Moodakare Sahana | ARCI - Academia.edu (original) (raw)
Papers by Moodakare Sahana
Journal of Power Sources, 2021
Abstract Lithium-rich layered oxide (LLO) with a large specific capacity (>250 mAhg−1) and the... more Abstract Lithium-rich layered oxide (LLO) with a large specific capacity (>250 mAhg−1) and the wider voltage window (2.0–4.8 V) delivers an energy density of about 1000 Wh/kg. However, oxygen release from the surface of LLO and decomposition of electrolyte solvents leads to increased electrode-electrolyte interface resistance. To achieve the maximum energy density of LLO, it becomes mandatory to protect the surface structure and simultaneously activate the cationic and anionic redox reaction. Here, we demonstrate a novel in-situ carbon encapsulation on Li1.15Ni0.23Co0.08Mn0.54O2 by the industrially viable co-precipitation process followed by solid-state reaction. Effect of carbon encapsulation on structure formation, chemical composition, and elemental oxidation states of Li1.15Ni0.23Co0.08Mn0.54O2 are analyzed by the techniques such as X-ray diffraction, scanning and transmission electron microscopy, and X-ray photoelectron spectroscopy. The enhanced electrochemical performance is confirmed by increased coulombic efficiency, reduced interfacial resistance, and suppressed voltage fading. Moreover, carbon-coated LLO retains an excellent capacity of 94% after 300 cycles at 2C rate cycling, while the pristine LLO retained only 77.8% of capacity. Further, electrochemical cycling of carbon encapsulated LLO with pre-lithiated graphite delivers an energy density of 500 Wh/kg after 100 cycles at 0.5C rate (150 mAg−1).
Handbook of Advanced Ceramics and Composites, 2019
RSC Adv., 2014
Mn-rich nanoscale secondary phases were identified in LiFe1−xMnxPO4, despite of known complete so... more Mn-rich nanoscale secondary phases were identified in LiFe1−xMnxPO4, despite of known complete solubility for the LiFePO4–LiMnPO4 system and observed linear increase in the lattice parameters of LiFe1−xMnxPO4 with increasing Mn concentration.
Photonic, Electronic and Atomic Collisions, 2006
We report a narrow angular distribution of 0.8°, close to that expected from the aspect ratio, fo... more We report a narrow angular distribution of 0.8°, close to that expected from the aspect ratio, for guiding of highly charged ions through a well-ordered, parallel SiO 2 nanocapillaries target. These capillaries were obtained by thermally oxidizing a 25-m-thick membrane of silicon nanocapillaries fabricated by photoassisted electrochemical etching. The diameter of the uniformly distributed capillaries was 100 nm. We observed Ne 7+ ions being transmitted through these nanocapillaries with a decreasing transmitted intensity up to a factor 100, when increasing the capillary tilt angles up to 4°. The narrower angular distribution in comparison to polyethylene terephthalate capillaries is discussed and it is shown that the SiO 2 results support the model of selforganized charge patches formed at the capillary entrance.
Tin dioxide is considered to be one of the promising anode materials for Li-ion battery because i... more Tin dioxide is considered to be one of the promising anode materials for Li-ion battery because it has high energy density (˜780 mAhg-1). We synthesized SnO2-x thin films by a facile cost effective method of metalorganic decomposition technique using Tin 2 ethylhexanoate as the precursor. Ten layers of precursor solution are spin coated on stainless steel substrates and processed at 500 ^circC for two minutes after each coating. The resulting films were annealed at various ambient such as air, hydrogen (10% in Ar) and high vacuum (10-6 torr) at different temperatures from 500^circC to 700^circC. The structure and composition of these films were analyzed by Raman spectroscopy, x-ray diffraction, scanning and transmission electron microscopy, and X-ray photoelectron spectroscopy to study the effect of synthesis condition on crystallinity, microstructure, and chemical composition. We also prepared thin films on ITO coated glass/quartz substrates under identical conditions for optical a...
