Browsing by Author "Hung, Sheng-Chun"

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Dip Pen Nanolithography of Conductive Silver Traces
(2010-06-03)
Hung, Sheng-Chun
;
Nafday, Omkar A.
;
Haaheim, Jason R.
;
Ren, Fan
;
Chi, G. C.
We report the first demonstration of sub mu m, sub-50-mu Omega.cm conductive traces directly written by Dip Pen Nanolithography (DPN). We achieved sub mu m Ag lines with 28.8 mu Omega.cm average resistivity after direct-write printing from a silver nanoparticle-based ink suspension and annealing at 150 degrees C for 10 min. This compares to Ag bulk resistivity of 1.63 mu Omega.cm, where the difference is within the range of previously reported variations in conductivity of Ag-based inks due to annealing conditions and larger width scales. We leveraged DPN's ability to directly place materials at specific locations in order to fabricate and characterize these conductive silver (Ag) traces on electrode patterns and multiple substrates (SiO(2), Kapton, mica). The low viscosity of the AgNP ink solution allowed write speeds up to 1600 mu m/s, almost 4 orders of magnitude higher than typical thiol-on-gold DPN writing speeds. This direct-write methodology paves the way for site-specific deposition of metallic materials for use in applications such as circuit repair, sensor element functionalization, failure analysis, gas sensing, and printable electronics.
UV ozone treatment for improving contact resistance on graphene
(2012-11-01)
Chen, Chung Wei
;
Ren, Fan
;
Chi, Gou-Chung
;
Hung, Sheng-Chun
;
Huang, Y. P.
Optimized UV ozone cleaning of graphene layers on SiO2/Si substrates is shown to improve contact resistance of e-beam evaporated Ti/Au contacts by three orders of magnitude (3 x 10(-6) Omega-cm(2)) compared to untreated surfaces (4 x 10(-3) Omega-cm(2)). Subsequent annealing at 300 degrees C lowers the minimum value achieved to 7 x 10(-7) Omega-cm(2). Ozone exposure beyond an optimum time (6 min in these experiments) led to a sharp increase in sheet resistance of the graphene, producing degraded contact resistance. The UV ozone treatment is a simple and effective method for producing high quality contacts to graphene. (C) 2012 American Vacuum Society. [http://dx.doi.org/10.1116/1.4754566]