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[en] The optical properties of Pr3+ ions in some borate based glasses with varying concentration of lead oxide have been studied. The concentration of lead oxide has been varied from 0 to 50 mol%. The Judd-Ofelt intensity parameters (Ωλ) and other radiative properties for the glasses have been calculated. Variations of Judd-Ofelt intensity parameters are discussed on the basis of structural analysis. It is observed from fluorescence spectra that the fluorescence yield increases with addition of lead oxide and is about five times greater at 40% PbO than that at 0% PbO
[en] Silicon nitride films have been deposited on p-type Si (100) by mercury-sensitized photo-chemical vapor deposition (photo-CVD) method varying deposition pressure and substrate temperature. Energy dispersive X-ray fluorescence spectra of the samples show that the incorporation of mercury in the films, if any, is below 20 ppm. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy studies show the incorporation of oxygen and hydrogen in all the films, which is a function of the deposition parameters. Higher substrate temperature favors the formation of Si-H bonds and reverse is the case for the formation of SiN-H bonds. The sample deposited at low temperature (170 deg. C) shows the presence of less unreacted silicon (4%) in comparison to the sample (12.5% unreacted silicon) deposited at higher deposition temperature (250 deg. C), but the variation of pressure shows no significant change in terms of the unreacted silicon. The incorporated hydrogen and oxygen passivate surface defects thereby influencing interface electronic state densities (Dit) and fixed insulating charges (Qss)
[en] Graphical abstract: Improved field emission properties have been achieved for Indium (In) decorated MWCNTs and are shown using the schematic of field emission set up with In/CNT cathode, and a plot of J-E characteristics for pristine and In decorated CNTs. - Highlights: • Field emission (FE) properties have been studied for the first time from Indium (In) decorated MWCNT films. • Observed increased density of states near the Fermi level for In decorated films. • Superior field emission properties have been achieved for In decorated CNT films. - Abstract: Multi-walled carbon nanotube (MWCNT) films were grown using thermal chemical vapor deposition (T-CVD) process and were decorated with indium metal particles by thermal evaporation technique. The In metal particles are found to get oxidized. The In decorated films show 250% enhancement in the FE current density, lower turn-on and threshold fields, and better temporal stability as compared to their undecorated counterpart. This improvement in field emission properties is primarily attributed to increased density of states near the Fermi level. The presence of O 2p states along with a small contribution from In 5s states results in the enhancement of density of states in the vicinity of the Fermi level.
[en] Fe/c-Si devices have been irradiated with 100 MeV swift heavy ions of Fe7+ at a dose of 1014 ions cm-2. The devices have been studied using XRD and SEM. Electronic transport across the interface of the devices (i.e. in current perpendicular to the plane (CPP) of the device) has been measured from room temperature to liquid N2 temperature. The CPP current has also been studied in a magnetic field (up to 10 kG which has been applied along the plane of the device). Unirradiated devices do not show any effect of the magnetic field whereas large magnetoresistance (MR) up to 2400% giant magnetoresistance (GMR) has been observed for the irradiated devices. An M-H study of the irradiated devices shows a behaviour of coupled magnetic nanograins. The results have been understood by considering the formation of a nanogranular magnetic silicide phase (of Fe5Si3) due to intermixing at the interface (as evidenced from XRD and SEM features). The electronic and magnetotransport characteristics of the irradiated devices show that the interface becomes intimate enough (due to the irradiation induced strong intermixing) to result in a tunnel transmission of carriers. A tunnelling barrier seems to form (for the irradiated ones) between Fe5Si3 magnetic nanocrystals separated by a nanometre scaled silicon tunnelling barrier. The observed very large (strong) GMR could be due to the spin dependent interface scattering in the presence of the strong AF coupling across the tunnelling barrier
[en] The surface electronic structure as a function of the oxygen content has been studied by means of photoemission of sintered 1-2-3 and BISCCO powders. The influence of oxygen stoichiometry on the core level lineshapes of O, Ba and Cu of YBCO has been reported. Our results indicate that in the YBCO compound, the 531 eV peak of O ls spectra arises because of an extrinsic contribution only. Oxygen present on the surface and the intergranular space give rise to this peak. The shape of Ba 4d spectra is found to be influenced by ordering of oxygen vacancies in the basal plane. It appears that the low binding energy component (∼ 87 eV) of l a 4d spectra is a measure of the Meissner fraction of the sample. Cu 2p spectra show the presence of Cu 1+ and 2+, and absence of 3+ in the ground state.(author). 23 refs., 4 figs
[en] In this paper, Mn substituted at Cu site in YBa2Cu3-xMnxOy (x = 0.0, 0.03, 0.09, 0.15, 0.21, 0.30) system has been studied. It is discussed that the resistivity upturn at low temperature in heavily doped samples may be due to the presence of Mn derived impurity phase. Mn appeared to reduce hole density without affecting the 1/T behavior of the Hall coefficient (RH). An attempt has been made to correlate the results of susceptibility with resistivity, hole density and structural changes with the Mn content
[en] The disappearance or weakening of traditional shell closures and appearance of new magic numbers for very neutron-rich nuclei is mainly due to tensor force. In this work the low lying spectra, transition rates B(E2) and quadrupole moment of neutron rich 22O, 24O, 26F and 28F isotopes were studied by performing shell model calculations for somewhat different types of interactions.
[en] The role of Cu3+ in high-Tc superconductors was discussed. A lot of studies on electronic structure of high temperature superconductors have been done using high energy spectroscopies. (NHA). 19 figs