Professor Thorsten Hesjedal FInstP

Abstract:

The University of Waterloo, Waterloo, ON, Canada, is home to North America's first undergraduate program in nanotechnology. As part of the Nanotechnology Engineering degree program, a scanning probe microscopy (SPM)-based laboratory has been developed for students in their fourth year. The one-term laboratory course Nanoprobing and Lithography is accompanied by a preceding one-term lecture course, Nanoprobing and Lithography. The lecture course lays the theoretical foundation for the concepts covered in the laboratory course. The students work in groups of two and obtain hands-on experience in biweekly 3-h laboratory sessions. The labs use a dedicated undergraduate SPM teaching facility consisting of five atomic force microscope stations. The laboratory course covers all common standard modes of operation, as well as force spectroscopy, electrostatic force microscopy, magnetic force microscopy, and scanning probe lithography by electrochemical oxidation and scratching/ploughing of resist. In light of the breadth of the nanotechnology engineering educational program in terms of synthesis and characterization of nanomaterials, the authors designed a dedicated SPM lab with a capacity of up to 130 students per term. © 2010 IEEE.

Abstract:

V-shaped domain transitions in αMnAs nanowires were investigated by micromagnetic simulations. These rather unusual domain patterns are commonly observed experimentally by surface-sensitive magnetic imaging techniques. It has been speculated that the accompanying inclined domain walls in MnAs are the result of either an exchange biasing effect between ferromagnetic αMnAs wires and antiferromagnetic βMnAs wires or possibly due to competing exchange mechanisms in MnAs. Here we present evidence that these domain features are in fact transitions between three-dimensional flux-closure domains of opposite chirality and can therefore rule out the involvement of an antiferromagnetic biasing effect or anisotropic exchange. The formation of the energetically unfavorable V-shaped domain transitions is discussed in the context of the magneto-structural phase transition of the sample. © 2011 Elsevier B.V.

Abstract:

Single-walled carbon nanotubes (SWNTs) were grown using methane CVD with lava as a catalyst and substrate. Metal-oxide phases embedded in the lava are reduced in the presence of hydrogen, thereby promoting catalytic growth. Scanning electron microscopy and energy-dispersive X-ray spectroscopy show a correlation between the growth of carbonaceous nanomaterials and the presence of iron in the alumina matrix. Raman spectroscopy of the carbon deposits proves the occurrence of SWNTs. Although this growth route lacks ef-ficiency, it provides evidence for the claim that SWNTs are a natural allotrope of carbon and that volcanoes may provide an environment for their synthesis. © 2011 Bentham Science Publishers Ltd.

Abstract:

Few-layer graphene is obtained in atmospheric chemical vapor deposition on polycrystalline copper in a roll-to-roll process. Raman and x-ray photoelectron spectroscopy were employed to confirm the few-layer nature of the graphene film, to map the inhomogeneities, and to study and optimize the growth process. This continuous growth process can be easily scaled up and enables the low-cost fabrication of graphene films for industrial applications. © 2011 American Institute of Physics.

Abstract:

The teaching of the different aspects of a sensor system, with a focus on the involved nanotechnology, is a challenging, yet important task. We present the development of an electronic nose system that utilizes a nanoscale amperometric sensing mechanism for gas mixtures. The fabrication of the system makes use of a basic microfabrication facility, as well as an undergraduate chemistry laboratory for material synthesis and preparation. The sensing device consists of an array of cross-reactive sensors composed of metal-oxide semiconducting nanoparticles. Each sensor in the array produces a unique response in the presence of a target gas, allowing the sensor to determine the identity and concentration of multiple gases in a mixture. The educational aspects include microheater simulation and fabrication, design and fabrication of interdigitated electrodes, development of interfacing circuitry and software, development and calibration of a sensory array, sol-gel processing of nanoparticle films and their characterization, and details of the fundamental chemical sensing mechanism. © 2011 IOP Publishing Ltd.