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Rational design and fabrication of phase junction is an important way and strategy to enhance the photocatalytic performance. In this paper, rutile/anatase phase junction is obtained in rutile nanoparticles decorated anatase thin film by laser ablation. The hydrogen generation of rutile/anatase composite film is 49.6 μL, which is remarkably higher than that of both anatase thin film and rutile decorated layer. The quantity of phase junctions between rutile and anatase is considered as a key factor of photocatalytic improvement by varying the amount of rutile nanoparticles. Moreover, the excellent photocatalytic stability of rutile/anatase composite film is also exhibited. [ABSTRACT FROM AUTHOR]

Cu 2 O nanoparticles decorated TiO 2 thin films were fabricated by laser ablation. The effects of Cu 2 O nanoparticles on the structure, optical properties and photocatalytic performance of TiO 2 thin film were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectrometer system, optical absorption and photocatalytic evaluation system, respectively. XRD patterns indicate that the decoration has the effect of lowering the grain orientation of Cu 2 O. The photocatalytic performance in hydrogen generation of Cu 2 O decorated TiO 2 composite thin film was significantly improved compared with that of either Cu 2 O nanoparticles or TiO 2 single layer thin film with 1.70 and 1.77 times, respectively. The oxidation of Cu 2 O was demonstrated to dominate the photocatalytic performances of Cu 2 O/TiO 2 composite thin films by varying the laser ablation powers. • The photocatalytic activity of TiO 2 thin films was enhanced by the decoration of Cu 2 O nanoparticles with laser ablation. • The Cu 2 O ratio dominates the photocatalytic performances of Cu 2 O/TiO 2 composite thin films. • The porous structure of Cu 2 O and the heterojunction between Cu 2 O and TiO 2 contributed to enhance photocatalytic performance. [ABSTRACT FROM AUTHOR]

Electron beam (EB) irradiation experiments on Indium-tin (In-Sn) alloy thin films are reported. The structure and the optical properties of the samples were investigated by atomic force microscopy, X-ray diffraction, UV-vis-NIR double beam spectrometer and Raman system, respectively. Those results show that EB irradiation has the effects of changing the preferred orientation, improving the crystalline, enhancing the absorption, and improving the surface-enhanced Raman scattering (SERS) of samples. In addition, Finite-Difference Time-Domain (FDTD) was performed for the surface plasmon resonance properties of the as-irradiated samples, and the results are in good agreement with the experiments. [ABSTRACT FROM AUTHOR]

Abstract: The effects of Fe-dopant concentration on the structure, optical, and magnetic properties of ZnO thin films were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), optical transmittance, absorption, photoluminescence (PL), and magnetic measurements. XRD spectra indicated that the doping of Fe atoms could not only change the lattice constant of ZnO but also improve the crystalline quality of ZnO thin films. And the Zn (002) diffraction peak at round 36.34°(2θ) was detected with increasing Fe content for the substitution of the Zn in the ZnO film. The band gap edge shifted toward longer wavelength with increase in Fe doping. Moreover, near band edge emission gradually increased with increase in Fe content (up to about 0.82wt%), and then abruptly decreased due to the concentration quenching effect. Magnetic measurements confirmed that the ferromagnetic behavior of Fe-doped ZnO was correlated with the dopant concentration. [ABSTRACT FROM AUTHOR]

Abstract: A series of silver films with different thickness were prepared under identical conditions by direct current magnetron sputtering. The optical properties of the silver films were measured using spectrophotometric techniques and the optical constants were calculated from reflection and transmission measurements made at near normal incidence. The results show that the optical properties and constants are affected by films'' thickness. Below the critical thickness of 17 nm at which Ag film forms a continuous film, the optical properties and constants vary significantly as the thickness of films increases and then tends to a stable value which is reached at 41 nm. X-ray diffraction measurements were carried out to examine the structure and stress evolution of the Ag films as a function of films'' thickness. It was found that the interplanar distance of (111) orientation decreases when the film thickness increases and tends to be close to that of bulk material. The compressive strains also decrease with increasing thickness. [Copyright &y& Elsevier]

Abstract: A series of ZnO thin films were deposited on ZnO buffer layers by DC reactive magnetron sputtering. The buffer layer thickness determination of microstructure and optical properties of ZnO films was investigated by X-ray diffraction (XRD), photoluminescence (PL), optical transmittance and absorption measurements. XRD results revealed that the stress of ZnO thin films varied with the buffer layer thickness. With the increase of buffer layer thickness, the band gap edge shifted toward longer wavelength. The near-band-edge (NBE) emission intensity of ZnO films deposited on ZnO buffer layer also varied with the increase of thickness due to the spatial confinement increasing the Coulomb interaction between electrons and holes. The PL measurement showed that the optimum thickness of the ZnO buffer layer was around 12nm. [Copyright &y& Elsevier]

