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研究ハイライト - 最新の学術論文




Schema of few-layered MoSe2 back-gated field-effect phototransistors.
 

High photosensitivity few-layered MoSe2 back-gated field-effect phototransistors

In this paper, we report on the fabrication and optoelectronic properties of high sensitive phototransistors based on few-layered MoSe2 back-gated field-effect transistors, with a mobility of 19.7 cm2V-1s−1 at room temperature. We obtained an ultrahigh-photoresponsivity of 97.1AW−1 and an external quantum efficiency (EQE) of 22 666% using 532 nm laser excitation at room temperature...[See more]

A Abderrahmane, P J Ko, T V Thu, S Ishizawa, T Takamura, A Sandhu, Nanotechnology 25(36):365202 (2014).


SEM images of Fe3O4–GO membranes, (a) low-magnification; (b) cross-sectional view.
 

Chemical synthesis of Fe3O4–graphene oxide nanohybrids as building blocks for magnetic and conductive membranes

We have developed a facile and scalable method for synthesising superparamagnetic Fe3O4 nanocrystals (NCs) anchored on graphene oxide (GO) sheets by a co-precipitation reaction. As-synthesized Fe3O4–GO nanohybrids (NHs) were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, field-emission. ...[See more]

T. V. Thu, and A. Sandhu, Materials Science and Engineering: B 189, 13 (2014).


Schematic illustration of the preparation of Ni-ABS nanocomposites and SEM images
 

Preparation and characterization of magnetic thermoplastic-based nanocomposites

We developed a facile method for the preparation of magnetic nanocomposites based on the popular thermoplastic, acrylonitrile butadiene styrene (ABS). The nanocomposites were produced by liquid blending of ABS and Ni nanorods (NRs), followed by solvent evaporation. The characterizations showed that the nanocomposites were magnetic and Ni NRs were uniformly distributed in ...[See more]

T. V. Thu, T. Takamura, D. Tsetserukou and A. Sandhu, AIP Conference Proceedings 1585, 141 (2014).


SEM images of Ni-rGO NHs, Ag-rGO NHs and Au-rGO. and Time-dependent UV-vis spectra of aqueous solution of 4-NP (0.1 mM) reduced by NaBH4 (8 mM) in presence of Au-rGO (5 g.mL-1)
 

Graphene oxide as an advanced two-dimensional support for functional nanoparticles

We utilized graphene oxide (GO) as a support to grow nickel, silver, gold (Ni, Ag, Au) and iron oxide ( Fe3O4 ) nanoparticles (NPs). The synthesis was facile, simple, and scalable. Anchored NPs were stable against the aggregation. Ni, Ag, and Au NPs grown on GO exhibited high catalytic activity towards the reduction of 4-nitrophenol, while Fe3O4 NPs grown on GO exhibited good magnetic properties...[See more]

T. V. Thu and A. Sandhu, AIP Conference Proceedings 1585, 136 (2014).


Temperature dpendence of the series resistance of the protons irradiated AlGaN/GaN sensors during heating and cooloing
 

Effect of annealing on proton irradiated AlGaN/GaN based micro-Hall sensors

The effect of annealing at 673 K on irradiated micro-Hall sensors irradiated with protons at 380keV and fluences of 1014, 1015 and 1016 protons/cm2 is reported. Cathodoluminescence measurements were carried out at room temperature before and after annealing and showed improvement in the band edge band emission of the GaN layer. After annealing a sensor irradiated by 1015 protons/cm2 the device became operational with improvements in its magnetic sensitivity...[See more]

A. Abderrahmane, H. Takahashi, T. Tashiro, P. J. Ko, H. Okada, S. Sato, T. Ohshima and A. Sandhu, AIP Conference Proceedings 1585, 123 (2014).


(a) Microscope image, (b) Raman mapping and (c) Raman spectra
before and after etching
 

High precision laser induced etching of multilayered MoS2

We demonstrate a method for reducing the thickness of multilayered MoS2 to few and single layers by irradiation with a 532 nm wavelength laser spot. The morphology and optical properites of the etched MoS2 were were measured by atomic force microscopy (AFM) and Raman spectroscopy before and after laser etching. Our laser etching method is a simple and highly effective tool for the fabrication of single, and few layered MoS2 for atomic scale optical and electronic device appli...[See more]

P. J. Ko, T. V. Thu, H. Takahashi, A. Abderrahmane, T. Takamura and A. Sandhu, AIP Conference Proceedings 1585, 73 (2014).


