Optical emission spectroscopic studies were carried out on the plasma produced by ablation of zinc
oxide target using the third harmonic 355 nm of Q-switched Nd:YAG laser, in vacuum and at three
different ambient gas oxygen pressures. The spatial variations of electron density Ne and electron
temperature Te were studied up to a distance of 20 mm from the target surface. The kinematics of
the emitted particles and the expansion of the plume edge are discussed. The optimum conditions
favorable for the formation of high quality zinc oxide thin films are thereby suggested.
Zinc oxide (ZnO) thin films were deposited on quartz, silicon, and polymer substrates by pulsed laser deposition (PLD)
technique at different oxygen partial pressures (0.007 mbar to 0.003 mbar). Polycrystalline ZnO films were obtained at
room temperature when the oxygen pressure was between 0.003 mbar and .007 mbar, above and below this pressure the
films were amorphous as indicated by the X-ray diffraction (XRD). ZnO films were deposited on Al2O3 (0001) at
different substrate temperatures varying from 400oC to 600oC and full width half maximum (FWHM) of XRD peak is
observed to decrease as substrate temperature increases. The optical band gaps of these films were nearly 3.3 eV. A
cylindrical Langmuir probe is used for the investigation of plasma plume arising from the ZnO target. The spatial and
temporal variations in electron density and electron temperature are studied. Optical emission spectroscopy is used to
identify the different ionic species in the plume. Strong emission lines of neutral Zn, Zn+ and neutral oxygen are
observed. No electronically excited O+ cations are identified, which is in agreement with previous studies of ZnO plasma
plume.
Jayaraj, M K(American Institute of Physics, January 4, 2006)
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Abstract:
The radio frequency plasma generated during the sputtering of Indium Tin Oxide target using Argon
was analyzed by Langmuir probe and optical-emission spectroscopy. The basic plasma parameters
such as electron temperature and ion density were evaluated. These studies were carried out by
varying the RF power from 20 to 50 W. A linear increase in ion density and an exponential decrease
in electron temperature with rf power were observed. The measured plasma parameters were then
correlated with the properties of ITO thin films deposited under similar plasma conditions.
The differaction efficiency,sensitivity and storage life of Methylene Blue sencitized poly (vinyl chloride) film was improved by the addition of an electron donor in the matrix. The
addition of pyridine enhanced the diffraction efficiency by two times and storage life of the
gratings was increased to 2-3 days.
Sudha Kartha,C(Japan society of applied physica, November 8, 2006)
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Abstract:
Copper doped methylene blue sensitized poly(vinyl alcohol) (MBPVA)–acrylamide films were fabricated to improve the
storage life of recorded gratings. The films were fabricated using gravity settling method and the copper chloride
concentration was optimized as 3:18 10 3 mol/l for a dye concentration of 6:2 10 4 mol/l. The gratings recorded on the
optimized film constitution could be stored for months with stable diffraction efficiency (24%) without any chemical or
thermal fixing techniques. The resolution of the material is found to be unaffected with the addition of copper chloride.
Louis, Godfrey; Santhosh Kumar, A(Springerlink, January 1, 2006)
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Abstract:
A red rain phenomenon occurred in Kerala, India starting from 25th July 2001,
in which the rainwater appeared coloured in various localized places that are spread
over a few hundred kilometers in Kerala. Maximum cases were reported during
the first 10 days and isolated cases were found to occur for about 2 months. The
striking red colouration of the rainwater was found to be due to the suspension
of microscopic red particles having the appearance of biological cells. These particles have no similarity with usual desert dust. An estimated minimum quantity
of 50,000 kg of red particles has fallen from the sky through red rain. An analysis of this strange phenomenon further shows that the conventional atmospheric
transport processes like dust storms etc. cannot explain this phenomenon. The
electron microscopic study of the red particles shows fine cell structure indicat-
ing their biological cell like nature. EDAX analysis shows that the major elements
present in these cell like particles are carbon and oxygen. Strangely, a test for DNA
using Ethidium Bromide dye fluorescence technique indicates absence of DNA in
these cells. In the context of a suspected link between a meteor airburst event and
the red rain, the possibility for the extraterrestrial origin of these particles from
cometary fragments is discussed.