Apr 29, 2008
Luminescent nanowires grow horizontally
Gallium oxide (Ga2O3) nanowires measuring hundreds of microns and even millimetres in length could prove useful in helping microbiologists to track the migration of cells across a substrate. Grown by scientists in Taiwan, the linear structures emit blue light (400–500 nm) when irradiated with an ultraviolet source (254 nm) and provide a much clearer reference pattern compared with a series of quantum dots.
There are other advantages too, especially when it comes to manipulating the material. "With ultra-long nanowires, the use of an electron microscope may be unnecessary to guide the fabrication of electrodes for device measurement," Michael Huang of National Tsing Hua University's Nanomatarials Laboratory told nanotechweb.org. "Instead, you might be able to use a good optical microscope."
The researchers found that they could encourage the nanowires to grow horizontally by first annealing the silicon substrate in oxygen to form a 100 nm thick SiO2 film. Next the surface was sputtered with a gold catalyst and then placed inside a tube reactor raised to a temperature of 750 °C. Inside the reactor, the sample is exposed to a source of gallium and subjected to a continuous flow of nitrogen gas for 5 hours.
According to Huang, the sample's SiO2 layer appears to provide the oxygen source that facilitates the Ga2O3 nanowires' horizontal growth pattern. The team hopes to exploit this effect as a means of offering better directional coverage. In addition, the scientists plan to use a similar reaction scheme to explore the horizontal growth of other oxide nanowires.
The researchers presented their work in Nanotechnology.
About the author
James Tyrrell is the editor of nanotechweb.org.