Dinesh Pathak

Characterization of AgInSe2 Films Deposited by Hot-Wall Vacuum Evaporation Method

Hot-wall technique was used to prepare AgInSe2 films that work close to thermodynamic equilibrium and, therefore, are considered most suitable for growth at low temperatures. The samples were grown on the glass substrate kept at 135°C. The technique can be described as semiclosed growth reactor consisting of a vertically mounted quartz cylinder heated by three separately temperature-controlled ovens and is closed on the top by the substrate. The first oven heats the source material and controls the growth rate, while the second oven heats the wall between source and substrate, and the substrate temperature is controlled by the third one. The structural and optical properties of AgInSe2 films grown by hot-wall technique were studied. X-ray diffraction (XRD) pattern indicates that the prepared films are highly oriented in the (112) direction. The band gap was found to be 1.19 and 2.09 eV, which is due to the fundamental absorption edge and transition originating from crystal field splitting, respectively. The crystallite size of 47 nm and 94% transparency at 890 nm wavelength was observed for the films.

CRYSTALLINE AgInSe2 FILMS ON GLASS BY LASER ABLATION

Laser ablation has attracted special interest for the formation of thin films compared with other formation technique. A distinctive feature of laser ablation is that it allows high quality and stoichiometry of films of even very complex element material. In this presentation, laser ablation of AgInSe2 chalcopyrite semiconductor will be discussed in which it is difficult to maintain stoichiometry by conventional method. High Quality AgInSe2 (AIS) films were grown on Glass substrates by the ultra-high-vacuum pulsed laser deposition technique from the AIS target synthesized from high-purity materials. The X-ray diffraction studies of the films show that films are textured in (112) direction. The substrate temperature appears to influence the properties of films. Increase in substrate temperature results in a more ordered structure. Compositional analysis has been carried out by EDAX. It is observed that compositional stoichiometry is maintained to a greater extent by PLD technique than other traditional methods like thermal evaporation. The optical studies of the films show that the optical band gap is about 1.20 eV.

GROWTH OF AgInSe2 ON Si(100) SUBSTRATE BY PULSE LASER ABLATION

Laser ablation has attracted special interest for the growth of thin films. It allows the formation of high quality layers and maintain stoichiometry in the films of even very complex elemental materials. In this work, high quality AgInSe2 (AIS) films were grown onto Si(100) substrates kept at different temperatures using ultra high vacuum pulsed laser deposition (PLD) technique from the AIS target synthesized from high-purity materials. It has been observed that compositional stoichiometry is largely maintained in the films. This suggests that PLD could be used as technique for fabrication of ternary semi-conducting films. The X-ray diffraction studies of the films show that films are textured in (112) direction. The structural and optical properties have been investigated as a function of substrate temperature. An increase in substrate temperature results in a more ordered structure. Roughness of the films is found to increase at higher deposition temperatures. The optical studies of the films show that the optical band gap lies in the range 1.20–1.27 eV.

Infiltrated Silica Photonic Crystal With Liquid Crystal And Various Organic Liquids

Tunable photonic crystal has been developed by infiltration of nematic liquid crystal (NLC) and different organic liquids in the void of silica microspheres. Optical properties were investigated by ultraviolet–visible (UV–Vis) spectroscopy. It has been observed that the position of photonic band gap (PBG) shifts from 336nm to 326nm with the increase of applied field from 0V to 9V and 316nm to 324nm after the infiltration of the organic liquids. The refractive index of infiltrated liquid crystal (LC) is calculated at different applied electric field. The present results could be suited for implementation of low cost and compact design tunable devices with low power consumption for high density integrated optics.

SYNTHESIS OF RGO–ZnO COMPOSITES FOR THERMAL, ELECTRICAL AND ANTIBACTERIAL STUDIES

Materials composed of single or a few pure/modified graphitic layers can be easily synthesized using chemical methods. In the present work, nanocomposites of reduced graphene oxide (RGO) with zinc oxide (ZnO) have been prepared via in situ reduction of graphite oxide (GO). X-ray diffraction spectra (XRD) confirmed the coexistence of RGO and ZnO crystal planes. The XRD results were complimented by Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy. Incorporation of ZnO phase into the graphitic layers has been identified with the help of scanning electron microscopy (SEM). Incorporation of ZnO into graphitic layers has enhanced the thermal and optical characteristics of RGO but turned out with the reduced electrical conductivity. These nanocomposites illustrated fascinating antimicrobial activities against human pathogens E. coli and S. aureus.