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Title: Molecular beam epitaxy growth of semiconductor nanowires for novel applications in optoelectronic devices

Ezekiel Anyebe

Federal University of Agriculture, Nigeria

Biography

Dr. Anyebe, Ezekiel A. studied at the Federal University of Maiduguri, Nigeria and graduated with a BSc. Physics in 2002. He then proceeded to the Federal University of Agriculture, Makurdi, Nigeria where he obtained a master’s degree in Engineering Physics in 2009. He received his doctorate in Physics from Lancaster University, United Kingdom in 2015. His current research interests include Graphene, Nanotechnology, growth of semiconductor Nanostructures for optoelectronic device applications. He has published several research articles in peer reviewed and high impact journals.

Abstract

The advent of the two-dimensional graphene, has sparked enormous research interest owing to its extraordinary electronic and optical properties including ultra-high carrier mobility exceptionally high thermal conductivity, flexibility and high optical transparency which offers huge potential for applications in transparent, stretchable and flexible electronics. On the other hand, semiconductor nanowires (NWs) have emerged as potentially important building blocks for novel photonic and electronic devices due to their unique properties including epitaxial growth insensitive to lattice mismatch. The monolithic integration of semiconductor NWs on graphene has stimulated enormous research interest over the recent years as it would enable the exploitation of the exceptional qualities of the former with the intriguing properties of the latter and provide a unique platform for the development of high performance, sophisticated, flexible, cost-effective and functional hybrid nanodevices such as solar cells and light emitting diodes.

The growth of InAs and InAsSb NWs on graphite by solid-source molecular Beam Epitaxy is reported. Mechanically exfoliated graphite films from highly oriented pyrolytic graphite (HOPG) were transferred onto Si (111) substrates and subsequently loaded into the system and thermally outgassed. Indium (In) droplets were pre-deposited on the films prior to growth initiation at pre-optimised conditions. The InAs and InAsSb NWs were then grown at a temperature of 450°C to 500°C by the spontaneous opening of the shutters for all growth precursors. The surface morphology of the NWs was investigated using a FEI XL30 SFEG scanning electron microscope (SEM) while Transmission electron microscope (TEM) images were taken with a JEOL-JEM 2100 microscope working at 200 kV.

The nanowires are vertically well aligned with no observable tapering. Figure 1a shows the 45° tilted SEM image of InAs NWs grown on graphite while the selective area electron diffraction pattern and typical HRTEM image of as-grown NWs are shown in Figures 1b and c respectively. InAs-NWs/graphite heterojunction devices exhibiting rectifying behaviour was fabricated. A Room temperature photovoltaic response with a cut-off wavelength of 3.4 μm was realized. This unravels a promising technique for the monolithic integration of InAs NWs with graphite for applications in flexible Infrared Optoelectronic Devices

Audience take away:

• It will provide the audience with new information on the methodology for the fabrication of nanowires.
• The technique for the development of nanowire based infrared photovoltaic detectors will be unraveled.
• The audience would be able to fabricate similar nanowires of this and other material system for advanced functional devices.
• It explicates a promising route towards the monolithic integration of InAs nanowires with graphite for flexible and functional hybrid devices.