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Ganesan, R.

Publications and source records attributed to Ganesan, R..

Growth of high quality single crystals of Bi{sub 2}Se{sub 3} topological insulator via solid state reaction method

Recently discovered, Topological Insulators (TIs) have garnered enormous amount of attention owing to its unique surface properties which has potential applications in the field of spintronics and other modern technologies. For all this, it should require a very good quality samples. There are a number of techniques suggested by people for the growth of good quality TIs. Here, we are reporting the growth of high quality single crystals of Bi{sub 2}Se{sub 3} (a TI) by slow cooling solid-state reaction method. X-ray diffraction measurements performed on a cleaved flake of single crystal Bi{sub 2}Se{sub 3} showed up with proper orientations of the crystal planes. High energy X-ray diffraction has been performed to confirm the stoichiometry of the compound and also recorded Laue patterns prove the single crystalline nature of Bi{sub 2}Se{sub 3}. Moreover, angle resolved photo-emission spectroscopy (ARPES) carried out on a flat crystal flake shows distinct Dirac dispersion of surface bands at the gamma point clarifying it as a 3D topological insulator.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Mixed-mode high-power impulse magnetron sputter deposition of tetrahedral amorphous carbon with pulse-length control of ionization

High-power impulse magnetron sputtering (HiPIMS) is used to deposit amorphous carbon thin films with sp{sup 3} fractions of 13% to 82%. Increasing the pulse length results in a transition from conventional HiPIMS deposition to a “mixed-mode” in which an arc triggers on the target surface, resulting in a large flux of carbon ions. The films are characterized using X-ray photoelectron spectroscopy, Raman spectroscopy, ellipsometry, nanoindentation, elastic recoil detection analysis, and measurements of stress and contact angle. All properties vary in a consistent manner, showing a high tetrahedral character only for long pulses, demonstrating that mixed-mode deposition is the source of the high carbon ion flux. Varying the substrate bias reveals an “energy window” effect, where the sp{sup 3} fraction of the films is greatest for a substrate bias around −100 V and decreases for higher or lower bias values. In the absence of bias, the films' properties show little dependence on the pulse length, showing that energetic ions are the origin of the highly tetrahedral character.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Structural and optical modification in Bi doped As{sub 40}S{sub 60} thin films

The influence of substitution of Bi atom instead of S atoms on the structural and optical properties of thin films of As{sub 40}S{sub 60} are reported. The density is found to be increased with the addition Bi heavy metal into As{sub 2}S{sub 3}. The amorphous to polycrystalline structure of the bulk sample is observed for Bi more than 7%. The glass transition temperature is found to be decreased with addition of Bi. The absorption edge shifts to shorter wavelength, thereby decreasing optical band gap of Bi{sub x}As{sub 40}S{sub 60-x} (x=0,2 and 4% here) film. The optical parameter change is discussed from the stand point of chemical bonds formed in the films and related to the defect states produced due to incorporation of Bi atoms in place of chalcogenide S atoms.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Effect of Te addition into As{sub 2}Se{sub 3} thin film: Optical property study by FTIR and XPS

In the present work, we report the effect of Te deposition onto As{sub 2}Se{sub 3} film which affects the optical properties. The Te/As{sub 2}Se{sub 3} film was illuminated with 532 nm laser to study the photo induced diffusion. The prepared As{sub 2}Se{sub 3}, Te/As{sub 2}Se{sub 3} films were characterized by X-ray diffraction which show a completely amorphous nature. On the basis of optical transmission data carried out by Fourier Transform infrared Spectroscopy, a non direct transition was found for these films. The optical bandgap is found to be decreased with Te deposition and photo darkening phenomena is observed for the diffused film. The change in the optical constants are also supported by the corresponding change in different types of bonds which are being analyzed by X-ray photoelectron spectroscopy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