For information on Silicon Photonics click here.
Areas of Interest 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
- 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.
- 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.
- 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.
- 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.