MRS Proceedings, 2002
ABSTRACTThin films of VO2(B), a metastable polymorph of vanadium dioxide, have been grown on glas... more ABSTRACTThin films of VO2(B), a metastable polymorph of vanadium dioxide, have been grown on glass by low-pressure metalorganic chemical vapor deposition (MOCVD). The films grown for 90 minutes have atypical microstructure, comprising micrometer-sized, island-like entities made up of numerous small, single-crystalline platelets (≅1 μm) emerging orthogonally from larger ones at the center. Microstructure evolution as a function of deposition time has been examined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The metastable VO2(B) transforms to the stable rutile (R) phase at 550°C in inert ambient, which on cooling convert reversibly to M phase. Electron microscopy shows that annealing leads to the disintegration of the VO2(B) platelets into small crystallites of the rutile phase VO2(R), although the platelet morphology is retained. The magnitude of the jump in resistance at the semiconductor-to-metal, VO2(M)→VO2(R) phase transition depends...
Scripta Materialia, 2010
... Coexistence of anion and cation vacancy defects in vacuum-annealed In 2 O 3 thin films. C. Su... more ... Coexistence of anion and cation vacancy defects in vacuum-annealed In 2 O 3 thin films. C. Sudakar a , Corresponding Author Contact Information , E-mail The Corresponding Author , A. Dixit a , Sanjiv Kumar b , MB Sahana a , G. Lawes a , R. Naik a and VM Naik c. ...
Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions With Materials and Atoms, 2007
Dilute magnetic oxide semiconductors are new materials that are semiconducting oxides substituted... more Dilute magnetic oxide semiconductors are new materials that are semiconducting oxides substituted with magnetic or other transition elements. Several oxide films such as TiO2 and ZnO have gained important in recent years in spintronic applications and for photocatalytic applications. This paper deals with oxide films of TiO2 and V2O5 deposited by metal organic decomposition (MOD) technique. The method involves deposition
Oxides containing polyanions such as XO4^2- (X = S, Mo, P and W) as lithium insertion hosts are p... more Oxides containing polyanions such as XO4^2- (X = S, Mo, P and W) as lithium insertion hosts are promising cathode materials due to their high thermal stability. However, the larger separation of the transition metal ions can be expected to reduce the electron mobility. As observed in LiFePO4, this can be overcome either by coating the cathode materials with carbon
Thin Solid Films, 2009
... The effect of titanium on the lithium intercalation capacity of V 2 O 5 thin films. MB Sahana... more ... The effect of titanium on the lithium intercalation capacity of V 2 O 5 thin films. MB Sahana a , Corresponding Author Contact Information , E-mail The Corresponding Author , C. Sudakar a , C. Thapa a , VM Naik b , GW Auner c , R. Naik a and KR Padmanabhan a. ...
Physical Review A, 2006
We report a narrow angular distribution of 0.8°, close to that expected from the aspect ratio, fo... more We report a narrow angular distribution of 0.8°, close to that expected from the aspect ratio, for guiding of highly charged ions through a well-ordered, parallel SiO2 nanocapillaries target. These capillaries were obtained by thermally oxidizing a 25-mum -thick membrane of silicon nanocapillaries fabricated by photoassisted electrochemical etching. The diameter of the uniformly distributed capillaries was 100nm . We observed Ne7+ ions being transmitted through these nanocapillaries with a decreasing transmitted intensity up to a factor 100, when increasing the capillary tilt angles up to 4°. The narrower angular distribution in comparison to polyethylene terephthalate capillaries is discussed and it is shown that the SiO2 results support the model of self-organized charge patches formed at the capillary entrance.
