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Manu Jaiswal
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Manu Jaiswal
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Manu Jaiswal
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Jaiswal, Manu
Jaiswal, M.
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8 results
Now showing 1 - 8 of 8
- PublicationMultilayer graphene as an effective corrosion protection coating for copper(10-04-2018)
;Ravishankar, Vasumathy; Graphene grown by chemical vapor deposition (CVD) has been studied as a protective layer against corrosion of copper. The layer number dependence on the protective nature of graphene has been investigated using techniques such as Tafel analysis and Electroimpedance Spectroscopy. Multiple layers of graphene were achieved by wet transfer above CVD grown graphene. Though this might cause grain boundaries, the sites where corrosion is initiated, to be staggered, wet transfer inherently carries the disadvantage of tearing of graphene, as confirmed by Raman spectroscopy measurements. However, Electroimpedance Spectroscopy (EIS) reflects that graphene protected copper has a layer dependent resistance to corrosion. Decrease in corrosion current (Icorr) for graphene protected copper is presented. There is only small dependence of corrosion current on the layer number, Tafel plots clearly indicate passivation in the presence of graphene, whether it be single layer or multiple layers. Notwithstanding the crystallite size, defect free layers of graphene with staggered grain boundaries combined with passivation could offer good corrosion protection for metals. - PublicationIsotropic charge transport in conducting PEDOT:PSS thin films on pre-strained stretchable substrates(10-04-2018)
;Sarkar, Biporjoy; In this work, we engineer the film morphology of 3,4-(poly ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) thin film on a stretchable poly dimethyl siloxane (PDMS) substrate to achieve strain-insensitive response. A strongly anisotropic transport is observed in pristine PEDOT:PSS thin film under uniaxial applied strain in parallel geometry. This anisotropy originates from extrinsically formed quasi periodic parallel cracks perpendicular to the applied strain. On the contrary, the transport remains isotropic with the uniaxial applied strain in both parallel and perpendicular geometry, for substrates which are subject to pre-straining before casting the conducting polymer dispersion. We discuss the isotropic nature of transport with reference to morphological features such as buckles, wrinkles and cracks. - PublicationThermal expansion coefficient of multilayer graphene with rotational stacking faults(25-10-2021)
;Mohapatra, Akash ;Rao, M. S.RamachandraRecent studies on twisted bilayer and multi-layer graphene have opened new avenues of research in condensed matter physics. These artificially made superlattices showed very intriguing electrical properties, including superconductivity at certain commensurate rotation angles between the stacked layers. Even though electrical properties are studied to some extent, the effect of rotation angle on the thermal properties has not received adequate attention. In particular, the thermal expansion of these systems is not well understood. In this direction, we have studied thermal expansion coefficient of few-layer graphene samples with rotational misorientation. These samples were synthesized using chemical vapor deposition technique from a solid carbon precursor. The Raman spectra of these samples indicated the presence of rotational stacking faults, which was confirmed by selected area electron diffraction measurements. Finally, the in-plane thermal expansion coefficient of this system was obtained using temperature dependent Raman spectroscopy for T = 4.5 to 300K. Thermal expansion coefficient was determined to be negative in this temperature range and the corresponding room temperature value was obtained to be ≈ -3.47 × 10-6 K-1. This value is comparable to that of few- layer graphene. We suggest that the thermal expansion of multilayer graphene with rotational stacking faults follows the thermal expansion of the individual few-layer crystallites rather than showing bulk graphitic behavior. - PublicationCorrelating Chemical Structure and Charge Transport in Reduced Graphene Oxide for Transparent Conductor and Interconnect Applications(15-03-2016)
