Jul 23, 2008
Optical switches based on Bi2S3 nanowire network film
One-dimensional (1D) semiconductor materials possess novel electronic and optical properties for the construction of advanced functional devices, including field-effect transistors, lasers, sensors and optical switches. In particular, Bi2S3 nanowire network films exhibit pronounced positive photoconductivity upon visible light exposure and are a good candidate for optical switches. Demonstrated applications of this nanostructure range from the synthesis of nanowire network films at a centimeter scale, to the fabrication of optical switch arrays.
To fabricate applicable devices, the functional nanoscale components need to be assembled in a micro- or macro-scale. This requires feasible and economic nanoengineering approaches. One of the efforts toward this goal is direct synthesis or assembly of macro-scaled complex architectures, such as arrays, networks or hierarchical structures, which are composed of well defined nanostructures.
In a systematic study that was recently published in Nanotechnology it was found that a centimetre-scale Bi2S3 nanowire network film is synthesized by a facile hydrothermal method and can be easily tape-transferred and further used to fabricate an optical switch array.
The interconnected Bi2S3 nanowire network, which is composed of large quantity nanowires with widths of 60–200 nm and lengths of several microns, was first synthesized on a Teflon foil by a hydrothermal process. By placing the obtained Teflon foil with a black film on a plastic tape and removing the foil, the centimetre-scale film was easily printed onto the plastic substrate. Thick-film screen-printing technology was used to fabricate an optical switch array, in which the commercial silver paste was printed on the Bi2S3 film to form an electrode array by using a semi-automatic screen printer.
The Bi2S3 nanowire network has a pronounced increase in conductance upon exposure to visible light with different wavelengths and possesses a very fast response time of about 2 ms. A dark conductivity of ~8.27 × 10–3 S/cm of the nanowire network was obtained from calculation of the experimental data. The conductivity rapidly increased by 24 times upon exposure to a 2.03 mW/cm2 white light. This work provides a simple and economical method to fabricate high-performance optical switch arrays and could render great potential for a low cost, mass manufacturing process.
About the author
Haifeng Bao is a research fellow at the School of Chemical and Biomedical Engineering, Nanyang Technological University (NTU). Chang Ming Li is professor, head of the Division of Bioengineering, and director of the Center for Advanced Bionanosystems at NTU. Xiaoqiang Cui recently moved to the National Institute of Advanced Industrial Science and Technology (AIST), Japan, as a research staff. Qunliang Song and Hongbin Yang are research fellows at the School of Chemical and Biomedical Engineering, NTU. Jun Guo is a senior laboratory executive at the School of Materials Science and Engineering, NTU.