Dann, V J; Dr.Nampoori,V P N; Dr.Nandakumaran,V M(Cochin University of Science & Technology, October , 2008)
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Abstract:
Laser induced plasma (LIP) emissions from some metal oxide targets were
studied with corresponding metal targets of pure quality as a reference. Atomic emissions
in the visible region were used in the spectroscopic procedures of LIP characterization.
The studies were meant to throw light into LIP dynamics and they provided many
experimental results which improved the general awareness of plasma state.When target materials were photo-ablated with an energetically suitable laser
pulse, they developed electric charges in them.An electrical signal which was delivered
from the target served as an alternative probe signal for the diagnostics of LIP and to
track different charged states in the plasma. The signal showed a double peak distribution
with positive polarity and a modified time of flight with various voltage levels of a given
polarity.The expansion dynamics of LIP in magnetic field were also investigated
by monitoring the voltage transients generated at the target.
Description:
International School of Photonics,
Cochin University of Science and Technology
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.
Harilal, S S; Bindhu, C V; Nampoori, V P N; Vallabhan, C P G(Applied Spectroscopy, 1998)
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Abstract:
Spectroscopic studies of laser -induced plasma from a high-temperature
superconducting material, viz., YBa2Cu3O7 (YBCO), have
been carried out. Electron temperature and electron density measurements
were made from spectral data. The Stark broad ening of
emission lines was used to determine the electron density, and the
ratio of line in tensities was exploited for the determination of electron
temperature. An initial electron temperature of 2.35 eV and
electron density of 2.5 3 1017 cm2 3 were observed. The dependence
on electron temperature and density on different experimental parameters
such as distance from the target, delay time after the in itiation
of the plasm a, and laser irradiance is also discussed in detail.
Index Headings: Laser -plasma spectroscopy; Plasma diagnostics;
Emission spectroscop y; YBa2Cu3O7.