[en] We have investigated the effects of high energy nitrogen ion (N⁺) irradiated n-GaAs Schottky barrier diodes using deep level transient spectroscopy. The diodes have been irradiated (fluences of 1 x 10¹² and 1 x 10¹³ cm^-2) at 77 K. Three electron trap levels (labeled as En1, En2 and En3) are observed for the diodes irradiated with the fluence of 1 x 10¹² cm². Activation energies and capture cross-sections of the levels are calculated. The electron trap level En2 (691 meV) is attributed to N_Ga defects produced by the irradiation. Trap level and shallow level concentrations of the irradiated diodes are found to be decreased. It is due to trapping of charge carriers by the irradiation induced defects. Photo carrier life times of the control and irradiated samples have been measured using time resolved photoluminescence spectroscopy. After the irradiation, a decrease in the PL decay time of the sample has been observed

[en] We analysed the effect of 70 keV nitrogen ion implantation in n-GaN to 10¹⁴-10¹⁶ cm^-2 dose by optical absorption, Raman spectroscopy and photoluminescence. Optical absorption spectra of unimplanted samples gave a band gap of 3.4 eV. On implantation with N⁺, the optical absorption was noticeable at energy below the band gap, also presumably, arising out of defects and disorder produced by ion implantation. E₂ (high) and A₁ (LO) Raman modes of GaN layer have been observed and analysed. The behavior of Raman shift and FWHM of GaN modes with N⁺ dose are explained on the basis of implantation-induced lattice damage. The PL spectra of unimplanted samples showed a peak at 3.4 eV corresponding to the band gap of GaN and an emission at 2.3 eV which is normally attributed to N_Ga antisite defects. On irradiation with N⁺ ion there was a drastic increase in the intensity of emission at 2.3 eV. This suggests that the defect responsible for the emission of 2.3 eV increases on N⁺ implantation. At higher doses, additional emission bands at 2.2 and 2.45 eV were observed in the PL spectra, which might be due to the defect complexes

[en] Raman scattering measurements on liquid-encapsulated Czochralski-grown Fe-doped semi-insulating InP(1 0 0) single crystal substrates have been carried out before and after 120 keV N⁺ implantation for various doses from 10¹³ to 10¹⁵ cm^-2 and also after post-implantation rapid thermal annealing of these samples. It is observed that LO phonon mode frequency decreases and full width at half maximum (FWHM) increases with fluence due to implantation-induced lattice damage. Forbidden Raman TO mode in (1 0 0) cut InP is observed at the doses of 5x10¹³ and 5x10¹⁴ cm^-2. This might have appeared due to the polycrystalline and/or misoriented regions created during implantation. TO mode is not observed for high doses in as-implanted samples due to excessive lattice damage induced by the implantation. On rapid thermal annealing at 573 K for 30 s, the implanted samples show a partial recovery of LO phonon mode frequency and FWHM due to partial annealing of the damage. On partial annealing of the implantation-induced defects, TO mode FWHM decreases and area under the peak increases for all the doses from 10¹³ to 10¹⁵ cm^-2

[en] 110 keV nitrogen ions (N⁺) of fluences 1 x 10¹⁴-1 x 10¹⁷ cm^-2 have been implanted in liquid encapsulated Czochralski grown Fe-doped semi-insulating indium phosphide (InP) single crystal substrates. Grazing incidence X-ray diffraction measurements on as-grown and implanted samples have been carried out and analyzed. At all above fluences, a broad hump in the region of InP(1 1 1) peaks is observed. It might have resulted from implantation-induced misoriented grains along certain preferred orientations. The peak observed at a d-value of 1.77 A for all the fluences becomes more pronounced as the implantation fluence increases up to 1 x 10¹⁶ cm^-2. This could indicate formation of an Indium phosphide nitride alloy. Post-implantation annealing reduces the structural defects and assists in the growth of the nitride phase

[en] Hexagonal phase InN was synthesized by 50 keV nitrogen ion implantation at 400 deg. C on an (1 0 0) InP single crystal substrate. The implanted samples were characterised using glancing incidence X-ray diffraction (GIXRD) and Raman spectroscopy. At low implantation dose the metallic In is observed to form due to the implantation-induced decomposition of the InP at 400 deg. C. As the implantation dose is increased complete nitridation takes place resulting in the disappearance of the metallic indium and formation of InN phase

