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Structural and Optical Properties of Epitaxial Iron Oxide Thin Films Deposited by Pulsed Laser Deposition
摘要： Iron oxides have been intensively studied owing to potential applications related to energy conversion and storage systems. In this paper, we investigated crystal structures and optical properties of iron oxide thin films deposited at various oxygen partial pressures and temperatures using pulsed laser deposition. The iron oxide thin films were epitaxially grown on Al2O3 (0001) substrates confirmed by X-ray diffraction measurements. With increasing the growth temperature from 450 K to 800 K, the films exhibited better crystalline hematite phase, alpha-Fe2O3. When the pressure was decreased to 0.5 mTorr, the magnetite phase, Fe3O4, was formed. We found that the optical band gaps of iron oxides mainly originated from O 2p to Fe 3d could be modulated from 2.18 eV to 2.42 eV, applicable for energy conversion systems.
关键词： Absorption,Functional devices,Pulsed laser deposition,Fe2O3,Thin films
更新于2025-09-23 15:21:01
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Low-Temperature Laser Synthesis of Thin Electrochromic WO3 Films
摘要： Amorphous dielectric WO3 films with a surface roughness from 4 to 5 nm have been grown by room-temperature pulsed laser deposition on quartz and c-sapphire substrates using metallic targets. We have examined the effect of the nature of the substrates and the oxygen pressure during the growth process on the transmission spectrum of the WO3 films in the range from 400 to 2000 nm. The parameters of the films have been shown to depend on the oxygen pressure during the growth process. Raising the oxygen pressure from 20 to 60 mTorr during the film growth process increases the transmission of the WO3 films from 40 to 75% in the visible and UV spectral regions and from 10 to 70% in the IR. With increasing oxygen pressure during film growth, the band gap of the WO3 films increases from 3.01 to 3.34 eV in the case of sapphire substrates and from 2.95 to 3.42 eV in the case of quartz substrates, being only slightly dependent on the nature of the substrate. Using a WO3 film grown at room temperature, we have fabricated the first thin-film liquid-electrolyte electrochromic cell. Its transmission in the spectral range from 300 to 900 nm drops by 30% at an applied voltage of 2.5 V, with a coloration time on the order of 2 min.
关键词： electrochromic cell,room-temperature pulsed laser deposition,thin WO3 films
更新于2025-09-23 15:21:01
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Pulsed Laser Deposition Films Based on CdSe-Doped Zinc Aluminophosphate Glass
摘要： A composite material with applications in optoelectronics has been investigated. Pulsed laser deposition CdSe-doped glass film was prepared by the combinatorial deposition from two targets, namely pure CdSe and glass belonging to the 20Li2O-10Al2O3-7BaO-2La2O3-2ZnO-59P2O5 system. Exciton peaks in the Vis domain, related to electron–hole pairs transitions from the valence band to the conduction band, were revealed in the optical absorption spectra of the CdSe-doped film. CdSe quantum dots (QDs) band gap energy depends on the CdSe quantum confinement effect. CdSe-doped film photoluminescence exhibits peaks in the red domain assigned to CdSe transitions from the excited state to the ground state. The size of CdSe nanoclusters, determined from x-ray diffraction is correlated with scanning electron microscopy–energy dispersive x-ray spectroscopy and atomic force microscopy results. Vibration modes specific both to CdSe QDs and to the vitreous network have been evidenced by Fourier transform infrared and Raman spectroscopy.
