Mohan Rao Gowravaram - Academia.edu (original) (raw)
Papers by Mohan Rao Gowravaram
IEEE Transactions on Plasma Science, Sep 1, 2009
Purity of the glow-discharge plasma at atmospheric pressure for surface modification applications... more Purity of the glow-discharge plasma at atmospheric pressure for surface modification applications is always debatable, since it works at ambient atmosphere. We have demonstrated on the use of optical emission spectroscopy to test the purity of this kind of plasma. The effect of gas flow pattern, nature of gas, and its flow rate on the plasma chemistry was studied. The importance of proper system design in maintaining a uniform flow of heavy and inert gases as carrier gas in atmospheric glow-discharge plasma was confirmed. The surface of a plasma-treated PET sample was analyzed using X-ray photoelectron spectroscopy to verify the studies on plasma purity done using emission spectrum.
Nucleation and Atmospheric Aerosols, 2017
Zinc sulfide thin films are deposited on glass substrates using thermal evaporation technique. Ef... more Zinc sulfide thin films are deposited on glass substrates using thermal evaporation technique. Effect of thickness on the properties of as-deposited ZnS films is studied. ZnS films exhibited cubic structure with preferential orientation along (111) plane. All the films exhibited n-type conductivity with resistivity ranging in the order of 105 to 106 Ω-cm. The transmittance in the visible region is in the range of 80 to 89% and the band gap of the material varied from 3.65 to 3.52 eV. The as-deposited films can be used as window layer for fabrication of hetero-junction solar cell.
Advanced Materials Letters, Oct 1, 2013
In the preset study dye-sensitized solar cells (DSSC) have been fabricated on a flexible titanium... more In the preset study dye-sensitized solar cells (DSSC) have been fabricated on a flexible titanium metal foil substrate with mesoporous anatase Titania microsphers (TMS) as the electron transport layer for photo anode. These microspheres perform dual function of light scattering and efficient dye absorption. A light to electricity conversion efficiency of 2.93% is achieved with illumination through the counter electrode. Additionally electrochemical impedance spectroscopy (EIS) is used to analyze the electron transport processes occurring at the various interfaces.
Journal of vacuum science & technology, Jul 1, 2018
Cold atmospheric plasmas are generous sources of chemically active species, the reaction rates wh... more Cold atmospheric plasmas are generous sources of chemically active species, the reaction rates which can be predicted only if the electron number density and the electron energy distribution function are known. Here, the authors present a procedure for estimating both these parameters from the optical emission spectrum of an argon plasma. The peaks in the spectrum were curve fitted with Voigt profiles, and their widths and areas were mapped to the number density and energy distribution of electrons in the plasma, using the mathematical models for Stark broadening and Corona population, respectively. These plasma parameters were optimized to establish a good match between the simulated and the experimental peak attributes. This analysis estimated the value of the electron number density to be approximately 1.5 Â 10 15 cm À3 and the mean electron temperature to be approximately 0.37 eV in their plasma. It also predicted that the energy distribution of electrons can be closely approximated using a Maxwellian distribution.
Journal of Electronic Materials
Li 2 FeSiO 4 and its carbon composite are prepared by an urea-assisted combustion method. The syn... more Li 2 FeSiO 4 and its carbon composite are prepared by an urea-assisted combustion method. The synthesis has been carried out in different urea concentrations, namely 1 Molar (M), 2 M and 3 M urea in the cost-effective ambient atmospheric condition. The x-ray diffraction analysis confirms the orthorhombic structure of Li 2 FeSiO 4 compounds. The urea-assisted combustion reaction enhanced the phase purity of the compound and prevented the oxidation of ferrous ions in Li 2 FeSiO 4. The x-ray photo electron spectroscopy analysis further confirmed the reduction of Fe 3+ concentration in Li 2 FeSiO 4 while adding urea. The Li 2 FeSiO 4 compound formation in the presence of urea occurred at a temperature< 623 K. The one-pot synthesis of Li 2 FeSiO 4 /C with the help of starch and urea in ambient atmospheric condition resulted in Li 2 FeSiO 4 with an orthorhombic crystal structure. The carbon coating in an amorphous nature is observed and the lattice dimension values of Li 2 FeSiO 4 /C are 6.248 Å , 5.330 Å , and 5.029 Å. The lattice parameter has remained unchanged with carbon addition. The addition of 5% carbon to Li 2 FeSiO 4 improves the electrical conductivity and lithium diffusion coefficient to 7.24 9 10 À4 S cm À1 and 5.54 9 10 À6 cm 2 , respectively. The coulombic efficiency and capacity retention after 50 cycles of Li 2 FeSiO 4 /C composite are around 83% and 95%, respectively.
