Skip to content Mobile Contact Library A-Z
myRMIT login Login

Metal oxide films for chemical sensors, photovoltaic devices and MOS technology

ARC Discovery Project DP0666883 (2006-2009)

RMIT University Team

  • Prof. Dougal McCulloch, Team Leader
  • Dr. Jim Partridge, Research Fellow
  • Mr. Nemo Biluš Abaffy, PhD student
  • Mr. Matthew Field, PhD student

Design and synthesis of low reflectance metal/metal-oxide optical coatings

There is an increasing need to develop new and improved optical coatings as greater efficiency is required for improved heat mirrors, smart windows and for antireflection coatings in photovoltaic devices. Metal/metal-oxide multilayers are often used for low emissivity coatings and optical filters. In this work, we investigate the synthesis of trilayer Al2O3/Al/Al2O3 films using a Filtered Cathodic Vacuum Arc (FCVA). We have used simulations to predict the optimum design for a trilayer low reflectance coating and then replicated this experimentally. We are also investigating graded index optical films synthesized by FCVA and ALD.

Methods

  • Filtered Cathodic Vacuum Arc deposition (FCVA)
  • Atomic Layer Deposition (ALD)
  • Scanning Transmission Electron Microscopy (STEM)
  • Electron Energy Loss Spectroscopy (EELS)
  • Atomic Force Microscopy (AFM)
  • Auger Electron Spectroscopy (AES) depth profiling
  • X-ray Photoelectron Spectroscopy (XPS)
  • Variable Angle Spectroscopic Ellipsometry (VASE)

Trilayer design for low-reflectance coating

Trilayer design for low-reflectance coating

Cross-sectional TEM image of the trilayer design

Cross-sectional TEM image of the trilayer design

Measured optical response of trilayers with different thicknesses of Al (as indicated)

Measured optical response of trilayers with different thicknesses of Al (as indicated)

Metal oxide thin films for gas sensing

Nanoporous metal oxides are a class of materials that have been widely used in modern high-performance gas sensors.

In our current work, we deposit high quality metal oxide films using physical vapour deposition techniques including Filtered Cathodic Vacuum Arc and Magnetron Sputtering. We also employ advanced microscopy techniques to examine the composition and structure of nanoporous tin and titanium oxide gas sensing films. The information gathered from this analysis is related to the film growth processes, sensing performance and the long term stability of functioning devices.

Methods

  • Physical vapour deposition
  • Nanolithography/Focussed Ion Beam etching
  • Transmission Electron Microscopy
  • X-ray Photoelectron Spectroscopy
  • Atomic Force Microscopy
  • Secondary Ion Mass Spectrometry

Inter-digital electrodes within a SnO<sub>2</sub>thin film sensor

Inter-digital electrodes within a SnO2  thin film sensor

SnO<sub>2</sub>clusters on focused ion beam etched edges of a Si<sub>3</sub>N<sub>4</sub>membrane

SnO2clusters on focused ion beam etched edges of a Si3N4  membrane

Response to NO<sub>2</sub>gas of a nano-structured thin film SnO<sub>2</sub>sensor

Response to NO2gas of a nano-structured thin film SnO2  sensor

Metal oxide thin films for MOS devices

The drive to reduce feature sizes and increase packing density of transistors on next generation computer chips has led to the exploration of new materials for Metal-Oxide-Semiconductor devices. Hafnium Oxide could replace Silicon Oxide as the material which separates the gate from the active channel within MOSFET transistors.

We have deposited HfO2 films using a Filtered Cathodic Vacuum Arc system and used advanced microscopy techniques to examine their composition and structure. FEFF multiple scattering code has also been employed to investigate the fine structure from the O k-edge and the simulations have been compared with experimental spectra obtained using EELS. The fundamental aim is to find links between the microstructure of these films and their electrical properties.

Methods

  • Filtered Cathodic Vacuum Arc deposition
  • Transmission Electron Microscopy
  • X-ray Photoelectron Spectroscopy
  • Atomic Force Microscopy
  • FEFF Multiple scattering code
  • Electrical measurements

Crystallite within a FCVA deposited HfO<sub>2</sub>film observed using cross-sectional TEM

Crystallite within a FCVA deposited HfO2  film observed using cross-sectional TEM

The oxygen K-edge produced by the three phases of HfO<sub>2</sub>

The oxygen K-edge produced by the three phases of HfO2

Publications

N. Biluš Abaffy, J. G. Partridge, J. du Plessis and D. G. McCulloch, ‘Optically absorbing trilayer films fabricated using a Filtered Cathodic Vacuum Arc’, Physica Status Solidi A 205, pp. 1439-1442, 2008.

