May 7, 2009
Nanowire band structure engineering finds route in solution
In contrast with vapour phase techniques, much less success has been achieved for the growth of magnesium-alloyed ZnO nanowires using wet chemical synthesis routes. This is largely due to a significant difficulty in alloying magnesium into ZnO lattices at typically much lower processing temperatures than those used in the vapour phase methods. However, undoubtedly, wet chemical methods such as the hydrothermal synthesis process have several unique advantages, which include low cost, large yield, environmental friendliness and low reaction temperature.
In a recent issue of Nanotechnology, researchers at the University of Connecticut, US, have reported a successful route to semiconductor nanowire alloying in solution. Using a densely packed array of ZnO nanowires as a localized reaction and interdiffusion template, magnesium-alloying into ZnO nanowire lattices was achieved during a 155 °C hydrothermal MgO deposition. The localized magnesium alloying process has been confirmed by an array of electron microscopies and spectroscopies.
Room temperature and low-temperature photoluminescence spectroscopy revealed enhanced and blue-shifted near-band-edge ultraviolet emissions in the grown MgO/ZnO composite nanowire arrays, compared with the ZnO nanowire arrays. This is due to the bandgap widening via successful semiconductor alloying of magnesium into the ZnO nanowires. These results proved that it is possible to rationally engineer the band structures of semiconductor nanostructures using a low-temperature solution route without having to use post-annealing treatments.
Currently the team is looking to further develop solution-based routes to broaden the semiconductor alloying range and enhance near-band edge emissions, striving towards energy efficient and cost-effective band structure engineering in semiconductor nanowires.
About the author
The work was performed in the Nanomaterials Science Laboratory (NSL) at the University of Connecticut. Paresh Shimpi is a PhD student in the NSL. His research focuses on semiconductor nanostructure assembly, band structure engineering and photovoltaic nanodevices. Dr Pu-Xian Gao is an assistant professor in the Department of Chemical, Materials and Biomolecular Engineering & Institute of Materials Science. He is the founding director of the NSL at the University of Connecticut since 2007. Dr Gao has authored or co-authored more than 40 publications with more than 2200 citations. His expertise and research interests lie in synthesis, characterization and growth theory studies of low-dimensional nanomaterials; energy, environmental and sensing/actuating applications of low-dimensional nanomaterials. He is a member of ACS, APS, IEEE and MRS.