;Rai, Vikas ;Kavitha, M. K.Graphene oxide is solution-process able and widely tunable semiconductor which has potential applications as transparent electrode materials in organic solar cells as well as chemical sensors and interconnects. It is also amenable to micro-patterning with laser-induced heating. Density of defects and water permeation are among the major factors affecting the degree of conduction in reduced graphene oxide. The wide tunability of conduction is related to the nature and density of defects. In this work, we correlate micro structural parameters of reduced graphene oxide with parameters obtained from our transport studies. The quantitative estimation of defect density from IR and Raman spectroscopy is, however, non-trivial. Here, we outline a procedure for carefully extracting the defect density for graphene oxide films subject to varied degrees of thermal reduction. This density of defect scatterers is then correlated with transport length scales extracted from frequency and temperature dependent charge transport studies. Furthermore, the effect of uniaxial strain on the dc and frequency-dependent ac transport in graphene oxide films is studied towards their potential application as hole-transporting layer for flexible solar cells. - PublicationGraphene: Polymer composites as moisture barrier and charge transport layer toward solar cell applications(08-05-2018)
;Sakorikar, Tushar ;Kavitha, M. K. ;Tong, Shi Wun; ;Loh, Kian PingGraphene: polymer composite based electrically conducting films are realized by a facile solution processable method. Ultraviolet Photoelectron Spectroscopy (UPS) measurements on the composite films, reveal a low work function of reduced graphene oxide (rGO) obtained from hydrazine hydrate reduction of graphene oxide (GO). We suggest that the low work function could potentially make rGO: PMMA composite suitable for electron conducting layer in perovskite solar cells in place of traditionally used expensive PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) layer. Further, we demonstrate from the gravimetric experiments conducted on rGO: PMMA films, that the same coating is also resistant to moisture permeation. This latter property can be used to realize a protective coating layer for perovskite films, which are prone to moisture induced degradation. Thus, dual functionality of rGO-PMMA films is demonstrated towards integration with perovskite solar cells. Architecture of perovskite solar cell based on these concepts is proposed. - PublicationStructure-property correlations of carbon and nitrogen incorporated NiFe2O4(10-08-2017)
;Anoop Baby, K. B. ;George, L.; ; Nickel ferrite (NiFe2O4) has drawn significant attention due to its high saturation magnetisation and dielectric properties [1-3]. - PublicationGraphene interfaced perovskite solar cells: Role of graphene flake size(10-04-2018)
;Sakorikar, Tushar ;Kavitha, M. K. ;Tong, Shi Wun; ;Loh, Kian PingGraphene interfaced inverted planar heterojunction perovskite solar cells are fabricated by facile solution method and studied its potential as hole conducting layer. Reduced graphene oxide (rGO) with small and large flake size and Polyethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS) are utilized as hole conducting layers in different devices. For the solar cell employing PEDOT:PSS as hole conducting layer, 3.8 % photoconversion efficiency is achieved. In case of solar cells fabricated with rGO as hole conducting layer, the efficiency of the device is strongly dependent on flake size. With all other fabrication conditions kept constant, the efficiency of graphene-interfaced solar cell improves by a factor of 6, by changing the flake size of graphene oxide. We attribute this effect to uniform coverage of graphene layer and improved electrical percolation network. - PublicationOrganic doping of rotated double layer graphene(06-05-2016)
;George, LijinCharge transfer techniques have been extensively used as knobs to tune electronic properties of two- dimensional systems, such as, for the modulation of conductivity \ mobility of single layer graphene and for opening the bandgap in bilayer graphene. The charge injected into the graphene layer shifts the Fermi level away from the minimum density of states point (Dirac point). In this work, we study charge transfer in rotated double-layer graphene achieved by the use of organic dopant, Tetracyanoquinodimethane. Naturally occurring bilayer graphene has a well-defined A-B stacking whereas in rotated double-layer the two graphene layers are randomly stacked with different rotational angles. This rotation is expected to significantly alter the interlayer interaction. Double-layer samples are prepared using layer-by-layer assembly of chemical vapor deposited single-layer graphene and they are identified by characteristic resonance in the Raman spectrum. The charge transfer and distribution of charges between the two graphene layers is studied using Raman spectroscopy and the results are compared with that for single-layer and A-B stacked bilayer graphene doped under identical conditions.