Functional Materials
Pankaj Solanki; Mayur Vala; Sandip V. Bhatt; Dhananjay Dhruv; Bharat Kataria
Abstract
We report the results of studies on the rectifying behaviour and tunnelling conduction in GdMnO3/ZnO/STO and GdMnO3/Al:ZnO/STO thin film heterostructures comprising of p-n junctions fabricated using the Pulsed Laser Deposition (PLD) technique. A structural study using grazing angle mode XRD depicts polycrystalline ...
Read More
We report the results of studies on the rectifying behaviour and tunnelling conduction in GdMnO3/ZnO/STO and GdMnO3/Al:ZnO/STO thin film heterostructures comprising of p-n junctions fabricated using the Pulsed Laser Deposition (PLD) technique. A structural study using grazing angle mode XRD depicts polycrystalline growth and confirms the phase purity. The AFM micrographs reveals the different grain growth and grain sizes of the prepared thin film heterostructures. Room temperature Raman spectra shows the presence of various vibrational modes in both the thin film heterostructures, the transport studies using I–V measurements at room temperature is explained using various models. The temperature dependent transport studies using I-V measurements at various temperatures reveal the rectifying behaviour and the difference in the I-V behaviour at various temperature can be understood on the basis of interface effect at the junction, which has been attributed to the presence of the various conduction phenomena through the junctions and the change in barrier height with the temperature for both presently studied thin film heterostructures.
H. Jadhav; S. Sinha
Abstract
Thin film with immobilized particulates of Cobalt oxide (Co3O4) has been synthesized by Pulsed Laser Deposition (PLD) technique followed by thermal treatment in air. Surface morphology of the Co3O4 films was examined using Field Emission Scanning Electron Microscopy (FESEM). Crystalline structure of ...
Read More
Thin film with immobilized particulates of Cobalt oxide (Co3O4) has been synthesized by Pulsed Laser Deposition (PLD) technique followed by thermal treatment in air. Surface morphology of the Co3O4 films was examined using Field Emission Scanning Electron Microscopy (FESEM). Crystalline structure of Co3O4 films was investigated by X-ray Diffraction (XRD) and Raman spectroscopy was used to confirm the presence of Co3O4 phase on the surface. Efficient catalytic performance was obtained with these films for hydrolysis in Sodium Borohydride (NaBH4). A maximum hydrogen generation rate of ~5100 mL min -1 g -1 of catalyst was recorded at a temperature of 305 K with calculated activation energy of 62.96 kJ/mol. Good catalytic activity could be attributed to nanostructures of the films formed following heat treatment consisting of densely packed nanoparticles (NPs) which act as active catalytic centers, and the immobilized nature of the particles on the surface of the films. These catalyst films showed no major loss of activity even after five cycles of use allowing at the same time an advantage of easy separation from the solution. Our results thus demonstrate good catalytic performance and reusability of such PLD deposited Co3O4 nanostructured films towards hydrogen production by hydrolysis of NaBH4.
Partha P. Dey; Alika Khare
Abstract
In this letter, optical limiting property of the insufficiently oxidized silicon oxide (SiOx) thin films is reported. Films were deposited by Pulsed Laser Deposition technique using Q-switched Nd: YAG laser (532 nm) onto fused silica substrate at a substrate temperature of 400 °C by varying the O2 ...
Read More
In this letter, optical limiting property of the insufficiently oxidized silicon oxide (SiOx) thin films is reported. Films were deposited by Pulsed Laser Deposition technique using Q-switched Nd: YAG laser (532 nm) onto fused silica substrate at a substrate temperature of 400 °C by varying the O2 pressure in the range of 5×10 -5 to 0.5 mbar. Energy Dispersive X-Ray spectra showed the increase in oxygen content with increasing O2 pressure. Raman spectra of SiOx films depicted the presence of micron sized clusters composed of nanocrystalline Silicon embedded in uniform matrix of oxidized amorphous Silicon. The open Z-scan of the thin films, under cw He-Ne laser irradiation, showed strong reverse saturation absorption (RSA) features and non linear absorption (NLA) coefficient, β, was found to be decreasing from 23.5 cm/W to 1.64 cm/W, with increase in O2 pressure from 5×10 -5 to 10 -1 mbar, respectively. Also, the SiOx films except that with maximum oxygen content showed optical limiting, where limiting threshold increases with increasing transparency controlled by oxygen content. The key feature of the present work is the tunability in linear absorption, nonlinear RSA and optical limiting in the SiOx films which can be used as novel material for optical switching application.
