ساخت ترانزیستورهای اثرات میدانی نانولوله های کربنی به روش دی الکتروفورسیز AC

Single wall carbon nanotubes (SWNTs) suspended in isopropyl alcohol have been placed between two electrodes by AC dielectrophoresis method. The number of SWNTs bridging the two electrodes is controlled by SWNT concentration of the suspension and deposition time. Through selectively burning off the metallic SWNTs by current induced oxidation, the back-gate carbon nanotube field effect transistors (CNTFETs) with a channel current on–off ratio of up to 7 × 105 have been successfully fabricated. The success rate of the CNTFETs in 20 samples is 60%. These results suggest that AC dielectrophoresis placement method is an efficient technique to fabricate CNTFETs with some flexibilities of controlling CNT reconnection, length and orientation.

Single wall carbon nanotubes (SWNTs) are an ideal one-dimensional (1D) system because of their small diameter (of the order of 1 nm) and great length (of the order of micrometer). The 1D structure allows electrons to move in only two directions, leading to a reduced ‘‘phase space’’ for scattering processes [1]. In the absence of scattering, the transport is ballistic, which makes the carbon nanotube an ideal microelectronic device material, especially for field effect transistors (FETs). Since the first batch of CNT field effect transistors (CNTFETs) [2,3] were fabricated in 1998, their performance has been significantly improved in aspects of CNT channel current on–off ratio [4,5], hole mobility [6] and the CNT–metal electrode contacts [5]. However, how to selectively place semiconducting SWNTs in desirable locations is not solved. At present, two methods are generally used for CNTFET device fabrication. The first is to spin-coat SWNT suspension onto structured wafers [2,3,7,8]. However, the random distribution of SWNTs over the wafers is the major drawback of this method.

Single wall carbon nanotubes (SWNTs) are controllably placed between electrodes by AC dielectrophoresis method. Using the current-induced burn-off process, metallic SWNTs are easily broken down. The residual semiconducting SWNTs act as p-type channels of the CNTFETs, which have an on/off current ratio as high as 7 · 105. This technique provides a high success rate of fabricating CNTFETs with a flexibility of controlling the CNT alignment direction and the CNT length.