International Journal of Materials Research, 2018
The effect of anodization variables on the morphology and surface properties of oriented titania ... more The effect of anodization variables on the morphology and surface properties of oriented titania nanotube arrays (TNAs) was investigated. The arrays were synthesized using hydrofluoric acid based ethylene glycolelectrolyte. The results show that the anodization time plays a significant role in the surface properties as well as length of the nanotubes. However, the contribution of anodization potential to debris formation was found to be negligible within the investigated range of the potential. The F− ion concentration and aging of electrolyte were found to play crucial roles in the formation of ordered clean nanotubes. The studies conducted by employing these TNAs as photo-anodes for dye-sensitized solar cells (DSCs) show that the morphology variations alone alter the photovoltaic properties of DSCs to a great extent.
Thin Solid Films, 2005
Influence of the deposition parameters and the substrate bias voltage on the optical, composition... more Influence of the deposition parameters and the substrate bias voltage on the optical, compositional and the surface properties of DC magnetron-sputtered silicon nitride thin films are studied. Silicon nitride thin films are deposited on silicon (100) and quartz substrates at different partial pressures of nitrogen and discharge currents. The variation in the refractive index and the optical band gap of these films is studied. Compositional variation has been studied using Rutherford backscattering spectroscopy (RBS). Silicon nitride thin films ...
2008 IEEE 35th International Conference on Plasma Science, 2008
Summary form only given. Ions with low energy spread find immense applications in many fields suc... more Summary form only given. Ions with low energy spread find immense applications in many fields such as FIB, SIMS, ion beam lithography etc. The work has been started to design an efficient and compact plasma based ion source for the application of FIB. It is aimed to generate very low energy spread ions of various gaseous and metallic species. A
Thin Solid Films, 2012
The electrical switching behavior of amorphous GexSe35−xTe65 thin film samples has been studied i... more The electrical switching behavior of amorphous GexSe35−xTe65 thin film samples has been studied in sandwich geometry of electrodes. It is found that these samples exhibit memory switching behavior, which is similar to that of bulk Ge–Se–Te glasses. As expected, the switching voltages of GexSe35−xTe65 thin film samples are lower compared to those of bulk samples. In both thin film amorphous
Materials Science and Engineering: B, 2004
Tungsten nitride thin films were deposited using unbalanced magnetron sputtering system. The effe... more Tungsten nitride thin films were deposited using unbalanced magnetron sputtering system. The effect of the ratio of nitrogen partial pressure to the total pressure during deposition and the substrate bias on the tungsten nitride formation has been studied. The glow discharge characteristics of the process have been studied in order to determine the deposition parameters. It is observed that nitrogen partial pressure ratio 0.4 and cathode current of 200mA favors the formation of the W2N films. The variation in the electrical resistivity of the ...
Journal of Applied Physics, 2008
We determine the electronic properties and dielectric response of zirconia (ZrO2) with oxygen vac... more We determine the electronic properties and dielectric response of zirconia (ZrO2) with oxygen vacancies (O vacancies) and Ti doping using first-principles density functional theory calculations based on pseudopotentials and a plane wave basis. We find significantly enhanced static dielectric response in zirconia with Ti doping and introduction of oxygen vacancies. Softening of phonon modes are responsible for the enhanced dielectric
Journal of Alloys and Compounds, 2009
Copper aluminum oxide films were prepared by direct current (dc) reactive magnetron sputtering un... more Copper aluminum oxide films were prepared by direct current (dc) reactive magnetron sputtering under various substrate temperatures in the range of 303–648K and systematically studied their physical properties. The physical properties of the films were strongly affected by the substrate temperature. The films formed at substrate temperatures <373K were amorphous while those deposited at higher substrate temperatures (≥373K) were polycrystalline
IEEE Transactions on Plasma Science, 2009
AbstractPurity of the glow-discharge plasma at atmospheric pressure for surface modification app... more AbstractPurity of the glow-discharge plasma at atmospheric pressure for surface modification applications is always debatable, since it works at ambient atmosphere. We have demonstrated on the use of optical emission spectroscopy to test the purity of this kind of plasma. The ...