Abstract: ZnO:Zn phosphor thin films were prepared by face-to-face annealing at 450°C in air. The effects of the face-to-face annealing on the structural and optical properties of the ZnO films were investigated by X-ray diffraction (XRD), photoluminescence (PL), optical transmittance and absorption measurements. Measurement results showed that the crystal quality of ZnO films was improved by face-to-face annealing. Both UV light emission and visible light emission were enhanced compared to those of open annealing films. The UV emission peak was observed to have a blueshift towards higher energy. The optical band-gap edge of as-annealed films shifted towards longer wavelength. [Copyright &y& Elsevier]

Abstract: CO2 laser irradiation experiments on ZnO thin films are reported. The structural, optical, luminescent and vibrational properties of the samples were investigated by X-ray diffraction (XRD), transmittance, photoluminescence (PL) and Raman measurements. XRD results show that the crystalline of the irradiated films was improved. The (002) peaks of irradiated ZnO films shift to higher 2θ angles due to the stress relaxation in the case of laser beam irradiation. From optical transmittance spectra, all films exhibit high transmittance in the visible range, the optical band edge of irradiated films showed a redshift compared with that of as-grown films. Compared with the as-grown films, the photoluminescence emission (in particular the relative intensities of visible emissions) intensities of irradiated samples enhanced. In the Raman scattering spectra, both the A1 and E2 modes exhibited slight Raman blueshift. [Copyright &y& Elsevier]

Abstract: Zinc oxide (ZnO) films with c-oriented were grown on fused quartz glass substrates at room temperature using dc reactive magnetron sputtering. The as-grown films were annealed at 700°C in air and bombarded by ion beam, respectively. The effects of post-treatments on the structural and optical properties of the ZnO films were investigated by X-ray diffraction (XRD), photoluminescence (PL), optical transmittance and absorption measurements. The XRD spectra indicate that the crystal quality of ZnO films has been improved by both the post-treatments. Compared with the as-grown sample, both annealed and bombarded samples exhibited blueshift in the UV emission peaks, and a strong green emission was found in the annealed ZnO film. In both optical transmittance and absorption spectra, a blueshift of the band-gap edge was observed in the bombarded film, while a redshift was observed in the annealed film. [Copyright &y& Elsevier]

The defective titanium dioxide (TiO 2) thin films decorated with silver (Ag) nanoparticles (NPs) were fabricated by pulsed laser ablating the Ag/TiO 2 composite films deposited with ion beam assisted deposition (IBAD). The morphology, crystal structure, element status and optical property of the films were investigated. We found the pulsed laser had a marked impact on the size and distribution of Ag NPs and on the oxidation state of titanium. The localized surface plasmon resonance (LSPR) and defect state were efficiently tuned as well. With the laser power increasing, a blue shift in the LSPR peak, and a reduction in the defect content occurred coincided. Additionally, the SERS intensity of the as-ablated Ag/TiO 2 thin film is about triple that of as-deposited Ag/TiO 2 thin film. Furthermore, the synergistic effect of electromagnetic enhancement and charge transfer was demonstrated to be the main reason for the improvement of SERS performance. Image 1 • The states of Ag nanoparticles and content of TiO 2 defect are tunable for Ag/TiO 2 composite films fabricated by pulsed laser ablation. • The formation of Ag nanoparticles and self-doping of Ti3+ are synchronous. • The as-ablated film is a kind of convenient thin film component with improved Raman enhancement ability. [ABSTRACT FROM AUTHOR]

Tunable permittivity of Epsilon-Near-Zero (ENZ) of ITO thin films were realized by Nd: YAG pulse laser irradiation. The effects of different pulsed laser power irradiation on the structure, morphology and optical properties of the samples were investigated via X-ray diffraction, atomic force microscopy, UV-VIS-NIR double beam spectrometer, spectroscopic ellipsometry and Raman system, respectively. Those results indicate that pulse laser irradiation has the effects on the preferential orientation and the permittivity wavelength region of ENZ from 1137 to 2001 nm. The variations of Raman spectra further confirms that the laser irradiation can induce some defects driving the special optical characteristics of ITO films. In addition, the results of Finite-Difference Time-Domain are in good agreement with those of the experiments. Image 1 • The tunable Epsilon-Near-Zero ITO films with the range from 1137 to 2001 nm were obtained by pulsed laser irradiation at ambient conditions. • Surface roughness dependent preferential orientation was observed in as-irradiated ITO films. • Laser induced defects driving the special optical characteristics of ITO films was confirmed by Raman scattering spectra. • The simulation results of FDTD regarding the electric field distribution of samples are consistent with those of experiments. [ABSTRACT FROM AUTHOR]

