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Silicon and silicon-based materials are among the important modern materials with application in many fields of technology from electronics to energy materials. For some applications, for example the use of Si in Li-ion batteries, nanometer-sized dimensions are required. A cost-effective, environmentally sustainable, scalable, and versatile formation of functional Si films and materials is therefore of large interest. In this work, we report on the electrodeposition of amorphous silicon-based films onto planar and onto nanoporous copper substrates using different organic electrolytes. The morphology and composition of the Si-based coatings are dependent on the solvent used for electrodeposition. Acetonitrile, as a low viscosity solvent, leads to the faster formation of thicker, mostly metallic, and homogeneous electrodeposited Si films. Propylene carbonate, a higher-viscosity solvent generates thinner and more heterogeneous coatings. The Si electrodeposition presented in this work could be transferred onto other complex substrate morphologies, with potential applications in the fields of heterogeneous photocatalysis or energy storage. [ABSTRACT FROM AUTHOR]

This study presents a novel approach for achieving a high deposition rate of nanocrystalline hydrogenated silicon (nc-Si:H) thin films using dusty plasma, eliminating the need for hydrogen dilution. Contrary to conventional beliefs, the research demonstrates that crystalline seeds can nucleate directly from the plasma environment itself. The investigation explores the relationship between plasma parameters and the degree of crystallinity in the deposited films, along with the characterization of structural inhomogeneities throughout the film's thickness. Raman spectroscopy, X-ray diffraction, and Transmission Electron Microscopy (TEM) are utilized for detailed analysis. The results reveal intriguing variations in crystallinity along the film's thickness, with higher crystallinity observed near the surface compared to regions closer to the substrate interface. In-depth analysis of grain size variation reveals that the average crystallite size decreases near the surface and increases in the bulk volume of the material. Additionally, deposition parameters, specifically power and pressure, are found to influence grain sizes, with higher values promoting larger grain growth. Notably, the observation of conical growth in layers deposited from dusty plasma presents a promising avenue for achieving controlled and desirable microstructures. This study sheds light on the critical influence of deposition parameters on film properties and the potential of dusty plasma for achieving desirable microstructures in nc-Si:H thin films. The findings offer valuable insights for tailoring thin film properties in diverse technological applications. • Structural heterogeneities in nc-Si:H films with high deposition rates. • Use of argon-diluted silane PECVD for film synthesis. • Power and pressure are key parameters for introducing crystallinity. • Powders in plasma can enhance film quality. • Conical growth observed in dusty plasma-deposited films. [ABSTRACT FROM AUTHOR]

Silicon (Si) holds great promise as an anode material for high energy density lithium ion batteries owing to its theoretical capacity of up to 3579 mAh g−1. However, this potential comes at the expense of major challenges, because the solid electrolyte interphase (SEI) at Si anodes hardly provides long‐term protection due to severe volume expansion. Yet, when it comes to the SEI, the formation mechanism is not thoroughly understood. Here, thin AlF3 coatings are deposited on Si thin film to stabilize the SEI. To evaluate the SEI, systematic observation utilizing X‐ray photoelectron spectroscopy is performed at different (de‐)lithiation states, allowing stage‐by‐stage analysis to reveal the role, mechanism, and impact of AlF3 coating. Results show that the capacity retention is significantly improved for 90% after 100 cycles. The transformation of AlF3 into Li‐Al‐F compounds, as confirmed by ion chromatography, is responsible for an enhanced performance due to its high ionic conductivity. Moreover, the SEI of coated Si thin films is rich in inorganic species (i.e., LiF) which is beneficial to prevent electrons to pass through. This work will deepen the understanding of SEI on Si anodes with respect to the coating approach, suggesting future directions to improve coating layers on Si. [ABSTRACT FROM AUTHOR]

