透明导电AZO/Cu双层薄膜制备及其性能

采用直流磁控溅射方法在玻璃衬底上室温生长了AZO/Cu双层薄膜,Cu层厚度控制在9nm,研究了AZO层厚度对薄膜电学和光学性能的影响。当AZO层厚度为20～80nm时,AZO/Cu双层薄膜具有良好的综合光电性能,方块电阻为12～14Ω/sq,可见光平均透过率为70～75%,品质因子为2×10-3～5×10-3Ω-1。AZO/Cu双层薄膜可以观察到Cu（111）和ZnO（002）的XRD衍射峰。通过退火研究表明,AZO/Cu双层薄膜的光电性能可在400℃下保持稳定,具有良好的热稳定性。本研究制备的透明导电AZO/Cu双层薄膜具有室温制程、综合光电性能良好、结晶性能较好、稳定性高的优点,可以广泛应用于光电器件透明电极及镀膜玻璃等领域。     

Refractive index sensor based on the diamond like carbon diffraction grating

In this work we present an optical refractive index (RI) sensor based on the spectral analysis of anomalies in the optical response from the diffraction grating employing polarized polychromatic light. The sensor consists of holographic diffraction grating (period 423.5 nm) coated with a thin (110 nm) SiO_x doped diamond like carbon film (DLC) that defines sensitivity of the sensor as well as the range of the spectral analysis. The deposition of the DLC film (synthesized by the direct ion beam deposition from the hydrocarbon source) has influence on the shape but not on the position of the anomalies observed in the specular reflection spectrum. From the reflection spectra the RI dispersion curve of liquid analyte-water was obtained.     

Size dependent structural, optical and morphological properties of ZnS:Cu thin films

ZnS:Cu thin films have been deposited on glass substrate by a simple neutral pH solution synthesis route and chemical bath deposition technique. The copper concentration was varied between 0 and 0.1 M%. The X-ray diffraction and scanning electron microscope studies show the average size of the nanoparticles are below 4 nm (Bohr diameter). The effect of film thickness on the optical and structural properties has been studied. The optical absorption studies show the band gap energy of ZnS:Cu films decreases from 3.68 to 3.43 eV as thickness varied from 318.3 to 334.1 nm. The structural estimation shows the variation in particle size from 2.67 to 3.14 nm with thickness. The insignificant change in band gap may be due to the increase in particle size and quantum size effect.     

ZnO/Cu/ZnO multilayer films: Structure optimization and investigation on photoelectric properties

A series of ZnO/Cu/ZnO multilayer films has been fabricated from zinc and copper metallic targets by simultaneous RF and DC magnetron sputtering. Numerical simulation of the optical properties of the multilayer films has been carried out in order to guide the experimental work. The influences of the ZnO and Cu layer thicknesses, and of O₂/Ar ratio on the photoelectric and structural properties of the films were investigated. The optical and electrical properties of the multilayers were studied by optical spectrometry and four point probe measurements, respectively. The structural properties were investigated using X-ray diffraction. The performance of the multilayers as transparent conducting coatings was compared using a figure of merit. In experiments, the thickness of the ZnO layers was varied between 4 and 70 nm and those of Cu were between 8 and 37 nm. The O₂/Ar ratios range from 1:5 to 2:1. Low sheet resistance and high transmittance were obtained when the film was prepared using an O₂/Ar ratio of 1:4 and a thickness of ZnO (60 nm)/Cu (15 nm)/ZnO (60 nm).     

Optimal implementation of a microspectrometer based on a single flat diffraction grating

An analytical model has been developed and applied to explore the limits in the design of a highly miniaturized planar optical microspectrometer based on an imaging diffraction grating. This design tool has been validated as providing the smallest possible dimensions while maintaining acceptable spectral resolution. The resulting planar spectrometer is composed of two parallel glass plates, which contain all components of the device, including a reflective slit and an imaging diffraction grating. Fabrication is based on microelectromechanical system technology and starts with a single glass wafer; IC-compatible deposition and lithography are applied to realize the parts in aluminum, which makes the microspectrometer highly tolerant for component mismatch. The fabricated spectrometer was mounted directly on top of an image sensor and takes up a volume of only 50 mm(3). The measured spectral resolution of 6 nm (FWHM) in the 100 nm operating wavelength range (600-700 nm) is in agreement with a model calculation.     