N. Bilus-Abaffy, J. G. Partridge and D. G. McCulloch, ‘Antireflective trilayer films fabricated using a filtered cathodic vacuum arc’, SPIE CD Photovoltaic Cell and Module Technologies II conference proceedings: Paper 7045-8 Aug 2008 DOI:10.1117/12.795634

M. R. Field, D. G. McCulloch, S. N. H. Lim, A. Anders, V. J. Keast and R. W. Burgess, ‘The electronic structure of tungsten oxide thin films prepared by pulsed cathodic arc deposition and plasma-assisted pulsed magnetron sputtering’, J. Phys.: Condensed Matter 20, 17 175216, 2008.

J. G. Partridge, M. R. Field, J. L. Peng, A. Z. Sadek, K. Kalantar-zadeh, J. Du Plessis and D. G. McCulloch, ‘Nanostructured SnO2 films prepared from evaporated Sn and their application as gas sensors’, Nanotechnology 19, 125504, 2008.

Conference Presentations

N. Biluš Abaffy, G. Triani, P. Evans and D. G. McCulloch, ‘Characterisation of Alumina and Titania Films Grown by Atomic Layer Deposition’, ICONN2008, 25th -29th February 2008 (Melbourne, Victoria)

N. Biluš Abaffy, M. Field, J. G. Partridge, J. Du Plessis and D. G. McCulloch, ‘Deposition of high quality metal oxide thin films using a filtered cathodic vacuum arc’, 15th AINSE Conference on Nuclear and Complementary Techniques of Analysis (NCTA) 21st – 23rd November 2007 (Melbourne, Australia)

N. Biluš Abaffy, J. G. Partridge and D. G. McCulloch, "Antireflective trilayer films fabricated using a filtered cathodic vacuum arc", SPIE Optics and Photonics 2008 - Photovoltaic Cell and Module Technologies II conference, 10th - 14th August 2008 (San Diego, California)

N. Biluš Abaffy, P. Evans, G. Triani and D. G. McCulloch, ‘Multilayer alumina and titania optical coatings prepared by atomic layer deposition’, SPIE Optics and Photonics 2008 - Nanostructured Thin Films conference, 10th - 14th August 2008 (San Diego, California)

K. Kalantar-zadeh, A. Z. Sadek, Y. Li, X. F. Yu, J. G. Partridge, D. G. McCulloch, P. G. Spizzirri and W. Wlodarski, ‘Study of nanoporous titanium oxide anodized onto smooth thin films’, 2nd International Symposium on Transparent Conductive Oxides, 22 - 26 October, 2008 (Crete, Greece)

M. R. Field, D. G. McCulloch, S.N.H. Lim, A. Anders, V. J. Keast, R. W. Burgess, ‘The synthesis and characterisation of tungsten oxide thin films’, ACMM Conference, 11th -15th February 2008 (Perth, Australia).

J. G. Partridge, N. Biluš Abaffy, J. du Plessis and D. G. McCulloch, ‘Optically absorbing trilayer films fabricated using a filtered cathodic vacuum arc’, Poster at Trends in Nanotechnology, 1st - 5th Sept. 2007 (San Sebastian, Spain).

J. G. Partridge, M. Field, J. Du Plessis, J. Yu and D. G. McCulloch, ‘A study of the morphology and stoichiometry of nanostructured SnO2 thin films’, Poster at ICONN 08, January 2008 (Melbourne, Australia).

J. G. Partridge, M. Field, N. Biluš Abaffy, J. Du Plessis and D. G. McCulloch, ‘Analysis of metal oxide thin films deposited using a filtered cathodic vacuum arc’, ACMM Conference, 11th-15th February 2008 (Perth, Australia).

A. Z. Sadek, Y. Li, X. F. Yu, J. G. Partridge, D. G. McCulloch, W. Wlodarski, and K. Kalantar-zadeh, ‘Nanoporous TiO2 Thin Film Based Conductometric H2 Sensor’, 2nd International Symposium on Transparent Conductive Oxides, 22 - 26 October, 2008 (Crete, Greece)