[en] Liquid-encapsulated Czochralski (LEC) grown undoped semi-insulating (SI) gallium arsenide (GaAs) single crystals have been implanted with 120 keV nitrogen ion (N⁺) of fluences 1x10¹⁴, 1x10¹⁵ and 1x10¹⁶ cm^-2. Raman scattering studies of the as-grown and implanted samples have been carried out at room temperature and analyzed. It is observed that the A₁(LO) phonon mode frequency decreases with increase of fluence, whereas the full width at half maximum (FWHM) increases and the area under the peak decreases. All these effects are due to the lattice disorder induced by the implantation. The implanted samples have been annealed at 673 K. They show a partial recovery of the A₁(LO) phonon mode frequency and the FWHM which tend towards the unimplanted values due to partial annealing of the implantation-induced lattice damage. The post-implantation annealed samples show an increase of the area under the peak due to the enhanced Raman scattering caused by the surface roughness which was caused by the implantation. This increase in area was less at high fluences because of the residual lattice damage induced by the implantation, which caused the decrease of the area

[en] The excited state dynamics and electron transfer reactions of luminescent probes bound to hosts with different properties provide a means to compare the systems. Although photoinduced electron transfer reactions between photoexcited ruthenium(II)-poly pyridines and various acceptors have been known in the literature, relatively a few reports are available on reactions with cobalt(III) complexes as quenchers. The current interest in ruthenium-poly pyridines and micro heterogeneous systems such as micelles and DNA led us to study the effect of micelles on the quenching of the emission of *Ru(bpy)₃²⁺ by some cobalt(III) amine complexes. The results obtained on the photochemical electron transfer between excited Ru(bpy)₃²⁺ and several cobalt(III) amine complexes by emission quenching studies in ordinary aqueous solution as well as in micellar solutions have been presented in this report. (author)

[en] The effect of low energy N⁺ ion irradiation on InP samples has been studied using depth resolved Doppler S-parameter measurements. InP samples have been irradiated with 85 keV N⁺ ions to a dose of 1 x 10¹³ to 1 x 10¹⁶ cm^-2. Defect sensitive lineshape S-parameter and the complimentary W-parameter have been deduced at various depths. From the variation of S and from the slope of S-W correlation plots, it is concluded that monovacancies are present up to a dose of 1 x 10¹⁵ cm^-2, while divacancies are present in 1 x 10¹⁶ cm^-2 dose sample. (author)

[en] The InN phase is grown in crystalline InP(100) substrates by 50 keV N⁺ implantation at an elevated temperature of 400 deg. C followed by annealing at 525 deg. C in N₂ ambient. Crystallographic structural and Raman scattering studies are performed for the characterization of grown phases. Temperature- and power-dependent photoluminescence studies show direct band-to-band transition peak ∼1.06 eV at temperatures ≤150 K. Implantations at an elevated temperature with a low ion beam current and subsequent low temperature annealing step are found responsible for the growth of high-quality InN phase

[en] A facile and “Green” route has been applied to fabricate graphene oxide (GO) reinforced polymer composites utilizing “deionized water” as solvent. The GO was reinforced into water soluble poly(vinyl alcohol) (PVA) and poly-2-acrylamido-2-methyl-1-propanesulfonic acid (PAMPS) matrix by ultrasonication followed by mechanical stirring. The incorporation and dispersion of the GO in the polymer matrix were analyzed by XRD, FE-SEM, AFM, FT-IR, and TGA. Further, the FE-SEM and AFM images revealed that the surface roughness and agglomeration of the GO in the polymer matrix increased by increasing its concentration. Ionic exchange capacity, proton conductivity, and tensile texture results showed that the reinforcement of GO in the polymer matrix enhances the physicochemical properties of the host polymer. These PVA/PAMPS/GO nano composites showed improved mechanical stability compared to the pristine polymer, because of strong interfacial interactions within the components and homogeneous dispersion of the GO sheets in the PVA/PAMPS matrix.