The formation of thin film coatings of polymers in glow discharge systems was recognized as early... more The formation of thin film coatings of polymers in glow discharge systems was recognized as early as the 19th century. However, they were considered as by-products of electrical discharges and hence little attention was paid. Only the period after 1950s saw their renaissance, as practical ways to make special coatings on metals. Since then, much research has been done in plasma induced polymers and interesting, as well as, industry relevant applications have been identified for polymers deposited using plasmas because of their flawless thin film structure, excellent adhesion to the substrate, chemical inertness and low dielectric constant. In this chapter the significance of Plasma Induced polymer coatings is presented with more emphasis on the process aspects, general methods of characterization of these polymers and application of such polymers in super hard coatings. In the first part, a clear distinction has been made between Plasma Polymerized and Plasma Induced Polymerized coa...
ABSTRACT CuInSe2 chalcopyrite thin films were deposited on glass substrates by hot wall depositio... more ABSTRACT CuInSe2 chalcopyrite thin films were deposited on glass substrates by hot wall deposition method. As grown films are polycrystalline in nature showing diffraction peaks corresponding to CuInSe2 chalcopyrite. After annealing a narrowing and an increasing of intensity of these diffraction peaks are observed, due to an improvement in the crystallanity and an increase in the grain size in the films. The annealing process of CuInSe2 films in vacuum does not affect considerably [Cu]∕[In] ratio but leads to a decrease of Selenium. The optical absorption coefficient is slightly influenced by the annealing temperature. Variation of band gap energy of CuInSe2 thin films with annealing temperature were studied. In the high temperature range (T>385 K) the conductivity would be dominated by the transport of holes through the thermal excitation of carriers. In the low temperature range (T
International Journal of Nanoscience, 2011
We present a mechanism that can explain the growth direction of the carbon nanotubes (CNT), based... more We present a mechanism that can explain the growth direction of the carbon nanotubes (CNT), based on the observation of the catalyst particle's shape, that is present along with the CNT. We claim the mechanism holds good for the tip growth as well as the base growth model for CNTs formation. The morphological studies performed using simple geometry show that for encapsulated catalyst, (i) the contact angle is less along the forward direction than that of backward direction, (ii) the growth direction of CNT is along the flow direction of the catalyst particle in the fluid state, (iii) the distance between the centre of two imaginary spheres (circles in 2D) drawn at the front and back of the catalyst particle, qualitatively predicts the difference in growth rate of the CNT and flow of the catalyst particle inside the CNT. In order to support the above claims, a generalized model is proposed, irrespective of the position of the catalyst.
Vacuum, 2009
Deposition of good quality thin films of Lithium Cobalt Oxide (LiCoO 2), by sputtering is precede... more Deposition of good quality thin films of Lithium Cobalt Oxide (LiCoO 2), by sputtering is preceded by target conditioning, which dictates the surface composition, morphology and electrochemical performance of the deposited film. Sputtering from a virgin target surface, results in films with excess of the more reactive elements. The concentration of these reactive elements in the films decreases until the system reaches a steady state after sufficient sputtering from the target. This paper discusses the deposition kinetics in terms of target conditioning of LiCoO 2. The composition, morphology and texturing of deposited film during various hours of sputtering were analyzed using X-ray photoelectron spectroscopy (XPS) and Field Emission Scanning electron microscopy (FESEM). The compositional stability is not observed in the films formed during the initial hours of sputtering from the fresh target, which becomes stable after several hours of sputtering. The Li and Co concentration in the films deposited subsequently is found to be varying and possible causes are discussed. After the compositional stability is reached, electrochemical analysis of LiCoO 2 thin films was performed, which shows a discharge capacity of 129 mAh/cm 2 .
Thin Solid Films, 1993
ABSTRACT The characteristics of the high pressure oxygen-sputtering plasma in the pressure range ... more ABSTRACT The characteristics of the high pressure oxygen-sputtering plasma in the pressure range 0.8–2.4 mbar have been studied using the Langmuir probe technique. The variation in plasma parameters such as positive ion density, electron density, mean electron energy and floating potential with pressure and temperature has been investigated. It has been observed that the positive ion density increases at high substrate temperatures whereas the negative ion density decreases. The study of the variation in mean electron energy and floating potential also indicated the possibility that the number of negative ions is less when the substrates are at elevated temperatures. Since the negative ions are supposed to cause re-sputtering and make the films off-stoichiometric, the reduction in the negative ion density as observed at elevated substrate temperatures is better suited for depositing stoichiometric YBa2Cu3O7−δ superconducting thin films.