 Absorption spectra of R6G with various concentrations of Ag-rGO and Z-scan profiles.
 

Charge transfer in graphene oxide-dye system for photonic applications

The fluorescence of a standard dye Rhodamine 6G (R6G) in solution decreases on addition of reduced graphene oxide (rGO). The absorption spectra and lifetime measurements confirm that no excited-state but a ground-state complex formation is responsible for this effect. Forsilver decorated rGO (Ag-rGO), the quenching efficiency and ground state complex formation process is small. Z-scan measur...[See more]

Sudhakara Reddy Bongu, Prem B. Bisht, Tran V. Thu and Adarsh Sandhu, AIP Conference Proceedings 1585, 21 (2014).


 The proton fluence dependence of the A1(LO) and E2high linewidths
 

Partial recovery of the magnetoelectrical properties of AlGaN/GaN-based micro-Hall sensors irradiated with protons

The effect of annealing on the magnetoelectrical properties of proton-irradiated micro-Hall sensors at an energy of 380 keV and very high proton fluences was studied. Recovery of the electron mobility and a decrease in the sheet resistance of the annealed micro-Hall sensors, as well as an enhancement in their magnetic sensitivity were reported. Trap removal and ...[See more]

A. Abderrahmane, T. Tashiro, H. Takahashi, P. J. Ko, H. Okada, S. Sato, T. Ohshima and A. Sandhu, Applied Physics Letters 104, 023508 (2014).


 Mechanism for the reduction of 4-NP and the digital photos of aqueous solutions of 4-NP reduced by NaBH4
 

Room-temperature synthesis and enhanced catalytic performance of silver-reduced graphene oxide nanohybrids

The synthesis of supported, ultrasmall metallic nanoparticles (NPs) is of great importance for catalytic applications. In this study, silver-reduced graphene oxide nanohybrids (Ag–rGO NHs) were prepared by reducing Ag ions and graphene oxide (GO) at room temperature using sodium borohydride (NaBH4) and trisodium citrate. The resulting products were characterized using UV–Vis spectroscopy, X-ray ...[See more]

Tran Viet Thu, Pil Ju Ko, Nguyen Huu Huy Phuc, Adarsh Sandhu, Journal of Nanoparticle Research. 15:1975 (2013).


 Optical scattering of 130 nm SPBs with respect to the angle (θ) between the external magnetic field and the incident laser light
 

Observation of the dynamics of magnetically induced chains of sub-micron superparamagnetic beads in aqueous solutions by laser light scattering

Optical monitoring the behaviour of magnetically induced self-assembled chains of superparamagnetic beads (SPBs) are of interest for biomedical applications such as biosensors. However, it is difficult to directly monitor magnetically induced self-assembly of sub-micron nano-beads with conventional optical microscopes. Here, we describe the optical observation of the dynamics of magnetically induced self-assembled ...[See more]

Y Tanizawa, T Tashiro, P J Ko and A Sandhu,Journal of Physics: Conference Series, 2013


The magnetoresistance of AlGaN/GaN micro-Hall sensor before and after irradiation
 

Effect of Proton Irradiation on 2DEG in AlGaN/GaN Heterostructures

Low temperature Hall effect measurements were carried on AlGaN/GaN micro-Hall effect sensors before and after irradiation with 380 keV and fluence of 1014 protons/cm2. The sheet electron density after irradiation did not show significant changes but there was a dramatic decrease in the electron mobility of the heterostructures. Prior to irradiation, the observation of well-defined Landau plateaus and Shubnikov-de Haas ...[See more]

A Abderrahmane, S Koide, T Tahara, S Sato, T Ohshima, H Okada and A Sandhu,Journal of Physics: Conference Series, 2013



Absorption spectrum of graphite nanoplatelets
 

Synthesis and characterization of graphite nanoplatelets

We report a facile method for the synthesis of graphite nanoplatelets (GNPs) from a carbon rod. GNPs were produced by vacuum filtration of a suspension obtained from electrochemically exfoliated carbon rods. The resulting GNPs were characterized using scanning electron microscopy, atomic force ...[See more]

T V Thu, Y Tanizawa, N H H Phuc, P J Ko and A Sandhu,Journal of Physics: Conference Series, 2013


 Comparison of Raman spectra of the graphene transferred on PDMS by different methods

Simple method to transfer graphene from metallic catalytic substrates to flexible surfaces without chemical etching

