactive Magnetron Sputtering: Optical and Structural Properties

Mertin, Stefan  
•
Marot, Laurent
•
Sandu, Cosmin S
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2015
Advanced Engineering Materials

In this work, we study MgF2 thin-film synthesis by reactive pulsed DC magnetron sputtering from a metallic magnesium target in a gas mixture of argon, oxygen, and carbon tetrafluoride (CF4). Nanocrystalline films on silicon and glass substrates with excellent properties for optical application are achieved. The plasma discharge is analyzed with a differentially pumped mass spectrometer before and during the deposition process. Without breaking the vacuum, monochromatic photoelectron spectroscopy (XPS) is performed for in situ determination of the atomic C and O concentration. Film microstructure, topography, and thickness are investigated by electron microscopy (SEM and TEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). The optical constants n and k are determined by spectroscopic ellipsometry and spectrophotometry: a consistent parametric fit of the ellipsometric angles and spectral transmittance and reflectance based on three Lorentz oscillators to determine n and k is achieved for a wide spectral range (300–2 300 nm). At 550 nm, a refractive index of 1.382 and near-zero absorption is obtained, which is in excellent agreement with n = 1.383 of polycrystalline MgF2. The measured light reflection at 760 nm is reduced by 3% for a quarter-wave nanocrystalline MgF2 coating on glass compared to the uncoated glass substrate.

  • Details
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Type
research article
DOI
10.1002/adem.201500129
Web of Science ID

WOS:000367538600018

Author(s)
Mertin, Stefan  
Marot, Laurent
Sandu, Cosmin S
Steiner, Roland
Scartezzini, Jean-Louis  
Muralt, Paul  
Date Issued

2015

Publisher

Wiley-Blackwell

Published in
Advanced Engineering Materials
Volume

17

Issue

11

Start page

1652

End page

1659

Subjects

magnesium fluoride

•

reactive magnetron sputtering

•

optical coating

•

low refractive index

•

nanocrystalline microstructure

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LC  
LESO-PB  
Available on Infoscience
August 28, 2014
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/106074
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