Metallurgical and Materials Transactions B, 1996
IEEE Transactions on Plasma Science, Sep 1, 2009
Purity of the glow-discharge plasma at atmospheric pressure for surface modification applications... more Purity of the glow-discharge plasma at atmospheric pressure for surface modification applications is always debatable, since it works at ambient atmosphere. We have demonstrated on the use of optical emission spectroscopy to test the purity of this kind of plasma. The effect of gas flow pattern, nature of gas, and its flow rate on the plasma chemistry was studied. The importance of proper system design in maintaining a uniform flow of heavy and inert gases as carrier gas in atmospheric glow-discharge plasma was confirmed. The surface of a plasma-treated PET sample was analyzed using X-ray photoelectron spectroscopy to verify the studies on plasma purity done using emission spectrum.
Nucleation and Atmospheric Aerosols, 2017
Zinc sulfide thin films are deposited on glass substrates using thermal evaporation technique. Ef... more Zinc sulfide thin films are deposited on glass substrates using thermal evaporation technique. Effect of thickness on the properties of as-deposited ZnS films is studied. ZnS films exhibited cubic structure with preferential orientation along (111) plane. All the films exhibited n-type conductivity with resistivity ranging in the order of 105 to 106 Ω-cm. The transmittance in the visible region is in the range of 80 to 89% and the band gap of the material varied from 3.65 to 3.52 eV. The as-deposited films can be used as window layer for fabrication of hetero-junction solar cell.
Advanced Materials Letters, Oct 1, 2013
In the preset study dye-sensitized solar cells (DSSC) have been fabricated on a flexible titanium... more In the preset study dye-sensitized solar cells (DSSC) have been fabricated on a flexible titanium metal foil substrate with mesoporous anatase Titania microsphers (TMS) as the electron transport layer for photo anode. These microspheres perform dual function of light scattering and efficient dye absorption. A light to electricity conversion efficiency of 2.93% is achieved with illumination through the counter electrode. Additionally electrochemical impedance spectroscopy (EIS) is used to analyze the electron transport processes occurring at the various interfaces.
Journal of vacuum science & technology, Jul 1, 2018
Cold atmospheric plasmas are generous sources of chemically active species, the reaction rates wh... more Cold atmospheric plasmas are generous sources of chemically active species, the reaction rates which can be predicted only if the electron number density and the electron energy distribution function are known. Here, the authors present a procedure for estimating both these parameters from the optical emission spectrum of an argon plasma. The peaks in the spectrum were curve fitted with Voigt profiles, and their widths and areas were mapped to the number density and energy distribution of electrons in the plasma, using the mathematical models for Stark broadening and Corona population, respectively. These plasma parameters were optimized to establish a good match between the simulated and the experimental peak attributes. This analysis estimated the value of the electron number density to be approximately 1.5 Â 10 15 cm À3 and the mean electron temperature to be approximately 0.37 eV in their plasma. It also predicted that the energy distribution of electrons can be closely approximated using a Maxwellian distribution.
Journal of Electronic Materials
Li 2 FeSiO 4 and its carbon composite are prepared by an urea-assisted combustion method. The syn... more Li 2 FeSiO 4 and its carbon composite are prepared by an urea-assisted combustion method. The synthesis has been carried out in different urea concentrations, namely 1 Molar (M), 2 M and 3 M urea in the cost-effective ambient atmospheric condition. The x-ray diffraction analysis confirms the orthorhombic structure of Li 2 FeSiO 4 compounds. The urea-assisted combustion reaction enhanced the phase purity of the compound and prevented the oxidation of ferrous ions in Li 2 FeSiO 4. The x-ray photo electron spectroscopy analysis further confirmed the reduction of Fe 3+ concentration in Li 2 FeSiO 4 while adding urea. The Li 2 FeSiO 4 compound formation in the presence of urea occurred at a temperature< 623 K. The one-pot synthesis of Li 2 FeSiO 4 /C with the help of starch and urea in ambient atmospheric condition resulted in Li 2 FeSiO 4 with an orthorhombic crystal structure. The carbon coating in an amorphous nature is observed and the lattice dimension values of Li 2 FeSiO 4 /C are 6.248 Å , 5.330 Å , and 5.029 Å. The lattice parameter has remained unchanged with carbon addition. The addition of 5% carbon to Li 2 FeSiO 4 improves the electrical conductivity and lithium diffusion coefficient to 7.24 9 10 À4 S cm À1 and 5.54 9 10 À6 cm 2 , respectively. The coulombic efficiency and capacity retention after 50 cycles of Li 2 FeSiO 4 /C composite are around 83% and 95%, respectively.
