Influence of Post-Implantation Annealing Parameters on the Focused Ion Beam Directed Nucleation of InAs Quantum Dots

M. Mehta,D. Reuter,M. Kamruddin,A. K. Tyagi,A. D. Wieck 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.4

We present the effect of post-implantation annealing conditions on the structural and optical quality of InAs quantum dots (QDs) grown by combination of focused ion beam (FIB) and molecular beam epitaxy (MBE) approach. A FIB of Ga+ ion was employed to pattern a homogeneously GaAs buffer layers and then, an in situ annealing step followed by InAs deposition was performed. Three different post-implantation annealing conditions were tested and under well-optimized conditions, a dislocation and defect-free InAs QDs growth on FIB patterned surface was successfully achieved. Furthermore, using photoluminescence (PL) study, we demonstrate that our best sample shows almost similar optical quality as MBE grown QDs on unimplanted GaAs surface. The patterning technique described here can presumably be applied to systems other than InAs/GaAs and highly interesting for site-controlled nucleation of QDs that finds its potential applications in nanooptoelectronic devices.

Plasma-electric field controlled growth of oriented graphene for energy storage applications

Ghosh, Subrata,Polaki, S R,Kamruddin, M,Jeong, Sang Mun,Ostrikov, Kostya (Ken) IOP 2018 Journal of Physics. D, Applied Physics Vol.51 No.14

<P>It is well known that graphene grows as flat sheets aligned with the growth substrate. Oriented graphene structures typically normal to the substrate have recently attracted major attention. Most often, the normal orientation is achieved in a plasma-assisted growth and is believed to be due to the plasma-induced <I>in-built</I> electric field, which is usually oriented normal to the substrate. This work focuses on the effect of an <I>in-built</I> electric field on the growth direction, morphology, interconnectedness, structural properties and also the supercapacitor performance of various configurations of graphene structures and reveals the unique dependence of these features on the electric field orientation. It is shown that tilting of growth substrates from parallel to the normal direction with respect to the direction of <I>in-built</I> plasma electric field leads to the morphological transitions from horizontal graphene layers, to oriented individual graphene sheets and then interconnected 3D networks of oriented graphene sheets. The revealed transition of the growth orientation leads to a change in structural properties, wetting nature, types of defect in graphitic structures and also affects their charge storage capacity when used as supercapacitor electrodes. This simple and versatile approach opens new opportunities for the production of potentially large batches of differently oriented and structured graphene sheets in one production run.</P>

Pre- and post-breakdown electrical studies in ultrathin Al2O3 films by conductive atomic force microscopy

K. Ganesan,S. Ilango,Mariyappan Shanmugam,M. Farrokh Baroughi,M. Kamruddin,A.K. Tyagi 한국물리학회 2013 Current Applied Physics Vol.13 No.9

The loss of local dielectric integrity in ultrathin Al2O3 films grown by atomic layer deposition is investigated using conducting atomic force microscopy. IeV spectra acquired at different regions of the samples by constant and ramping voltage stress are analyzed for their pre- and post-breakdown signatures. Based on these observations, the thickness dependent dielectric reliability and failure mechanism are discussed. Our results show that remarkable enhancement in breakdown electric field as high as 130 MV/cm is observed for ultrathin films of thickness less than 1 nm.

Designing metal oxide-vertical graphene nanosheets structures for 2.6V aqueous asymmetric electrochemical capacitor

Ghosh, Subrata,Polaki, S.R.,Sahoo, Gopinath,Jin, En-Mei,Kamruddin, M.,Cho, Jung Sang,Jeong, Sang Mun Elsevier 2019 Journal of industrial and engineering chemistry Vol.72 No.-

