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AREAS OF RESEARCH INTERESTS AND EXPERTISE
Defect studies in crystalline and amorphous materials Positron annihilation spectroscopy Deposition and characterization of silicon-based thin films for optoelectronic applications Aspects of plasma enhanced chemical vapour deposition Silicon photonics
In the Thin Film Laboratory, we are focusing on the Fabrication and Characterization of Nanostructures. There are several ongoing projects, among them
(a) Silicon nanocrystals - a major focus of my group has been the exploration and description of the formation of silicon nanocrystals in silicon-rich oxides, nitrides, and oxy-nitrides, produced by post-deposition annealing of thin films grown by ECR-PECVD or inductively coupled plasma (ICP) CVD. Of particular interest are the effects of annealing in materials that are highly silicon rich, for applications in future nano-photonic devices. For such devices, nano-structured silicon shows substantial promise as quantum confinement effects make luminescence possible, which serves as the foundation of the rapidly emerging field of silicon photonics.
(b) Rare-earth-doped structures - in collaboration with industrial partners, we have demonstrated very high, optically active concentrations of Er, Td, Ce, and Eu by using in-situ doping processes. Studies at the Canadian Light Source synchrotron facility (see below) have provided critical information on the luminescence mechanisms and the incorporation characteristics of the RE in various Si-based matrices. Most exciting form a practical perspective is the potential for tunability of the emission wavelength and/or the generation of white light.
(c) Synchrotron studies - A more and more important aspect of our work is the application of synchrotron-based techniques to the investigation of the luminescence mechanisms in rare earth doped, silicon-based structures. The results provide evidence that luminescence from these materials is correlated with the excitation of O-related energy states, and demonstrate that the composition and bonding structure of the silicon oxide host matrix play an active role in determining the luminescent properties, even though the microstructure of the films may vary from sample to sample. In order to optimize the luminescence from such materials it is, therefore, necessary to consider the local bonding environment of the RE-ions and specific details of electronic states associated with the host matrix.
(d) CdTe nanostructures - in collaboration with John Preston’s group in the Brockhouse Institute for Materials Research we have demonstrated our ability to fabricate CdTe-based nanostructures (nano-rods and -wires) in both zinc-blende and wurtzite configurations and align them vertically on various substrates, commensurate with the substrate surface conditions. This work is of interest from both, a fundamental materials growth perspective and the potential photonics applications, e.g, for photovoltaics. We are investigating the optical and structural properties of such films for their potential use as optical elements in all-optical integrated circuits.
Positrons are a unique probe of materials that provides information that is highly complementary to light, and other particle-based probes.
The McMaster Positron Laboratory is one of only three of its kind in Canada and very few in all of North America. Our work is concerned with the characterization of defect structures – principally through positron annihilation spectroscopy - in materials utilized in the development and fabrication of electronic and photonic devices. One of the most important research programs is concerned with the characterization of Cd- and Zn-based II-VI compound materials. Newer initiatives include studies of the defect chemistry of complex perovskites, which are of importance as dielectrics in microwave devices; a recently established collaboration with an industrial partner on the defect characteristics of epoxies used in semiconductor device packaging; a project on ion implantation induced amorphization of silicon as part of the processing sequence of silicon-based photonic components, and a project on intermetallic alloys.
The McMaster Intense Positron Beam Facility (MIPBF), funded jointly by the Canada Foundation of Innovation (CFI) and the Ontario Ministry of Research and Innovation (MRI), will be one of only four such facilities worldwide and will support the engineering of new materials with properties and capabilities not found in nature. By using positrons to help probe and characterize new materials, we are aiming to accelerate the development of such materials, thereby giving Ontario’s advanced manufacturing industry an important competitive advantage. The MIPBF Surface Analysis System will reduce the measurement times of surfaces from many hours to a few minutes, ensuring the integrity of the surface being probed without recourse to in-situ cleaning. This will enable the determination of the growth kinetics of ultra-thin layers on metals, semiconductors and dielectrics, as well as the detailed study of nanostructures. The Positron Defect Probe will provide the ability to probe the nature of thin layers and interfaces, with depth resolution and with spectroscopic capacity. The Positron Storage and Interaction System will allow for the accumulation of cold-trapped positrons at a rate 100 times higher than at existing facilities, enabling experiments not possible with existing positron systems, including the production of positronic atoms for precision measurements, development of formation processes applicable to antihydrogen research, and production and studies of bound molecular states consisting of matter and antimatter.