Aerosol based fabrication of a Cu/polymer and its application for electromagnetic interference shielding

The effect of a catalytic surface activation on the electromagnetic interference shielding of Cu deposited polymer substrates was investigated. The surface of polymer substrates was catalytically activated by different methods respectively adopted Pd aerosol nanoparticles and Sn-Pd wet chemical processes. Although both activations initiated the deposition of Cu on the substrates, differences such as morphology (Pd aerosol: ~80 nm vs Sn-Pd: ~ 140 nm, in Cu grain size) and composition (Pd aerosol: Cu and Pd vs Sn-Pd: Cu, Pd, Sn, and Cl) of Cu deposits were presented. Specimens activated using Pd aerosol nanoparticles showed a higher range of shielding effectiveness by about 4-10 dB than those activated by Sn-Pd processes in 2-18 Ghz frequencies.     

Enhancement in photovoltaic performance of CZTS Thin-film solar cells through varying stacking order and sulfurization time

The CZTS samples were produced by a two-stage method, which includes deposition of Cu, Sn, Zn, and ZnS layers using magnetron sputtering to obtain CuSn/Zn/Cu and CuSn/ZnS/Cu stacks. The latter stage involves the sulfurization process of stacked films at 550 °C for varied sulfurization time (60, 90, 120, and 150 s) employing Rapid Thermal Processing (RTP) method to attain CZTS structure. The prepared CZTS thin films were analyzed utilizing several characterization methods. The energy-dispersive X-ray spectroscopy (EDX) measurements revealed that all sulfurized samples had Cu-poor and Zn-rich chemical composition. All samples showed that diffraction peaks belonged to pure kesterite CZTS phase subject to their XRD patterns. Besides, it was observed that the sulfurization time had a crucial effect on the crystal size of the samples. The Raman spectra of the samples verified the constitution of kesterite CZTS phase and it provides detection of some CTS-based secondary phases. The scanning electron microscopy (SEM) image of the films revealed that polycrystalline surface structures were observable in all the samples. However, plate-like surface features were observed in some samples that may refer to CTS-based secondary phases depending on chemical composition. From 1.40 to 1.48 eV optical band gap values were obtained from (αhν)² vs. photon energy (hν) plots. The Van der Pauw measurements exhibited that the CZTS samples produced employing CuSn/ZnS/Cu stack had lower resistivity (~?10^–3 Ω cm), higher carrier concentration values (~?10²¹ cm^?3), and higher charge mobility. The solar cells prepared using the most promising CZTS samples employing CuSn/Zn/Cu and CuSn/ZnS/Cu precursor films revealed 1.95% and 3.10% conversion efficiencies, respectively.

     

Size reduction in crystal grains in LiNb0.5Ta0.5O3 thin films by controlling nucleation density during thermal plasma spray chemical vapor deposition

Two approaches were applied to thermal plasma spray chemical vapor deposition (TPS CVD) in order to reduce crystal grain size or/and surface roughness of LiNb_0.5Ta_0.5O₃ thin films while retaining the advantages of this method, such as high deposition rate. The first method consists of a two-step deposition, where the nucleation density is controlled in the first step and the film with high crystallinity is deposited in the second step. The surface roughness and grain size could be reduced from 1 nm to 7.7 nm, and from 200-350 nm to 120-180 nm, respectively. In the second approach, employing a one-step TPS CVD process, the conventional precursor was substituted by a double-alkoxide precursor and grain size in the deposited films could be reduced to 50-80 nm. Both approaches adopted in this work permitted to reduce the optical propagation loss.     

