Influence of doping on the properties of vanadium oxide gel films (original) (raw)
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Nano-structural of vanadium pentoxide (V 2 O 5 ) thin films were deposited by chemical spray pyrolysis technique (CSPT). Nd and Ce doped vanadium oxide films were prepared, adding Neodymium chloride (NdCl 3 ) and ceric sulfate (Ce(SO 4 ) 2 ) of 3% in separate solution. These precursor solutions were used to deposit un-doped V 2 O 5 and doped with Nd and Ce films on the p-type Si and glass substrate at 250°C. The structural, optical and electrical properties were investigated. The X-ray diffraction study revealed a polycrystalline nature of the orthorhombic structure with the preferred orientation of (010) with nano-grains. Atomic force microscopy (AFM) was used to characterize the morphology of the films. Un-doped V 2 O 5 and doped with 3% concentration of Nd and Ce films have direct allowed transition band gap. The mechanisms of dc-conductivity of un-doped V 2 O 5 and doped with Nd and Ce films at the range 303 K to 473 K have been discussed.
Investigation on V2O5 Thin Films for Field Effect Transistor Applications
Advances in Materials Science and Engineering
V2O5 thin films are analyzed for the substitution of SiO2 to reduce the leakage current in devices when SiO2 becomes ultrathin in submicron technology. Vanadium pentoxide (V2O5) has a high-k dielectric constant of 25 and can be replaced as a gate oxide in the field-effect transistor. V2O5 is deposited using pulsed laser deposition (PLD) in the oxygen (O2) environment at room temperature and characterized. The films surface morphology has been examined by scanning electron microscopy. The capacitance, dielectric constant, and dielectric loss are analyzed for fabricated metal oxide semiconductor (MOS) structure using Solartron SI-1260 impedance analyzer. The transfer characteristic of the fabricated device is analyzed using National Instruments NI-PXI 4110. The ION/IOFF ratio of 106 and threshold voltage (VTH) of 0.6 V is obtained.
Morphology, Structural and Dielectric Properties of Vacuum Evaporated V2O5 Thin Films
Physics Procedia, 2013
Vanadium pentoxide (V 2 O 5) thin films were deposited on well cleaned glass substrate using evaporation technique under the pressure of 10-5 Torr. The thickness of the films was measured by the multiple beam interferometry technique and cross checked by using capacitance method. Metal-Insulator-Metal (MIM) structure was fabricated by using suitable masks to study dielectric properties. The dielectric properties were studied by employing LCR meter in the frequency range 12 Hz to 100 kHz for various temperatures. The temperature coefficient of permittivity (TCP), temperature coefficient of capacitance (TCC) and dielectric ound to be very low. The activation energy was found to be increasing with increase in frequency. The obtained low value of activation energy suggested that the hopping conduction may be due to electrons rather than ions.
Electronic, thermoelectric and optical properties of vanadium oxides: VO2, V2O3 and V2O 5
2015
Correlated electrons in vanadium oxides are responsible for their extreme sensitivity to external stimuli such as pressure, temperature or doping. As a result, several vanadium oxides undergo insulator-to-metal phase transition (IMT) accompanied by structural change. Unlike vanadium pentoxide (V3O3), vanadium dioxide (VO3) and vanadium sesquioxide (V3O3) show I MT in their bulk phases. In this study, we have performed one electron Kohn-Sham electronic band-structure calculations of VO3, V3O3 and V2O5 in both metallic and insulating phases, implementing a full ab-initio simulation package based on Density Functional Theory (DFT), Plane Waves and Pseudopotentials (PPs). Electronic band structures are found to be influenced by crystal structure, crystal field splitting and strong hybridization between O2p and V3d bands. “Intermediate bands”, with narrow band widths, lying just below the higher conduction bands, are observed in V2O5 which play a critical role in optical and thermoelectr...
Vanadium oxide thin films produced by magnetron sputtering from a V2O5 target at room temperature
Infrared Physics & Technology, 2013
Multiphase VO x thin films were grown by RF magnetron sputtering from V 2 O 5 target. Computational thermodynamics was used to simulate vanadium-oxygen phase diagram. The films were deposited in argon atmosphere with 0 to 20% oxygen partial pressure. VO x thin film with TCR of À1.8% K À1 was produced by single step at room temperature. The developed method is a cheaper alternative to produce bolometer sensitive layers.
