May 26, 2010
Patterning and integration of nanowire bundles into devices
Single-crystal metal oxide nanowires are extremely promising materials for a series of cutting-edge technological applications, including optoelectronics, gas sensing, energy harvesting and nanopiezotronics. However, the direct integration of nanowires into functional devices can represent a major challenge.
To address the issue, researchers at Sensor Lab and Brescia University, both in Italy, have developed a simple, cheap and large-area scalable methodology for integrating metal oxide nanowire bundles into functional devices. The method relies on the sequential application of two techniques, namely high-temperature vapour transport and condensation (to fabricate metal oxide nanowires), and wet etching of a silicon dioxide sacrificial layer.
After removal of the sacrificial layer, a clean substrate surface is obtained for the deposition of stable metal contacts. The hydrofluoric acid solution used to remove the SiO2 layer does not affect the structure and morphology of the nanowires in the case of SnO2 and In2O3.
The methodology was proven to be effective for a gas sensor application. Electrical measurements indicate that a slightly rectifying Schottky junction is present at low temperature (up to T=150 °C) between nanowires and platinum electrodes, which vanishes as the temperature increases or when the voltage bias is raised above 3 V.
One of the main advantages of the approach is that only standard techniques and equipment are needed to obtain the desired result: sputtering apparatus for deposition of the sacrificial layer and the electric contacts; a low-pressure tubular furnace for nanowire growth; wet etching for removal of the sacrificial layer.
The study paves the way for the growth and integration of nanowire bundles directly into devices, overcoming the need for expensive and time-consuming nanomanipulation techniques.
Full details can be found in the journal Nanotechnology.
About the author
The mission of CNR IDASC Sensor Lab at Brescia University, Department of Chemistry and Physics for the Engineering and Materials, is to create a centre of excellence for basic and applied research on semiconducting metal oxide in three main research areas: gas sensors, artificial olfactory systems and third-generation solar cells. The main scientific tasks of Sensor Lab are the preparation and functional characterization of gas/flavour sensors and third-generation excitonic solar cells based on engineered semiconducting oxide nanostructures. Alberto Vomiero is a permanent staff member at CNR IDASC Sensor Lab. Andrea Ponzoni is a postdoc researcher at Brescia University, Sensor Lab. Elisabetta Comini and Matteo Ferroni are assistant professors, Guido Faglia is an associate professor and Giorgio Sberveglieri is a full professor, all at Brescia University, Department of Chemistry and Physics for Engineering and Materials. Giorgio Sberveglieri has been head of Sensor Lab since its foundation in 1987.