• Ag thin film aggregates on the surface of MoO x in the form of particles. • Laser irradiation will introduce numerous oxygen vacancy defects in MoO x. • The NLA response of Ag/ir-MoO x is larger than that of Ag/MoO x and single layer Ag. • The oxygen vacancies will promote the rate of charge transfer. Defect plays a key role in the optical properties of silver thin films. Herein, we introduced the oxygen vacancy defects by laser modification and fabricated the Ag/ir-MoO x thin film. The effects of ir-MoO x on the structure and optical properties of Ag thin films were investigated. We found that laser irradiation and effective silver trap will introduce numerous oxygen vacancy defects. The nonlinear absorption response of Ag/ir-MoO x was significantly improved compared with that of the single layer Ag. The increased concentration of oxygen vacancies in the composite film will promote the rate of charge transfer and enhance the nonlinear saturation absorption. [ABSTRACT FROM AUTHOR]

In this work, Ag/MoS 2 composite thin films were fabricated. The effects of MoS 2 layer on the structure and optical properties of Ag thin film were investigated. XRD results show that MoS 2 buffer layer has the effects of promoting grain growth of Ag and increasing their particle sizes confirmed by SEM images. The surface plasmon resonance (SPR) wavelength of Ag was observed to shift from 432 nm to 1650 nm with the introduction of MoS 2 buffer layer. The nonlinear absorption (NLA) response of Ag/MoS 2 composite thin films was significantly improved compared with that of the Ag single layer, which is attributed to the SPR of the Ag/MoS 2 composite thin films and the enhanced electric field induced by SPR. Moreover, the simulation results of Finite-Difference Time-Domain (FDTD) are in good agreement with the experimental results. • MoS 2 buffer layer has the effects of promoting grain growth of Ag and increasing their particle sizes. • The SPR wavelength of Ag was observed to shift from 432 nm to 1650 nm with the introduction of MoS 2 buffer layer. • The NLA response of Ag/MoS 2 was significantly improved compared with that of the Ag single layer. [ABSTRACT FROM AUTHOR]

• The surface of the patterned Ag thin films is covered by periodic microstructure. • The volume fractions of Ag and Ag 2 O are dependent on laser scanning rate. • LSPR was observed in the as-irradiated samples. • These samples exhibit tunable self-defocusing nonlinearity. Patterned Ag thin films were obtained through laser irradiation at ambient conditions. We investigated the effects of laser scanning rate for the structure and optical properties of patterned Ag films. XPS results show that the volume fractions of Ag and Ag 2 O are dependent on the laser scanning rate. The localized surface plasmon resonance was observed in the as-irradiated samples and increased with the acceleration of the scanning rate. Moreover, with the variations of laser scanning rates and excitation energy, these samples exhibit tunable self-defocusing nonlinearity caused by charge transfer and the enhanced electromagnetic field at the interface between Ag and Ag 2 O. [ABSTRACT FROM AUTHOR]

Defect-induced tunable permittivity of Epsilon-Near-Zero (ENZ) in indium tin oxide (ITO) thin films via annealing at different temperatures with mixed gases (98% Ar, 2% O2) was reported. Red-shift of λENZ (Epsilon-Near-Zero wavelength) from 1422 nm to 1995 nm in wavelength was observed. The modulation of permittivity is dominated by the transformation of plasma oscillation frequency and carrier concentration depending on Drude model, which was produced by the formation of structural defects and the reduction of oxygen vacancy defects during annealing. The evolution of defects can be inferred by means of X-ray diffraction (XRD), atomic force microscopy (AFM), and Raman spectroscopy. The optical bandgaps (Eg) were investigated to explain the existence of defect states. And the formation of structure defects and the electric field enhancement were further verified by finite-difference time domain (FDTD) simulation. [ABSTRACT FROM AUTHOR]