Photodeposition of Ag and Cu binary co-catalyst onto TiO2 for improved optical and photocatalytic degradation properties

This paper deals with the influence of binary co-deposition of Ag and Cu metals on TiO₂ photocatalyst to investigate its adsorption, optical and photocatalytic properties relative to monometallic (Ag/Cu) deposition. Hence, different proportion of Ag and Cu has been simultaneously deposited on TiO₂ in an inert (argon) atmosphere under UV irradiations. It was found that the plasmonic absorption bands appeared in the visible region (480 and 640?nm for Ag and Cu, respectively) due to the binary deposition of Ag-Cu nanoparticles (～9–20?nm) onto TiO₂ surface as revealed by TEM size analysis and EDS/elemental mapping. The fluorescence spectrum of Ag-Cu-TiO₂ showed higher quenching of emission peak intensities at λ?>?450?nm in a different extent due to efficient charge separation as compared to respective monometallic (Ag/Cu)-TiO₂ nanocomposites. The photocatalytic activities of binary Ag-Cu-TiO₂ for the degradation of methylene blue and salicylic acid under UV and visible irradiations were found to be notably higher than monometallic deposited TiO₂. The reaction rates and CO₂ formation exhibited due to binary deposition always gives enhanced photoactivity which could be useful for removal of toxic environmental pollutants under solar radiations.     

Microstructure and physical properties of nanofaceted antimony doped tin oxide thin films deposited by chemical vapor deposition on different substrates

Antimony doped tin oxide SnO₂: Sb thin films have been fabricated by atmospheric pressure chemical vapour deposition at substrate temperature varying between 350 °C and 420 °C in a horizontal reactor, from a mixture of hydrated SnCl₂, SbCl₃ and O₂ gas. The films were grown on glass substrates and onto polished and porous n-type silicon. Doped films fabricated with various Sb (Sb/Sn %) contents ranging from undoped 0% to 4% were characterised employing different optical characterisation techniques, like X-ray diffraction, transmittance and reflectance in the wavelength range of 300 to 2500 nm and ellipsometry. The films exhibit the usual cassiterite diffraction pattern with high crystalline structure. Examination of the surface by scanning electron microscopy (SEM) showed that the films are textured made up of many pyramidal crystallites with nanofaceted surfaces, indicating highly stabilised material. The presence of inverted pyramids indicates that the crystallites grown by coalescence. The surface morphology was found to be independent on the kind of the substrate. From X-Ray spectra and SEM observations we get the texture the lattice constant and the grain size. The optical results provide information on film thickness, optical parameters and transmittance upon antimony concentration. The microstructure of the films, the grain growth topics (nucleation, coalescence…) depend strongly on deposition conditions and doping concentration. The observed variations of both the resistivity ρ and transmittance T are correlated to antimony atoms concentration which induced variation in the microstructure and in the size of SnO₂ nanograins (typically 20-40 nm). In this work, we have determined the feasibility of incorporating the correct amount of Sb atoms in tin oxide film by means of resistivity and transmission. SEM observations showed that the substrate do not affect the morphology.     

A 100 nm thick InGaN/GaN multiple quantum-well column-crystallized thin film deposited on Si(111) substrate and its micromachining

A 100?nm thick InGaN/GaN multiple quantum-well column-crystallized thin film was deposited on Si(111) substrate, with InN as the interlayer, by molecular beam epitaxy. The diameter of the column crystal is about 40?nm. Transmission electron microscopy images showed clear five-period well layers. Photoluminescence measurements demonstrated a wide emission wavelength from about 500 to 800?nm with the full width at half maximum of 107?nm at room temperature. An unusual photoluminescence peak position shift was observed from the optical measurement. The selected area electron diffraction image demonstrated the hexagonal wurtzite structure of the column crystal. A self-supported GaN-based active subwavelength grating was proposed, and the active subwavelength grating structure was fabricated from the InGaN/GaN quantum-well thin film by a Si micromachining process.     

Fabrication of Cu2ZnSnS4 absorber layers with adjustable Zn/Sn and Cu/Zn+Sn ratios

In this work Cu₂ZnSnS₄ (CZTS) thin films were successfully prepared by sulfurization of spin coated CuO + ZnO precursor films under Sn and S ambience with different time. Precursor films were synthesized using air-stable inks consist of carboxylate-capped metal oxide nanoparticles. The composition, microstructure and properties of CZTS thin films prepared with different sulfurization time were investigated using inductively coupled plasma-mass spectrometry, X-ray diffraction, scanning electron microscopy, Raman spectroscopy and UV–vis–NIR spectroscopy. The inductively coupled plasma-mass spectrometry results show that mole ratios of Zn/Sn and Cu/(Zn + Sn) in the films can be adjusted by controlling sulfurization time. A composition of Cu/Zn + Sn = ~0.8, and Zn/Sn = ~1.2 can be reached after sulfurizating with proper time. The influence of element composition change was also studied in our work using X-ray diffraction and Raman scattering. Two laser sources of 325 and 514 nm were involved in the Raman scattering analyze in order to identify secondary phases such as ZnS and Cu_2?xS. The as-prepared CZTS films with a composition of Cu/Zn + Sn = ~0.8, and Zn/Sn = ~1.2 exhibit a direct optical band gap about 1.45 eV.     

