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Characteristics of Ultrathin Ni Films
摘要： Conductive and transparent ultra-thin Nickel films are grown by RF sputtering on fused silica substrates. The characteristics of Ni films (thickness, refractive index, and extinction coefficient) are obtained by fitting multi-angle spectrophotometric and ellipsometric data. Films thickness inferred by X ray reflection (XRR) measurements is in good accordance with ellipsometric results. XPS analysis reveals that Ni metal phase is present in the film surface together with Ni mixed oxide phases, which explains the high electrical stability of such films.
关键词： optical measurements,ultrathin films,transparent conductive films,Ni films
更新于2025-09-23 15:23:52
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Structural characterization of bulk and nanoparticle lead halide perovskite thin films by (S)TEM techniques
摘要： Lead halide (APbX3) perovskites, in polycrystalline thin films but also perovskite nanoparticles (NPs) have demonstrated excellent performances to implement a new generation of photovoltaic and photonic devices. The structural characterization of APbX3 thin films using (scanning) transmission electron microscopy ((S)TEM) techniques can provide valuable information that can be used to understand and model their optoelectronic performance and device properties. However, since APbX3 perovskites are soft materials, their characterization using (S)TEM is challenging. Here, we study and compare the structural properties of two different metal halide APbX3 perovskite thin films: bulk CH3NH3PbI3 prepared by spin-coating of the precursors in solution and CsPbBr3 colloidal NPs synthetized and deposited by doctor blading. Both specimen preparation methods and working conditions for analysis by (S)TEM are properly optimized. We show that CH3NH3PbI3 thin films grown by a one-step method results in the formation of tetragonal perovskite thin films with good adherence to an underlying TiO2 layer, which is characterized by a photoluminescence (PL) emission band centered at 775 nm. The perovskite thin films based on CsPbBr3 colloidal NPs, which are used as the building blocks of the film, they are preserved by the deposition process, even if small gaps are observed between adjacent NPs. The crystal structure of CsPbBr3 NPs is cubic, which is beneficial for optical properties due to its optimal band gap. The absorption and PL spectra measured in both the thin film and the colloidal solution of CsPbBr3 NPs are very similar, indicating a good homogeneity of the thin films and the absence of aggregation of NPs. However, a particular care was required to avoid long electron irradiation times during our structural studies, even at a low voltage of 80 kV, as the material was observed to decompose through Pb segregation.
关键词： structural characterization,TEM,thin films,optoelectronics,STEM,nanoparticles,perovskite
更新于2025-09-23 15:23:52
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Tailoring Shape and Crystallographic Phase of Copper Sulfide Nanostructures Using Novel Thiourea Complexes as Single Source Precursors
摘要： Copper sulfide thin films and nanoparticles have been prepared via aerosol assisted chemical vapour deposition and solvothermal hot injection routes, respectively. Both routes employed heterocyclic amine based benzoylthioureato-copper(II) complexes as single source precursors. Copper sulfide thin films of diverse morphologies ranging from cubic to snowy or irregular crystallites depending on the deposition temperature were observed. Powder X-ray diffraction studies of the as deposited thin films have indicated the formation of hexagonal and cubic phases of copper sulfide. In the case of the nanoparticles, Roxbyite (Cu1.75S) phase was obtained in dodecanethiol at temperatures of 150, 190 and 230 °C. However, a preferred growth of nanoparticles was observed in the presence of oleylamine whereas the roxbyite phase was obtained at temperatures of 150, 200 and 250 °C. Also transmission electron microscopy showed the formation of close to spherical, hexagonal nano-disk and rod shaped nanoparticles.