In this paper, a series of MoS 2 films with various thicknesses were fabricated by laser ablation technique at ambient conditions. The influences of thickness on the optical properties and structure of MoS 2 films were investigated. X-ray diffraction (XRD) results show that the diffraction intensity firstly increased and then decreased with the decrease of thickness. The band gap of samples increased with the decrease of thickness. The plasmonic absorption peaks in the range of 250 nm–320 nm show a red-shift and then a blue ones with the thickness decreasing. With the decrease of thickness, the nonlinear absorption performance of the samples reduced with saturation absorption and then turned to reverse saturation absorption. [Display omitted] • A series of MoS 2 films with various thicknesses were fabricated by laser ablation technique at ambient conditions. • The defects in MoS 2 would be introduced through the high-energy oxygen from the plasma. • The light absorption response of the MoS 2 films can be affected by the size of MoS 2 particles. • Thickness-dependent nonlinear optical properties of the MoS 2 films was obtained. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rich oxygen vacancies are introduced on the WO 3-x film substrate through simple heat treatment techniques. • The red shift of the plasma absorption peak is achieved by the change of thermal treatment parameters. • The changes in the surface structure of the film caused by the thermal treatment and the defect energy provided by the oxygen vacancies lead to the SERS enhancement. A series of WO 3-x thin films with defects were obtained by thermal treatments from laser irradiation and annealing, respectively. The corresponding tunability of localized surface plasmon resonance properties and the enhancement of Raman scattering intensity were realized due to the defects in the WO 3-x thin films after thermal treatments. With the changes of either laser power or annealing temperature, the crystalline quality of WO 3-x thin film was declined with a red shift of the surface plasmon resonance wavelength from 464 nm to 482 nm. The as-treated WO 3-x film shows good uniformity and reproducibility in Surface-enhanced Raman spectroscopy measurement, the detection limit for dye methylene blue can reach 10−8 mol/L, and enhancement factor is 1.38 × 106. Furthermore, the simulation result of finite-difference time-domain showed a substantial agreement with experimental results. [ABSTRACT FROM AUTHOR]

• The Cu 2 O/MoS 2 nanocomposite film was fabricated through pulsed laser ablation assisted electron beam evaporation. • The nonlinear absorption coefficient (β) of Cu 2 O/MoS 2 composite samples are about 24.34 and 1.76 times greater than single-layer Cu 2 O and MoS 2 samples. • Transient absorption spectroscopy confirms that the faster carrier movement of the thinner Cu 2 O-MoS 2 sample leads to an enhanced synergy and a corresponding increase in nonlinear performance. In this paper, Cu 2 O/MoS 2 composite films with excellent nonlinear properties were fabricated. X-ray diffraction, Raman scattering and scanning electron microscope results show that Cu 2 O buffer layer has the effects on promoting the multiphase growth and improving both the particle size and the uniformity of MoS 2 film. The nonlinear optical response of the samples was investigated by Z-scan and ultrafast carrier dynamics, respectively. The nonlinear absorption coefficient β of Cu 2 O/MoS 2 composite sample was observed to reach the maximum value of −23.08 × 10-6 cm/W, which was 24.34 and 1.76 times than that of single-layer Cu 2 O and MoS 2 , respectively. In addition, the nonlinear enhancement mechanism of composite samples was confirmed by the results of both transient absorption spectroscopy measurements and finite difference time domain simulation calculation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu 2 O-Ag composite film, was prepared by a simple and effective method (thermal oxidation and electron beam evaporation) under ambient conditions. • Compared with Cu 2 O and Ag sample, the Raman scattering intensity of Cu 2 O/Ag composite film was increased by 19.97 and 1.48 times, respectively. • The composite exhibits good property as a SERS substrate for probing various molecules such as RhB, MB, and R6G. In this work, silver thin films with various thicknesses deposited on cuprous oxide (Cu 2 O) buffer layer were obtained. XRD and AFM results show that the Cu 2 O buffer layer has the effect of improving the surface quality and crystallinity of the Cu 2 O-Ag composite films. The coupling between Cu 2 O and localized surface plasmons of the silver thin films was investigated by optical absorption and Raman scattering experiments. The absorption spectra showed that the intensity of Cu 2 O/Ag composite thin films was increased and shifted from the visible to the near-infrared region with an increase of the silver layer thickness. Compared with single-layer sample, the Raman scattering intensity of Cu 2 O/Ag composite was increased by 19.97 and 1.48 times, respectively. By the FDTD simulation of single layer and composite films, the electric field enhancement characteristics of the composite structure are confirmed. At the same time, the composite also exhibits good property as a SERS substrate for probing various molecules such as RhB, MB, and R6G. [ABSTRACT FROM AUTHOR]

