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Dielectric and microhardness studies of methylene blue doped PMMA matrix

Adiyodi K., Joseph X., Jyothy P. V., Jose G., Unnikrishnan N. V.

Materials Science Poland

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2009

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Vol. 27, No. 1

297--305

EN

Pure and methylene blue (MB) doped poly(methyl methacrylate) (PMMA) samples were prepared by free radical vinyl polymerization. The effect of methylene blue, which itself is polar in nature, on the glass transition temperature, electric permittivity, and microhardness of the PMMA matrix was studied. It was found that incorporation of the dye increases the electric permittivity and decreases the glass transition temperature of the system. The maximum value of the loss tangent below the glass transition temperature suggests the rotation of the ester side group (ß relaxation). MB can also act as a retarder of free radical polymerization causing reduction in the hardness value.

2

Transport properties of as-deposited cadmium phthalocyanine Schottky-barrier devices

Samuel M., Menon C. S., Unnikrishnan N. V.

Materials Science Poland

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2007

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Vol. 25, No. 1

177--184

EN

Sandwich samples of the type (Au-CdPc-Al) have been fabricated by successive vacuum deposition of gold (Au), cadmium phthalocyanine (CdPc), and aluminium (Al) thin films on glass substrates. Good rectification properties have been observed in the device. Ohmic conduction in the lower voltage range has been identified from the forward bias current density-voltage characteristics at room temperature. At higher voltages, a space charge limited conductivity (SCLC) controlled by an exponential trapping distribution above the valence band edge has been observed. The transport properties of the material at ambient temperature have been obtained from an analysis of the samples in the SCLC region. Schottky emission has been identified at lower voltages from the analysis of the reverse bias characteristics.

3

Electrical and optical studies on thin films of indium phthalocyanine chloride

Mammen S., Menon C. S., Unnikrishnan N. V.

Materials Science Poland

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2005

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Vol. 23, No. 3

707--713

EN

Vacuum evaporated thin films of indium phthalocyanine chloride are prepared at room temperature. Post evaporation annealing is done at temperatures of 353 K, 403 K, 453 K and 503 K. The electrical conductivity and optical absorption spectra of these films are studied. From the optical absorption spectra, over a wavelength range of 200-900nm, the optical energy band gap Eg is calculated. A decrease in Eg is observed with an increase of annealing temperature. The thermal activation energy, Ea, is not notably affected by annealing. It is found that Ea is varied with a change in thickness of the film