Materials Science and Engineering: B, 2007
The electrochemical properties of V 2 O 5 thin films prepared by spin coating on indium tin oxide... more The electrochemical properties of V 2 O 5 thin films prepared by spin coating on indium tin oxide coated glass substrates using metalorganic, organic and inorganic sol-gel precursors have been investigated. The stoichiometry of the films was found to depend on the carbon to vanadium ratio in the precursors with a larger carbon content leading to a higher non-stoichiometry. The structural properties of the films were investigated by X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), Raman and UV-vis spectroscopy. The non-stoichiometry of the films was investigated by measuring the red shift in the shortest V O bond vibrational frequency between vanadium and terminal oxygen, which is consistent with the observation of planar defects in HRTEM-micrographs. The electrochemical studies by cyclic voltametry indicate that the Li + intercalation capacity and Li + diffusion coefficient are increased by an order of magnitude in the non-stoichiometric film, which may significantly improve the properties of vanadium oxide films as a cathode material for Li-ion batteries.
Journal of Physics: Condensed Matter, 2009
We have synthesized a range of transition-metal-doped BiFeO(3) thin films on conducting silicon s... more We have synthesized a range of transition-metal-doped BiFeO(3) thin films on conducting silicon substrates using a spin-coating technique from metal-organic precursor solutions. Bismuth, iron and transition-metal-organic solutions were mixed in the appropriate ratios to produce 3% transition-metal-doped samples. X-ray diffraction studies show that the samples annealed in a nitrogen atmosphere crystallize in a rhombohedrally distorted BiFeO(3) structure with no evidence for any ferromagnetic secondary phase formation. We find evidence for the disappearance of the 404 cm(-1) Raman mode for certain dopants indicative of structural distortions. The saturation magnetization of these BiFeO(3) films has been found to increase on doping with transition metal ions, reaching a maximum value of 8.5 emu cm(-3) for the Cr-doped samples. However, leakage current measurements find that the resistivity of the films typically decreases with transition metal doping. We find no evidence for any systematic variation of the electric or magnetic properties of BiFeO(3) depending on the transition metal dopant, suggesting that these properties are determined mainly by extrinsic effects arising from defects or grain boundaries.
Journal of Materials Research, 2012
... Inc., Cedarville, Ohio Zhixian Zhou Department of Physics and Astronomy, Wayne State Universi... more ... Inc., Cedarville, Ohio Zhixian Zhou Department of Physics and Astronomy, Wayne State University, Detroit, Michigan Prem Vaishnava Department of ... J. Power Sources 146, 521 (2005); Michel Armand, John B. Goodenough, Akshaya Padhi, Kirakodu Nanjundaswamy, Christian ...
Journal of Materials Chemistry, 2003
ABSTRACT Films comprised of nanowires of β-NaxV2O5 measuring 20–200 nm in diameter and 10–30 µm i... more ABSTRACT Films comprised of nanowires of β-NaxV2O5 measuring 20–200 nm in diameter and 10–30 µm in length have been prepared on glass substrates by metalorganic chemical vapor deposition using the β-diketonate complex, vanadyl acetyl acetonate, as precursor, but without the use of either templates or catalysts. Films consisting of nanowires of monophasic β-NaxV2O5 with a preferred orientation along (h0l) are formed only at 550 °C, whereas those deposited at 540 °C comprise a mixture of nanowires (β-NaxV2O5) and platelets (V2O5). The films deposited at lower temperatures are less crystalline and comprise a mixture of vanadium oxide phases. From the observations that nanowires are formed only in the narrow temperature range of 540–550 °C, and from the critical dependence of the formation of nanowires on the balance between the CVD growth rate and the evaporation rate of the film, it is inferred that the formation of nanowires of β-NaxV2O5 is due to chemical vapor transport.