Silicon (Si) is one of the most promising anode candidates to further push the energy density of lithium ion batteries. However, its practical usage is still hindered by parasitic side reactions including electrolyte decomposition and continuous breakage and (re‐)formation of the solid electrolyte interphase (SEI), leading to consumption of active lithium. Pre‐lithiation is considered a highly appealing technique to compensate for active lithium losses. A critical parameter for a successful pre‐lithiation strategy by means of Li metal is to achieve lithiation of the active material/composite anode at the most uniform lateral and in‐depth distribution possible. Despite extensive exploration of various pre‐lithiation techniques, controlling the lithium amount precisely while keeping a homogeneous lithium distribution remains challenging. Here, the thermal evaporation of Li metal as a novel pre‐lithiation technique for pure Si anodes that allows both, that is, precise control of the degree of pre‐lithiation and a homogeneous Li deposition at the surface is reported. Li nucleation, mechanical cracking, and the ongoing phase changes are thoroughly evaluated. The terms dry‐state and wet‐state pre‐lithiation (without/with electrolyte) are revisited. Finally, a series of electrochemical methods are performed to allow a direct correlation of pre‐SEI formation with the electrochemical performance of pre‐lithiated Si. [ABSTRACT FROM AUTHOR]

In this study, the effect of operating conditions of the chemical vapor deposition process on the silicon growth rate in a trichlorosilane-hydrogen (TCS-H2) system was evaluated. The influence of five parameters, including wafer rotation, TCS fraction, pressure, temperature, and mass flow rate was investigated. Response surface methodology (RSM) based on three-dimensional CFD simulations were used to analyze the coupled effect of the process parameters. A second-order polynomial model was used to predict the response. Analysis of variance showed that the model is statistically significant and only 1.22% of the total variations are not explained by the regression model. According to the RSM results, the growth rate increases as a function of the TCS fraction, pressure, and temperature. Additionally, the coupled effect of the TCS fraction and pressure has a significant effect on the growth rate while the coupled effect of wafer rotation speed and mass flow rate had the lowest effect. Finally, four confirmation tests were executed for a random combination of factors to verify the accuracy of the regression model. The maximum deviation between the CFD and regression model values of the silicon growth rate was found to be 4.4 %. [ABSTRACT FROM AUTHOR]

Abstract The silicon thin films has been prepared on glass substrates at room temperature by ion beam sputtering technology using Si targssset (99.999% purity) and then are annealed at different temperatures ranging from 150 ℃ to 450 ℃ for 24 h under vacuum conditions. The effects of the annealing temperatures on the optical and structural properties of the Si thin films were studied. The results show that the refractive index, extinction coefficient and forbidden band width of the Si thin films show a downward trend with the increase of annealing temperature, resulting in a significant improvement in the absorption of the Si thin films in the visible and near-infrared region. The roughness has the same trend. However, the crystal structure and surface morphology of the Si thin films have not changed significantly after annealed. The research indicates that annealing treatment can effectively change the optical properties and structural properties of the Si thin films which has guiding significance for the selection of optimal heat treatment temperature for Si film modification. [ABSTRACT FROM AUTHOR]

Monochlorosilane/argon/hydrogen (SiHCl-Ar-H) mixture of different ratios was investigated from the point of PECVD application. RF capacitive plasma discharge of 40.68 MHz frequency was used. The process of deposition was studied by optical emission spectroscopy. The silicon thin films of different phase composition were obtained. The thin films were characterized by Raman-spectroscopy, atomic force microscopy, and secondary ion mass spectrometry. The exhaust gas mixture was analyzed by IR-spectroscopy in outlet of the reactor during PECVD process. The chemical mechanism for the deposition process was also proposed. [ABSTRACT FROM AUTHOR]

