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Vibrational Energy Redistribution between CH Stretching Modes in Alkyl Chain Monolayers Revealed by Time-Resolved Two-Color Pump–Probe Sum Frequency Spectroscopy
摘要： The vibrational dynamics of the various CH stretching modes in a fatty acid Langmuir?Blodgett ?lm was studied using a resonant narrowband infrared (IR) laser pulse for pumping and a broadband femtosecond IR visible pulse pair for detection in a sum frequency spectroscopy setup. The resulting two-dimensional spectra indicate that pumping either the antisymmetric methyl or methylene stretch results in the transfer of energy to the other modes on a time scale faster than 2 ps. This rapid process is followed by energy redistribution to other modes, presumably the bending and internal rotational modes, with a time constant of approximately 85 ps. The formation of gauche defects is not observed within the ?rst 250 ps. The whole spectrum recovers on a time scale of several nanoseconds, indicating dissipation of the excitation energy into the substrate.
关键词： CH stretching modes,energy redistribution,vibrational dynamics,sum frequency spectroscopy,Langmuir?Blodgett ?lm
更新于2025-09-12 10:27:22
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Substrate Temperature Dependence of the Properties of Single-layer MoS2 Film deposited by Using Pulsed Laser Deposition
摘要： Single-layer MoS2 ?lms were deposited on sapphire substrates by using pulsed laser deposition. The substrate temperature dependence of the structural, optical and photoluminescence properties of single-layer MoS2 ?lms was investigated. An increased substrate temperature improved the surface morphology and the crystal quality of the MoS2 ?lms. Moreover, the absorption and the photoluminescence properties of the MoS2 ?lms were enhanced. In addition, the mechanism underlying the e?ect of substrate temperature on the properties of single-layer MoS2 ?lms is discussed.
关键词： Optical properties,Substrate temperature,Crystal quality,Single-layer MoS2 ?lm,Photoluminescence properties
更新于2025-09-12 10:27:22
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Degradation of Mg-doped zinc oxide buffer layers in thin film CdTe solar cells
摘要： Cadmium Sulphide is the conventional n-type bu?er layer used in thin ?lm Cadmium Telluride solar cells. It is well known that Cadmium Sulphide causes optical losses and sulphur di?uses into the absorber during high temperature activation. Sputter-deposited Mg-doped ZnO (MZO) has been shown to be an attractive bu?er layer for Cadmium Telluride solar cells due to its transparency and tuneable band gap. It is also stable to high temperature processing and avoids di?usion of elements into the cadmium telluride absorber during the cadmium chloride activation treatment. However, degradation is observed in solar cells incorporating MZO bu?er layers. Analysis of the MZO ?lm surface potential has revealed signi?cant ?uctuations in the thin ?lm work function once the layer is exposed to the atmosphere following deposition. These ?uctuations are attributed to the high reactivity to water vapour of the MgO contained in the MZO ?lms. This has been analysed using X-ray Photoelectron Spectroscopy to determine corresponding changes in the surface chemistry. The Zinc Oxide component is relatively stable, but the analysis shows that MgO forms a Mg(OH)2 layer on the MZO surface which forms a secondary barrier at the MZO/CdTe interface and/or at the interface between MZO and the Fluorine-doped SnO2. This a?ects the Fill Factor and as a consequence it degrades the conversion e?ciency.
关键词： Surface contamination,Degradation,Thin ?lm solar cells,Cadmium telluride,Magnesium-doped zinc oxide,Hydroxide,Bu?er
更新于2025-09-11 14:15:04
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Titanium Dioxide Hole-Blocking Layer in Ultra-Thin-Film Crystalline Silicon Solar Cells
摘要： One of the remaining obstacles to achieving the theoretical ef?ciency limit of crystalline silicon (c-Si) solar cells is high interface recombination loss for minority carriers at the Ohmic contacts. The contact recombination loss of the ultra-thin-?lm c-Si solar cells is more severe than that of the state-of-art thick cells due to the smaller volume and higher minority carrier concentration. This paper presents a design of an electron passing (Ohmic) contact for n-type Si that is hole-blocking with signi?cantly reduced hole recombination. By depositing a thin titanium dioxide (TiO2) layer, we form a metal-insulator-semiconductor (MIS) contact for a 2 μm-thick Si cell to achieve an open circuit voltage (Voc) of 645 mV, which is 10 mV higher than that of an ultra-thin cell with a traditional metal contact. This TiO2 MIS contact constitutes a step towards high-ef?ciency ultra-thin-?lm c-Si solar cells.
