K. K. Pandey

Publications (9) View all

• Article: Energy-dispersive X-ray diffraction beamline at Indus-2 synchrotron source

  K K PANDEY, H K POSWAL, A K MISHRA, ABHILASH DWIVEDI, R VASANTHI, NANDINI GARG, SURINDER M SHARMA
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  ABSTRACT: An energy-dispersive X-ray diffraction beamline has been designed, developed and commissioned at BL-11 bending magnet port of the Indian synchrotron source, Indus-2. The performance of this beamline has been benchmarked by measuring diffraction patterns from various elemental metals and standard inorganic powdered samples. A few recent high-pressure investigations are presented to demonstrate the capabilities of the beamline.
  Pramana 04/2013; 80(04):607-619. · 0.57 Impact Factor
• Article: Interface induced perpendicular magnetic anisotropy in Co/CoO/Co thin film structure: An in-situ MOKE investigation

  Dileep Kumar, Ajay Gupta, P. Patidar, K. K. Pandey, T. Sant, S. M. Sharma
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  ABSTRACT: Co /CoO/Co polycrystalline film was grown on Si (001) substrate and magnetic properties have been investigated using in-situ magneto-optic Kerr effect during growth of the sample. Magnetic anisotropy with easy axis perpendicular to the film surface has been observed in top Co layer, whereas bottom layer was found to be soft with in-plane magnetization without any influence of top layer. Ex-situ in-plane and out-of-plane diffraction measurements revealed that the growth of Co on oxidized interface takes place with preferential orientation of c-axis perpendicular to the film plane, which results in the observed perpendicular magnetic anisotropy. Texturing of the c-axis is expected to be a result of minimization of the interface energy due to hybridization between Co and oxygen at the interface.
  08/2012;
• Article: Study of pressure induced phase transformation in CTAB capped CdS nanoparticles

  Vineet kumar singh, Pratima Chauhan, K.K. Pandey
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  ABSTRACT: Effect of high pressure on as prepared 20 mM CTAB capped CdS nanoparticles (size ∼4 nm) has been analyzed in this paper. Raman scattering has been used to observe the phase transition pressure. X-ray diffraction pattern is used for structural characterization. Raman scattering predicts the phase transition occur from mixed cubical phase to rock salt phase above 6.6 GPa. One of the representative XRD pattern at 9.7 GPa confirms the existence of rock salt phase above 6.6 GPa.
  Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 06/2012; 92:64-66. · 2.10 Impact Factor
• Article: Computer simulations of crystallization kinetics in amorphous silicon under pressure Computer simulations of crystallization kinetics in amorphous silicon under pressure

  K. V. Shanavas, K. K. Pandey, Nandini Garg, Surinder M. Sharma
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  ABSTRACT: With the help of computer simulations we have studied the crystallization kinetics of amorphous silicon in solid phase epitaxial (SPE) and random nucleation growth processes. Our simulations employing classical molecular dynamics and first principles methods suggest qualitatively similar behavior in both processes. Pressure is found to reduce the difference in molar volumes and coordination numbers between the amorphous and crystalline phases, which in turn lowers the energy barrier of crystallization. The activation energy for the SPE growth of four coordinated diamond phase is found to reach a minimum (a maximum in growth rates) close to 10 GPa when its density becomes equal to that of the amorphous phase. The crystallization temperatures of successive high pressure phases of silicon are found to decrease, offering a possible explanation for the pressure induced crystallization reported in this material.
  Journal of Applied Physics 03/2012; 111:063509. · 2.17 Impact Factor
• Article: Pressure induced crystallization in amorphous silicon

  K. K. Pandey, Nandini Garg, K. V. Shanavas, Surinder M. Sharma, S. K. Sikka
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  ABSTRACT: We have investigated the high pressure behavior of amorphous silicon (a-Si) using x-ray diffraction and Raman scattering techniques. Our experiments show that a-Si undergoes a polyamorphous transition from the low density amorphous to the high density amorphous phase, followed by pressure induced crystallization to the primitive hexagonal (ph) phase. On the release path, the sequence of observed phase transitions depends on whether the pressure is reduced slowly or rapidly. Using the results of our first principles calculations, pressure induced preferential crystallization to the ph phase is explained in terms of a thermodynamic model based on phenomenological random nucleation and the growth process.
  Journal of Applied Physics 06/2011; 109:113511. · 2.17 Impact Factor