Recent Refereed Journal Publications
(Note: Students and research staff under my direct supervision are indicated in bold)
J103. T. Roschuk, P.R.J. Wilson, J. Li, O.H.Y. Zalloum, J. Wojcik, and P. Mascher, “Structure and luminescence of rare earth-doped silicon oxides studied through their X-ray absorption near edge structure and X-ray excited optical luminescence”, physica status solidi B 247, 248-253 (2010) – Editor’s Choice [CIPI, OCE, NSERC]
J102. G. Zatryb, A. Podhorodecki, J. Misiewicz, J. Wojcik, and P. Mascher, “Size-dependent indirect excitation of trivalent Er ions via Si nanocrystals embedded in a silicon-rich silicon oxide matrix”, J. Nanotechnology, Volume 2009, Article ID 769142, 5 pages [NSERC, CIPI]
J101. G.A. Devenyi, J. Li, R.A. Hughes, An-Chang Shi, P. Mascher, and J.S. Preston, “ Epitaxially Driven Formation of Intricate Supported Gold Nanostructures on a Lattice-Matched Oxide Substrate”, Nano Letters 9, 4258–4263 (2009) [NSERC]
J100. S. Neretina, E. Dreaden, Wei Qian, M.A. El-Sayed, R.A. Hughes, J.S. Preston, and P. Mascher, “ The Dependence of the Plasmon Field Induced Nonradiative Electronic Relaxation Mechanisms on the Gold Shell Thickness in Vertically Aligned CdTe-Au Core-Shell Nanorods”, Nano Letters 9, 3772-3779 (2009) [NSERC]
J98. A. Belous, O. Ovchar, B. Jancar, M. Spreitzer, G. Annino, D. Grebennikov, and P. Mascher, “The effect of chemical composition on the structure and dielectric properties of the columbites A2+Nb2O6”, J. Electrochem. Soc. 156, G206 – G212 (2009) [NATO, NSERC]
J97. S. Neretina, R.A. Hughes, J. Britten, N.V. Sochinskii, J.S. Preston and P. Mascher, “The role of substrate surface termination in the deposition of (111) CdTe on (0001) sapphire”, Appl. Phys. A 96, 429-433 (2009) [ORDCF, NSERC]
J96. A.P. Knights, J.N. Milgram, J. Wojcik, P. Mascher, I. Crowe, B. Sherliker, M.P. Halsall, and R.M. Gwilliam, “Observation of non-radiative de-excitation processes in silicon nanocrystals”, Phys. Status Solidi A 206, 969 – 972 (2009) [NSERC, OCE]
J95. D.E. Blakie, O.H.Y. Zalloum, J. Wojcik, E.A. Irving, A.P. Knights, P. Mascher, and P.J. Simpson, “Photoluminescence and positron annihilation spectroscopy of MeV Si+ ion-irradiated SiyO1-y:Er (y≈1/3) thin films”, J. Appl. Phys. 105, 053517 (2009) [NSERC, OCE]
J94. S. Neretina, R.A. Hughes, G.A. Devenyi, N.V. Sochinskii, J.S. Preston, and P. Mascher, “Atypical grain growth for (211) CdTe films deposited on surface reconstructed (100) SrTiO3 substrates”, Appl. Surf. Sci. 255, 5674 (2009) [ORDCF, NSERC]
J93. J. Li, O.H.Y. Zalloum, T. Roschuk, C.L. Heng, J. Wojcik, and P. Mascher, “The formation of light emitting cerium silicates in cerium-doped silicon oxides”, Appl. Phys. Lett. 94, 011112 (2009) [OCE, ORDCF, CIPI]
J92. C.L. Heng, E. Chelomentsev, Z.L. Pang, P. Mascher, and P.J. Simpson, “Photoluminescence and positron annihilation spectroscopy investigation of (Ge, Er) codoped Si oxides deposited by magnetron sputtering”, J. Appl. Phys. 105, 014312 (2009)
J91. C.L. Heng, E. Chelomentsev, O.H.Y. Zalloum, J. Wojcik, and P. Mascher, “Photoluminescence from Er-doped Si-rich silicon oxides deposited by magnetron sputtering in Ar or Ar+H2 plasmas”, J. Vac. Sci. Technol.. A 27, 101 (2009)
J90. S. Neretina, Wei Qian, E. Dreaden, M.A. El-Sayed, R.A. Hughes, J.S. Preston, and P. Mascher, “ Plasmon Field Effects on the Nonradaitive Relaxation of Hot Electrons in an Electronically Quantized System: CdTe-Au Core-Shell Nanowires”, Nano Letters 8, 2410-2418 (2008)