Balakrishnan G; Elangovan T; Shin-Sung Yoo; Dae-Eun- Kim; Kuppusami P; Venkatesh Babu R; Sastikumar D; Jung il Song
Abstract
Nanostructured single layer aluminium oxide (Al2O3), single layer zirconium oxide (ZrO2) and the (Al2O3/ZrO2) nano multilayer films were deposited on Si (100) substrates at an optimized oxygen pressure of 3×10 -2 mbar at room temperature by pulsed laser deposition. The Al2O3 layer was kept constant ...
Read More
Nanostructured single layer aluminium oxide (Al2O3), single layer zirconium oxide (ZrO2) and the (Al2O3/ZrO2) nano multilayer films were deposited on Si (100) substrates at an optimized oxygen pressure of 3×10 -2 mbar at room temperature by pulsed laser deposition. The Al2O3 layer was kept constant at 5 nm, while ZrO2 layer thickness was varied from 5 nm to 20 nm. The X-ray diffraction (XRD) studies of single layer of Al2O3 film indicated the cubic γ-Al2O3, while the single layer of ZrO2 indicated both the monoclinic and tetragonal phases. The Al2O3/ZrO2 multilayer films of 5/5 nm and 5/10 nm indicated the tetragonal phase of ZrO2 with nanocrystalline nature. The FESEM and AFM studies showed the dense and smooth morphology of the films. The pin-on disc revealed that the 5/10 nm multilayer film has low friction coefficient ~ 0.10. The wear rate of multilayers film is half of the wear rate of the single layer films and 5/10 nm multilayer film showed a reduced wear rate when it is compared to other single and multilayers. The Al2O3-ZrO2 ceramics find wide applications in wear and corrosion resistance components, high temperature applications and bio-implant materials.
Sudip. K. Sinha
Abstract
We report the thermal annealing effect of ZnO-SnO2 composite thin films deposited by pulsed laser deposition on its structural, electrical, and optical properties. The results present a consistent portrayal of the evolution of ZnO-SnO2 composite oxide films phase formation in post-annealed condition ...
Read More
We report the thermal annealing effect of ZnO-SnO2 composite thin films deposited by pulsed laser deposition on its structural, electrical, and optical properties. The results present a consistent portrayal of the evolution of ZnO-SnO2 composite oxide films phase formation in post-annealed condition and its subsequent effect on various physical properties. X-ray diffraction confirms that the films transform from nearly amorphous to fully crystalline state on thermal annealing at 600 °C. X-ray photoelectron spectroscopy reveals a small shift in Sn-3d peak towards lower energy and O-1s and Zn-2p < /em> peaks towards higher binding energy with increasing ZnO concentration and confirms the formation of combined oxides of ZnO and SnO2. The average optical transmission is greater than 80 % in the visible region of the annealed ZnO-SnO2 composite films. The lowest electrical resistivity of 9.8 × 10 -4 Ωcm has been obtained in the film containing 25 wt % ZnO. Our results suggest that annealed ZnO-SnO2 composite films with improved electrical and optical properties could find potential use in thin film solar cells or touch pad control panels.
Pragati Kumar; Nupur Saxena; Avinash Agarwal; Vinay Gupta
Abstract
Influence of growth temperature on swift heavy ion (SHI) induced structural and optical functionality in CdS thin films is explored for photonic applications. Intense green emission is observed in nanocrystalline CdS thin films grown by pulsed laser deposition (PLD) at two different substrate temperatures ...
Read More
Influence of growth temperature on swift heavy ion (SHI) induced structural and optical functionality in CdS thin films is explored for photonic applications. Intense green emission is observed in nanocrystalline CdS thin films grown by pulsed laser deposition (PLD) at two different substrate temperatures (Ts): room temperature (RT) and 200 ºC. The role of Ts and its implications on the effect of dense electronic excitation provoked by swift heavy ion irradiation (SHII) on various optical and structural properties of CdS films is investigated under the influence of 70 MeV 58 Ni +6 ion beam. It reveals from the present studies that Ts may crucially affect the crystalline structure, vibrational and electronic states of the film and thereafter the functionality induced by ion beam. It is found that ion beam is capable to transform structural phase from mixed phase of cubic and hexagonal structure to either pure cubic or pure hexagonal phase of CdS depending upon the pre-existing preferred orientation in pristine film. The modification in crystallite size and band gap due to impact of ion beam is found to be strongly dependent on pre-existing structural phase, as determined by Ts. The studies presented here confirm that initial growth conditions play a key role even after post deposition SHII treatment in selecting precisely the functional behavior of the films.
Gurpreet Kaur; Anirban Mitra; K.L. Yadav
Abstract
Al-doping of 1.5% by weight, in ZnO (Al:ZnO), thin films are deposited on glass substrates at temperature 400 °C and varying oxygen gas pressure (PO2) from 1.33 Pa to 5.32 Pa via Pulsed Laser Deposition (PLD) technique. The single crystalline nature of the thin films is confirmed from the X-ray diffraction ...
