Large-area and highly uniform carbon nanotube film for nigh-performance thin film transistors

Carbon nanotube thin film transistors （CNT-TFTs） are a potential TFT technology for future high-performance macroelectronics. Practical application of CNT-TFTs requires the production of large-area, highly uniform, density-controllable, repeatable, and high-throughput CNT thin films. In this stud35 CNT films were fabricated on 4-inch Si wafers and 2.5th generation （G2.5） backplane glasses （370 mm×470 ram） by dip coating using a chloroform-dispersed high-purity semiconducting CNT solution. The CNT density was controlled by the solution concentration and coating times, but was almost independent of the substrate lifting speed （1-450 mm.min-1）, which enables high-throughput CNT thin film production. We developed an image processing software to efficiently characterize the density and uniformity of the large-area CNT films. Using the software, we confirmed that the CNT films are highly uniform with coefficients of variance （Cv） 〈 10% on 4-inch Si wafers and - 13.8% on G2.5 backplane glasses. High-performance CNT-TFTs with a mobility of 45-55 cm2-V-l.s-1 were obtained using the fabricated CNT films with a high-performance uniformity （Cv =11%-13%） on a 4-inch wafer. To our knowledge, this is the first fabrication and detailed characterization of such large-area, high-purity, semiconducting CNT films for TFT applications, which is a significant step toward manufacturing CNT-TFTs.

Ultraviolet/ozone and oxygen plasma treatments for improving the contact of carbon nanotube thin film transistors

Carbon nanotube thin film transistor(CNT-TFT) is an emerging technology for future macroelectronics,such as chemical and biological sensors,optical detectors,and the backplane driving circuits for flat panel displays.The mostly reported fabrication method of CNT-TFT is a lift-off based photolithography process.In such fabrication process,photoresist(PR) residue contaminates the interface of tube-metal contact and deteriorates the device performance.In this paper,ultraviolet ozone(UVO) and oxygen plasma treatments were employed to remove the PR contamination.Through our well-designed experiments,the UVO treatment is confirmed an effective way of cleaning contamination at the tube-metal interface,while oxygen plasma treatment is too reactive and hard to control,which is not appropriate for CNT-TFTs.It is determined that 2–6 min UVO treatment is the preferred window,and the best optimized treatment time is 4 min,which leads to 15% enhancement of device performance.