We propose a theoretical study for Si thin film thickness measurement that is based on incident low energy electron beam on the film and counting the transmitted/incident electron fraction. It estimates the thin film thickness distribution from an exponential relation which obtained from counting the fraction of transmitted/incident electron at different thicknesses. By using this obtained equation, it is possible to estimate unknown thickness of the Si thin film. In order to calculate the Si thin film thickness estimation, the energy of the incident electron beams is varied from 6 to 12 keV, while the thickness of the Si film is varied between 100 and 400 nm. The most significant feature of this method is that no expensive instruments are required. As anticipated, the proposed method shows that there is a relationship between film thickness and incident beam energy, which by using this relationship, we can find unknown film thickness in 1-D and 2-D conditions. Other advantages include wide measurement range, no calibration need and simple method. Additionally, an investigation by different beam energies helps to avoid artifact from this method. [ABSTRACT FROM AUTHOR]

Optimisation of femtosecond pulsed laser deposition parameters for the fabrication of silicon thin films is discussed. Substrate temperature, gas pressure and gas type are used to better understand the deposition process and optimise it for the fabrication of high-quality thin films designed for optical and optoelectronic applications. [ABSTRACT FROM AUTHOR]

Abstract: Microcrystalline silicon (μc-Si) thin films are widely used for silicon thin film solar cells, especially in the high performance tandem solar cells which comprise an amorphous silicon junction at the top and a μc-Si junction at the bottom. One of the major factors affecting the photovoltaic properties of μc-Si thin film solar cells of thin films is the quality of the μc-Si thin films. In this work, we investigated the effect of substrates on the crystallization characteristics and growth behaviors of μc-Si thin films grown by the plasma enhanced chemical vapor deposition method (PECVD), and found that substrates have a strong effect on the crystallization characteristics of μc-Si thin films. In addition, the growth rate of μc-Si thin films was also highly influenced by the substrates. Three types of substrates, quartz glass, single crystalline silicon and thermally oxidized single crystalline silicon, were used for growing μc-Si thin films from SiH4/H2 with a flow rate ratio 2:98 at different temperatures. Crystallization characteristics of these μc-Si thin films were studied by Raman scattering and X-ray diffraction techniques. [Copyright &y& Elsevier]

Abstract: Excimer laser annealing (ELA) is frequently employed to fabricate low-temperature polycrystalline silicon films on glass substrate. The grain size and crystallinity of polycrystalline silicon films are significantly affected by the resolidification behavior during ELA. A real-time in situ time-resolved optical measurement system is developed to record the rapid phase transformation process during ELA. The average solidification velocity of liquid-Si is calculated from these optical spectra using MATLAB and Excel softwares. Field emission scanning electron microscopy images reveal maximum grain size of poly-Si films with a diameter of 1μm, which is obtained in the complete melting regime of both frontside ELA and backside ELA. Recrystallization mechanisms of complete melting of Si thin films in frontside ELA and backside ELA are demonstrated. Resolidification scenarios of partial melting, near-complete melting and complete melting in frontside ELA and backside ELA are proposed. [Copyright &y& Elsevier]

Abstract: Microcrystalline silicon (μc-Si) thin films with high deposition rate have been fabricated by VHF hollow electrode enhanced glow plasma transportation (VHF–HEEPT). Plasma observation is performed in the discharge chamber and the deposition chamber, and plasma emission spectroscopy is performed in the deposition chamber. The results of the plasma emission spectroscopy indicate that VHF–HEEPT yields a plasma with lower electron temperature compared to RF–HEEPT and conventional capacitively-coupled VHF plasmas. The structural and electrical properties of μc-Si thin films are estimated as a function of the SiH4/H2 ratio. The thin films made by VHF–HEEPT are microcrystalline and have a high deposition rate (12.5nm/s), while thin films made by RF–HEEPT become amorphous for deposition rates over 10nm/s. [Copyright &y& Elsevier]

