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Diptonil Banerjee,Kalyan Kumar Chattopadhyay,Arunava Jha 한국고분자학회 2012 Macromolecular Research Vol.20 No.10
A simple low-temperature synthesis method of amorphous carbon nanotubes (a-CNTs) and poly(vinyl alcohol) (PVA) composite thin films has been reported. Initially the a-CNTs have been functionalized by acid treatment for getting better dispersion in water. The functionalized a-CNTs show much enhanced solubility in water. The microstructures of the as-prepared tubes, functionalized tubes, and PVA-a-CNTs composite have been investigated with the help of a field emission scanning electron microscope. A detailed study on the structural, optical, and thermal properties and a hardness test of the composite has revealed that a-CNTs can act as good reinforcement materials such as crystalline CNTs, when composites are made with polymers. Also, it has been shown that the sheet resistance of the PVA-a-CNTs composite monotonically decreases with increasing a-CNTs concentrations in the composites. Optical studies showed a shift in the optical gap indicating the formation of cross-linking into the host matrix. The composite shows a higher crystallinity with increased a-CNTs concentration, compared to pure PVA. The swelling test shows that due to the introduction of the carboxylic group into a-CNTs’ walls, it gradually becomes hydrophilic.
Namita Dutta Gupta,Supratim Maity,Kalyan Kumar Chattopadhyay 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.5
Polypyrrole–multiwalled carbon nanotubes (PPy–MWCNT) nanocomposites with high field emission characteristics have been fabricated by a very simple and effective in situ chemical polymerization technique that bypasses the need of de-agglomerating the MWCNT. Based on structural characterization, we have proposed formation of a three tier structure of PPy–MWCNTs composite with granular PPy on the top. Field emission studies, explained on the basis of band bending at the PPy–MWCNT interface, show drastic increase of field enhancement factor (~4664) and low turn on field (1.7 V/mm), opening new possibilities of improvement of PPy/PPy–MWCNT composites.
Mandal Prasanta,Mazumder Nilesh,Saha Subhajit,Ghorai Uttam Kumar,Roy Rajarshi,Das Gopes Chandra,Chattopadhyay Kalyan Kumar 한국물리학회 2021 Current Applied Physics Vol.25 No.-
Delafossite compounds are layered ternary oxides known for simultaneous exhibition of significant carrier conduction and optical transparency. To survey effect of simultaneous cationic and anionic hole doping in prototype delafossite CuCrO2, we have analyzed the structural, optical, impedance and transport mechanism of CuCr1 xLixO2 ySy (x and y ranging 0–2 atomic %) prepared by solid state heating. The substitutional site occupancy of Li•• Cr and S×O are confirmed and quantified by Rietveld analysis. Valence band dispersion is demonstrated upon Li•• Cr and S×O co-doping by x-ray photoelectron spectroscopy with extended contribution from shallow S 3p antibonding states. From diffuse reflectance spectra, the optical gap (~3.5 eV) is evaluated to be wide even upon co-doping. Carrier density and hole mobility for CCO/(Li•• Cr +S×O ) to be 5.32 × 1015 cm 3 and 23.50 cm2V 1s 1, respectively. This scheme of band engineering is indicative of a more persuasive alternative to reach the hole conductivity bottleneck threshold.
Supratim Maity,Nirmalya Sankar Das,Saswati Santra,D. Sen,Kalyan Kumar Chattopadhyay 한국물리학회 2016 Current Applied Physics Vol.16 No.10
Carbon nanotubes (CNTs) are the most famous cold cathodes for display technology. However, graphene and other two dimensional carbon nanostructures and advanced II-VI semiconductor nanostructures are strongly emerging as strong competitors challenging the well established performance of CNTs in this field. Hence several technologies to improve field emission (FE) properties of CNTs are being developed. Here we report a facile technique to improve the cold emission performance of multiwalled CNTs (MWCNTs) by coating the same with chalcogenide semiconductor. MWCNT thin films were synthesized via chemical vapor deposition (CVD) technique and the same was coated by cadmium sulfide (CdS) nanoparticles via radio frequency magnetron sputtering technique. The pure and coated thin films were characterized by Fourier transform infrared spectroscopy and Raman spectroscopy to confirm presence of CdS on CNT surfaces. X-ray photoelectron spectroscopy revealed the compositional and valance state information of the as prepared samples. Field emission scanning electron microscopy and high resolution transmission electron microscopic studies were carried out to obtain information regarding morphology and nanocrystallinity of the CNTs and the coated CdS nanoparticles. Field assisted electron emission of pristine CNTs developed significantly with improved turn-on field and very high current density by CdS nanoparticle coating.
Aniruddha Mondal,Jay Chandra Dhar,P Chinnamuthu,Naorem Khelchand Singh,Kalyan Kumar Chattopadhyay,Sanat Kumar Das,Santosh Ch Das,Anirban Bhattacharyya 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.2
Symmetrical TiO2 nanowire (NW) arrays have been synthesized on Si by using glancing angle deposition technique. The Raman spectrum of TiO2 thin film (TF) and TiO2 NWs sample indicates the presence of both anatase and rutile phase TiO2. The electrical properties of the vertically ordered TiO2 NW arrays have been measured. The leakage current for high-k TiO2/Si capacitance reduced with the addition of TiO2 NWs on 30 nm TF. TiO2 NW dielectric was employed to achieve large conduction band offset between oxide layer and Si. A high gate capacitance has been observed due to NW effect. The barrier height between Ag/TiO2-NW interfaces was 0.9 eV and an exclusively lowest leakage current of 8.8 × 10−7 A/cm2 (at +1 V)was reported for the TiO2 NW device.