J89. J. Li, O.H.Y. Zalloum, T. Roschuk, C.L. Heng, J. Wojcik, and P. Mascher, “Light Emission from Rare-Earth Doped Silicon Nanostructures”, Advances Opt. Technol. Vol. 2008, Article ID 295601, 10 pages (invited paper)
J88. S. Neretina, R.A. Hughes, G.A. Devenyi, N.V. Sochinskii, J.S. Preston, and P. Mascher, “The role of substrate surface alteration in the fabrication of vertically aligned CdTe nanowires”, Nanotechnology 19, 185601, 8 pages (2008)
J87. C.L. Heng, O.H.Y. Zalloum, J. Wojcik, T. Roschuk, and P. Mascher, “On the effects of double-step anneal treatments on light emission from Er-doped Si-rich silicon oxide”, J. Appl. Phys. 103, 024309 (2008)
J86. J. N. Milgram, J. Wojcik, P. Mascher, and A. P. Knights, "Optically pumped Si nanocrystal emitter integrated with low loss silicon nitride waveguides," Opt. Express 15, 14679-14688 (2007)
J85. A. Podhorodecki, G. Zatryb, J. Misiewicz, J. Wojcik, and P. Mascher, “Influence of the annealing temperature and silicon concentration on the absorption and emission properties of Si nanocrystals”, J. Appl. Phys. 102, 043104 (2007)
J84. S. Neretina, R.A. Hughes, J.F. Britten, N.V. Sochinskii, J.S. Preston, and P. Mascher, “Vertically aligned wurtzite CdTe nanowires derived from a catalytically driven growth mode”, Nanotechnology 18, 275301 (2007) [paper chosen as a featured article and for the cover page]
J83. M. Motyka, G. Sek, R. Kudrawiec, P. Sitarek, J. Misiewicz, J. Wojcik, B.J. Robinson, D.A. Thompson, and P. Mascher, “Probing the indium clustering in InGaAs/GaAs quantum wells by room temperature contactless electroreflectance and photoluminescence spectroscopy”, J. Appl. Phys. 101, 116107 (2007)
J82. C.L. Heng, O.H.Y. Zalloum, T. Roschuk, D. Blakie, J. Wojcik, and P. Mascher, “Photoluminescence study of an Er-doped Si-rich SiOx film”, Electrochem. and Solid-State Lett. 10, K20 (2007)
J81. P.J. Foster, P. Mascher, A.P. Knights, and P.G. Coleman, “Implantation profile of 22Na continuous energy spectrum positrons in silicon”, J. Appl. Phys. 101, 043702 (2007)
Recent Papers in Refereed Conference Proceedings
(Note: Students and research staff under my direct supervision are indicated in bold)
C90. O. Ovchar, A. Belous, O. Kramarenko, D. Mischuk, B. Jancar, M. Spreitzer, D. Suvorov, G. Annino, D. Grebennikov, and P. Mascher, “The Effect of Impurity Phases on the Structure and Properties of Microwave Dielectrics based on Complex Perovskites Ba(Co2+1/3 Nb2/3)O3”, Ferroelectrics 387, 189-196 (2009)
C89. A. Belous, O. Ovchar, O. Kramarenko, D. Mischuk, B. Jancar, M. Spreitzer, D. Suvorov, G. Annino, D. Grebennikov, and P. Mascher, “Low-loss Perovskite Niobates Ba(M2+1/3 Nb2/3)O3: Composition, Structure, and Microwave Dielectric Properties”, Ferroelectrics 387, 36-45 (2009)
C88. A.P. Knights, J.N. Milgram, J. Wojcik, P. Mascher, I. Crowe, B. Sherliker, M.P. Halsall, and R.M. Gwilliam, “Observation of non-radiative de-excitation processes in silicon nanocrystals”, Phys. Status Solidi A 206, 969 – 972 (2009)
C87. T. Roschuk, P.R.J. Wilson, J. Li, J. Wojcik, and P. Mascher, “X-ray spectroscopy studies of luminescent Si-based materials”, Proc. 5th IEEE International Conference on Group IV Photonics (GFP), IEEE, Piscataway, NJ, USA (2009)
C86. I.F. Crowe, T. Roschuk, U. Bangert, B. Sherliker, M.P. Halsall, A. Knights, and P. Mascher, “Combined Super-STEM imaging, EEL and PL spectroscopy of undoped and Er-doped SRSO on Si”, COMMAD 2008, pp. 163-165
C85. A. Martinez, F. Cuesta-Soto, J. Garcia, J. Marti, N.V. Sochinskii, M. Abellan, J. Rodriguez-Fernandez, S. Mengali, A. Mercuri, C. Corsi, I. Reid, M. Robertson, S. Neretina, R.A. Hughes, J. Wojcik, J.S. Preston, and P. Mascher, “Cadmium Telluride: a Silicon-compatible optical material as an alternative technology for building all-optical photonic devices”, Proc. Of SPIE Vol. 6996, 699608-1 (2008)
