Silicon Layer Research Articles

Optical absorption in roughened silicon photovoltaic module

Photovoltaic current electric generation is directly related to the sunlight absorption in the active layers. The active layer material type and the optical losses remain the principal parameters, which have a greater effect on the amount of this absorption. This study focuses on improving the absorption in the silicon active layer of a silicon photovoltaic module by roughening the rear surface of the silicon layer. According to the Generalized Transfer Matrix Method, we derive the transmission from the incoherent multilayered module structure with a rough surface. We follow the optical model developed by Krauter and Hanitsch to derive the transmission into the silicon layer. Then the absorption is deduced from the difference between the transmission from the module and the transmission into the silicon. The effect of the incidence angles on the absorption is considered for different polarizations of light. The results of this study show a significant enhancement in the absorption in comparison to the absorption of the module with a polished rear surface. The short circuit current generated by the module with a rough rear surface silicon layer obtained is greater than that of the module with a polished rear surface.

A Floatable and Highly Water-Durable TiO2-Coated Net for Photocatalytic Antibacterial Water Treatment in Developing Countries

A TiO2-coated net with photocatalytic antibacterial properties that purifies water for practical use in developing countries was fabricated. The TiO2 particles were modified with a silane coupling agent, aminopropyltriethoxysilane or hexadecyltrimethoxysilane, to improve particle dispersibility. The net comprises three layers: a TiO2-silicone photocatalyst layer, a silicone layer to protect the net substrate from the oxidizing power of TiO2, and a polypropylene net substrate. The net is flexible and light enough to float on the surface of water. By modifying the surface of the TiO2 particles, we succeeded in preparing a highly water-durable photocatalyst coating that can be maintained for 49 days of outdoor exposure. The inactivation of E. coli by the TiO2-coated net under 1.0 mW/cm2 of UV irradiation was confirmed. Furthermore, the antibacterial properties were investigated under natural sunlight. The number of E. coli decreased from 320,000 to 10 CFU/mL under natural sunlight in just 2 h. The results showed that the photocatalyst-coated polypropylene net effectively eliminates E. coli from water, reducing the risk of infectious diseases.

Effect of 2-D nanomaterials on sensitivity of plasmonic biosensor for efficient urine glucose detection

This paper presents a multi-layered Kretschmann configuration-based Surface Plasmon Resonance (SPR) biosensor for the detection of urine glucose. The modelling, simulation, and analysis have been done by using Silver (Ag) and Gold (Au) layer on the low refractive index prism BK-7 separately, which created two structures: structure-I (BK7/Ag/Bio-sample) and structure-II (BK7/Au/Bio-sample). Urine samples from a non-diabetic person (0–15 mg/dL) and a diabetic person (.625 gm/dL, 1.25 gm/dL, 2.5 gm/dL, 5 gm/dL, and 10 gm/dL) with the corresponding refractive indices of 1.335, 1.336, 1.337, 1.338, 1.341, and 1.347, respectively, have been used as a bio-sample that has been put on the top layer of the sensor. An investigation was conducted to improve the performance parameters of the proposed plasmonic biosensor by layering different 2-D nanomaterials (graphene, BP) and TMDC materials (MoS2, MoSe2, WS2, and WSe2) over the silicon (Si) layer in both structures at a visible wavelength of 633 nm, using Transfer Matrix Method (TMM). With layer thickness optimization, Structure-I (BK7/Ag (56 nm/Si (3 nm)/WS2 (.8 nm)/Bio-sample) shows a sensitivity of 200 °/RIU which is enhanced up to 1.7 times that of the conventional biosensor (BK7/Ag/Bio-sample) and 1.3 times that of the BK7/Ag (56 nm)/Si (3 nm)/Bio-sample based biosensor. Whereas in Structure-II (BK7/Au (50 nm)/Si (3 nm)/BP (.53 nm)/Bio-sample) with optimised layer thickness, we obtained a sensitivity of 273.4°/RIU, which is enhanced up to 2.2 times that of the conventional biosensor (BK7/Au/Bio-sample) and 1.3 times that of the BK7/Au (50 nm)/Si (3 nm)/Bio-sample. Other performance parameters such as detection accuracy for Structure-I and Structure-II are .5617 degree−1 and .134 degree−1 respectively. The Figure of merit for Structure-I and Structure-II are 112.35/RIU and 36.89/RIU respectively. Therefore, we expect Structure-I (BK7/Ag (56 nm/Si (3 nm)/WS2 (.8 nm)/Bio-sample) and Structure-II (BK7/Au (50 nm)/Si (3 nm)/BP (.53 nm)/Bio-sample) have the potential to detect the glucose concentration with quick response and high sensitivity in terms of the resonance angle shift in SPR curves.

