CONTROL OF CARBON NANOTUBE GROWTH USING SELF-ORGANIZED CATALYST NANOCLUSTERS AND ITS APPLICATION TO NANODEVICES

采用一种新型探针系统测量了碳纳米管的电导率。碳纳米管通过热CVD与自组织催化剂纳米团簇或将商业碳纳米管分散在图案电极上在电极之间桥接。此外，钛电极沉积在碳纳米管桥的两端，以减少碳纳米管和电极之间的接触电阻。制作了一种具有碳纳米管通道的场效应晶体管（FET）测试装置。在真空中对桥接的碳纳米管进行退火后，接触电阻降低，表明在电极界面处形成了碳化钛。此外，利用光刻和剥离技术在碳纳米管的两端沉积Ti电极，从而降低了接触电阻。电导与A/L和B/L成正比，其中A、B和L是CNTs的横截面、周长和长度。这意味着扩散输运发生在碳纳米管中。我们利用碳纳米管制作了FET测试装置。通过改变栅极电压来测量漏极电流。漏极电流由栅极电压调制。发现FET测试器件的单位沟道宽度的跨导值与传统的p型MOSFET相当。通过改变沟道长度或电极结构，可以提高FET测试器件的性能。

Electrical conductance of carbon nanotubes (CNTs) was measured by a newly developed probe system. The CNTs were bridged between the electrodes by using thermal CVD with self-organized catalyst nanoclusters or dispersing commercial CNTs on the patterned electrodes. Furthermore, Ti electrodes were deposited over both ends of the CNT bridges in order to reduce the contact resistance between CNTs and electrodes. A test device of field effect transistor (FET) with a channel of CNTs was fabricated.After annealing the CNTs bridging between the electrodes in a vacuum, the contact resistance was reduced, indicating the Ti carbide could form at the interface of the electrodes. Furthermore, Ti electrodes were deposited over both ends of the CNTs using photolithography and lift-off technique, resulting in reduction of the contact resistance. The conductance was found to be proportional to A/L as well as B/L, where A, B, and L is the cross section, circumference, and length of CNTs. This means that diffusive transport occurs in our CNTs.We have fabricated an FET test device using CNTs. The drain current was measured with changing gate voltages. The drain current was modulated by the gate voltages. The value of transconductance per unit channel width of the FET test devices was found to be comparable to that of conventional p-type MOSFET. The performance of the FET test devices could be improved by changing the channel length or the structure of the electrodes.