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Featured researches published by R.K. Puri.


Thin Solid Films | 1996

Refractive index and adhesion of Al2O3 thin films obtained from different processes — a comparative study

P.V. Patil; D.M. Bendale; R.K. Puri; Vijaya Puri

Abstract Al 2 O 3 thin films ranging from 50 to 200 nm in thickness are deposited by four different methods viz, electron beam evaporation of Al 2 O 3 with and without chopping, and the oxidation of aluminium films by hot water and by steam. The prepared films are also subjected to heat at 120°C for 3 h and moisture for 3 h. The pre ambient and post ambient refractive index and adhesion are compared for the four types of films. The chopped electron beam evaporated Al 2 O 3 films give the highest refractive index and adhesion. The adhesion of steam oxidised aluminium films compare well with electron beam deposited Al 2 O 3 films. The post ambient refractive index changes are thickness dependent especially for both the types of oxidised aluminium films. The post ambient changes do not seem to be only porosity dependent but some composite oxide formation seems to be taking place.


Materials Chemistry and Physics | 1997

Comparison of adhesion and intrinsic stress of chopped and non-chopped ZnS thin films

P.V. Patil; R.K. Puri; Vijaya Puri

Abstract The adhesion and intrinsic stress of chopped and non-chopped ZnS thin films in the thickness range 50 to 200 nm and the changes occurring due to exposure to moisture, heat (120 °C) and air (30 days) are reported in this paper. The preambient adhesion is higher and the intrinsic stress substantially lower for chopped ZnS films. The post-ambient changes in adhesion and intrinsic stress are less for the chopped films. Chopping seems to increase preferential orientation and to assist in the grain growth, so that structural inhomogeneities are reduced. Reduction of voids and defects also occur as a result of chopping thereby improving the mechanical properties.


Japanese Journal of Applied Physics | 1993

Adhesion Enhancement of Thin Film Deposits by Chopping

Vijaya Puri; R.K. Puri

The chopping technique has been successfully used to enhance the adhesion of MgF2, ZnS and copper films. Chopping does not appreciably alter the adhesion of aluminium and chromium films. Chopping seems to increase the surface mobility of adatoms and prevent growth of large crystallites whereby producing more defect-free thin films because of higher relaxation leading to higher adhesion. The adhesion of chopped MgF2 and ZnS films compare well with those deposited on heated substrate and after glow discharge cleaning. The enhanced adhesion of copper films is being explained in terms of enhanced oxygen affinity at interface similar to that observed for aluminium and chromium. Chopping technique might provide a simple and cost effective process of depositing good adherent thin film coatings.


Journal of Adhesion Science and Technology | 1996

Adhesion improvement and intrinsic stress decrease in cerium oxide thin films by chopping

P.V. Patil; U. V. Nerle; Vijaya Puri; R.K. Puri

The effect of chopping on the adhesion and internal stress of cerium oxide thin films and their response to ambient aging are reported here. Chopping increases the adhesion and decreases the stress in the films. The chopped cerium oxide films are able to withstand ambient aging effects better than non-chopped films. Both chopped and non-chopped films show a decrease in adhesion and an increase in stress upon exposure to air and humidity and an increase in adhesion on heating. The decreased stress and increased adhesion due to chopping are discussed in terms of modification of the wetting characteristics and thereby changes in the morphology of the film. Chopping also seems to enhance the oxygen affinity of the adatoms. X-ray diffraction results confirm the presence of excess oxygen in the chopped film. The chopping technique offers a low-temperature alternative for obtaining films with adhesion similar to those deposited on a heated substrate.


Journal of Physics: Conference Series | 2008

Properties of vacuum evaporated vapour chopped polyaniline thin film: effect of synthesis method

J.B. Yadav; S Jhadav; R.K. Puri; Vijaya Puri

The paper reports optical properties and adhesion of polyaniline thin film prepared by vacuum evaporated polyaniline powder synthesized in acidic and nonacidic medium respectively. The effect of vapour chopping on its optical and adhesion properties is also studied. Maximum transmittance 85% and 90% was obtained for polyaniline thin film deposited from polyaniline powder synthesized from nonacidic and acidic medium respectively. Due to non-acidic medium, the film showed absorption peak at 420 nm, whereas due to acidic medium it shifts below 350 nm. Refractive index of PANI from nonacidic medium is higher than the refractive index from acidic medium. After vapour chopping the refractive index decreases and transmittance increases. Adhesion of the film measured by direct pull of method was higher due to acidic medium ~68 Kgf/cm2 After chopping adhesion of the film increases. Polyaniline thin film deposited from acidic polyaniline powder are more stable and gives lower refractive index with higher adhesion. Vapour chopping also improves the properties of these thin films.


