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Spray_Deposited Titanium-Oxide Films For Infrared Optics, Photonics, And Solar Cell Applications.
| Title: | Spray_Deposited Titanium-Oxide Films For Infrared Optics, Photonics, And Solar Cell Applications. |
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| Name(s): |
Alhasan, Sarmad, Author Peale, Robert, Committee Chair Sundaram, Kalpathy, Committee CoChair Mikhael, Wasfy, Committee Member Abdolvand, Reza, Committee Member Kar, Aravinda, Committee Member University of Central Florida, Degree Grantor |
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| Type of Resource: | text | |
| Date Issued: | 2017 | |
| Publisher: | University of Central Florida | |
| Language(s): | English | |
| Abstract/Description: | Self-assembled TiO2 foam-like films, were grown by the water based Streaming Process for ElectrodelessElectrochemical Deposition (SPEED). The morphology of the 1 m thick films consistsof a tangled ropy structure with individual strands of 200 nm diameter and open pores of 0.1to 3 micron dimensions. Such films are advantageous for proposed perovskite solar cell comprisingCH3NH3PbI3 absorber with additional inorganic films as contact and conduction layers,all deposited by SPEED. Lateral film resistivity is in the range 20 - 200 k-cm, increasing withgrowth temperature, while sheet resistance is in the range 2 ?? 20 108 /Sq. Xray diffractionconfirms presence of TiO2 crystals of orthorhombic class (Brookite). UV-vis spectroscopy showshigh transmission below the expected 3.2 eV TiO2 bandgap. Transmittance increases with growthtemperature. This is a Ropy TiO2 thin film.We also prepared a Smooth TiO2 thin film. Self-assembled TiO2 film deposited by aqueous-spraydeposition was investigated to evaluate morphology, crystalline phase, and infrared optical constants.The Anatase nano-crystalline film had 10 nm characteristic surface roughness sparselypunctuated by defects of not more than 200 nm amplitude. The film is highly transparent throughoutthe visible to wavelengths of 12 m. The indirect band gap was determined to be 3.2 eV. Importantfor long-wave infrared applications is that dispersion in this region is weak compared with themore commonly used dielectic SiO2 for planar structures. The low-cost, large-area, atmosphericpressure,chemical spray deposition method allows conformal fabrication on flexible substrates forlong-wave infrared photonics.For comparison TiO2 films deposited by electron-beam evaporation were evaluated to determinemorphology, crystalline phase, and optical transparency.The evaporated TiO2 film was amorphous but crystallized into Anatase phase after annealing.Such film is attractive as electron conductor of unprecedented thinness and flexibility for proposedperovskite solar cell comprising CH3NH3PbI3 absorber with additional inorganic films as contactand conduction layers. The spray deposition method would allow conformal solar cell fabricationon flexible substrates for wearable power generation. Band gap of Evaporated TiO2 film is 4.0 eV.We prepared BaTiO3 thin film to know infrared pyroelectric response.Self-assembled nano-crystalline BaTiO3 films on stainless steel foil substrates, were grown by thewater based Streaming Process for Electrodeless Electrochemical Deposition (SPEED). SPEED isan aqueous process that deposits self-assembled nano-crystalline inorganic thin films over largeareas, without a vacuum, providing a scalable and manufacturing friendly process to fabricatedurable films. The morphology of the 1m thick films comprises single crystals of micron dimensionsimbedded in a matrix of nanocrystals. XRD confirms presence of BaTiO3 crystals ofhexagonal phase for samples annealed at 500C. Subsequent annealing at 600C transforms thefilm to the cubic phase. Potential applications include dielectric layers, capacitors, waveguides,ferroelectric RAM, pyroelectric infrared detectors, and phosphors. Characterization of infraredpyroelectric response at 10m wavelength shows an initially good sensitivity that reversibly decaysover a period of days due to water vapor absorption. A short-lived photo-response due topoling of the hydrated sample is also observed. We studied BaTiO3 to know hysteresis loop.Pyroelectric photoresponse of aqueous spray deposited thin films containing BaTiO3 nano-crystalsis reported. X-ray diffraction data indicate the presence of hexagonal BaTiO3 nano-crystals with20 nm crystalline domains in a matrix of some as yet unidentified nano-crystalline material.When the film is annealed at 600C, the X-ray pattern changes significantly and indicates a conversionto one of the non-hexagonal phases of BaTiO3 as well as a complete change in the matrix.With suitable amplifier, the measured photoresponse was 40V/W.Ferroelectric hysteresis on a film with significant presence of hexagonal BaTiO3 shows saturatedpolarization which is about 5-times smaller than for the bulk tetragonal phase. | |
| Identifier: | CFE0006710 (IID), ucf:51899 (fedora) | |
| Note(s): |
2017-08-01 Ph.D. Engineering and Computer Science, Electrical Engineering and Computer Engineering Doctoral This record was generated from author submitted information. |
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| Subject(s): | SPEED -- Deposition -- TiO2 -- BaTiO3 -- Photonics -- Optics. | |
| Persistent Link to This Record: | http://purl.flvc.org/ucf/fd/CFE0006710 | |
| Restrictions on Access: | public 2017-08-15 | |
| Host Institution: | UCF |
