Fabrication of Nano Metal Meshes by Nanoimprint Lithography for Organic Electronics Device Applications
Date Issued
2015
Date
2015
Author(s)
Fang, Xiang
Abstract
Owing to the rapid development of flexible electronic devices in recent years, the solution-processed organic transistors have shown their great potential in many applications by employing low-cost, roll-to-roll, and large-area mass production. This thesis mainly focuses on the performance improvement on space-charge-limited organic transistor (SCLT), jointly developed by Prof. Zan’s, Prof. Meng’s and our groups. Though SCLT usually has high output current, high ON/OFF current ratio and relatively low operational voltage, its performance is still unstable due to the defects in fabrication process. The nano sphere is used as an evaporation mask for base-electrode in the colloidal lithographic process. But accommodation effect may occur because of the random arrangement of spheres. It may produce larger hole on the electrode, causing larger leakage current of SCLT. To solve this problem, we fabricate the well-regular-ordered metal mesh base-electrode by combing interference lithography (IL) and nanoimprint. Since the resolution of IL is limited by the wavelength of light source, sub-100 nm metal mesh cannot be realized. In addition, the ion contamination caused by wet-etching may induce large base leakage current. We therefore introduce the atomic layer deposition process to reduce the hole diameter of photoresist pattern down to smaller than 100 nm. And the mechanical strength of photoresist structure also has been reinforced to be hard enough as an imprint mold at the same time. Then we adopt the strip-off method to replace wet-etching method in mesh fabrication. We successfully combine nanoimprint with strip-off method to fabricate large area (> 4 cm2) and sub-100 nm resolution metal mesh. The base leakage current has been reduced by nearly an order of magnitude. And the process tolerance and reproducibility of SCLT remain high at the same time. The output current of SCLT device reaches 4.64 mA/cm2 and the ON/OFF current ratio increases to more than 105, setting a new milestone on the road of SCLT development.
Subjects
interference lithography
nanoimprint
ALD
organic transistor
space-charge-limited transistor
Type
thesis
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