- Raja Ramanna Centre for Advanced Technology
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Rajendra Nagar, Indore 452 013 - 09425077030
- My current research interest includes growth of thin films and nano-structures of metal oxide semiconductors and high... moreMy current research interest includes growth of thin films and nano-structures of metal oxide semiconductors and high K dielectric oxides using pulsed laser deposition (PLD) and atomic layer deposition (ALD) techniques and their characterizations for photonic and electronic device applications such as oxide semiconductors for UV-blue photonic, transparent electronic and plasmonic devices, Rare earth oxide thin films and nano-laminated structures for MOSFET and RRAM devices, Graphene oxide thin films for flexible memories.edit
Forming-free resistive random access memory (ReRAM) devices having low switching voltages are a prerequisite for their commercial applications. In this study, the forming-free resistive switching characteristics of graphene oxide (GO)... more
Forming-free resistive random access memory (ReRAM) devices having low switching voltages are a prerequisite for their commercial applications. In this study, the forming-free resistive switching characteristics of graphene oxide (GO) films embedded with gold nanoparticles (Au Nps), having an enhanced on/off ratio at very low switching voltages, were investigated for non-volatile memories. The GOAu films were deposited by the electrophoresis method and as-grown films were found to be in the low resistance state; therefore no forming voltage was required to activate the devices for switching. The devices having an enlarged on/off ratio window of ∼10(6) between two resistance states at low voltages (<1 V) for repetitive dc voltage sweeps showed excellent properties of endurance and retention. In these films Au Nps were uniformly dispersed over a large area that provided charge traps, which resulted in improved switching characteristics. Capacitance was also found to increase by a f...
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It is believed that this is the first time that laser molecular beam epitaxy, ie pulsed laser deposition (PLD), deposited epitaxial indium zinc oxide (epi-IZO) thin films on float glass, n100m Si, GaAs and InP wafers have been applied to... more
It is believed that this is the first time that laser molecular beam epitaxy, ie pulsed laser deposition (PLD), deposited epitaxial indium zinc oxide (epi-IZO) thin films on float glass, n100m Si, GaAs and InP wafers have been applied to semiconductor insulator semiconductor type ...
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This paper addresses the effect of disorder on the carrier transport mechanism of atomic layer deposited ZnO thin films as has been investigated by temperature dependent electrical resistivity measurements in the temperature range of 4.2K... more
This paper addresses the effect of disorder on the carrier transport mechanism of atomic layer deposited ZnO thin films as has been investigated by temperature dependent electrical resistivity measurements in the temperature range of 4.2K to 300K. Films were grown on (0001) sapphire substrate at different substrate temperatures varying from 150 to 350 C. The defects and structural disorder in the films were found to be strongly dependent on their growth temperature. The films grown at 150, 300 and 350 C were found to be semiconductor-like in the whole measurement temperature range of resistivity due to the enhanced disorder in these films. However, a metal to semiconductor transition (MST) at low temperature has been observed in the films grown at 200 and 250 C. It was also observed that the film grown at 250 C with higher residual resistivity, the transition temperature shifted towards the higher value due to the increased disorder in this film as compared to that grown at 200 C. T...
ABSTRACT In pulsed laser deposited silicon nanoparticles (Si-nps) embedded in silicon nitride, we have observed that crystalline planes of higher Miller indices grow with increasing time of deposition having noticeable shape and size... more
ABSTRACT In pulsed laser deposited silicon nanoparticles (Si-nps) embedded in silicon nitride, we have observed that crystalline planes of higher Miller indices grow with increasing time of deposition having noticeable shape and size dispersion. Chemical composition of the silicon nitride film was found to have silicon (Si) in all the valence states from 1+ to 4+ and the elemental Si having valence state 0 was found to be present only in the samples which host Si-nps. The transmission spectra showed a red shift with increasing time of deposition plausibly due to enhanced morphological inhomogeneity in the Si-nps. Stokes Raman spectra of the as-grown Si-nps deposited for different growth times showed LA, LO, TA and TO phonon mediated transitions of amorphous and nanocrystalline Si. Significant improvement in the crystalline quality of the nanoparticles was confirmed by the Raman spectra of the annealed samples. The photoluminescence (PL) spectra of as-grown Si-nps showed multiple transitions due to a combined effect of the morphological inhomogeneity and quantum confinement of charge carriers in the nanoparticles. Annealing of the samples reduced the line width and number of transitions of the PL spectra of the Si-nps for all the deposition times. Amongst the annealed samples the line width of the PL spectra of the Si-nps increased with the deposition time. The silicon nitride thin films also showed a distinct PL spectrum due to defect states, which was found to diminish on annealing. These studies provide further insight into the basic optical processes in Si-nps.