Fabrication of optical gratings by shrinkage of a rubber material

Ordered wavy surface structures generated by deposition of a metal thin film on a pre-stretched PDMS plate were fabricated and its potential application for optical gratings was proposed. The orientation of the generated structures was always perpendicular to the pre-stretched direction and the pitch of the structure could be adjusted ranging from 4.5 μm to 6.8 μm by controlling the strength of the pre-stretched strain and the thickness of the surface metal film. Based on these periodic structures, various optical gratings were demonstrated. With a slight modification of the fabrication scheme, gratings with different orientations can be fabricated on both sides of the PDMS plate, the double-sided gratings, could be fabricated. It is believed the current method has the potential for the fabrication of a large-scale diffractive grating at lower costs.     

Metal phosphate planar waveguides for biosensors

Hard, impermeable, glassy, metal phosphate films have been fabricated inexpensively by the use of a spin-coating and low-temperature-curing technique. Films that are suitable for use as monomode waveguides in biosensors have been identified through an examination of the optical and chemical properties of films containing Fe, Al, Ga, In, Cr, or V. The refractive index is controlled over the range 1.49-1.78 by varying the film composition. The film thickness is controlled over the range 50-1200 nm by varying the spin speed and the deposition temperature. Films can be patterned by photolithography or by embossing. Input coupling through an embossed grating of 833-nm pitch is demonstrated.     

Top-down fabrication of vertical silicon nano-rings based on Poisson diffraction

Vertical Si nano-rings with a uniform thickness of about 100 nm have been fabricated by conventional optical photolithography with a low cost based on Poisson diffraction. Moreover, the roughness of the Si nano-rings can be effectively reduced by sacrificial oxidation. In order to increase the density of the nano-rings, coaxial twin Si nano-rings have been fabricated by the Poisson diffraction method combined with the spacer technique. The thickness of both the inner and outer Si nano-rings is about 60 nm, and the gap between the twin nano-rings is about 100 nm.     

Highly-efficient thin film LiNbO3 surface couplers connected by ridge-waveguide subwavelength gratings

The ridge waveguide integrated grating couplers (GCs) in lithium niobate on insulator (LiNbO₃, LNOI) were designed, fabricated and characterized. Two ends of the tapered GCs were connected by the subwavelength gratings (SWG) waveguide of a sub-micrometric-diameter, the photonic-wire SWG structure was featured with the profile of side-walls corrugations, and the effect of geometrical dimensions on the output optical response was investigated. All the devices structure patterns for the integrated LNOI GCs could be simultaneously defined by one step of electron-beam lithography, and then easily fabricated by the optimized dry-etching processes, followed by samples surface cleaning. After the fabrication, a low coupling loss of ? 5.1 dB/coupler at the telecommunication wavelength of 1561 nm was measured in the best thin-film LiNbO₃ (TFLN) surface grating coupler for quasi-transverse-electric (quasi-TE) polarized signals, and a broad 3-dB optical bandwidth of wider than 95 nm was also obtained. The compact components exhibited magnificent performance, and might show the potential functionalities for the TFLN-based integrated optical waveguide devices.

     

Effect of thickness: a case study of electrodeposited CdS in CdS/CdTe based photovoltaic devices

The effect of electrodeposition technique on CdS thickness incorporated in CdS/CdTe-based solar cell has been investigated using all-electrodeposited g/FTO/n-CdS/n-CdTe/p-CdTe multilayer device configuration. The optical, morphological and structural properties of the electroplated CdS were investigated for CdS thicknesses between 50 and 200 nm. The observed CdS bandgap ranges between 2.42 and 2.46 eV. The morphological analysis shows full coverage of underlying g/FTO substrate for all CdS thicknesses except for the 50 nm which shows the presence of gap in-between grains. The structural analysis shows a preferred orientation of H(101) for all the CdS thicknesses except the 50 nm thick CdS which shows either a weak crystallinity or an amorphous nature. The fabricated solar cell shows a maximum conversion efficiency of ~11 % using CdS thickness ranging between 100 and 150 nm. These results show that although low CdS thickness is desirable for photovoltaic application, the effect of nucleation mechanism of deposition technique should be taken into consideration.     