Systems composed of small Ag clusters adsorbed on the Si(111):H surface have been computationally studied by methods of density functional theory (DFT) and time-dependent DFT, to obtain information on properties of photoexcitations and electronic structure. The systems have been modeled as slabs with varying numbers of layers, and an increasing number of Ag atoms in the adsorbed clusters. Ab initio electronic structure, atomic conformations, excitation energies, electron binding energies, and electronic oscillator strengths are obtained using two different implementations of DFT, as provided by the Vienna Ab-initio Simulation Package and Gaussian03 computational packages. Time-independent results from extended and finite models establish a general trend regarding the energy band gaps increase with slab thickness and decrease with cluster sizes. Resulting trends in oscillator strength versus photon energies, from time-dependent calculations, establish a consistent picture with an increase of light absorption at the lower photon energies as the size of clusters and number of slab layers is increased. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [ABSTRACT FROM AUTHOR]

The influence of hydrogen in high-rate and low-temperature silicon epitaxy under mesoplasma conditions has been investigated from growth precursors and film structural evolution points of view. In situ small-angle X-ray scattering measurement has confirmed that silicon nanoclusters that are around 2 nm in size and having a loosely bound structure were formed as growth precursors, independent of the amount of hydrogen. Surface morphological analysis, on the other hand, has revealed that the deposition mechanism changes from surface diffusion to primarily step flow with hydrogen addition due potentially to the anisotropic etching of the silicon surface. Atomically smooth epitaxial films with Hall mobilities of up to 300 cm2 / (V ∙ s) were deposited accordingly at high partial pressures of hydrogen (> 220 mtorr), while polycrystalline films were produced at lower hydrogen amounts and still retaining relatively high electric properties. [ABSTRACT FROM AUTHOR]

Abstract: We investigated epitaxial silicon films deposited on differently oriented substrates by pulsed magnetron sputtering at temperatures of 500–550°C. Our scanning and transmission electron microscopic as well as electron backscattering investigations show that epitaxial films grow not only on (100)-oriented substrates, but also on (210)-, (411)- and (311)-oriented ones. A change to the (100) orientation is found for the growth on (111)- , (321)- and close to (110)-oriented substrates. For these orientations transmission electron microscopic investigations show stacking faults, microtwins and small amorphous inclusions in a region starting at the substrate–film interface up to thicknesses of 150–200nm. With increasing film thickness above 200nm the crystalline perfection of the epitaxial layers improves. [Copyright &y& Elsevier]

Abstract: Melting and crystallization scenario of amorphous silicon (a-Si) thin films have been investigated using in situ time-resolved optical reflection and transmission measurements. The explosive crystallization phenomenon is observed using a single-mode continuous wave He–Ne probe laser for thickness of 50 nm and 90 nm a-Si thin films upon 25 ns pulse duration of XeF excimer laser irradiation, respectively. The explosive crystallization phenomenon is easier to observe in the large thickness of a-Si thin films, a sample with pure a-Si microstructure and under longer pulse duration of excimer laser irradiation by time-resolved optical reflection and transmission measurements. [Copyright &y& Elsevier]

Liquid phase epitaxy (LPE) and, in particular, epitaxial lateral overgrowth (ELO) is an attractive method of thin film deposition, owing to the simplicity of its technology and a reduced growth temperature. In this paper, we present recent results of the ELO of silicon layers carried out by means of LPE using Ar as an ambient gas, without any addition of hydrogen, potentially explosive gas, which makes this deposition technique a very safe process. The aim of the this work focused on the silicon ELO growth on partially masked substrates was to determine optimal conditions of growth resulting in ELO layers of the maximum aspect ratio and minimum defect density. Data presented herein clearly show that the epitaxial layers characterized by the maximum value of the aspect ratio can be obtained by application of the 0.25 °C/min cooling rate. Noteworthy is the fact that in the same conditions the defect density achieves the minimum value of 1.07x104 cm-2, which is the amount smaller by the factor of 10 than the defect density of Si substrates used (1.7x105 cm-2). It confirms the ELO technique as a promising tool for the fabrication of low-defect density silicon layers of good morphology. [ABSTRACT FROM AUTHOR]