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ABSTRACT We have grown Ga doped ZnO (GZO) thin films at moderate temperatures with Ga concentrations in the range varying from 0.25 to 3 at.% on sapphire substrates using buffer assisted pulsed laser deposition. Room temperature... more
ABSTRACT We have grown Ga doped ZnO (GZO) thin films at moderate temperatures with Ga concentrations in the range varying from 0.25 to 3 at.% on sapphire substrates using buffer assisted pulsed laser deposition. Room temperature resistivity measured was ∼5.1 × 10−5 Ω cm with a electron mobility of ∼41.9 cm2/V s for an optimum Ga concentration of ∼0.75 at.% in the GZO films. Buffer assisted growth methodology maintains relatively good crystalline quality of the GZO thin films, thereby improving the electron mobility even at high dopant concentrations. This plays a key role in decreasing the resistivity of GZO films to the aforementioned value, which to the best of our knowledge is the lowest so far. These highly conducting GZO thin films with good mobility are potential candidates for transparent conducting oxide (TCO) applications in various optoelectronic devices.
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ABSTRACT A clear signature of disorder induced quantum-interference phenomena leading to phase-coherent electron transport was observed in (Zn, Al)Ox thin films grown by atomic layer deposition. The degree of static-disorder was tuned by... more
ABSTRACT A clear signature of disorder induced quantum-interference phenomena leading to phase-coherent electron transport was observed in (Zn, Al)Ox thin films grown by atomic layer deposition. The degree of static-disorder was tuned by varying the Al concentration through periodic incorporation of Al2O3 sub-monolayer in ZnO. All the films showed small negative magnetoresistance due to magnetic field suppressed weak-localization effect. The temperature dependence of phase-coherence length ( l φ ∝ T − 3 / 4 ), as extracted from the magnetoresistance measurements, indicated electron-electron scattering as the dominant dephasing mechanism. The persistence of quantum-interference at relatively higher temperatures up to 200 K is promising for the realization of ZnO based phase-coherent electron transport devices.
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We report the use of non-magnetic Al2O3 nano particles deposited between two ferromagnetic La0.5Pr0.2Sr0.3MnO3 (LPSMO) manganite layers with an aim to improve the electronic and magnetotransport properties of the layered supper lattice... more
We report the use of non-magnetic Al2O3 nano particles deposited between two ferromagnetic La0.5Pr0.2Sr0.3MnO3 (LPSMO) manganite layers with an aim to improve the electronic and magnetotransport properties of the layered supper lattice grown on single crystal STO(100) substrate using Pulsed Laser Deposition (PLD) technique. We studied the electronic-transport and magnetotransport properties of this system wherein Al2O3 particles are expected to act as insulating scattering centers between two ferromagnetic LPSMO layers. The scattering due to additional scattering centers (insulating Al2O3 nano particles) could be controlled by application of external field, resulting in high magnetoresistance (MR) approximately 72% as compared to pristine LPSMO film (MR approximately 51%) at temperature close to their T(M) values. In addition, incorporation of nanostructured Al2O3 barrier between the two ferromagnetic LPSMO layers results in a 2-3 fold increase in the values of temperature coefficie...
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ABSTRACT A detailed analysis of leakage current density-gate voltage measurements of gate stacks composed of PLD grown ultra thin films of LaGdO3 (LGO) on p-type silicon substrates with 8.4 Å EOT is presented. Temperature dependent... more
ABSTRACT A detailed analysis of leakage current density-gate voltage measurements of gate stacks composed of PLD grown ultra thin films of LaGdO3 (LGO) on p-type silicon substrates with 8.4 Å EOT is presented. Temperature dependent leakage measurements revealed that forward bias current was dominated by Schottky emission over trap assisted tunneling below 1.2 MV/cm and quantum mechanical tunneling above this field. The physical origin of the reverse bias current was found to be a combination of Schottky emission and trap assisted tunneling. Low leakage current densities in the range from 2.3×10-3 to 29×10-3 A/cm2 were recorded for films with EOT from 1.8 to 0.8 nm, that are at least four or more orders below the ITRS specifications and its SiO2 competitors.