Uniformly dispersed Pd nanoparticles anchored Co(OH)<Subscript>2</Subscript>/Cu(OH)<Subscript>2</Subscript> hierarchical nanotube array as high active structured catalyst for Suzuki–Miyaura coupling reactions

Up to now, although tremendous effort has been made in exploring Pd-based catalysts for the Suzuki–Miyaura coupling reactions, there is still much room to enhance its catalytic performance by synthesis catalyst with define-designed and tailored structure. Herein, a new kind of Pd-based structured catalyst with hierarchical hollow structure (Pd/Co(OH)₂/Cu(OH)₂/copper foam) has been successfully synthesized by three facile steps. As framework, the hierarchical hollow nanoarray structure of Co(OH)₂/Cu(OH)₂/copper foam is fabricated by immersion and electrolytic deposition methods. Uniformly dispersed Pd nanoparticles with a narrow size distribution (1.5?±?0.2 nm) are anchored on the surface of the hierarchical nanotube array through an in situ spontaneous redox reaction between Co(OH)₂ and PdCl₄^2? without any surfactant at room temperature. Compared with other synthesis approaches, it just takes less than 1 h for the whole fabrication process in our strategy, exhibiting very high efficiency. In order to evaluate the catalytic performance of the as-prepared structured catalyst, 16 kinds of reagents were chosen as substrates for Suzuki–Miyaura coupling reaction, exhibiting excellent activity and reusability under mild conditions. We hope this simple and efficient method will open a new strategy to design and prepare structured catalysts.     

Supercritical fluid attachment of palladium nanoparticles on aligned carbon nanotubes

Nanocomposite materials consisting of Pd nanoparticles deposited on aligned multi-walled carbon nanotubes have been fabricated through hydrogen reduction of palladium-beta-diketone precursor in supercritical carbon dioxide. The supercritical fluid processing allowed deposition of high-density Pd nanoparticles (approximately 5-10 nm) on both as-grown (unfunctionalized) and functionalized (using HNO3 oxidation) nanotubes. However, the wet processing for functionalization results in pre-agglomerated, bundle-shaped nanotubes, thus significantly reducing the effective surface area for Pd particle deposition, although the bundling provides more secure, lock-in-place positioning of nanotubes and Pd catalyst particles. The nanotube bundling is substantially mitigated by Pd nanoparticle deposition on the unfunctionalized and geometrically separated nanotubes, which provides much higher catalyst surface area. Such nanocomposite materials utilizing geometrically secured and aligned nanotubes can be useful for providing much enhanced catalytic activities to chemical and electrochemical reactions (e.g., fuel cell reactions), and eliminate the need for tedious catalyst recovery process after the reaction is completed.     

Effect of complexing agents: investigations on structural,morphological, topographical and optical analysis of copper iron sulphide thin films deposited by chemical bath deposition method

Copper iron sulphide (FeCuS₂) thin films deposited by chemical bath deposition method using ferrous sulphate and copper sulphate as cationic sources and sodium sulphide as anionic source with complexing agents, EDTA and Leishman stain were reported. The structural, optical and morphological studies were carried out using X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV–Visible spectroscopy techniques. The X-ray spectrum reveals that the films are polycrystalline nature and also showed the deposition of cubic phases at room temperature. The SEM images for prepared films have clear morphology influenced by the complexing agents used in deposition process. The result of AFM studies shown that the particles in the film have grain size around ~?60–70 nm and also have almost similar thickness. Based on the optical absorbance spectra the FeCuS₂ film exhibited a high absorbance in the visible region. The absorption edge shifted toward lower wavelength with varying complexing agents. The band gap value obtained was found to be 3.57–3.85 eV. From these results, it is indicated that the prepared films are suitable candidate for solar cell applications.