Spray deposition of V4O9 and V2O5 thin films and post-annealing formation of thermochromic VO2
Journal of Alloys and Compounds, 2017
Vanadium oxide (VO x) thin films were deposited at various substrate temperatures (T s) by spray pyrolysis technique using 0.05 M vanadyl acetylacetonate precursor. V 4 O 9 films are formed at T s = 300ºC, while mixed V 2 O 5 phases are formed at higher T s (400 and 500ºC). Annealing in forming gas of V 4 O 9 films shows the formation of higher content of thermochromic VO 2 phase than V 2 O 5 films. V 4 O 9 films show little higher electric resistivity (ρ), higher temperature coefficient of resistance (TCR), and higher thermal carrier activation energy (E a) than V 2 O 5 films. Annealed VO x films show a 2-3 order of magnitude change in ρ, optical transmission switch of 19-39%, and higher E a than to the as deposited films. Annealed films deposited at T s =500ºC presents a high TCR of-4.6%K-1. Optical absorption, electronic transitions, and energy gaps of the formed VO x phases have been discussed in relation to its electronic band structure.
Effects of microstructure and nonstoichiometry on electrical properties of vanadium dioxide films
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1989
Voided growth structures of sputter-deposited films affect strongly their optical and electrical properties. Vanadium dioxide is an interesting material to study effects of film microstructure and nonstoichiometry on electrical properties because its phase transition makes it possible to investigate electrical behavior both in a semiconducting phase and in a metallic phase. We have deposited vanadium oxide films with different vanadium/oxygen ratios for substrate temperatures between 250 and 550°C by dc reactive magnetron sputtering. The resistivity ratios between a semiconducting phase and a metallic phase are limited to 10 3 order by voided boundaries and oxygen vacancies. The voided boundaries are defined by columnar structure and agglomerated grain growth. The results emphasize the necessity of a combination of deposition to obtain the film with a favorable structure and postdeposition annealing to control the film stoichiometry.
2014
A two-step method is offered for the synthesis of vanadium oxide films to purposely change their functional properties. Vanadium oxide films were deposited on glass and silicon substrates by using magnetron sputtering of the vanadium target at various substrate temperatures (180-500°C). During deposition, the substrate temperature predetermines structural and functional properties of the films after their following low-temperature (250-350°C) annealing. In the films deposited at low substrate temperatures (200-220°C), after lowtemperature annealing there formed are flat crystallites of vanadium dioxide with lateral sizes 1 to 2 μm, which provides a high thermochromic effect. In the films deposited at temperatures of 250-300°C, during the following low-temperature annealing the microcrystalline mixture of different vanadium oxides (50-150 nm) is formed, which provides a high value of the thermal coefficient of resistance for these films (7%/K). The low temperature annealing practically does not change the properties of films deposited at temperatures of 450-500°C.
Effect of solution molarity on the characteristics of vanadium pentoxide thin film
Applied Surface Science, 2006
Vanadium pentoxide (V 2 O 5) thin films have been prepared by spray pyrolysis technique. The influence of solution molarity on the characteristics of the V 2 O 5 has been investigated. X-ray diffraction analysis (XRD) showed that, the films deposited at !0.1 M were orthorhombic structure with a preferential orientation along h0 0 1i direction. Moreover, the crystallinity was improved by increasing solution molarity. The microstructure parameters have been evaluated by using a single order Voigt profile method. The optical band gaps, determined by using Tauc plot, have been found to be 2.50 AE 0.02 and 2.33 AE 0.02 eV for the direct and indirect allowed transition, respectively. Also the complex optical constants for the wavelength range 300-2500 nm are reported. At room temperature, the dark conductivity as a function of solution molarity showed the range of 5.74 Â 10 À2 AE 0.03 to 3.36 Â 10 À1 AE 0.02 V À1 cm À1. While at high temperature, the behaviour of electrical conductivity dominated by grain boundaries. The values of activation energy and potential barrier height were 0.156 AE 0.011 and 0.263 AE 0.012 eV, respectively.