<P><B>Abstract</B></P> <P>The asymmetric electrochemical capacitor was realized by MnO<SUB>2</SUB>/Vertical graphene nanosheets (VGN) and Fe<SUB>2</SUB>O<SUB>3</SUB>/VGN as positive and negative electrodes, respectively. The surface of VGN skeleton is independently decorated with MnO<SUB>2</SUB> having sponge gourd-like morphology and Fe<SUB>2</SUB>O<SUB>3</SUB> having nanorice like morphology. Both the electrodes have shown around 250 times higher charge-storage capacity than the bare VGN (0.47mF/cm<SUP>2</SUP>) with the specific capacitance of 118 (MnO<SUB>2</SUB>/VGN) and 151mF/cm<SUP>2</SUP> (Fe<SUB>2</SUB>O<SUB>3</SUB>/VGN). The fabricated asymmetric device exhibited a specific capacitance of 76mF/cm<SUP>2</SUP> and energy density of 71μWh/cm<SUP>2</SUP> with an excellent electrochemical stability up to 12,000 cycles, over a potential window of 2.6V.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Metal oxide-vertical graphene electrodes were prepared. </LI> <LI> Metal oxide-vertical graphene nanoshees structure was found to be super-hydrophilic. </LI> <LI> A plausible formation mechanism of metal oxides on the surface of vertical graphene is propsed. </LI> <LI> As fabricated asymmetric supercapacitor device was operated in an extended window of 2.6V. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Enhanced tribo-chemical properties of oxygen functionalized mechanically exfoliated hexagonal boron nitride nanolubricant additives

Sahu, Jayakrushna,Panda, Kalpataru,Gupta, Bhavana,Kumar, Niranjan,Manojkumar, P.A.,Kamruddin, M. Elsevier 2018 Materials chemistry and physics Vol.207 No.-

<P><B>Abstract</B></P> <P>Two dimensional (2D) materials with layered lattice structure as nanofluid additives are useful to improve the tribological properties of metallic sliding interfaces. To enhance the tribological efficiency, the bulk crystalline hexagonal boron nitride (h-BN) powder sample was mechanically exfoliated by ball milling, and further processed through ultrasonication for de-aggregation. High resolution X-ray diffraction (HR XRD) and high resolution transmission electron microscopy (HR TEM) results clearly indicate the exfoliation of bulk h-BN into thinner two-dimensional (2D) crystalline sheets without creating noticeable structural defects. The topography of exfoliated nanosheets is well confirmed by atomic force microscopy (AFM). Oxygen functionalization into the h-BN nanosheets after the mechanical exfoliation was investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Oxygen functionalization of h-BN improved the cohesive compatibility between h-BN and commercial 10W30 lubricant oil for stable dispersion. Friction coefficient and wear of sliding metallic interfaces were reduced significantly in the presence of few layered exfoliated h-BN nanofluid as compared to neat lubricated oil. Micro- XPS and energy-disperse X-ray spectroscopy (EDX) analysis demonstrated the presence of adsorbed h-BN tribofilm in the metallic wear track. Thin 2D sheets of h-BN nanofluid was effective as an additive for low shear resistance under the tribo stressed condition which is the main reason for significant reduction in friction coefficient. Moreover, the enhanced wear resistance of exfoliated h-BN additives was explained by low shear resistance and high compressive/tensile strength of planer sheets which restricted the mechanical damage and protected the metallic interfaces against deformation and wear.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mechanical exfoliation of bulk 3D into 2D hexagonal boron nitride. </LI> <LI> Chemical functionalization of 2D hexagonal boron nitride during ball milling. </LI> <LI> Chemical compatibility of 2D hexagonal boron nitride with 10W30 commercial oil. </LI> <LI> High tribo-mechanical efficiency of 2D hexagonal boron nitride. </LI> <LI> High efficient 2D hexagonal boron nitride as nanolubricant modifiers in 10W30 commercial oil. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Designing metal oxide-vertical graphene nanosheets structures for 2.6 V aqueous asymmetric electrochemical capacitor

Subrata Ghosh,S.R. Polaki,Gopinath Sahoo,En Mei Jin,M. Kamruddin,조정상,정상문 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.72 No.-

The asymmetric electrochemical capacitor was realized by MnO2/Vertical graphene nanosheets (VGN)and Fe2O3/VGN as positive and negative electrodes, respectively. The surface of VGN skeleton isindependently decorated with MnO2 having sponge gourd-like morphology and Fe2O3 having nanoricelike morphology. Both the electrodes have shown around 250 times higher charge-storage capacity thanthe bare VGN (0.47 mF/cm2) with the specific capacitance of 118 (MnO2/VGN) and 151 mF/cm2 (Fe2O3/VGN). The fabricated asymmetric device exhibited a specific capacitance of 76 mF/cm2 and energydensity of 71 mWh/cm2 with an excellent electrochemical stability up to 12,000 cycles, over a potentialwindow of 2.6 V.