Graphene shows promise for applications in flexible electronics. Here, we describe our procedure to transfer graphene grown on copper substrates by chemical vapor deposition to polydimethylsiloxane (PDMS) and SiO2/Si surfaces. The transfer of graphene was achieved by a simple, etching-free method ...[See more]

P J Ko, H Takahashi, S Koide, H Sakai, T V Thu, H Okada and A Sandhu,Journal of Physics: Conference Series, 2013



(top) CP-AFM local resistance mapping. (Bottom) topography mapping of the samples


Characterization of graphene oxide reduced through chemical and biological processes


The study of new materials for transparent electrodes or new heterojunctions made of 2D materials combinations is a very active research topic. Challenges to overcome are the modulation of the optoelectronic properties of such materials to achieve competitive photovoltaic devices. In this work, graphene oxide was reduced into graphene through different chemical
..[See more]


M Boutchich, A Jaffré, D Alamarguy, J Alvarez, A Barras, Y Tanizawa, R Tero, H Okada, T V Thu, J P Kleider and A Sandhu; Journal of Physics: Conference Series, 2013


Temperature dependence of the sheet resistance after proton irradiation.


Effect of proton irradiation on AlGaN/GaN micro-Hall sensors


The magnetoelectric properties of AlGaN/GaN micro-Hall effect sensors were studied after 380 keV proton irradiation. After irradiation the current-voltage measurements, stability of the magnetic sensitivity of the sensors, and the sheet electron density were degraded with a dramatic decrease of the electron mobility at high temperatures. Raman
..[See more]


A. Abderrahmane, S. Koide, H. Okada, H. Takahashi, S. Sato, T. Ohshima, and A. Sandhu; Applied Physics Letters, 2013


Schematic representation of I – V measurement configuration
setup for a graphene-based FET.


Ecofriendly Route for the Synthesis of Highly Conductive Graphene Using Extremophiles for Green Electronics and Bioscience


Highly conductive biocompatible graphene is synthesized using ecofriendly reduction of graphene oxide (GO). Two strains of non-pathogenic extremophilic bacteria are used for reducing GO under both aerobic and anaerobic conditions. Degree of reduction and quality of bacterially reduced graphene oxide (BRGO) are monitored using UV–vis
..[See more]


S. Raveendran, N. Chauhan, Y. Nakajima, H. Toshiaki, S. Kurosu Y. Tanizawa, R. Tero, Y. Yoshida, T. Hanajiri, T. Maekawa, P. M. Ajayan, A. Sandhu, and D. S. Kumar, Particle & Particle Systems Characterization, 2013


Temperature dependence of the sensitivity of AlGaN/GaN and InAsSb
micro-hall sensors.

 
Robust Hall Effect Magnetic Field Sensors for Operation at High Temperatures and in Harsh Radiation Environments


We describe the fabrication and magnetoelectric properties of robust, high sensitivity Hall effect sensors fabricated using AlGaN/GaN and AlInSb/InAsSb/AlInSb heterostructures with a two dimensional electron gas at the heterointerface. The sensitivity of AlInSb/InAsSb/AlInSb clearly degrades above ~150°C. The AlGaN/GaN 2DEG Hall sensors were stable up to at 400°C and even after irradiation
..[See more]


A. Abderrahmane , S. Koide , S. Sato , T. Ohshima , A. Sandhu and H. Okada, IEEE Transactions on Magnetics, 2012
   

Biosensing Based on Magnetically Induced Self-Assembly of Particles in Magnetic Colloids

Superparamagnetic beads and nonmagnetic beads of different sizes were assembled to form a “ring-structure“ in a magnetorheological (MR) fluid solution by the application of external magnetic fields. For superparamagnetic beads and non-magnetic beads ...[See more]

Ye Yang, Y. Morimoto, T. Takamura, and A. Sandhu, Journal of Nanoscience and Nanotechnology, 2012


Cross image of SEM of single PSi penetrated with 130 nm-diameter of SPBs into the 400 nm-diameter of pores.

Fabrication and Optical Characterization of p-type Single Macro-Porous silicon for Detection of Nano-Sized Functionalized Superparamagnetic Beads

Porous silicon (PSi) shows tremendous potential for applications including optical devices and biochemical biosensors due to the large surface area and convenience of surface functionalization of pores. Recently, variations of the Fabry–Pérot fringes shift with the refractive ...[See more]

P. J.Ko, H. Sohn, and A. Sandhu, Journal of Non-Crystalline Solids (Available online), 2012


AFM image of reduced GO sheets
on a SiO2/Si substrate.