The properties of silicon films prepared by plasma-enhanced chemical vapor deposition (PECVD) at low temperatures (<400 °C) are controlled by the physical and chemical processes that occur in the gas phase, at the top-most film surface, within the first several monolayers of the surface, and even well into the film bulk. Recent advances in understanding these processes have led to several new developments in silicon PECVD. The advances include: (i) novel concepts for depositing high-rate, device-quality silicon films, and (ii) deposition phase diagrams for optimizing silicon films for high-stability, high-performance devices. In situ and real time probes of the gas phase, the film surface, and its sub-surface have played key roles in these advances. [Copyright &y& Elsevier]

Material failure is the main obstacle in fulfilling the potential of electrodes in lithium batteries. To date, different failure phenomena observed experimentally in various structures have become challenging to model in numerical simulations. Moreover, their mechanisms are not well understood. To fill the gap, here we develop a coupled chemo-mechanical model based on peridynamics, a particle method that is suitable for simulating spontaneous crack growth, to solve the fracture problems in silicon thin films due to lithiation/delithiation. The model solves mechanical and lithium diffusion problems, respectively, and uses a coupling technique to deal with the interaction between them. The numerical examples of different types of Si films show the advantage of the model in this category and well reproduce the fracture patterns observed in the experiments, demonstrating that it is a promising tool in simulating material failure in electrodes. [ABSTRACT FROM AUTHOR]

We have investigated the mechanism of silicon thin film deposition by ArF excimer laser irradiation of silane gas diluted with argon. The Si films were deposited by a focused laser beam irradiating in parallel to silicon and silicon dioxide substrates at a gas flow rate of 20 SCCM, total pressure of 60 Torr and repetition rate of 15 Hz. At laser energy fluences higher than 160 mJ/cm the deposition rate was almost independent of the incident laser energy, while at a lower energy the deposition rate depended strongly on the laser energy. A 3/2 power law was found for absorption measurements carried out at the same pressure under flow conditions and for several repetition rates at average laser power above 300 mW, regardless of the laser repetition rate. This kind of behavior is typical of a multiphoton absorption process involving saturation effects caused by focusing of the laser beam. Below 300 mW the power dependence indicated a two-photon absorption process. From the observed photochemical yield we found the value 5.7×10 cm s molec for the two-photon absorption cross section. A Gaussian-shaped transverse thickness distribution of the deposited layer was obtained with a maximum value corresponding to the center of the laser beam spatial profile. This distribution depended on the deposition parameters, and was attributed to the diffusion process of silane decomposition products in the gas phase in the substrate. Analysis of the adsorption features of the process showed that the major product adsorbed on the substrate surface is silicon. An Arrhenius plot of the deposition rate versus the substrate temperature exhibits two regimes, each associated with a different activation energy. Between 340°C and 460°C the activation energy is 0.25-0.3 e. V, while between 500°C and 560°C it is 1.1 e. V. The activation energy in the higher temperature regime is similar to that found for thermal nonlaser assisted chemical vapor deposition. However, in the lower temperature regime the deposition process is mainly laser induced, and the value of the activation energy is due to the process of adsorption of the gas species on the substrate. [ABSTRACT FROM AUTHOR]

• A tunable procedure of heat rectification is proposed, based on the influence of applied stress on heat conductivity. • The effects of an inhomogeneous distribution of a tensile applied stress are studied in silicon films and graphene ribbons. • The rectification coefficient is obtained as a function of the strain, the length of the system, and the external heat flux. • For these systems we find a rectification coefficient tunable between 1 and 1.3, for the considered applied stresses. We explore an externally tunable way of producing heat rectification, by means of application of an inhomogeneous distribution of a tensile mechanical stress on heat conducting silicon thin films and graphene ribbons. The resulting strain modifies the thermal conductivity of the material, which, in this way, may be partially tuned from the outside. We calculate the rectification coefficient R as function of the applied strain, of the length of the system, and of the external heat flux. The rectification coefficient of a single device results in R ≃ 1.3 for both systems under consideration. Such a value can be enhanced by connecting in series several devices. [ABSTRACT FROM AUTHOR]