External Gettering of Metallic Impurities by Black Silicon Layer

Black silicon (b‐Si) has many attractive properties and is currently being adopted in various fields of semiconductor technology. It is shown here that b‐Si during thermal activation may serve as an external gettering layer to remove metallic impurities and associated defects from bulk Si. The gettering efficiency by b‐Si is estimated according to the results of studying the resistivity, defect density, interstitial iron concentration, and effective minority carrier lifetime on gettered test and ungettered reference Si samples. It is shown that in the thermal oxidation process, the b‐Si layer serves as an effective drain for excess iron atoms and other fast‐diffusing impurities, thereby significantly reducing the density of oxidation‐induced stacking faults in Si. In addition, the resistivity of the substrates decreases, and the bulk carrier lifetime increases significantly. Finally, gettering by b‐Si is introduced into the solar cells fabrication process and its effect on solar cell current–voltage characteristics is investigated. It has been shown that all electronic parameters of the solar cells are improved. The conversion efficiency of ungettered solar cells is 16.8%, and for gettered solar cells, depending on the oxidation temperature, it increases by 1.36–1.96%.

1-Dimensional silicon photonic crystal pressure sensor for the measurement of low pressure

In this article we proposed a one-dimensional (1D) silicon photonic-crystal (PC) as a highly sensitive pressure sensor to measure the applied hydrostatic pressure. A 1D flexible silicon layer is formed at the top of the proposed structure. The proposed sensor is designed to measure the low pressure in the range of 10kpa to 20kpa. An FEM tool Comsol Multiphysics is used to design, simulate and analyze the structure. A central cavity is created to support the resonant mode and shift in the resonant mode is observed with the varying boundary load. With the variation in the applied pressure from 10kpa to 20kpa, shift in the resonant mode towards higher wavelength region was observed. The defect cavity length and number of layers were tuned to get optimized results. The novelty of this work includes, use of silicon material to sense the applied pressure, design and its simulation to obtain electric field distribution in the multi-layer structure and its analysis for sensing the applied boundary load using an FEM tool. Simulation results shows that the proposed sensor has a very high sensitivity of 350 nm/GPa and Q-factor of 40,104 with the transmission of 99.99 %.

Asymmetry in particle transport in slightly non-homogeneously doped silicon layers in low injection regime and quasi-neutrality condition

In this work a 1D slightly doped n-type Silicon layer is considered. Irreversible thermodynamics transport equations are used to obtain the spatial particle distribution in isothermal stationary state. The excess particle transport is studied in low injection regime and quasineutrality condition. The material is subjected to Dirichlet-Neumann (N-D) conditions at the boundaries. We wonder if an asymmetry of the particle flux exists when the boundary conditions are inverted. We find that the asymmetry does exist and a rectification factor may reach the value 0.35. We conclude that particle flux rectification seems to be featuring the particle transport in slightly non-homogeneously doped semiconductor when the excess hole concentration is smaller than the equilibrium hole concentration

Combined polysilicon and silicon gratings for dual-wavelength-band waveguide grating couplers.

We proposed a novel, to the best of our knowledge, design for a dual-wavelength-band waveguide grating coupler. The proposed structure works in both the C band and O band. The proposed device is optimized from an initial design of two independent gratings formed on the silicon and polysilicon overlay layers, respectively. We designed the up layer (polysilicon) for the C band and the down layer (silicon) for the O band as the initial optimization seed. After numerical optimization of this structure using a genetic algorithm, the grating coupler has a coupling efficiency of -3.86 dB at the C band and -4.46 dB at the O band. We validate the approach in a commercial foundry using 193-nm photolithography in a multi-project wafer, and the experimental result has coupling efficiencies of -4.37 dB in the C band and -5.8 dB in the O band.