Microorganism Mediated Synthesis of Reduced Graphene Oxide Films

The wide-ranging industrial application of graphene and related compounds has led researchers to devise methods for the synthesis of high quality graphene. We recently reported on the chemical synthesis, patterning, and doping of graphene films...[See more]

Y Tanizawa, Y Okamoto, K Tsuzuki, Y Nagao, N Yoshida, R Tero, S Iwasa, A Hiraishi, Y Suda, H Takikawa, R Numano, H Okada, R Ishikawa and A Sandhu, Journal of Physics: Conference Series, 2012

Fabrication of Supported Lipid Bilayer on Graphene Oxide

Planar lipid bilayers of dioleoylphosphatidylcholine was prepared on graphene oxide (GO), as a fundamental platform for biosensing in plasma membrane model using graphene. The GO flakes were prepared according to modified Hummer's method, and deposited on ...[See more]

Y Okamoto, K Tsuzuki, S Iwasa, R Ishikawa, A Sandhu and R Tero, Journal of Physics: Conference Series, 2012

Schematic of the structure of lipid membranes on r-GO/SiO2.

Reduced graphene Oxide as the Support of Lipid Bilayer Membrane

Supported lipid membranes of dioleoylphosphatidylcholine (DOPC) were formed on reduced graphene oxide (r-GO) by the vesicle fusion method. Graphene oxide prepared by chemical exfoliation was deposited on a thermally oxidized SiO2/Si substrate, and ...[See more]

K Tsuzuki, Y Okamoto, S Iwasa, R Ishikawa, A Sandhu and R Tero, Journal of Physics: Conference Series, 2012


Dependence of sheet carrier density of AlGaN/GaN heterostructure after 380 keV proton dose irradiation.

Effects of Proton Irradiation on the Magnetoelectric Properties of 2DEG AlGaN/GaN Micro-HGall Sensors

The effects of irradiating AlGaN/GaN micro-Hall sensors with 380 keV protons on were investigated by magnetoresistance measurements. The sheet resistance increased after irradiation with a proton dose of 1.1013cm−2 due to the decrease ...[See more]

H Okada, A Abderrahmane, S Koide, H Takahashi, S Sato, T Ohshima and A Sandhu, Journal of Physics: Conference Series, 2012


The quintessential idea for MT-improvement protocol: longer length difference results in stronger MT effect.

Behavior of Multi-Component Magnetic Colloidal Systems in Tunable Magnetic Fields and Applications in Biosensing

A system consisting of multiple-component beads, such as superparamagnetic beads, nonmagnetic beads and magnetorheological (MR) fluid, can display some very amazing and special properties when subjected to an external magnetic field because...[See more]

Ye Yang, Zhengcao Li, Pil Ju Ko and Adarsh Sandhu, Journal of Physics: Conference Series, 2012


A schematic diagram of our innovative EPD procedure.

Electrophoretic Deposition of High Quality Transparent Conductive Graphene Films on Insulating Glass Substrates

Graphene is a promising material for transparent conductive films (TCFs) because of its high electrical conductivity and excellent optical transparency over a wide spectral range. We have previously reported on an inexpensive means of producing graphene-based ...[See more]

R Ishikawa, P J Ko, Y Kurokawa, M Konagai and A Sandhu, Journal of Physics: Conference Series, 2012


The variation of magnetically induced linear chain with frequency.

Optical Transmittance for Analysis of the Dynamics of Self-Assembled Rotating Chains of Superparamagnetic Micro- and Nano-Beads in solution

Optically monitoring biosensing procedures based on the dynamics of an aqueous solution containing functionalized superparamagnetic beads in the application of the external rotating magnetic field has been developed for a rapid, highly sensitive, and ...[See more]

Pil Ju Ko, Tsukasa Takamura and Adarsh Sandhu,Journal of Physics: Conference Series, 2012

Temperature dependence of current-related
magnetic sensitivity.

High Temperature Hall Sensors Using AlGaN/GaN HEMT Structures


Hall effect sensors are the most widely used magnetic sensors, and are commonly fabricated using narrow band-gap semiconductors such as InSb and GaAs. However, the operation of InSb and GaAs-based Hall sensors
...[See more]

Koide, H Takahashi, A Abderrahmane, I Shibasaki and A Sandhu, Journal of Physics, 2012



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