Journal of Materials Chemistry, 2002
Thin films of vanadium dioxide have been deposited on glass by low pressure metal-organic chemica... more Thin films of vanadium dioxide have been deposited on glass by low pressure metal-organic chemical vapour deposition using the b-diketonate complex, vanadyl acetylacetonate, as the precursor. It is found that nearly monophasic, monoclinic VO 2 (M) films are formed in the narrow temperature range 475-520 uC, films formed outside this range comprising significant proportions of other vanadium oxide phases beside VO 2 (M). The microstructure of these well-crystallized films varies significantly with temperature in this range. Films grown at 475 uC are dense and have a very strong (200) orientation. At 520 uC, films are somewhat porous, and display little preferred orientation. Film microstructure influences the semiconductor-metal transition noticeably. Films deposited at 475 uC have a large change in resistance at 66 uC, and display a small temperature hysteresis in the transition. The transition temperature in films grown at 520 uC is higher (72 uC), whereas the change in resistance is smaller and the hysteresis larger. An attempt has been made to understand the unusual microstructure of VO 2 films grown on glass substrates. The variation in the phase transition characteristics is interpreted in terms of the observed film microstructure. The thermal properties of the CVD precursor are also reported.
Journal of Applied Physics, 2002
... C. Cesari, Ch. Leroux, and G. Nihoul, Key Eng. Mater. 155156, 227 (1998). S. Deki, Y. Aoi, a... more ... C. Cesari, Ch. Leroux, and G. Nihoul, Key Eng. Mater. 155156, 227 (1998). S. Deki, Y. Aoi, and A. Kajinami, J. Mater. Sci. 32, 4269 (1997). ... Sci. Technol. A 7, 1314 (1989). MB Sahana, MS Dharmaprakash, and SA Shivashankar, J. Mater. Chem. 12, 333 (2002). ...
Journal of Applied Physics, 2007
... P. Kharel, C. Sudakar, MB Sahana, G. Lawes, R. Suryanarayanan, R. Naik, VM Naik. Abstract. ..... more ... P. Kharel, C. Sudakar, MB Sahana, G. Lawes, R. Suryanarayanan, R. Naik, VM Naik. Abstract. ... Rev. Lett. 91, 077205 (2003). M.Venkatesan, CBFitzgerald, JGLunney, and JMDCoey, Anisotropic Ferromagnetism in Substituted Zinc Oxide, Phys. Rev. Lett. 93, 177206 (2004). ...
Journal of Power Sources, 2021
Abstract Lithium-rich layered oxide (LLO) with a large specific capacity (>250 mAhg−1) and the... more Abstract Lithium-rich layered oxide (LLO) with a large specific capacity (>250 mAhg−1) and the wider voltage window (2.0–4.8 V) delivers an energy density of about 1000 Wh/kg. However, oxygen release from the surface of LLO and decomposition of electrolyte solvents leads to increased electrode-electrolyte interface resistance. To achieve the maximum energy density of LLO, it becomes mandatory to protect the surface structure and simultaneously activate the cationic and anionic redox reaction. Here, we demonstrate a novel in-situ carbon encapsulation on Li1.15Ni0.23Co0.08Mn0.54O2 by the industrially viable co-precipitation process followed by solid-state reaction. Effect of carbon encapsulation on structure formation, chemical composition, and elemental oxidation states of Li1.15Ni0.23Co0.08Mn0.54O2 are analyzed by the techniques such as X-ray diffraction, scanning and transmission electron microscopy, and X-ray photoelectron spectroscopy. The enhanced electrochemical performance is confirmed by increased coulombic efficiency, reduced interfacial resistance, and suppressed voltage fading. Moreover, carbon-coated LLO retains an excellent capacity of 94% after 300 cycles at 2C rate cycling, while the pristine LLO retained only 77.8% of capacity. Further, electrochemical cycling of carbon encapsulated LLO with pre-lithiated graphite delivers an energy density of 500 Wh/kg after 100 cycles at 0.5C rate (150 mAg−1).
Handbook of Advanced Ceramics and Composites, 2019
RSC Adv., 2014
Mn-rich nanoscale secondary phases were identified in LiFe1−xMnxPO4, despite of known complete so... more Mn-rich nanoscale secondary phases were identified in LiFe1−xMnxPO4, despite of known complete solubility for the LiFePO4–LiMnPO4 system and observed linear increase in the lattice parameters of LiFe1−xMnxPO4 with increasing Mn concentration.