The present work reports for the first time in the open literature the formation of 4-μm thick film with alternate layers of nickel and silicon by the magnetron sputtering method. Of the two kinds of samples prepared, the first is composed of alternate nanometer thick (<15 nm) Ni rich and Si rich layers. Employing a novel conceptual design to further improve the film's mechanical properties, a second sample is produced in which additional Ni rich layers (60 nm thick) are deposited over each micron thick of Ni/Si bilayers. The morphological, structural, mechanical and electrochemical test results show that silicon in the coating increases the capacity of the electrode and Ni atoms that are electrochemically inactive versus Li create conductive pathways throughout the film section. In the film design, the high diffusion rate of Ni in Si leads to the formation of amorphous solid solution which improves the reversibility of the lithiation/delithiation reactions. Additionally, the presence of 60 nm thick Ni rich layers works as 'skelton' to maintain the integrity of the coating upon cycling, and hence increases the electro-mechanical resistance of the negative electrode. Due to this new design the stress-strain distribution in the coating is improved such that sample 2 delivers 881 mA h g−1 discharge capacity even at high current loads of 500 mA g−1 (with 80% 1st cycle coulombic efficiency) after 300 cycles. This outstanding performance of the metallic framed layered film is believed to hold a great prospect for designing electrodes of the next generation high energy density batteries. Image 1 • Firstly, 4 μm thick alternately bilayered NiSi film is fabricated (Sample 1). • Innovatively, Ni frame is induced in the bilayered electrode design (Sample 2). • Ni rich layers increase mechanical and physical properties of the electrode. • Alternately bilayered design improves the capacity, cycleability and rate performance. • Sample 2 delivers 877 mA h/g after 300 cycles under the load of 500 mA/g. [ABSTRACT FROM AUTHOR]

In photovoltaics (PV) and microelectronics, there is an ongoing need for fabrication of silicon thin films with excellent material properties and with minimum production cost at the same time. To overcome fabrication gaps we present reached results for depositing silicon thin films by crucible-free electron beam physical vapor deposition (EB-PVD) and for plasma pretreatment of the substrates. The crucible-free EB-PVD process could be improved regarding critical aspects, e.g. occurrence of ingot cracks during heating up of monocrystalline Si evaporation material and spill out of the Si melt on the melting pool edges. Deposition rates above 500 nm/s, corresponding to 30 μm/min, have been reached. Relating heat fluxes will be presented and discussed. By using a double ingot arrangement and superposing vapor from multiple sources the relative deviation of layer thickness could be reduced to < ±5% on a substrate width of 200 mm. Image 1 • Si was evaporated from 8″ high pure Si boule without using a crucible. • Si vapor was deposited on plasma cleaned Si wafers. • Deposition rates of more than 500 nm/s have been achieved. • Layer thickness deviation was reduced to < ±5% on 200 mm width. [ABSTRACT FROM AUTHOR]

The authors review selected topics in the development of hydrogenated amorphous silicon (a‐Si:H), from its emergence some 50 years ago to its present status as a mature thin‐film semiconductor, with market successes including flat‐panel displays, solar modules, and x‐ray scanners. By altering process gas mixtures and deposition conditions, films with a range of atomic, structural, and amorphous/crystalline phase compositions may be deposited, offering tunable bandgap, refractive index, and light‐scattering properties. Films thus "functionalized" have greatly increased scope and utility. Three emerging applications are reported, and more extensive sections on two topics of current importance are presented: 1) Multi‐junction thin film silicon solar cells for water splitting applications; and 2) thin‐film silicon solar cells on flexible substrates. [ABSTRACT FROM AUTHOR]