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PAPER Fabrication and characterization of graphene/AlGaN/GaN ultraviolet Schottky photodetector To cite this article: M Kumar et al 2016 J. Phys. D: Appl. Phys. 49 275105 View the article online for updates and enhancements. Recent citations Hybrid graphene/GaN ultraviolet phototransistors with high responsivity and speed Huijun Tian et al -Rectified photocurrent in a planar ITO/graphene/ITO photodetector on SiC by local irradiation of ultraviolet light Junwei Yang et al -This content was downloaded from IP address 139.179.72.75 on 21/05/2018 at 09:15 1 AbstractWe report on the fabrication and characterization of a Schottky ultraviolet graphene/AlGaN/ GaN photodetector (PD). The fabricated device clearly exhibits rectification behaviour, indicating that the Schottky barrier is formed between the AlGaN and the mechanically transferred graphene. The Schottky parameters are evaluated using an equivalent circuit with two diodes connected back-to-back in series. The PD shows a low dark current of 4.77 × 10 −12 A at a bias voltage of −2.5 V. The room temperature current-voltage (I-V ) measurements of the graphene/AlGaN/GaN Schottky PD exhibit a large photo-to-dark contrast ratio of more than four orders of magnitude. Furthermore, the device shows peak responsivity at a wavelength of 350 nm, corresponding to GaN band edge and a small hump at 300 nm associated to the AlGaN band edge. In addition, we examine the behaviour of Schottky PDs with responsivities of 0.56 and 0.079 A W −1 at 300 and 350 nm, respectively, at room temperature.

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Abstract. The paper focuses on a series of blends prepared with different contents of polystyrene-block-poly-(ethylene-ranbutylene)-block-polystyrene (SEBS) and polypropylene (PP) for the purpose of examining the potential as proton exchange membranes. Polymer blends were prepared by twin-screw extrusion and then compressed by means of a hot-press device into thin films of 125 μm and then ionic sides were created by solid state sulfonation in a chlorosulfonic acid solution. Obtained films were characterized by means of water-uptake, mechanical properties, ion-exchange capacities (IEC) and ion conductivities. It was observed that the rigidity of the films increased with rising sulfonation durations. However humidity absorption from the air decreased the rigidity at high sulfonation levels. Improved water uptake values were obtained when compared to previously reported values in the literature. On the other hand ion exchange values showed an increase parallel to the sulfonation duration up to 45 minutes, but a decrease thereafter was observed due to the diffusion of some sulfonated polymer chains into the ion-exchange medium thereby calculated ion exchange values of S-SEBSH45 and S-SEBSH60 were found less than expected. All films showed ion conductivities up to 432 mS/cm at 25°C. Only S-SEBSH45 and S-SEBSH60 were successful in conducting protons at 80°C owing to the high water retaining capacity.

a b s t r a c tFabrication and characterization of metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector (PD) based on Ga doped ZnO (ZnO:Ga)/graphene is presented in this work. A low dark current of 8.68 nA was demonstrated at a bias of 1 V and a large photo to dark contrast ratio of more than four orders of magnitude was observed. MSM PD exhibited a room temperature responsivity of 48.37 A/W at wavelength of 350 nm and UV-to-visible rejection ratio of about three orders of magnitude. A large photo-todark contrast and UV-to-visible rejection ratio suggests the enhancement in the PD performance which is attributed to the existence of a surface plasmon effect at the interface of the ZnO:Ga and underlying graphene layer.

Low-molecular-weight atactic poly(propylene oxide) and poly(epichlorohydrin) (PECH) were chlorinated on average up to 4.42 chlorine atoms per repeat unit. A study of the products showed that chlorine substitution preferentially occurred on already chlorinated repeat units, yielding chlorine -rich and chlorine -poor sequences. As the extent of chlorine substitution increased, the glass-transition temperature of the polymers markedly increased, and their solubility in most of the organic solvents drastically decreased. The chlorinated polymers were azidified with NaN 3 in dimethyl sulfoxide solutions. An analysis showed that azide groups replaced 99.8 -99.9% of the initially present chlorine atoms. As the azide content of the samples increased, initially opaque polymers become dark brown, and their solubility increased in water but decreased in organic solvents. Samples with approximately four or more azide groups per repeat unit were only soluble in dimethyl sulfoxide and water. The standard enthalpy of formation of the polymers became increasingly positive as the azide content increased. The enthalpy of formation of a sample with 4.42 N 3 /repeat unit was 6929 kJ/repeat unit, whereas this value was only 103 kJ/mol for classical GAP. An azidified sample from PECH (4.42 N 3 /repeat unit) was crosslinked with a commercial triisocyanide into a rubbery product. The density and ultimate tensile strength of the rubbery product were 1.44 g/cm 3 and 4.84 MPa, and it swelled about 10% at 20°C in water. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: [3785][3786][3787][3788][3789][3790] 2004 Key words: crosslinking; thermal properties; mechanical properties; calorimetry; NMR EXPERIMENTAL MaterialsAll solvents were purified by fractional distillation.Poly(propylene oxide) (PPO) was synthesized as described by Steiner et al. 1 The number-average molecular weight of PPO was 4000, which was calculated by end-group determination. Poly(epichlorohydrin) (PECH) was obtained from 3M Co.Chlorine gas was obtained from the oxidation of NaCl with KMnO 4 . The reaction flask was flushed with N 2 gas before the addition of concentrated H 2 SO 4 (ca. 40 wt %). Excess chlorine was absorbed in aqueous NaOH solutions. ProcedureThe chlorination of the polymers were achieved by the bubbling of Cl 2 gas into solutions of the polymers in carbon tetrachloride (2.5 wt %) at 60°C for several days. The rate of chlorination apparently increased with the intensity of sunlight, the partial pressure of Cl 2 , and the temperature. However, at temperatures higher than 60°C, because of the decrease in the solubility of Cl 2 , the rate of reaction slowed down. At the end of the chlorination, the solvent was distilled off, and the residue was extracted with benzene and neutralized with aqueous NaHCO 3 . Finally, the benzene solution was washed with distilled water and freezedried.The extent of chlorination was determined from both the stoichiometry of the reaction, through the measurement of the increase in the mass of the polymer, and the vo...

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