Dec 3, 2009
Flexible CNT array batch fabricated using MEMS technology
Scientists in Taiwan have developed a flexible carbon nanotube (CNT) photosensor array. The bendable device features CNTs embedded in parylene-C film and is batch fabricated using micromachining techniques associated with the preparation of microelectromechanical systems (MEMS). To test the device, the group used the photosensor array to detect the position of a light beam.
There are many ways of integrating CNTs with flexible polymer film. For example, stamp transfer, microwave welding, direct mixing and low-temperature growth. However, there are some drawbacks to these techniques such as poor adhesion, patterning challenges and poor material properties. To overcome these hurdles, researchers from National Tsing Hua University have established a batch micro fabrication process to create and pattern CNTs on a silicon wafer, and then integrate the patterned CNTs with flexible polymer film.
To produce the bendable CNTs-parylene-C composite, the team first grew vertically aligned CNTs on a silicon substrate with polysilicon and patterned iron layers. Then the researchers deposited vapor-phase parylene-C to bind the CNTs. The flexible CNT photosensor array was achieved after removing the polysilicon film by vapor-phase XeF2.
Measurements show that the output photocurrent varies linearly with the input light intensity and can be modulated by bias-voltage. The quantum efficiency of CNTs is about 0.063% in 760 Torr ambient, and becomes 1.93% in 3 mTorr ambient.
MEMS technology provides a promising way of delivering flexible CNT-polymer devices using wafer-level batch-fabrication processes. In the future, the group plans to apply the CNTs-polymer composite to produce physical sensors on a single chip.
The researchers presented their work in the journal Nanotechnology.
About the author
This photosensor was fabricated and tested at the Micro Device Laboratory at National Tsing Hua University, Taiwan. Chia-Min Lin is a PhD student studying CNT MEMS at the Institute of NanoEngineering and MicroSystems at National Tsing Hua University, Taiwan. Prof. Weileun Fang is the head of Micro Device Laboratory (in the Department of Power Mechanical Engineering) and the Institute of NanoEngineering and MicroSystems at National Tsing Hua University, Taiwan.