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ABSTRACT In pulsed laser deposited silicon nanoparticles (Si-nps) embedded in silicon nitride, we have observed that crystalline planes of higher Miller indices grow with increasing time of deposition having noticeable shape and size... more
ABSTRACT In pulsed laser deposited silicon nanoparticles (Si-nps) embedded in silicon nitride, we have observed that crystalline planes of higher Miller indices grow with increasing time of deposition having noticeable shape and size dispersion. Chemical composition of the silicon nitride film was found to have silicon (Si) in all the valence states from 1+ to 4+ and the elemental Si having valence state 0 was found to be present only in the samples which host Si-nps. The transmission spectra showed a red shift with increasing time of deposition plausibly due to enhanced morphological inhomogeneity in the Si-nps. Stokes Raman spectra of the as-grown Si-nps deposited for different growth times showed LA, LO, TA and TO phonon mediated transitions of amorphous and nanocrystalline Si. Significant improvement in the crystalline quality of the nanoparticles was confirmed by the Raman spectra of the annealed samples. The photoluminescence (PL) spectra of as-grown Si-nps showed multiple transitions due to a combined effect of the morphological inhomogeneity and quantum confinement of charge carriers in the nanoparticles. Annealing of the samples reduced the line width and number of transitions of the PL spectra of the Si-nps for all the deposition times. Amongst the annealed samples the line width of the PL spectra of the Si-nps increased with the deposition time. The silicon nitride thin films also showed a distinct PL spectrum due to defect states, which was found to diminish on annealing. These studies provide further insight into the basic optical processes in Si-nps.
Nannocrystalline and nanoporus thin films of ZnO were synthesized on glass substrates by using wet chemical drop casting method. X-ray diffraction measurements on these samples confirmed the formation of ZnO nanocrystallites in hexagonal... more
Nannocrystalline and nanoporus thin films of ZnO were synthesized on glass substrates by using wet chemical drop casting method. X-ray diffraction measurements on these samples confirmed the formation of ZnO nanocrystallites in hexagonal wurtzite phase with mean size of ~20 nm. Photo sensitization of these nanostructured ZnO thin films was carried out using three types of dyes Rhodamine 6 G,
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Lanthanum hexaboride films were grown on tungsten and rhenium tips and foils by pulsed laser deposition. The X-ray diffraction spectra of the PLD LaB6 films on both the substrates show crystalline nature with average grain size... more
Lanthanum hexaboride films were grown on tungsten and rhenium tips and foils by pulsed laser deposition. The X-ray diffraction spectra of the PLD LaB6 films on both the substrates show crystalline nature with average grain size approximately 125 nm. The field emission studies of pointed and foil specimens were performed in conventional and planar diode configurations, respectively, under ultra-high vacuum condition. An estimated current density of approximately 1.2 x 10(4) A/cm2 was drawn at the electric field of 3 x 10(3) and 6 x 10(3) V/microm from the LaB6 coated tips of tungsten and rhenium, respectively. The Fowler-Nordheim plots were found to be linear showing metallic behavior of the emitters. The field enhancement factors were calculated from the slopes of the Fowler-Nordheim plots, indicating that the field emission is from LaB6 nanoscale protrusions present on emitter surfaces. The emitters were operated for long time current stability (3 h) studies. The post-field emission surface morphology of the emitters showed no significant erosion of LaB6 films during 3 h continuous operation. The observed behavior indicates that it is linked with the growth of LaB6 films on W and Re. These results reveal that the LaB6 films exhibit high resistance to ion bombardment and excellent structural stability and are more promising emitters for practical applications in field emission based devices.