Photonic, Electronic and Atomic Collisions, 2006
We report a narrow angular distribution of 0.8°, close to that expected from the aspect ratio, fo... more We report a narrow angular distribution of 0.8°, close to that expected from the aspect ratio, for guiding of highly charged ions through a well-ordered, parallel SiO 2 nanocapillaries target. These capillaries were obtained by thermally oxidizing a 25-m-thick membrane of silicon nanocapillaries fabricated by photoassisted electrochemical etching. The diameter of the uniformly distributed capillaries was 100 nm. We observed Ne 7+ ions being transmitted through these nanocapillaries with a decreasing transmitted intensity up to a factor 100, when increasing the capillary tilt angles up to 4°. The narrower angular distribution in comparison to polyethylene terephthalate capillaries is discussed and it is shown that the SiO 2 results support the model of selforganized charge patches formed at the capillary entrance.
Tin dioxide is considered to be one of the promising anode materials for Li-ion battery because i... more Tin dioxide is considered to be one of the promising anode materials for Li-ion battery because it has high energy density (˜780 mAhg-1). We synthesized SnO2-x thin films by a facile cost effective method of metalorganic decomposition technique using Tin 2 ethylhexanoate as the precursor. Ten layers of precursor solution are spin coated on stainless steel substrates and processed at 500 ^circC for two minutes after each coating. The resulting films were annealed at various ambient such as air, hydrogen (10% in Ar) and high vacuum (10-6 torr) at different temperatures from 500^circC to 700^circC. The structure and composition of these films were analyzed by Raman spectroscopy, x-ray diffraction, scanning and transmission electron microscopy, and X-ray photoelectron spectroscopy to study the effect of synthesis condition on crystallinity, microstructure, and chemical composition. We also prepared thin films on ITO coated glass/quartz substrates under identical conditions for optical a...
MRS Proceedings, 2002
ABSTRACTThin films of VO2(B), a metastable polymorph of vanadium dioxide, have been grown on glas... more ABSTRACTThin films of VO2(B), a metastable polymorph of vanadium dioxide, have been grown on glass by low-pressure metalorganic chemical vapor deposition (MOCVD). The films grown for 90 minutes have atypical microstructure, comprising micrometer-sized, island-like entities made up of numerous small, single-crystalline platelets (≅1 μm) emerging orthogonally from larger ones at the center. Microstructure evolution as a function of deposition time has been examined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The metastable VO2(B) transforms to the stable rutile (R) phase at 550°C in inert ambient, which on cooling convert reversibly to M phase. Electron microscopy shows that annealing leads to the disintegration of the VO2(B) platelets into small crystallites of the rutile phase VO2(R), although the platelet morphology is retained. The magnitude of the jump in resistance at the semiconductor-to-metal, VO2(M)→VO2(R) phase transition depends...
Scripta Materialia, 2010
... Coexistence of anion and cation vacancy defects in vacuum-annealed In 2 O 3 thin films. C. Su... more ... Coexistence of anion and cation vacancy defects in vacuum-annealed In 2 O 3 thin films. C. Sudakar a , Corresponding Author Contact Information , E-mail The Corresponding Author , A. Dixit a , Sanjiv Kumar b , MB Sahana a , G. Lawes a , R. Naik a and VM Naik c. ...
Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions With Materials and Atoms, 2007
Dilute magnetic oxide semiconductors are new materials that are semiconducting oxides substituted... more Dilute magnetic oxide semiconductors are new materials that are semiconducting oxides substituted with magnetic or other transition elements. Several oxide films such as TiO2 and ZnO have gained important in recent years in spintronic applications and for photocatalytic applications. This paper deals with oxide films of TiO2 and V2O5 deposited by metal organic decomposition (MOD) technique. The method involves deposition
Oxides containing polyanions such as XO4^2- (X = S, Mo, P and W) as lithium insertion hosts are p... more Oxides containing polyanions such as XO4^2- (X = S, Mo, P and W) as lithium insertion hosts are promising cathode materials due to their high thermal stability. However, the larger separation of the transition metal ions can be expected to reduce the electron mobility. As observed in LiFePO4, this can be overcome either by coating the cathode materials with carbon
Thin Solid Films, 2009
... The effect of titanium on the lithium intercalation capacity of V 2 O 5 thin films. MB Sahana... more ... The effect of titanium on the lithium intercalation capacity of V 2 O 5 thin films. MB Sahana a , Corresponding Author Contact Information , E-mail The Corresponding Author , C. Sudakar a , C. Thapa a , VM Naik b , GW Auner c , R. Naik a and KR Padmanabhan a. ...
Physical Review A, 2006
We report a narrow angular distribution of 0.8°, close to that expected from the aspect ratio, fo... more We report a narrow angular distribution of 0.8°, close to that expected from the aspect ratio, for guiding of highly charged ions through a well-ordered, parallel SiO2 nanocapillaries target. These capillaries were obtained by thermally oxidizing a 25-mum -thick membrane of silicon nanocapillaries fabricated by photoassisted electrochemical etching. The diameter of the uniformly distributed capillaries was 100nm . We observed Ne7+ ions being transmitted through these nanocapillaries with a decreasing transmitted intensity up to a factor 100, when increasing the capillary tilt angles up to 4°. The narrower angular distribution in comparison to polyethylene terephthalate capillaries is discussed and it is shown that the SiO2 results support the model of self-organized charge patches formed at the capillary entrance.
Materials Science and Engineering: B, 2007
The electrochemical properties of V 2 O 5 thin films prepared by spin coating on indium tin oxide... more The electrochemical properties of V 2 O 5 thin films prepared by spin coating on indium tin oxide coated glass substrates using metalorganic, organic and inorganic sol-gel precursors have been investigated. The stoichiometry of the films was found to depend on the carbon to vanadium ratio in the precursors with a larger carbon content leading to a higher non-stoichiometry. The structural properties of the films were investigated by X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), Raman and UV-vis spectroscopy. The non-stoichiometry of the films was investigated by measuring the red shift in the shortest V O bond vibrational frequency between vanadium and terminal oxygen, which is consistent with the observation of planar defects in HRTEM-micrographs. The electrochemical studies by cyclic voltametry indicate that the Li + intercalation capacity and Li + diffusion coefficient are increased by an order of magnitude in the non-stoichiometric film, which may significantly improve the properties of vanadium oxide films as a cathode material for Li-ion batteries.
Journal of Physics: Condensed Matter, 2009
We have synthesized a range of transition-metal-doped BiFeO(3) thin films on conducting silicon s... more We have synthesized a range of transition-metal-doped BiFeO(3) thin films on conducting silicon substrates using a spin-coating technique from metal-organic precursor solutions. Bismuth, iron and transition-metal-organic solutions were mixed in the appropriate ratios to produce 3% transition-metal-doped samples. X-ray diffraction studies show that the samples annealed in a nitrogen atmosphere crystallize in a rhombohedrally distorted BiFeO(3) structure with no evidence for any ferromagnetic secondary phase formation. We find evidence for the disappearance of the 404 cm(-1) Raman mode for certain dopants indicative of structural distortions. The saturation magnetization of these BiFeO(3) films has been found to increase on doping with transition metal ions, reaching a maximum value of 8.5 emu cm(-3) for the Cr-doped samples. However, leakage current measurements find that the resistivity of the films typically decreases with transition metal doping. We find no evidence for any systematic variation of the electric or magnetic properties of BiFeO(3) depending on the transition metal dopant, suggesting that these properties are determined mainly by extrinsic effects arising from defects or grain boundaries.