关键词： quantum dots,optoelectronics,zinc aluminophosphate glass,pulsed laser deposition,CdSe
更新于2025-09-23 15:21:01
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Kinetics of graphitization of thin diamond-like carbon (DLC) films catalyzed by transition metal
摘要： In this paper, we have studied the kinetics of graphitization at 773K of thin diamond-like carbon (DLC) films coated with minute amount of Ni metallic particles. DLC films are deposited at room temperature by pulsed laser deposition (PLD) on a transparent quartz substrate, and Ni is deposited on the surface of DLC using molecular beam epitaxy technique at room temperature. The ultra-high vacuum thermal (range 573-873K with 60 min annealing treatments) and kinetic (range 30-3760 min at 773K) behaviors of the deposited films are investigated. Surface and interface characterizations indicate that the growth of graphitic sp2 clusters starts at temperatures lower than 573K. The kinetics of graphitization is recorded at 773K. Thus, the continuous growth of graphitic clusters leads to a long-range kinetics. These clusters are responsible for the increase in the electrical conductivity and carrier mobility, reaching values of 6.103 Siemens/cm and 20 V/cm2?s, respectively. This continuous change is not only explained by the nucleation and growth of graphitic clusters, but also by some reorientation of them alongside both the surface and the quartz substrate. The obtained results demonstrate that thermally post-treated catalytic metal/DLC films are promising materials for conductive electrodes and sensing applications.
关键词： Raman spectroscopy,thermal treatment,electric transport measurements,optical transmission and absorption,diamond-like carbon,thin graphite films,pulsed laser deposition,metal catalyst
更新于2025-09-23 15:21:01
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Enhanced green emission from Er-doped (AlGa) <sub/>2</sub> O <sub/>3</sub> films grown by pulsed laser deposition
摘要： Erbium (Er) doped (AlGa)2O3 films were deposited on sapphire substrates using pulsed laser deposition. The transmittance spectra and X-ray photoelectron spectroscopy measurements show that transparent (AlGa)2O3:Er films with a wider bandgap can be achieved by increasing the Al content in the targets. All films exhibit the strongest pure green emission at 550 nm with the wavelength independent of the alloy compositions. A maximum intensity observed at Al content of 0.34 is several times higher than that in Ga2O3:Er films, indicating that the intensity of green emission can be enhanced by increasing the host bandgap. Our study also reveals that too high Al content has decreased the photoluminescence intensity, which should be related to the degraded crystallinity proved by X-ray rocking curve. These results suggest that (AlGa)2O3:Er film is a promising material for fabricating efficient green luminescent devices.
关键词： photoluminescence,bandgap,green emission,pulsed laser deposition,Er-doped (AlGa)2O3
更新于2025-09-23 15:21:01
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Effects of oxygen pressure on PLD-grown Be and Cd co-substituted ZnO alloy films for ultraviolet photodetectors
摘要： We report on the synthesis of Be and Cd co-substituted ZnO (BexCdyZn1?x?yO) quaternary alloy films on c-plane sapphire substrates by pulsed laser deposition. The results show that all deposited films exhibit single-phase wurtzite structure with a surface roughness less than 1.5 nm. By adjusting the O2 pressure during growth, the optical bandgap of the film is tuned from ~3.3 to ~3.52 eV. At 5 V bias, the BexCdyZn1-x-yO-based photodetector exhibits a remarkable photoresponse in the ultraviolet region with low dark current (~ 16.2 pA) and high detectivity (9.31· 1010 Jones). The rise and decay times of the photodetectors based on BexCdyZn1-x-yO (order of seconds) are clearly faster than those based on pure ZnO (order of minutes). Higher O2 pressure results in better crystalline quality of BexCdyZn1-x-yO film and thus lower dark current and faster photoresponse in the device due to the decrease of oxygen vacancy-related defects under oxygen-rich growth conditions. These results indicate that oxygen pressure plays an important role in the growth of high-quality BexCdyZn1-x-yO alloy films, which have great potential in fabricating high-performance ultraviolet photodetectors.
关键词： Bandgap engineering,BexCdyZn1-x-yO alloys,UV photodetectors,Pulsed laser deposition
更新于2025-09-23 15:21:01
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Optical properties of diamond-like carbon films prepared by pulsed laser deposition onto 3D surface substrate
摘要： It is difficult to grow uniform film by pulsed laser deposition because the spatial distribution of the laser-induced plume is a forward-directed cone-shape. A 3D-motional deposition setup was founded, and the correlative mathematical model of the film thickness on the 3D curved surface was deduced. Based on simulation and optimization, the diamond-like carbon (DLC) film was grown onto the large curved silicon substrate. According to the infrared transmittance spectra, the optical constants of the DLC film samples at different regions on the curved substrate were similar, indicating that the DLC film prepared onto the curved surface was homogeneous. Meanwhile, the deviation of average transmittance in the medium infrared band was below 2.3%, which could improve the imaging performance of the infrared detection. This research is useful to expand the application of the pulsed laser deposition in the optical field.