关键词： Aerosol assisted chemical vapour deposition,Nanoparticles,Heterocyclic thiourea,Copper sulfide,Thermolysis,Thin films
更新于2025-09-23 15:23:52
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Liquid switchable radial polarization converters made of sculptured thin films
摘要： A radial polarization converter is a super-structured optical retarder that converts a conventional linearly polarized light beam into a structured beam with radial or azimuthal polarization. We present a new type of these sophisticated optical elements, which is made of porous nanostructured sculptured single thin films or multilayers prepared by physical vapor deposition at an oblique angle. They are bestowed with an axisymmetric retardation activity (with the fast axis in a radial configuration). In particular, a Bragg microcavity multilayer that exhibits a tunable transmission peak in the visible range with a retardance of up to 0.35 rad has been fabricated using this methodology. Owing to the highly porous structure of this type of thin films and multilayers, their retardance could be switched off by liquid infiltration. These results prove the possibility of developing wavelength dependent (through multilayer optical design) and switchable (through vapor condensation or liquid infiltration within the pore structure) radial polarization converters by means of oblique angle physical vapor deposition.
关键词： radial polarization converters,q-plates,oblique angle deposition,sculptured thin films
更新于2025-09-23 15:23:52
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Fabrication of 2D thin-film filter-array for compressive sensing spectroscopy
摘要： We demonstrate 2D filter-array compressive sensing spectroscopy based on thin-film technology and a compressive sensing reconstruction algorithm. To obtain different spectral modulations, we fabricate a set of multilayer filters using alternating low- and high-index materials and reconstruct the input spectrum using a small number of measurements. Experimental results show that the fabricated filter-array provides compatible spectral resolution performance with a conventional spectrometer in monochromatic lights and LEDs. In addition, the fabricated filter-array covers a wide range of wavelengths with a single exposure.
关键词： Compressive sensing,Thin films,Spectroscopy,Inverse problems
更新于2025-09-23 15:23:52
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Tuning the excitonic properties of ZnO:Sn thin films
摘要： The effects of Sn doping, deposition temperature, and post-annealing treatment on the excitonic behavior of ZnO:Sn (SZO) thin films deposited by dc-unbalanced magnetron sputtering have been studied. Sn doping induces the decrease of grain size and promotes the formation of oxygen vacancy-related trap states as indicated by A1 LO mode in Raman spectra and green emission in photoluminescence spectra. Using a critical point analysis of the dielectric functions from spectroscopic ellipsometry data analysis, Sn doping blueshifts the excitonic absorption and decreases the exciton lifetime via screening the electron-hole Coulomb interaction. By varying the deposition temperature from room temperature up to 300 °C (SZO-3), there is no change in excitonic absorption. Then, annealing of SZO-3 at 600 °C under oxygen environment (SZO-6) strongly improves the excitonic absorption as well as its lifetime. Critical point analysis on SZO-6 sample clearly reveals the excitonic transition at 3.38 eV and exciton-phonon complexes at 3.66 eV. Thus, the result is important to improve the functionality of doped ZnO with strong excitonic absorption for optoelectronic applications.
关键词： Annealing,Dc-unbalanced magnetron sputtering,Exciton,Thin films,Sn doped ZnO
更新于2025-09-23 15:23:52
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Fe doping effect of vanadium oxide films for enhanced switching electrochromic performances
摘要： In the present study, Fe-doped V2O5 films showing impressive electrochromic (EC) performance were developed using the sol-gel spin-coating method. To confirm the optimized Fe-doping effect on the V2O5 films for the EC performance, we adjusted the Fe atomic percentages to 0.0, 0.5, 1.0, and 1.5 at%, respectively. With the effect of Fe doping on the V2O5 films, the obtained films resulted in the formation of the oxygen vacancies. As the result, when the optimum Fe atomic percentage was 1.0 at%, the enhanced switching speeds (3.7 s for the bleaching speed and 2.0 s for the coloration speed) and enhanced coloration efficiency value (47.3 cm2/C) compared to the other films were implemented. This can be attributed to the improved electrical conductivity and Li+ diffusion coefficient that led to efficient generation of the EC reaction activity and narrowing the optical bandgap at the coloration state to increase transmittance modulation. Therefore, this unique film can be a promising EC material to improve the performance for the EC devices.