Journal of Materials Research, 2012
... Inc., Cedarville, Ohio Zhixian Zhou Department of Physics and Astronomy, Wayne State Universi... more ... Inc., Cedarville, Ohio Zhixian Zhou Department of Physics and Astronomy, Wayne State University, Detroit, Michigan Prem Vaishnava Department of ... J. Power Sources 146, 521 (2005); Michel Armand, John B. Goodenough, Akshaya Padhi, Kirakodu Nanjundaswamy, Christian ...
Journal of Materials Chemistry, 2003
ABSTRACT Films comprised of nanowires of β-NaxV2O5 measuring 20–200 nm in diameter and 10–30 µm i... more ABSTRACT Films comprised of nanowires of β-NaxV2O5 measuring 20–200 nm in diameter and 10–30 µm in length have been prepared on glass substrates by metalorganic chemical vapor deposition using the β-diketonate complex, vanadyl acetyl acetonate, as precursor, but without the use of either templates or catalysts. Films consisting of nanowires of monophasic β-NaxV2O5 with a preferred orientation along (h0l) are formed only at 550 °C, whereas those deposited at 540 °C comprise a mixture of nanowires (β-NaxV2O5) and platelets (V2O5). The films deposited at lower temperatures are less crystalline and comprise a mixture of vanadium oxide phases. From the observations that nanowires are formed only in the narrow temperature range of 540–550 °C, and from the critical dependence of the formation of nanowires on the balance between the CVD growth rate and the evaporation rate of the film, it is inferred that the formation of nanowires of β-NaxV2O5 is due to chemical vapor transport.
Journal of Materials Chemistry, 2002
Thin films of vanadium dioxide have been deposited on glass by low pressure metal-organic chemica... more Thin films of vanadium dioxide have been deposited on glass by low pressure metal-organic chemical vapour deposition using the b-diketonate complex, vanadyl acetylacetonate, as the precursor. It is found that nearly monophasic, monoclinic VO 2 (M) films are formed in the narrow temperature range 475-520 uC, films formed outside this range comprising significant proportions of other vanadium oxide phases beside VO 2 (M). The microstructure of these well-crystallized films varies significantly with temperature in this range. Films grown at 475 uC are dense and have a very strong (200) orientation. At 520 uC, films are somewhat porous, and display little preferred orientation. Film microstructure influences the semiconductor-metal transition noticeably. Films deposited at 475 uC have a large change in resistance at 66 uC, and display a small temperature hysteresis in the transition. The transition temperature in films grown at 520 uC is higher (72 uC), whereas the change in resistance is smaller and the hysteresis larger. An attempt has been made to understand the unusual microstructure of VO 2 films grown on glass substrates. The variation in the phase transition characteristics is interpreted in terms of the observed film microstructure. The thermal properties of the CVD precursor are also reported.
Journal of Applied Physics, 2002
... C. Cesari, Ch. Leroux, and G. Nihoul, Key Eng. Mater. 155156, 227 (1998). S. Deki, Y. Aoi, a... more ... C. Cesari, Ch. Leroux, and G. Nihoul, Key Eng. Mater. 155156, 227 (1998). S. Deki, Y. Aoi, and A. Kajinami, J. Mater. Sci. 32, 4269 (1997). ... Sci. Technol. A 7, 1314 (1989). MB Sahana, MS Dharmaprakash, and SA Shivashankar, J. Mater. Chem. 12, 333 (2002). ...
Journal of Applied Physics, 2007
... P. Kharel, C. Sudakar, MB Sahana, G. Lawes, R. Suryanarayanan, R. Naik, VM Naik. Abstract. ..... more ... P. Kharel, C. Sudakar, MB Sahana, G. Lawes, R. Suryanarayanan, R. Naik, VM Naik. Abstract. ... Rev. Lett. 91, 077205 (2003). M.Venkatesan, CBFitzgerald, JGLunney, and JMDCoey, Anisotropic Ferromagnetism in Substituted Zinc Oxide, Phys. Rev. Lett. 93, 177206 (2004). ...