Physica Scripta | 2016

Impact of low-pressure glow-discharge-pulsed plasma polymerization on properties of polyaniline thin films

Aviraj A. Jatratkar; J.B. Yadav; R. R. Deshmukh; Harish C. Barshilia; Vijaya Puri; R.K. Puri

This study reports on polyaniline thin films deposited on a glass substrate using a low-pressure glow-discharge-pulsed plasma polymerization method. The polyaniline thin film obtained by pulsed plasma polymerization has been successfully demonstrated as an optical waveguide with a transmission loss of 3.93 dB cm−1, and has the potential to be employed in integrated optics. An attempt has been made to investigate the effect of plasma OFF-time on the structural, optical as well as surface properties of polyaniline thin film. The plasma ON-time has been kept constant and the plasma OFF-time has been varied throughout the work. The plasma OFF-time strongly influenced the properties of the polyaniline thin film, and a nanostructured and compact surface was revealed in the morphological studies. The plasma OFF-time was found to enhance film thickness, roughness, refractive index and optical transmission loss, whereas it reduced the optical band gap of the polyaniline thin films. Retention in the aromatic structure was confirmed by FTIR results. Optical studies revealed a π-π* electronic transition at about 317 nm as well as the formation of a branched structure. As compared with continuous wave plasma, pulsed plasma polymerization shows better properties. Pulsed plasma polymerization reduced the roughness of the film from 1.2 nm to 0.42 nm and the optical transmission loss from 6.56 dB cm−1 to 3.39 dB cm−1.


Journal of Physics: Conference Series | 2008

Intrinsic stress of bismuth oxide thin films: effect of vapour chopping and air ageing

R.B. Patil; R.K. Puri; Vijaya Puri

Bismuth oxide thin films of thickness 1000 A0 have been prepared by thermal oxidation (in air) of vacuum evaporated bismuth thin films (on glass substrate) at different oxidation temperatures and duration. Both the vapour chopped and nonchopped bismuth oxide thin films showed polycrystalline and polymorphic structure. The monoclinic bismuth oxide was found to be predominant in both the cases. The effect of vapour chopping and air exposure for 40 days on the intrinsic stress of bismuth oxide thin films has been studied. The vapour chopped films showed low (3.92 − 4.80 × 109 N/m2) intrinsic stress than those of nonchopped bismuth oxide thin films (5.77 − 6.74 × 109 N/m2). Intrinsic stress was found to increase due to air ageing. The effect of air ageing on the vapour chopped films was found low. The vapour chopped films showed higher packing density. Higher the packing density, lower the film will age. The process of chopping vapour flow creates films with less inhomogenety i.e. a low concentration of flaws and non-planar defects which results in lower intrinsic stress.


International Scholarly Research Notices | 2012

The Effect of Film Thickness on the Structural Properties of Vacuum Evaporated Poly(3-methylthiophene) Thin Films

Sandip V. Kamat; Vijaya Puri; R.K. Puri

This paper reports on the structural properties of poly(3-methylthiophene) P3MeT thin films prepared by vacuum evaporation on the glass substrates. The structural and surface morphology, wettability, adhesion, and intrinsic stress of these thin films were studied for three different thicknesses. The variation of the film thickness affects the structure, surface, and mechanical properties of P3MeT thin films. Vapor chopping also strongly influences the surface morphology, surface roughness, and wettability of the thin films. It was found that there is a decrease in the intrinsic stress and (RMS) roughness, while the adhesion increases with increase in film thickness.


Physica Scripta | 2011

Determination of the optical constants of a vacuum evaporated polythiophene thin film

Sandip V. Kamat; Vijaya Puri; R.K. Puri

This paper reports the optical properties of polythiophene thin films prepared by a vacuum evaporation technique on a glass substrate. The structural properties, surface morphology and wettability of the thin films were studied. Polythiophene thin films show a porous surface morphology and a hydrophobic nature. The refractive index and extinction coefficient of these thin films were studied by using the well-known envelope method from the transmittance spectra. The transmittance and extinction coefficient increase with an increase in wavelength, whereas the refractive index decreases in the visible region and remains nearly constant in the infrared region. The calculated optical band of the polythiophene thin film is 2.75 eV.


Japanese Journal of Applied Physics | 2003

Porous Al2O3 Cladded Chopped and Nonchopped Al2O3 Thin Film Waveguides: Effect of Moisture and Leafy Vegetation

R.K. Puri; Vijaya Puri

Chopped and nonchopped Al2O3 thin film optical waveguides with porous chopped and nonchopped Al2O3 claddings have been studied for effects due to moisture and leafy vegetation. The changes in the transmission of the cladded waveguide due to relative humidity have been reported in this paper. The changes are more significant when a non chopped waveguide is used. The hot-water-oxidized Al2O3 cladding decreases the output more than the steam-oxidized Al2O3 cladding. The effect of a leaf overlay on the cladded waveguide is also investigated. For the first time, overlay effects on cladded optical waveguides have been reported. The fresh leaves decrease the output significantly, the decrease being more than that when a cladded waveguide is directly exposed to ~90% moisture. As the leaves dry, leaf-type-dependent changes are observed. Use of the overlay technique for cladded optical waveguides may provide a direct method for moisture content determination.

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Sv Kamat

Sinhgad Institute of Technology

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Harish C. Barshilia

National Aerospace Laboratories

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Meng-Fan Luo

National Central University

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