C84. S. Neretina, D. Grebennikov, R.A. Hughes, M. Weber, K.G. Lynn, P.J. Simpson, J.S. Preston, and P. Mascher, “Defect characterization of CdTe thin films using a slow positron beam, phys. stat. sol. (c) 4, 3659-3663 (2007)
C83. D. Grebennikov, O. Ovchar, S. Neretina, A. Belous, and P. Mascher, “Characterization of columbite ceramics A1-xNb2O6 by positron annihilation spectroscopy”, phys. stat. sol. (c) 4, 3835-3838 (2007)
C82. C.L. Heng, O.H.Y. Zalloum, E. Chelomentsev, and P. Mascher, “Photoluminescence from magnetron sputtered SiO2 films co-doped with (Er,Ge) under excitation of a 325 nm He-Cd laser line”, ECS Trans. 6, 549 (2007)
C81. T. Roschuk, O.H.Y. Zalloum, J. Wojcik, H. Zhang, and P. Mascher, “A comparison of the effects of silicon oxide and silicon nitride host matrices on the photoluminescence from Si nanocrystals after high temperature annealing”, ECS Trans. 6, 523 (2007)
C80. J. Wojcik, T. Roschuk, O.H.Y. Zalloum, C.L. Heng, D.E. Blakie, A.P. Knights, and P. Mascher, “Fabrication and caharcterization of silicon nanostructures for integration in photonics devices and circuits”, 50th Ann. Tech. Con. Conf. Proc., Soc. Vacuum Coaters, 166 (2007) [invited]
SEMINARS, WORKSHOPS, AND CONFERENCES
Organization of Conferences and Workshops
Chair and Co-organizer of the Intl Symposium on Nanoscale Luminescent Materials at the 217th Meeting of the ECS, to be held at Vancouver, BC, April 25 – 29, 2010 Chair and Co-organizer of the 14th Canadian Semiconductor Technology Conference, held jointly with the 4th Intl Symp on Nano and Giga Challenges in Electronics, Photonics and Renewable Energy, McMaster (2009) Chair and Co-organizer of the Intl Symposium on Nanocrystal Embedded Dielectrics for Electronic and Photonic Devices at the 215th Meeting of the Electrochemical Society in San Francisco, CA (2009) Chair and/or Co-organizer of symposia on the Science and Technology of Dielectrics for Photonic Devices at meetings of the Electrochemical Society in Quebec City, Canada (2005), Cancun, Mexico (2006), Washington, DC (2007), and Honolulu, Hawaii (2008) Member of the Program Committee of the Canadian Semiconductor Technology Conferences in 1997, 1999, 2001, 2003, 2005, and 2007 Chair of the Organizing Committee of the 14th Intl Conf on Positron Annihilation, McMaster (2006)
Silicon Based Emission Technology (SiBET) 2009, Manchester, UK, on “Fabrication and Characterization of Rare-Earth Doped Silicon Nanostructures”, June 2009 Colloquium, Department of Chemistry and Nano4Laval, Universite Laval, Quebec, on”Light Emission from Silicon Nanostructures”, March 2009 Canada – Japan Advanced Materials Workshop, Tokyo, Japan, on ”McMaster University and its Automotive Focus - Models for an Interdisciplinary Approach”, February 2009 15th International Conference on Positron Annihilation, Kolkata, India, on “Integration of PAS in the Characterization of Nanostructured Materials Systems”, January 2009 International Workshop on Positron Studies of Defects, Prague, Czech Rep, on "Integration of PAS in the Characterization of Complex Materials Systems", September 2008 International Workshop on Sensitized Er-doped Waveguide Amplifiers/Lasers, Levico Terme, Italy, on "Light emission from rare-earth doped silicon nanostructures", April 2008 3rd Arizona Nanotechnology Symposium, Scottsdale, AZ, on "Nanoscience and Nanotechnology at McMaster - A Model for an Interdisciplinary Approach", April 2008