Browsing by Author "Pearton, Stephen J."

Now showing 1 - 4 of 4

Dip Pen Nanolithography of Conductive Silver Traces
(2010-06-03)
Hung, Sheng-Chun
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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.
Effect of thermal annealing for W/beta-Ga2O3 Schottky diodes up to 600 degrees C
(2019-11-01)
Xian, Minghan
;
Fares, Chaker
;
Ren, Fan
;
Gila, Brent P.
;
Chen, Yen-Ting
The electrical and structural properties of sputter-deposited W Schottky contacts with Au overlayers on n-type Ga2O3 are found to be basically stable up to 500 degrees C. The reverse leakage in diode structures increases markedly (factor of 2) for higher temperature annealing of 550-600 degrees C. The sputter deposition process introduces near-surface damage that reduces the Schottky barrier height in the as-deposited state (0.71 eV), but this increases to 0.81 eV after a 60 s anneal at 500 degrees C. This is significantly lower than conventional Ni/Au (1.07 eV), but W is much more thermally stable, as evidenced by Auger electron spectroscopy of the contact and interfacial region and the minimal change in contact morphology. The contacts are used to demonstrate 1.2 A switching of forward current to -300 V reverse bias with a reverse recovery time of 100 ns and a dI/dt value of 2.14 A/mu s. The on/off current ratios were >= 10(6) at -100V reverse bias, and the power figure-of-merit was 14.4 MW cm(-2). Published by the AVS.
Effects of semiconductor processing chemicals on conductivity of graphene
(2012-07-01)
Chen, Chung Wei
;
Ren, F.
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Chi, Gou-Chung
;
Hung, S. C.
;
Huang, Y. P.
"Graphene layers on SiO2/Si substrates were exposed to chemicals or gases commonly used in semiconductor fabrication processes, including solvents (isopropanol, acetone), acids, bases (ammonium hydroxide), UV ozone, H2O, and O-2 plasmas. The recovery of the initial graphene properties after these exposures was monitored by measuring both the layer resistance and Raman 2D peak position as a function of time in air or vacuum. Solvents and UV ozone were found to have the least affect, while oxygen plasma exposure caused an increase of resistance of more than 3 orders of magnitude. Recovery is accelerated under vacuum but changes can persist for more than 5 h. Careful design of fabrication schemes involving graphene is necessary to minimize these interactions with common processing chemicals. (C) 2012 American Vacuum Society. [http://dx.doi.org/10.1116/1.4732517]"
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]