关键词： uniform transmittance,Raman spectroscopy,3D curved surface,Pulsed laser deposition,DLC film,infrared spectrum
更新于2025-09-23 15:21:01
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Hierarchical core-shell tungsten oxide/TiO2 nanowires as an effective photocatalyst
摘要： In this letter, tungsten oxide(WO3)/TiO2 core-shell nanowires were prepared by depositing a layer of TiO2 nanoparticles on the surface of WO3 nanowires via a pulse laser deposition method. These TiO2 nanoparticles are qusi-aligned wire-like structure on the surface of WO3 nanowires. The number of laser pulses during the deposition adjusts the TiO2 thickness. When used as photocatalyst, these core-shell nanowires have photocatalytic activity in the degradation of rhodamine B (RhB). The photo-induced electron-hole separation effect between WO3 and TiO2 contributes to the improvement of the photocatalystic activity. This makes these nanowire arrays having good potential in wastewater treatment.
关键词： Pulsed laser deposition,Nanocomposites,Semiconductors
更新于2025-09-23 15:21:01
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Laser-generated plasmas in length scales relevant for thin film growth and processing: simulation and experiment
摘要： In pulsed laser deposition, thin film growth is mediated by a laser-generated plasma, whose properties are critical for controlling the film microstructure. The advent of 2D materials has renewed the interest in how this ablation plasma can be used to manipulate the growth and processing of atomically thin systems. For such purpose, a quantitative understanding of the density, charge state, and kinetic energy of plasma constituents is needed at the location where they contribute to materials processes. Here, we study laser-induced plasmas over expansion distances of several centimeters from the ablation target, which is the relevant length scale for materials growth and modification. The study is enabled by a fast implementation of a laser ablation/plasma expansion model using an adaptive Cartesian mesh solver. Simulation outcomes for KrF excimer laser ablation of Cu are compared with Langmuir probe and optical emission spectroscopy measurements. Simulation predictions for the plasma-shielding threshold, the ionization state of species in the plasma, and the kinetic energy of ions, are in good correspondence with experimental data. For laser fluences of 1–4 J cm?2, the plume is dominated by Cu0, with small concentrations of Cu+ and electrons at the expansion front. Higher laser fluences (e.g. 7 J cm?2) lead to a Cu+ -rich plasma, with a fully ionized leading edge where Cu2+ is the dominant species. In both regimes, simulations indicate the presence of a low-density, high-temperature plasma expansion front with a high degree of ionization that may play a significant role in doping, annealing, and kinetically-driven phase transformations in 2D materials.
关键词： pulsed laser deposition,plasma diagnostics,plasma processing of 2D materials,laser plasma simulation,2D materials,laser ablation,plasma assisted processing
更新于2025-09-23 15:19:57
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Selective area laser-assisted doping of SiC thin films and blue light electroluminescence
摘要： Laser-assisted doping combined with annealing technique is used in selective areas to form a p–n junction on a SiC thin film grown by the pulsed laser deposition on a Si substrate at a temperature of 800 °C. This approach in an aluminum chloride solution and a phosphoric solution has resulted in p-SiC/n-Si and n-SiC/p-Si hetero-structures, respectively. Further, a functional in-plane p–n junction is realized side-by-side on the post-deposited SiC thin film. I–V characteristics by two probe technique showed the p–n diode characteristics. Blue light (400 nm) electroluminescence from the p–n junction on SiC thin film was observed in the forward biased condition. Further, an improvement in the I–V reverse characteristics was observed by illuminating the p–n SiC thin film with green/blue light.
关键词： pulsed laser deposition,laser assisted doping,SiC thin film,electroluminescence,silicon carbide,selective area doping
更新于2025-09-23 15:19:57