Read More
Al-doping of 1.5% by weight, in ZnO (Al:ZnO), thin films are deposited on glass substrates at temperature 400 °C and varying oxygen gas pressure (PO2) from 1.33 Pa to 5.32 Pa via Pulsed Laser Deposition (PLD) technique. The single crystalline nature of the thin films is confirmed from the X-ray diffraction (XRD) pattern. The evaluated crystallite size is found to be <15 nm. Atomic Force Microscopy (AFM) study reveals the columnar grain formation in the thin films, with low surface roughness. The surface morphology of the grown thin films is significantly affected by PO2. Optical measurements depict that the thin films are highly transparent in the visible region with transmittance up to 80%. The optical band gap calculated from Tauc’s plot evinced that Al-doping results in band edge bending in Al:ZnO thin films, a red shift in the band gap is observed with increase in PO2 that is due to the contributing electrons from oxygen ions. Photoluminescence (PL) spectra of films indicate the visible emission peaks originating from defect states. Optical properties of the thin films confirm their applicability for optoelectronic devices. The room temperature, current-voltage (I-V) plots indicate low resistivity in the thin films ~ 10 -2 (Ω-cm).
R.S. Chauhan; Vijay Kumar; Anshul Jain; Deepti Pratap; D.C. Agarwal; R.J. Chaudhary; Ambuj Tripathi
Abstract
Nanocrystalline tin oxide (SnO2) thin films were fabricated using pulsed laser deposition (PLD) technique. The as-deposited films were irradiated at liquid nitrogen (LN2) temperature using 100 MeV Ag ions at different fluences ranging from 3×10 13 to 3×1014 ions/cm 2 and at 75o with respect ...
Read More
Nanocrystalline tin oxide (SnO2) thin films were fabricated using pulsed laser deposition (PLD) technique. The as-deposited films were irradiated at liquid nitrogen (LN2) temperature using 100 MeV Ag ions at different fluences ranging from 3×10 13 to 3×1014 ions/cm 2 and at 75o with respect to surface normal. Pristine and irradiated samples were characterized using XRD, AFM, Raman and I-V (current-voltage characteristics) for the study of modifications in structural, surface morphological, bond angle and resistivity respectively. XRD patterns show that the pristine film is highly polycrystalline and irradiation amorphizes the film systematically with increasing the irradiation fluence. The surface of the pristine film contains nanograins of tin oxide with roughness 5.2 nm. Upon irradiation at lower fluences agglomeration is seen and roughness increased to 10.8 nm. Highest fluence irradiation again develops nanograins with roughness 7.5 nm. Raman spectra and I-V characteristics also confirms the irradiation induced amorphization. The observed results are explained in the frame work of thermal spike model.
K. I. Gnanasekar; V. Jayaraman;T. Gnanasekaran; E. Prabhu
Abstract
High quality sensor grade nanostructured thin films of multicomponent semiconducting oxide sensors with superior sensitivity for monitoring trace levels of pollutant gases like NOx, NH3, H2 etc., in the ambient have been deposited by pulsed laser deposition technique. In-situ growth carried out at relatively ...
Read More
High quality sensor grade nanostructured thin films of multicomponent semiconducting oxide sensors with superior sensitivity for monitoring trace levels of pollutant gases like NOx, NH3, H2 etc., in the ambient have been deposited by pulsed laser deposition technique. In-situ growth carried out at relatively lower temperatures yield granular films composed of nanocrystals of the desired crystallographic phase which otherwise would require high temperatures to stabilize. At some specific deposition conditions, growth of thin films containing uniform sized nano-grains with optimum inter-granular connectivity can be readily achieved. Here, we present the superior sensing properties of the sensor grade films of selected materials and bring out the unique characteristics of pulsed laser deposition technique for exploratory research in nano-structured thin films of materials not amenable to conventional synthetic routes.
Komal Bapna; R.J. Choudhary; D.M. Phase
Abstract
We have prepared 4 at.% Fe doped TiO2 thin films on LAO (001) and Si (111) substrates by pulsed laser deposition. X-ray diffraction (XRD) studies suggest different structural properties of the films on the different substrates. Raman measurements corroborate the XRD findings. The thicknesses of the films ...
Read More
We have prepared 4 at.% Fe doped TiO2 thin films on LAO (001) and Si (111) substrates by pulsed laser deposition. X-ray diffraction (XRD) studies suggest different structural properties of the films on the different substrates. Raman measurements corroborate the XRD findings. The thicknesses of the films are also different on the two substrates, suggesting different nucleation process on the two substrates. Interestingly on both the substrates, Fe is not in metal clusters, suggesting their possible incorporation in TiO2 matrix.