关键词： titanium dioxide,Silicon photovoltaic,ultra-thin-?lm,selective contact
更新于2025-09-11 14:15:04
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Performance Investigation of Mott-Insulator LaVO3 as a Photovoltaic Absorber Material
摘要： Mott insulators have recently been identi?ed as potential solar energy conversion material due to their favorable parameters. In this paper, we have investigated the cell performance by exploring the photovoltaic properties of Mott Insulator LaVO3 (LVO). The LVO thin ?lms were grown by the sol–gel technique followed by a sintering pathway under various processing conditions. We investigated the in?uence of processing parameters on the structural, optical and electrical properties of the ?lms through different characterization techniques. A correlation between the material parameters with the device performance has been established to ensure LVO perovskite for photovoltaic applications. This analysis will aid researchers to realize Mott insulators as light absorber material.
关键词： photovoltaic material,Mott insulator,Thin ?lm solar cell,oxide perovskites
更新于2025-09-11 14:15:04
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Dependence of Photovoltaic Properties of Spray-Pyrolyzed F-Doped SnO2 Thin Film on Spray Solution Preparation Method
摘要： Spray pyrolysis deposition of SnCl2.2H2O- and NH4F-containing solution is an appropriate method for deposition of ?uorine-doped tin oxide (FTO), which has extensive applications in photovoltaic devices. According to a literature review, several spray preparation methods have been studied. These methods lead to both precipitated and unprecipitated spray solutions. Precipitated and unprecipitated solutions were used for deposition of FTO thin ?lms. FTO obtained from unprecipitated solution yielded the lowest sheet resistance and resistivity, which was due to its highest electron concentration (ne). However, precipitation had no in?uence on electron mobility. The x-ray diffraction patterns of precipitates showed the presence of Sn- and F-containing compounds, which implied partial depletion of F and Sn from solutions. As a result, a lower amount of F(cid:2) ions was incorporated into FTO, which led to lower ne. In addition, partial depletion of Sn led to slightly smaller FTO thickness. Finally, FTO thin ?lm deposited from unprecipitated solution gave the highest ?gure of merit. This means that precipitation in the precursor solution has deleterious effects on electrical and optical properties.
关键词： Fluorine-doped tin oxide,spray pyrolysis deposition,transparent conducting oxide,thin ?lm
更新于2025-09-11 14:15:04
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Coupled FPEDs using springs for broadband energy harvesting
摘要： In this paper, ?exible piezoelectric devices (FPEDs) connected by springs are discussed with the aim of improving operational bandwidth of an energy harvesting system. A theoretical method, based on beam theory, electromechanical coupling and the transfer matrix method, is presented for calculating displacement and voltage responses. Validity of the presented method is discussed by comparison with experimental results, which are obtained from coupled FPEDs excited by a shaker. The e?ects on system behaviour of attaching springs is discussed based on both the presented method and experimental results.
关键词： ?exible piezoelectric device,forced vibration,theoretical analysis method,engine vibration,Piezoelectric ?lm,renewable energy
更新于2025-09-11 14:15:04
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Tribological and adhesive properties of the tungsten-doped diamond-like carbon film prepared by double lasers deposition
摘要： The nanosecond and femtosecond lasers were used to ablate the graphite and tungsten targets simultaneously, and the tungsten-doped DLC ?lm with the di?erent tungsten concentration on the strip substrate was prepared. The content of the tungsten in the doped DLC ?lm varied continuously in the horizontal direction and was changeless in the vertical direction. The tungsten content in the doped DLC ?lm increased gradually when it was close to the center axis of the tungsten plasma generated by femtosecond laser. Surface roughness and the critical load of the tungsten-doped DLC ?lm increased with the increasing of tungsten content. On the other hand, the friction coe?cient of the tungsten-doped DLC ?lm decreased ?rstly and then increased when the tungsten content increased gradually. The minimal friction coe?cient was 0.086 when the tungsten content was about 8.07 at.%. The deposition method designed in this experiment also could be used for other doped ?lms in the ?eld of the function ?lms.
