Showing papers by "Somnath C. Roy published in 2008"
01 May 2008-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the structural, optical, and gas sensing properties of SnO 2 thin films were evaluated with 75 MeV Ni + beam at fluences ranging from 1.5 to 3.1 eV.
Abstract: Swift heavy ion irradiation has been successfully used to modify the structural, optical, and gas sensing properties of SnO 2 thin films. The SnO 2 thin films prepared by sol–gel process were irradiated with 75 MeV Ni + beam at fluences ranging from 1 × 10 11 ion/cm 2 to 3 × 10 13 ion/cm 2 . Structural characterization with glancing angle X-ray diffraction shows an enhancement of crystallinity and systematic change of stress in the SnO 2 lattice up to a threshold value of 1 × 10 13 ions/cm 2 , but decrease in crystallinity at highest fluence of 3 × 10 13 ions/cm 2 . Microstructure investigation of the irradiated films by transmission electron microscopy supports the XRD observations. Optical properties studied by absorption and PL spectroscopies reveal a red shift of the band gap from 3.75 eV to 3.1 eV, and a broad yellow luminescence, respectively, with increase in ion fluence. Gas response of the irradiated SnO 2 films shows increase of resistance on exposure to ammonia (NH 3 ), indicating p-type conductivity resulting from ion irradiation.
51 citations
TL;DR: In this paper, the authors reported novel p-type behaviour of undoped SnO 2 thin films irradiated with a 75 MeV Ni + ion beam, attributed to the holes generated by these interstitial oxygen ions.
Abstract: We report novel p-type behaviour of undoped SnO 2 thin films irradiated with a 75 MeV Ni + ion beam. Gas response of the irradiated films to NH 3 (reducing) and NO 2 (oxidizing) gases shows an increase and decrease in resistance, respectively, indicating p-type conduction that also increases with an increase in ion fluence. Photoluminescence spectroscopy of the irradiated films shows a strong yellow peak corresponding to interstitial oxygen ions. The observed p-type conductivity is attributed to the holes generated by these interstitial oxygen ions. The presence of interstitial oxygen ions is also confirmed by X-ray photoelectron spectroscopy. The conduction activation energy decreases with increasing the ion fluence, indicating an increase in hole density that supports the gas sensing and photoluminescence results.
48 citations
TL;DR: In this article, three binuclear Cu(II) complexes of two pyrimidine derived Schiff base ligands, 2-S -methyl-6-methyl-4-formyl pyridine- N (4)-ethyl thiosemicarbazone (HL 1 ) and salicyl hydrazone of 2-hydrazino-4,6-dimethylpyrimidine (HL 2 ), have been prepared.
46 citations
TL;DR: In this paper, two Schiff base ligands, HL1 and HL2, were synthesized for the first time in their laboratory and characterized by X-ray crystallography and spectroscopy.
40 citations
TL;DR: Two pyrimidine based NNS tridentate base ligands S-methyl-3 and S-benzyl-3 have been synthesized by 1:1 condensation of 2-S-methylmercapto-6-methylpyrimidine-4-carbaldehyde and s-methyl/S-benzinyl dithiocarbazate.
30 citations
TL;DR: In this article, the synthesis and structure of a pyrazole-based orthogonal ferromagnetic coupled tetracopper(II) 2 × 2 homoleptic grid complex [Cu4(PzOAPyz)4(ClO4)2]-ClO 42··6H2O (1)] is described.
26 citations
TL;DR: In this paper, a trinuclear mixed-valent Co(III/II/III) complexes with a different coordination geometry at each cobalt center of a pyrazole derived Schiff base and mononuclear cobalt (III) complex of another pyrazoles containing Schiff base having N-donor atoms have been prepared and structurally characterized.
19 citations
TL;DR: A superhydrophilic ZnO nanorod film is applied to the originally hydrophobic surface of a resonance-based magnetoelastic sensor, which results in the liquid completely spreading across the surface, removing unwanted air bubbles from the liquid/sensor interface.
Abstract: Air bubbles are known to form at the liquid/solid interface of hydrophobic materials upon immersion in a liquid (Holmberg, M.; Kduhle, A.; Garnaes, J.; Morch, K. A.; Boisen, A. Langmuir 2003, 19, 10510-10513). In the case of gravimetric sensors, air bubbles that randomly form at the liquid-solid interface result in poor sensor-to-sensor reproducibility. Herein a superhydrophilic ZnO nanorod film is applied to the originally hydrophobic surface of a resonance-based magnetoelastic sensor. The superhydrophilic coating results in the liquid completely spreading across the surface, removing unwanted air bubbles from the liquid/sensor interface. The resonance amplitude of uncoated (bare) and ZnO-modified sensors are measured in air and then when immersed in saline solution, ethylene glycol, or bovine blood. In comparison to the bare, hydrophobic sensors, we find that the standard deviation of the resonance amplitudes of the liquid-immersed ZnO-nanorod-modified sensors decreases substantially, ranging from a 27% decrease for bovine blood to a 67% decrease for saline. The strategy of using a superhydrophilic coating can be applied to other systems having similar interfacial problems.
17 citations
TL;DR: In this article, the effect of Zr addition on the crystalline structure, ferroelectric and gas sensing properties of sol-gel derived barium strontium titanate (BST) thin films have been studied.
14 citations
TL;DR: In this article, the authors report an enhancement of ammonia sensitivity of SnO2 thin films subjected to high-energy Ni+ ion irradiation, and the observed enhancement of NH3 sensitivity is discussed in context of ion beam generated electronic states in the SnO 2 thin films.
Abstract: Swift heavy ion irradiation is an effective technique to induce changes in the microstructure and electronic energy levels of materials leading to significant modification of properties. Here we report enhancement of ammonia (NH3) sensitivity of SnO2 thin films subjected to high-energy Ni+ ion irradiation. Sol-gel-derived SnO2 thin films (100nm thickness) were exposed to 75 MeV Ni+ ion irradiation, and the gas response characteristics of irradiated films were studied as a function of ion fluence. The irradiated films showed p-type conductivity with a much higher response to NH3 compared to other gases such as ethanol. The observed enhancement of NH3 sensitivity is discussed in context of ion beam generated electronic states in the SnO2 thin films.
13 citations
16 Dec 2008
TL;DR: In this article, the p-type behaviour in undoped SnO2 thin films irradiated with 75 MeV Ni+ ion beam has been reported and attributed to holes generated by these interstitial oxygen ions.
Abstract: We report novel p-type behaviour in undoped SnO2 thin films irradiated with 75 MeV Ni+ ion beam. Gas response of the irradiated films with NH3 (reducing) and NO2 (oxidizing) gases shows an increase and decrease in resistance respectively indicating p-type conduction that also increases with increase in ion fluence. Photoluminescence spectroscopy of the irradiated films shows strong yellow peak corresponding to interstitial oxygen ions. The observed p-type conductivity is attributed to holes generated by these interstitial oxygen ions. Presence of interstitial oxygen ions is also supported by X-ray photoelectron spectroscopy.