A series of Cu–Al–O thin films with excellent nonlinear absorption properties were prepared by magnetron sputtering at room temperature. An absorption peak at around 440 nm was observed in the as-deposited thin films, with CuAlO 2 as the main phase. After thermal oxidation at 400 °C, the surface roughness of the films decreased, the absorption peak was blue-shifted, with the optical band gap increased. Open aperture Z-scan measurements revealed that the as-deposited samples had strong saturable absorption and reached the maximum nonlinear absorption coefficient (β) of −6.29 × 10−5 cm/W. The nonlinear optical conversion from saturable absorption to reverse saturable absorption was observed in as-annealed samples with β values up to 2.592 × 10−5 cm/W. In addition, the time-domain finite-difference simulation results were basically consistent with those of the experimental results. [Display omitted] • The NLO properties of Cu–Al–O thin films were investigated by Z-scan system. • Blue-shift of absorption peak of Cu–Al–O thin films induced by thermal oxidation treatment. • A transition from saturated absorption to reverse saturable absorption of Cu–Al–O films was observed. [ABSTRACT FROM AUTHOR]

A perfect bidirectional dynamic tunable absorber working in the near-infrared based on an asymmetric Fabry–Pérot resonance in a thin film dielectric–metal multilayer structure is proposed. Perfect narrowband absorption occurs at the wavelength of 1023 nm (full width at half-maximum, 13 nm) when light is normally incident on the surface covered with a silver film with a saturation voltage applied to polymer-dispersed liquid crystal (PDLC). Illumination from the opposite direction results in ultra-broadband absorption (98.91% absorption averaged over 764–2476 nm). The narrowband absorption can be dynamically tuned in the 1023–1056 nm range via PDLC modulation. Furthermore, the excellent angular sensitivity of the narrowband absorption, as well as the good angular and polarization tolerances of the broadband absorption are demonstrated. • A design for a absorber with both tunable narrowband and ultra-broadband absorptions. • The angular sensitivity of the narrowband absorption and angular insensitivity of broadband absorption. • For the narrowband absorption, PDLC was used to achieve a wide tuning range. • Polarization tolerance and simple structure of the perfect absorber. [ABSTRACT FROM AUTHOR]

Silver (Ag) thin films decorated with carbon nanoparticles were achieved by ablating Ag / C thin film with an Nd:YAG fiber pulsed laser under the environmental conditions. The structure and optical properties of the Ag/C samples were investigated. In this study, the Surface plasmon resonance (SPR) wavelength of Ag/C samples shift from 457 nm to 527 nm was realized using a different laser scanning rate. Compared to Ag samples, Surface enhanced Raman scattering (SERS) of Ag/C samples was also observed due to decorating with nano-carbon, which demonstrates good steadiness and high SERS intensity with the concentration of Rhodamine 6G (Rh 6G) with 10 −5 mol/L. In additional, the simulation results of finite-difference-time-domain (FDTD) verify SERS performance. • Silver thin film with decorated carbon nanoparticles were fabricated by Nd:YAG fiber-pulsed laser irradiation. • The tunability of both LSPRwavelength and intensity was realized by changing the laser scanning rate. • A graphite-like carbon was formed on the surface of Ag film, which enhanced the SERS performance of the system. [ABSTRACT FROM AUTHOR]

Silver thin films covered with a graphene oxide (GO) colloid layer were fabricated in this study. The coupling between GO and localized surface plasmons of the silver thin films was investigated by optical absorption and Raman scattering experiments. The absorption spectra showed that the intensity of the plasma edge peak at 320 nm decreased but the intensity of the interband transition peak at 350 nm was enhanced by an increase of the GO colloid concentration. The surface plasmon resonance attributed to the increased absorption of incident light by the GO layer caused an increase of the Raman scattering intensities. Theoretical calculations were performed for the surface plasmon resonance properties of the GO/silver thin films, and the results were in good agreement with the experiments. [ABSTRACT FROM AUTHOR]

• Al-Cu bimetallic nanoparticles (NPs) thin films were fabricated by Nd:YAG fiber-pulsed laser irradiation. • The tunability of both localized surface plasmon resonance (LSPR) wavelength and intensity were realized. • SERS performance and FDTD simulation were applied to demonstration the potential application of tunable LSPR properties. Al-Cu bimetallic nanoparticles (NPs) thin film was fabricated by Nd:YAG fiber pulsed-laser irradiation of Al/Cu bilayers at ambient conditions. The effects of laser irradiation on the morphology, structure, composition and optical properties of the samples were investigated. The tunability of both localized surface plasmon resonance (LSPR) wavelength and intensity were realized by varying the pulse shot or relative thickness of Al/Cu bilayers. The SEM analysis with EDS results further revealed that the obtained particles consisted of a mean diameter of 36–80 nm bimetallic NPs system, being dependent on the Cu proportion. In addition, Surface-enhanced Raman spectroscopy (SERS) measurement and corresponding finite-difference time-domain (FDTD) simulation of before and after laser irradiation samples were discussed to verify the LSPR properties. [ABSTRACT FROM AUTHOR]