2, University of Science and Technology (UST), Daejeon, , Korea (the Republic of)
In this research, we attempt to fabricated carbon nanotube (CNT) electrode with nano meter scaled gap by using sequential application of an alternative current (AC) dielectrophoretic (DEP) force. The nano-gap in the middle of CNT is formed by electrical break down which is induced by Joule heating.
This fabrication method is conducted under atmospheric condition with low cost apparatus set up, and production yield can be also monitored in a real time by in-situ measurement of electrical signal. Therefore, we can fabricated about tens of nano meter scaled electrode gap through simple and low cost method as compared to conventional lithography techniques that needs to high vacuum environment and expensive instrument with complex fabrication process.
In addition, we could generate DEP force fully enough to manipulate quantum dot (QD) through the CNT electrode with nano-gap. In general, it is impossible to manipulate the QD by using DEP force. Because nano materials under 10 nm is dominated by thermal force associating with Brownian motion, rather than other external force. Therefore, to manipulate the QD by electric field, the large strength of electric field is need to overcome the thermal force.
Strength of electric field is inversely dependent upon both gap size of electrode and shape of electrode. So we used the CNT having large aspect ratio that can generate large electric field gradient, and we also fabricated nano-gap in the middle of CNT electrode to significantly increase the strength of electric field.
As a result, we could successfully fabricated the CNT electrode with nano-gap through the Joule heating followed by application of DEP force. The minimum size of nano-gap is 18.8 nm. We could also trap the PbS QDs between CNT electrode by DEP force, and the size of QD aggregates can be controlled by adjusting the magnitude of electric field.
Finally, we tested optoelectronic response of device comprising with CNT electrode and QD aggregates under infrared (IR) or ultra-violet (UV) illumination. This nano optoelectronic device showed that resistance value under zero bias well followed the input signal of UV or IR illumination. This experimental results indicated that this hybrid type optoelectronic device have potential to used in optical sensor applications, and might give some another way to improve the electronic performance of QD conducting film.