关键词： Films,Optical properties,Transition metal oxides,Electrical properties,Electrochromic performances
更新于2025-09-23 15:23:52
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Low-dielectric-constant aromatic homopolyimide and copolyimide derived from pyromellitic dianhydride, 4,4′-oxydianiline, 2,2-bis[4-(4-aminephenoxy)phenyl]propane, 1,4-bis(4-aminophenoxy)benzene, or 1,3-bis(4-aminophenoxy)benzene
摘要： Low-dielectric-constant aromatics, homopolyimide and copolyimide, were introduced. Homopolyimides were prepared by pyromellitic dianhydride (PMDA) as an anhydride monomer and 4,40-oxydianiline (ODA), 2,2-bis[4-(4-aminephenoxy)phenyl]propane, 1,4-bis(4-aminophenoxy)benzene, or 1,3-bis(4-aminophenoxy)benzene as an amine monomer. The copolyimides were prepared with PMDA as an anhydride monomer, ODA as an amine monomer with the addition of 2,2-bis[4-(4-aminephenoxy)phenyl]propane, 1,4-bis(4-aminophenoxy)benzene, or 1,3-bis(4-aminophenoxy)benzene as another amine monomer. The polyimides were well characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, thermomechanical analysis, dielectric measurements, and tensile testing. The homopolyimide and copolyimides showed lower dielectric constants than the homopolyimide formed by ODA and PMDA. The results also indicate that the interchain distance, the quantities of phenyl ether, and the position of the substitute are factors that not only affected the thermal performance of polyimide by improving the molecular ?exibility but also reduced the dielectric constant of polyimide by increasing the free volume of the molecular chain and decreasing the polarization points per unit volume.
关键词： dielectric properties,copolymers,polyimides,films
更新于2025-09-23 15:23:52
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CdS/CdSe nanoparticles co-deposited SnO2(TiO2) spherical structure film for photoelectrochemical application
摘要： Herein, SnO2 spherical structure was directly deposited on FTO substrate by hydrothermal synthesis. As light absorber, CdS and CdSe nanoparticles were assembled onto the TiCl4-treated SnO2 spherical particles (SnO2(TiO2)) films by using SILAR method. The number of CdS and CdSe deposition cycles that influence the optical and photoelectrochemical performance of the photoelectrodes are evaluated. The best-performed sample is the co-deposition of 5 cycles of CdS and 4 cycles of CdSe on SnO2(TiO2) photoelectrode, and its photocurrent density is about 2.61 mA cm?2 versus Ag/AgCl at 0 V. The significant photoelectrochemical performance is due to a synergistic contribution from the enhanced light absorption range of the hybrid nanocomposite and the formation of type-II heterostructure, which plays important role in the effective charge separation process. Our results show that CdS/CdSe co-deposition SnO2(TiO2) photoelectrode may have great potential application in photovoltaic field.
关键词： Heterostructure,Thin films,Photoelectrochemisty,Nanocomposites
更新于2025-09-23 15:23:52
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Effect of Nd doping on structural and opto-electronic properties of CdO thin films fabricated by a perfume atomizer spray method
摘要： A perfume atomizer-assisted spray pyrolysis method was employed to fabricate undoped and neodymium (Nd)-doped cadmium oxide (CdO) thin films. X-ray diffraction results reveal that all the films are polycrystalline with a cubic structure with a preferential orientation along the (200) direction. Scherrer’s formula was used to calculate the crystallite size of Nd-doped CdO films. Energy dispersive spectroscopy results show that Cd, Nd and O elements are present in Nd-doped CdO thin films. The optical absorption of the doped films is increased along with increasing Nd-doping level. The prepared CdO thin films have a high absorption coefficient in the visible region and the optical band gap is decreased on increasing Nd doping content. The electrical carrier concentration (n) of the deposited films is increased with increasing Nd doping concentration. Photoconductivity studies of a nanostructured Al/Nd–n-CdO/p-Si/Al device showed a non-linear electric characteristics indicating diode-like behaviour. Prepared Nd:CdO films could increase the photo-sensing effect of this n-CdO/p-Si heterostructure. These Nd-doped CdO thin films may open a new avenue for photodiode application in near future.
关键词： optical and electrical properties,Nd:CdO,thin films,spray using perfume atomizer
更新于2025-09-23 15:23:52