关键词： Continuously variated content,Critical load,Tungsten-doped DLC ?lm,Tribological property
更新于2025-09-11 14:15:04
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Correlation between composition, microstructure, and emission properties in Nd-doped Si-rich Si oxynitride films: investigation into the nature of the sensitizer
摘要： Rare earth (RE) ions doped in Si-based materials, compatible with Si technology, are promising compounds with regards to optical communication and energy conversion. In this article, we show the emission properties of Nd-doped Si-rich Si oxynitride (Nd-SRSON) ?lms, and their dependence on the dangling bond density and the nature of the sensitizer. These ?lms were prepared by reactive magnetron sputtering and post-annealing. The ?lm composition, microstructure, and emission properties were investigated as a function of deposition parameters and annealing temperatures. Both Fourier transform infrared (FTIR) and ellipsometry spectroscopy measurements have con?rmed that the sample composition (Si/N ratio) can be carefully tuned by varying the ratio of reactive nitrogen to argon in the sputtering plasma. Moreover, FTIR and x-ray photoelectron spectroscopy measurements demonstrate the existence of both nitrogen and oxygen dangling bonds (N? and O?) in as-deposited samples. These dangling bonds were passivated during annealing. Under non-resonant excitation at 488 nm, the ?lms exhibit a signi?cant photoluminescence (PL) signal from Nd3+ ions demonstrating the occurrence of an effective sensitization of Nd3+ ions in the host matrix. Both PL excitation and ellipsometry results (the energy band gap from new amorphous model) exclude the sensitization by an exciton with energy over the band gap, whereas the presence of Si agglomerates, at the atomic scale, have been identi?ed as effective sensitizers towards Nd3+ ions. This work not only provides knowledge to optimize Si-based materials for favorable emission properties, but also, presents a universal methodology to investigate the nature of sensitizers for RE emitters. This allows one to ?nd correlations between composition, microstructure, and emission properties.
关键词： photoluminescence,rare earth,neodymium,non-resonant excitation,thin ?lm,Si-rich Si oxynitride
更新于2025-09-10 09:29:36
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Observation of heterostructure epitaxy of Pt-doped Ni-monosilicide on Si(001)
摘要： The objective of this study was to determine detailed microstructure of a Ni1–xPtxSi ?lm formed via a melting/quenching process using high temperature laser annealing on a Si(001) substrate. The orthorhombic Ni1–xPtxSi ?lm was found to be able to epitaxially grow with a crystallographic relationship of Ni1–xPtxSi[010]//Si[110], Ni1–xPtxSi(400)//Si(331), and Ni1–xPtxSi (104)//Si(004). Volume expansion of the Ni1–xPtxSi ?lm due to Pt incorporation was mainly accommodated by an increase in only one direction nearly parallel to the ?lm surface (lattice parameter a). This was explained by the minimum coherent strain at the Ni1–xPtxSi (104)/Si(004) interface with an epitaxial growth tendency. Atomic-scale scanning transmission electron microscopy analyses revealed that the interface of Ni1–xPtxSi/Si had a repetitive atomic-step feature with energetically favorable Ni1–xPtxSi(004) terraces and (400) structural ledges that could increase the coherent area. By generating an array of mis?t dislocations with an extra half plane of Ni1–xPtxSi(020), the elastic strain was further relieved.
关键词： Ni-silicide,Epitaxy,Thin ?lm,Structural ledges,Interface,Microstructure
更新于2025-09-10 09:29:36