Browsing by Author "Huang, Kuo-Jung"

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Controlling vertical alignment of phthalocyanine nanofibers on transparent graphene-coated ITO electrodes for organic field emitters
(2012)
Huang, Kuo-Jung
;
Hsiao, Yu-Sheng
;
Huang, Jen-Hsien
;
Chu, Chih-Wei
;
Chen, Peilin
In this study, we developed a simple and efficient approach-using graphene coatings on ITO as transparent electrodes-for inducing the growth of 29H,31H-phthalocyanine (H2Pc) nanofiber arrays through a thermal evaporation process, with potential use in organic field emitters (FEs). By controlling the surface energy and temperature of the electrodes during evaporation, H2Pc molecules readily self-assemble, forming an out-of-plane morphology on reduced graphene oxide surfaces (rGO; surface energy: ca. 50 mJ m(-2)). The devices fabricated on rGO/indium tin oxide (FE-rGO) exhibited not only excellent FE performance but also outstanding anti-degradation capability during stability tests. This facile approach toward rGO coatings opens a new avenue for the transformation of small organic molecule films into vertically standing nanostructures on transparent electrodes, with various organic electronics applications.
Holographic recording characteristics and physical mechanism of zinc methacrylate/nitroaniline-co-doped poly(methyl methacrylate)/9,10-phenanthrenequinone photopolymers
(2013-06-01)
Ko, Cheng-Jung
;
Chen, Po-Lin
;
Hsiao, Yi-Nan
;
Lin, Shiuan-Huei
;
Whang, Wha-Tzong
In this study we developed an approach to improve the characteristics of photopolymers for holographic data storage. Through codoping different compounds, N,N-dimethyl-4-nitroaniline (DMNA) and zinc methylacrylate (Zn(MA)2), into 9,10-phenanthrenequinone (PQ) doped poly(methyl methacrylate) (PMMA), the diffraction efficiency and the value of dynamic range (M#) have been progressed. We enhanced the diffraction efficiency (from 36.1 to 86.2%) and the dynamic range (M#, from 2.9 to 10.7) of PQ-doped PMMA through codoping with DMNA and Zn(MA)2. Using mass spectrometry and X-ray photoelectron spectroscopy, we investigated the mechanism behind the improvements in optical storage induced by the presence of Zn(MA)2 and DMNA in PMMA/PQ. POLYM. ENG. SCI., 2013. (c) 2012 Society of Plastics Engineers
Low-temperature formation of self-assembled 1,5-diaminoanthraquinone nanofibers: Substrate effects and field emission characteristics
(2011-04-01)
Huang, Kuo-Jung
;
Hsiao, Yu-Sheng
;
Whang, Wha-Tzong
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this study, we used thermal evaporation with a low sublimation temperature (42 degrees C) to deposit 1,5-diaminoanthraquinone (DAAQ) in various morphologies-including nanorods, nanocornerstones, and nanofibers-onto various substrates. Three major factors influenced the growth of vertically aligned DAAQ nanofibers on the electrodes: a low water contact angle (WCA) for the substrate and intermolecular hydrogen bonding and pi-pi interactions between the DAAQ molecules. On Au and Ti substrates (low-WCA), the DAAQ nanofibers DAAQ-Au and DAAQ-Ti, respectively, possessed great verticality and high aspect ratios; they also exhibited field emission characteristics, with maximum emission current densities of 0.31 and 0.65 mA/cm(2), respectively, at an applied electric field of 12 V/mu m. The turn-on electric fields for producing a current density of 10 mu A/cm(2) were 8.5 V/mu m for DAAQ-Au and 8.25 V/mu m for DAAQ-Ti. From the slopes of Fowler-Nordheim plots, we calculated the field enhancement factors (beta) of DAAQ-Au and DAAQ-Ti to be 447 and 831, respectively. Field emission stability studies revealed that the DAAQ nanofibers possessed outstanding anti-degrading capability. The emission current did not decrease, but rather increased slightly, after 3000 s. Given the advantages of this simple low-temperature process and the impressive anti-degrading field emission characteristics, such DAAQ nanofibers have great potential for use in various electronics applications (e.g., as organic field emitters). (C) 2011 Elsevier B.V. All rights reserved.
Selective growth and enhanced field emission properties of micropatterned iron phthalocyanine nanofiber arrays
(2011-11-01)
Huang, Kuo-Jung
;
Hsiao, Yu-Sheng
;
Whang, Wha-Tzong
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this study, we developed a simple method for the micropatterned growth of iron phthalocyanine (FePc) nanofiber arrays using a thermal evaporation process. By controlling the surface energy and the temperature of the substrate (T(sub)), we obtained FePc films featuring a grain-like (in-plane) morphology on Si surfaces (higher surface energy) and a fiber-like (out-of-plane) morphology on Ag surfaces (lower surface energy) within a certain range of values of T(sub). On the Ag surfaces, these temperature-induced FePc nanofibers featured a high aspect ratio (AR) of 30.3 +/- 3.6, with a mean length of 699 +/- 216 nm and a mean radius of 22.2 +/- 4.3 nm, as-prepared at a value of T(sub) of 240 degrees C. The FePc films obtained at values of T(sub) of 25, 120, 180, and 240 degrees C all possessed alpha-phase crystalline structures. Because the growth structures of the FePc molecules on the Si and Ag substrates were quite different, we could control the growth of micropatterned 1D FePc nanofiber arrays on previously patterned Ag/Si substrates. From the comparison of the field emission (FE) properties in different ARs of patterned devices, higher AR (30.3 +/- 3.6) of devices (FE-240-P; T(sub) of 240 degrees C) exhibited better FE performance than lower AR (6.0 +/- 2.6) of devices (FE-180-P; T(sub) of 180 degrees C). The FE current density of devices (T(sub) of 240 degrees C) increased from 0.13 mA/cm(2) for the unpatterned device (FE-240-N) to 6.77 mA/cm(2) for the patterned device (FE240- P) at an applied electric field of 12 V/mu m. The turn-on electric fields required to produce a current density of 10 mu A/cm(2) were 7.7 and 10.3 V/mu m for the patterned and unpatterned FePc emitters, respectively. From the slopes of Fowler-Nordheim plots, we estimated the field enhancement factors (beta) of FE-240-P and FE-240-N to be 314 and 329, respectively. Studies of the emission current stability revealed that the FePc nanofibers possessed outstanding anti-degrading capability. During stability tests, the micropatterned FePc emitter (FE-240-P) displayed an efficient emission current with fluctuations of less than 20%. Because this facile platform allows control over the morphologies of films of small organic molecules merely by tuning the surface energy of the substrates, such micropatterned- FePc nanofibers might have great applicability in practical field emitters. (C) 2011 Elsevier B.V. All rights reserved.