| AVS 56th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Wednesday Sessions |
| Session NS-WeA |
| Session: | Nanotubes - Electronics and Functionalization |
| Presenter: | K. Matsumoto, Osaka University, Japan |
| Authors: | K. Matsumoto, Osaka University, Japan S. Iwasaki, Osaka University, Japan T. Kamimura, Osaka University, Japan K. Inoue, Osaka University, Japan T. Kishimoto, Osaka University, Japan Y. Ohno, Osaka University, Japan K. Mehashi, Osaka University, Japan |
| Correspondent: | Click to Email |
The direction control of the carbon nanotube(CNT) growth on the SiO2/Si substrate was first succeeded in at our will using the attractive force of “Casimir force” which concentrates at the upper edge of the corrugated pattern. By applying the present technique for CNT FET, the drain current was enhanced more than 10 times than the conventional CNT FET because of the effective bridging of CNTs between the source and drain electrodes.
The process for the direction control of CNT growth is as follows; The SiO2/Si substrate was processed to form the corrugated pattern using the electron beam lithography and CF4 plasma etching． The planed width and spacing of the corrugated pattern is 100nm and its depth is 40nm. After the formation of the corrugated pattern, 0.5nm thick Co catalyst is formed at the end of the corrugated pattern by the photolithography. Then the sample was set in the thermal CVD to grow the CNT at 800C. The CNTs which started to grow from the catalyst are attracted to the upper edge of the corrugated pattern and follow the direction of the corrugated pattern. So, the direction of the CNT growth can be controlled at our will only by forming the corrugated pattern on SiO2/Si substrate.
The direction controlled growth of CNT on the corrugated pattern was confirmed by SEM observation. The CNT grew more than 7mm straightforward along with the corrugated pattern. Furthermore, it becomes clear that the CNT follows not on the bottom edge but at the upper edge of the corrugated pattern by the SEM observation from the tilted angle. In order to clarify the reason why CNT is attracted to the upper edge of the corrugated pattern, the Casimir force, which is a kind of van der Waals force, along with the cross section of the corrugated pattern was calculated. In the calculated results, the density of the Casimir force shows the highest peaks near the upper edges of the corrugated pattern. Because of these highest peaks of the Casimir force density, it becomes clear that the carbon nanotube is attracted to the upper edge of the corrugated pattern and grow following the direction of the pattern.
By applying this technology, FET with the direction controlled CNT channel was fabricated and its electrical property was examined. From the SEM observation, it was confirmed 8 CNTs were bridged between the source and drain electrodes. The dependence of the drain current on the gate bias at room temperature was examined, and the drain current reached as high as 2.5mA at Vg = -5V, which is about ten times higher than the conventional CNT FET. This is because a number of CNTs bridged between the source and drain electrodes can work as channels of FET.