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... Pankaj Misra, BN Singh and Lalit M. Kukreja Thin Film Laboratory, Raja Ramanna CentreforAdvance Technology, Indore - 452013, India Corresponding Author E-mail: hod@physics.unipune ... 5) VN Tondare, BI Birajdar, N. Pradeep, D. S.... more
... Pankaj Misra, BN Singh and Lalit M. Kukreja Thin Film Laboratory, Raja Ramanna CentreforAdvance Technology, Indore - 452013, India Corresponding Author E-mail: hod@physics.unipune ... 5) VN Tondare, BI Birajdar, N. Pradeep, D. S. Joag, A. Lobo, and S. K. ...
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We demonstrate the room temperature polar switching and tunneling in PbZr0.52Ti0.48O3 (PZT) ultra-thin films of thickness 3-7 nm, sandwiched between platinum metal and ferromagnetic La0.67Sr0.33MnO3 (LSMO) layers, which also shows... more
We demonstrate the room temperature polar switching and tunneling in PbZr0.52Ti0.48O3 (PZT) ultra-thin films of thickness 3-7 nm, sandwiched between platinum metal and ferromagnetic La0.67Sr0.33MnO3 (LSMO) layers, which also shows magnetic field dependent tunnel current switching in Pt/PbZr0.52Ti0.48O3/La0.67Sr0.33MnO3 heterostructures. The epitaxial nature, surface quality and ferroelectric switching of heterostructured films were examined with the help of x-ray diffraction patterns, atomic force microscopy, and piezo force microscopy, respectively. The capacitance versus voltage graphs show butterfly loops above the coercive field (> ±3 V) of PZT for small probe area (∼16 μm(2)). The effect of ferroelectric switching was observed in current density versus voltage curves with a large variation in high-resistance/low-resistance (HRS/LRS) ratio (2:1 to 100:1), however, these effects were more prominent in the presence of in-plane external magnetic field. The conductance is fitted ...
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ABSTRACT We report enhancement of photovoltaic properties of highly oriented BiFeO3 (BFO) thin films. The single phase rhombohedral R3c space group structure was confirmed by XRD and Raman spectra in the films grown on SrTiO3 (111)... more
ABSTRACT We report enhancement of photovoltaic properties of highly oriented BiFeO3 (BFO) thin films. The single phase rhombohedral R3c space group structure was confirmed by XRD and Raman spectra in the films grown on SrTiO3 (111) substrates using RF magnetron sputtering. The films of BFO were characterized in planar geometry with top Pt electrodes having 200μm diameter, ∼40nm thickness and at a regular spacing of ∼150μm deposited by DC sputtering process. For photovoltaic studies the current voltage characteristic of as grown and poled samples were studied under the white light illumination having energy density of ∼1kW/m2. The as grown films showed open circuit voltage (Voc) of ∼3.9V which increased up to ∼17.8V on poling with 200V. This enhancement in Voc by poling was attributed to increase in net polarization due to alignment of domains in the direction of applied electric field and hence potential barriers between the domains.
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Transparent diode heterojunction on ITO coated glass substrates was fabricated using p-type AgCoO2 and n-type ZnO films by pulsed laser deposition (PLD). The PLD of AgCoO2 thin films was carried out using the pelletized sintered target of... more
Transparent diode heterojunction on ITO coated glass substrates was fabricated using p-type AgCoO2 and n-type ZnO films by pulsed laser deposition (PLD). The PLD of AgCoO2 thin films was carried out using the pelletized sintered target of AgCoO2 powder, which was synthesized in-house by the hydrothermal process. The band gap of these thin films was found to be ∼3.89 eV and
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Pulsed Laser Deposition of high crystalline quality thin ZnO films on sapphire substrates necessitates a growth temperature of about 750 °C or higher while sharp interfaces in a multilayer structure suitable for optoelectronic devices are... more
Pulsed Laser Deposition of high crystalline quality thin ZnO films on sapphire substrates necessitates a growth temperature of about 750 °C or higher while sharp interfaces in a multilayer structure suitable for optoelectronic devices are obtained at comparatively low growth temperatures. To meet these contradictory requirements a growth scheme has been evolved in which a ZnO buffer layer deposited at
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... Electron Devices 49 2141 CrossRef link. Your last 10 viewed. Optimized dual temperature pulsed laser deposition of TiO 2 to realize MTOS (metal-TiO 2 SiO 2 Si) capacitors with ultrathin gate dielectric Ravneet Singh et al 2005... more
... Electron Devices 49 2141 CrossRef link. Your last 10 viewed. Optimized dual temperature pulsed laser deposition of TiO 2 to realize MTOS (metal-TiO 2 SiO 2 Si) capacitors with ultrathin gate dielectric Ravneet Singh et al 2005 Semicond. Sci. Technol. 20 38. ...