International Journal of Materials Research, 2018
The effect of anodization variables on the morphology and surface properties of oriented titania ... more The effect of anodization variables on the morphology and surface properties of oriented titania nanotube arrays (TNAs) was investigated. The arrays were synthesized using hydrofluoric acid based ethylene glycolelectrolyte. The results show that the anodization time plays a significant role in the surface properties as well as length of the nanotubes. However, the contribution of anodization potential to debris formation was found to be negligible within the investigated range of the potential. The F− ion concentration and aging of electrolyte were found to play crucial roles in the formation of ordered clean nanotubes. The studies conducted by employing these TNAs as photo-anodes for dye-sensitized solar cells (DSCs) show that the morphology variations alone alter the photovoltaic properties of DSCs to a great extent.
Thin Solid Films, 2005
Influence of the deposition parameters and the substrate bias voltage on the optical, composition... more Influence of the deposition parameters and the substrate bias voltage on the optical, compositional and the surface properties of DC magnetron-sputtered silicon nitride thin films are studied. Silicon nitride thin films are deposited on silicon (100) and quartz substrates at different partial pressures of nitrogen and discharge currents. The variation in the refractive index and the optical band gap of these films is studied. Compositional variation has been studied using Rutherford backscattering spectroscopy (RBS). Silicon nitride thin films ...
2008 IEEE 35th International Conference on Plasma Science, 2008
Summary form only given. Ions with low energy spread find immense applications in many fields suc... more Summary form only given. Ions with low energy spread find immense applications in many fields such as FIB, SIMS, ion beam lithography etc. The work has been started to design an efficient and compact plasma based ion source for the application of FIB. It is aimed to generate very low energy spread ions of various gaseous and metallic species. A
Thin Solid Films, 2012
The electrical switching behavior of amorphous GexSe35−xTe65 thin film samples has been studied i... more The electrical switching behavior of amorphous GexSe35−xTe65 thin film samples has been studied in sandwich geometry of electrodes. It is found that these samples exhibit memory switching behavior, which is similar to that of bulk Ge–Se–Te glasses. As expected, the switching voltages of GexSe35−xTe65 thin film samples are lower compared to those of bulk samples. In both thin film amorphous
Materials Science and Engineering: B, 2004
Tungsten nitride thin films were deposited using unbalanced magnetron sputtering system. The effe... more Tungsten nitride thin films were deposited using unbalanced magnetron sputtering system. The effect of the ratio of nitrogen partial pressure to the total pressure during deposition and the substrate bias on the tungsten nitride formation has been studied. The glow discharge characteristics of the process have been studied in order to determine the deposition parameters. It is observed that nitrogen partial pressure ratio 0.4 and cathode current of 200mA favors the formation of the W2N films. The variation in the electrical resistivity of the ...
Journal of Applied Physics, 2008
We determine the electronic properties and dielectric response of zirconia (ZrO2) with oxygen vac... more We determine the electronic properties and dielectric response of zirconia (ZrO2) with oxygen vacancies (O vacancies) and Ti doping using first-principles density functional theory calculations based on pseudopotentials and a plane wave basis. We find significantly enhanced static dielectric response in zirconia with Ti doping and introduction of oxygen vacancies. Softening of phonon modes are responsible for the enhanced dielectric
Journal of Alloys and Compounds, 2009
Copper aluminum oxide films were prepared by direct current (dc) reactive magnetron sputtering un... more Copper aluminum oxide films were prepared by direct current (dc) reactive magnetron sputtering under various substrate temperatures in the range of 303–648K and systematically studied their physical properties. The physical properties of the films were strongly affected by the substrate temperature. The films formed at substrate temperatures <373K were amorphous while those deposited at higher substrate temperatures (≥373K) were polycrystalline
IEEE Transactions on Plasma Science, 2009
AbstractPurity of the glow-discharge plasma at atmospheric pressure for surface modification app... more AbstractPurity of the glow-discharge plasma at atmospheric pressure for surface modification applications is always debatable, since it works at ambient atmosphere. We have demonstrated on the use of optical emission spectroscopy to test the purity of this kind of plasma. The ...
