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Title: Microstructure, mechanical and electrical properties of nanocrystalline W-Mo thin films

 [1];  [1]
  1. Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968, USA
Publication Date:
Sponsoring Org.:
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Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
AIP Advances
Additional Journal Information:
Journal Volume: 7; Journal Issue: 12; Related Information: CHORUS Timestamp: 2017-12-01 08:39:19; Journal ID: ISSN 2158-3226
American Institute of Physics
Country of Publication:
United States

Citation Formats

Martinez, G., and Ramana, C. V. Microstructure, mechanical and electrical properties of nanocrystalline W-Mo thin films. United States: N. p., 2017. Web. doi:10.1063/1.5009008.
Martinez, G., & Ramana, C. V. Microstructure, mechanical and electrical properties of nanocrystalline W-Mo thin films. United States. doi:10.1063/1.5009008.
Martinez, G., and Ramana, C. V. 2017. "Microstructure, mechanical and electrical properties of nanocrystalline W-Mo thin films". United States. doi:10.1063/1.5009008.
title = {Microstructure, mechanical and electrical properties of nanocrystalline W-Mo thin films},
author = {Martinez, G. and Ramana, C. V.},
abstractNote = {},
doi = {10.1063/1.5009008},
journal = {AIP Advances},
number = 12,
volume = 7,
place = {United States},
year = 2017,
month =

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1063/1.5009008

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  • Thin-film silicon allows the fabrication of MEMS devices at low processing temperatures, compatible with monolithic integration in advanced electronic circuits, on large-area, low-cost, and flexible substrates. The most relevant thin-film properties for applications as MEMS structural layers are the deposition rate, electrical conductivity, and mechanical stress. In this work, n{sup +}-type doped hydrogenated amorphous and nanocrystalline silicon thin-films were deposited by RF-PECVD, and the influence of the hydrogen dilution in the reactive mixture, the RF-power coupled to the plasma, the substrate temperature, and the deposition pressure on the structural, electrical, and mechanical properties of the films was studied. Three differentmore » types of silicon films were identified, corresponding to three internal structures: (i) porous amorphous silicon, deposited at high rates and presenting tensile mechanical stress and low electrical conductivity, (ii) dense amorphous silicon, deposited at intermediate rates and presenting compressive mechanical stress and higher values of electrical conductivity, and (iii) nanocrystalline silicon, deposited at very low rates and presenting the highest compressive mechanical stress and electrical conductivity. These results show the combinations of electromechanical material properties available in silicon thin-films and thus allow the optimized selection of a thin silicon film for a given MEMS application. Four representative silicon thin-films were chosen to be used as structural material of electrostatically actuated MEMS microresonators fabricated by surface micromachining. The effect of the mechanical stress of the structural layer was observed to have a great impact on the device resonance frequency, quality factor, and actuation force.« less
  • Highlights: ► nc-Si:H films synthesized using HW-CVD method from silane and helium gas mixture without hydrogen. ► Volume fraction of crystallites and its size in the films decreases with increase in He dilution of SiH{sub 4}. ► Increase in Urbach energy and defect density with increase in He dilution of SiH{sub 4}. ► Increasing He dilution, hydrogen bonding in the films shifts from Si-H{sub 2} and (Si-H{sub 2}){sub n} complexes to Si-H. ► Hydrogen content films were found to be <2.2 at.% but the bandgap remains as high as 2.0 eV or even more. -- Abstract: We report influence ofmore » helium dilution of silane in hot wire chemical vapor deposition for hydrogenated nano-crystalline silicon films. Structural properties of these films have been investigated by using Raman spectroscopy, low angle x-ray diffraction, Fourier transform infra-red spectroscopy and non-contact atomic force microscopy. Optical characterization has been performed by UV–visible spectroscopy. It has been observed that in contrast to conventional plasma enhanced chemical vapor deposition, the addition of helium with silane in hot wire chemical vapor deposition has an adverse effect on the crystallinity and the material properties. Hydrogen content in the films was found <2.2 at.% whereas the bandgap remain as high as 2 eV or more. Increase in Urbach energy and defect density also suggests the deterioration effect of helium on material properties. The possible reasons for the deterioration of crystallinity and the material properties have been discussed.« less
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