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ABSTRACT Highly transparent and conducting Chromium doped ZnO (Cr:ZnO) thin films with preferential c-axis orientation were grown on (0 0 0 1) sapphire substrates using buffer assisted pulsed laser deposition. The resistivity of Cr:ZnO... more
ABSTRACT Highly transparent and conducting Chromium doped ZnO (Cr:ZnO) thin films with preferential c-axis orientation were grown on (0 0 0 1) sapphire substrates using buffer assisted pulsed laser deposition. The resistivity of Cr:ZnO thin films was found to decrease to a minimum value of ˜1.13×10-3Omega cm with the increasing Cr concentration up to ˜1.9 at.% and then increase with further increase of Cr concentration. On the contrary, the band gap and carrier concentration of Cr:ZnO thin films increased up to ˜3.37 eV and ˜2×1020 cm-3, respectively, with the increase of Cr concentration up to ˜1.9 at.%, then decreased with further increase of Cr concentration. The increase of carrier concentration and conductivity with Cr doping at low Cr concentrations (
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Nanocrystalline lanthanum hexaboride (LaB(6)) films have been deposited on molybdenum foil by the pulsed laser deposition (PLD) technique. The as-deposited films were characterized by x-ray diffraction (XRD), scanning electron microscopy... more
Nanocrystalline lanthanum hexaboride (LaB(6)) films have been deposited on molybdenum foil by the pulsed laser deposition (PLD) technique. The as-deposited films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The XRD pattern shows the cubic crystallinity of the LaB(6) film. The AFM studies reveal that the conical shaped LaB(6) nanostructures have height 60 nm, base 800 nm, and a typical radius of curvature ∼20 nm. A comparison of force and in situ current imaging AFM studies reveals that current contrast does not originate from the surface topography of the LaB(6) film. Field emission studies have been performed in the planar diode configuration. A current density of 4.4 × 10(-2) A cm(-2) is drawn from the actual emitting area. The Fowler-Nordheim plot is found to be linear, in accordance with the quantum mechanical tunneling phenomenon. The field enhancement factor is estimated to be 3585, indicating that the field emission is from LaB(6) nanocrystallites present on the emitter surface, as confirmed by the AFM. The emission current-time plots show current stability to the extent of 5% fluctuation about the average current over a period of 3 h.
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Research Interests: Materials Engineering, Materials Science, Solar Cell, Transparent Conducting Oxide Materials, Molecular beam epitaxy, and 13 moreZinc Oxide, Pulsed Laser Deposition, Thin Film, Band Gap, Grain size, Scanning Electron Microscope, Room Temperature, Single Crystal, Indium phosphide, Atomic Force Microscope, Thin film deposition, Gallium Arsenide, and Zno Thin Film
High-quality GaN epilayers were grown on Si (111) substrates by molecular beam epitaxy using a new growth process sequence which involved a substrate nitridation at low temperatures, annealing at high temperatures, followed by nitridation... more
High-quality GaN epilayers were grown on Si (111) substrates by molecular beam epitaxy using a new growth process sequence which involved a substrate nitridation at low temperatures, annealing at high temperatures, followed by nitridation at high temperatures, deposition of a low-temperature buffer layer, and a high-temperature overgrowth. The material quality of the GaN films was also investigated as a function of nitridation time and temperature. Crystallinity and surface roughness of GaN was found to improve when the Si substrate was treated under the new growth process sequence. Micro-Raman and photoluminescence (PL) measurement results indicate that the GaN film grown by the new process sequence has less tensile stress and optically good. The surface and interface structures of an ultra thin silicon nitride film grown on the Si surface are investigated by core-level photoelectron spectroscopy and it clearly indicates that the quality of silicon nitride notably affects the properties of GaN growth.
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