The formation of thin film coatings of polymers in glow discharge systems was recognized as early... more The formation of thin film coatings of polymers in glow discharge systems was recognized as early as the 19th century. However, they were considered as by-products of electrical discharges and hence little attention was paid. Only the period after 1950s saw their renaissance, as practical ways to make special coatings on metals. Since then, much research has been done in plasma induced polymers and interesting, as well as, industry relevant applications have been identified for polymers deposited using plasmas because of their flawless thin film structure, excellent adhesion to the substrate, chemical inertness and low dielectric constant. In this chapter the significance of Plasma Induced polymer coatings is presented with more emphasis on the process aspects, general methods of characterization of these polymers and application of such polymers in super hard coatings. In the first part, a clear distinction has been made between Plasma Polymerized and Plasma Induced Polymerized coa...
ABSTRACT CuInSe2 chalcopyrite thin films were deposited on glass substrates by hot wall depositio... more ABSTRACT CuInSe2 chalcopyrite thin films were deposited on glass substrates by hot wall deposition method. As grown films are polycrystalline in nature showing diffraction peaks corresponding to CuInSe2 chalcopyrite. After annealing a narrowing and an increasing of intensity of these diffraction peaks are observed, due to an improvement in the crystallanity and an increase in the grain size in the films. The annealing process of CuInSe2 films in vacuum does not affect considerably [Cu]∕[In] ratio but leads to a decrease of Selenium. The optical absorption coefficient is slightly influenced by the annealing temperature. Variation of band gap energy of CuInSe2 thin films with annealing temperature were studied. In the high temperature range (T>385 K) the conductivity would be dominated by the transport of holes through the thermal excitation of carriers. In the low temperature range (T
International Journal of Nanoscience, 2011
We present a mechanism that can explain the growth direction of the carbon nanotubes (CNT), based... more We present a mechanism that can explain the growth direction of the carbon nanotubes (CNT), based on the observation of the catalyst particle's shape, that is present along with the CNT. We claim the mechanism holds good for the tip growth as well as the base growth model for CNTs formation. The morphological studies performed using simple geometry show that for encapsulated catalyst, (i) the contact angle is less along the forward direction than that of backward direction, (ii) the growth direction of CNT is along the flow direction of the catalyst particle in the fluid state, (iii) the distance between the centre of two imaginary spheres (circles in 2D) drawn at the front and back of the catalyst particle, qualitatively predicts the difference in growth rate of the CNT and flow of the catalyst particle inside the CNT. In order to support the above claims, a generalized model is proposed, irrespective of the position of the catalyst.
Vacuum, 2009
Deposition of good quality thin films of Lithium Cobalt Oxide (LiCoO 2), by sputtering is precede... more Deposition of good quality thin films of Lithium Cobalt Oxide (LiCoO 2), by sputtering is preceded by target conditioning, which dictates the surface composition, morphology and electrochemical performance of the deposited film. Sputtering from a virgin target surface, results in films with excess of the more reactive elements. The concentration of these reactive elements in the films decreases until the system reaches a steady state after sufficient sputtering from the target. This paper discusses the deposition kinetics in terms of target conditioning of LiCoO 2. The composition, morphology and texturing of deposited film during various hours of sputtering were analyzed using X-ray photoelectron spectroscopy (XPS) and Field Emission Scanning electron microscopy (FESEM). The compositional stability is not observed in the films formed during the initial hours of sputtering from the fresh target, which becomes stable after several hours of sputtering. The Li and Co concentration in the films deposited subsequently is found to be varying and possible causes are discussed. After the compositional stability is reached, electrochemical analysis of LiCoO 2 thin films was performed, which shows a discharge capacity of 129 mAh/cm 2 .
Thin Solid Films, 1993
ABSTRACT The characteristics of the high pressure oxygen-sputtering plasma in the pressure range ... more ABSTRACT The characteristics of the high pressure oxygen-sputtering plasma in the pressure range 0.8–2.4 mbar have been studied using the Langmuir probe technique. The variation in plasma parameters such as positive ion density, electron density, mean electron energy and floating potential with pressure and temperature has been investigated. It has been observed that the positive ion density increases at high substrate temperatures whereas the negative ion density decreases. The study of the variation in mean electron energy and floating potential also indicated the possibility that the number of negative ions is less when the substrates are at elevated temperatures. Since the negative ions are supposed to cause re-sputtering and make the films off-stoichiometric, the reduction in the negative ion density as observed at elevated substrate temperatures is better suited for depositing stoichiometric YBa2Cu3O7−δ superconducting thin films.
Metallurgical and Materials Transactions B, 1996