Design and numerical simulation of a sensitive plasmonic-based nanosensor utilizing MoS2 monolayer and graphene

In this paper, a Kretschmann structure with a graphene-MoS2 hybrid layer has been used to design a sensitive biosensor for the detection of biomolecules. Here, by using a silicon layer, the sensitivity of the nanosensor is increased. Such a result is obtained from strong light-matter interaction between graphene and semiconductor layer. As a result, by changing the active metal and adding an additional silicon layer at a wavelength of 670 nm to access higher sensitivity and lower FWHM for the effective biosensor eventually we reach a sensitivity equal to 192°/RIU. The designed structure is investigated by numerical analysis and using the FDTD method, we numerically extract the optical characteristics of the surface plasmon polariton sensor. The detection range for the proposed structure is obtained with a refractive index of 0.005. Also, the basic parameters of the sensor to achieve the best conditions have been calculated and evaluated. In addition, the overall size of the sensor is 1112 nm × 2000 nm.

Arrays of Quasi-One-Dimensional GaAs Nanocrystals Grown on the Oxidized Surface of the Si/GaAs(001) Heterostructure: Effect of the Si Epitaxial Layer on the Array Structure

Structures with arrays of planar and tilted quasi-one-dimensional GaAs nanocrystals have been grown on GaAs(001) substrates. An epitaxial silicon layer oxidized in air was used as a passivation coating. The amount of silicon deposited varied from structure to structure and was equivalent to 1, 2, 4, and 6 atomic layers. It has been found that in the case of a passivation layer based on silicon with a thickness of 1 atomic layer, an array of planar nanocrystals is formed, and in other cases, inclined quasi-one-dimensional nanocrystals. Nanocrystals are surrounded by crystallites, the shape, size, orientation, and distribution density of which change with the amount of silicon. The lowest density of crystallites was achieved with a silicon layer 6 atomic layers thick. Keywords: molecular-beam epitaxial, GaAs, Si, quasi-one-dimensional nanocrystals, vapour-liquid-crystal.

Gravity-driven sliding and associated deformations along complex submarine slopes: a laboratory modeling approach based on constraints observed offshore Martinique Island (Lesser Antilles)

Submarine gravity-driven sliding of sediments are common processes in the vicinity of volcanic islands. In the Lesser Antilles arc, the Montagne Pelée volcano on Martinique Island underwent several flank-collapse events during its long-term eruptive history, resulting in debris avalanches. When the debris avalanches entered into the seawater, they were emplaced over the unstable slope of the volcano, triggering a seafloor sediment failure and massive landslides downslope. Using a laboratory modeling approach, we simulated the gravity-driven sliding of a sand layer lying above a silicone layer. The experiments were performed using various slope geometries (slope lengths and number of slope breaks separating the slopes with different angles), under both dry and aqueous conditions, and while varying the amount of additional sand inputs upslope. The resulting deformations were characterized in each experiment in order to compare the obtained structures with those shown by the seismic lines offshore to the west of Martinique Island. During all the experiments, a compressional frontal deformation zone made of several reverse faults formed downslope, often near the slope breaks. Downslope, a portion of the sediments was mostly displaced and poorly deformed in a damping zone, while an extensional deformation zone formed upslope. The displacements of the surficial markers were measured through time to characterize the sliding dynamics. Our study demonstrates that the slope geometry and additional sand inputs primarily favor and increase the sliding deformation, whereas the hydrostatic pressure plays a secondary catalytic role over time. These results provide new constraints on the driving factors and their consequences on gravity-driven sliding in terms of deformations and runout distance over time. This may have a significant impact on the associated hazard assessment related to offshore infrastructures, in a region known for its seismic and volcanic risks.

Массивы квазиодномерных нанокристаллов GaAs, выращенные на окисленной поверхности гетероструктуры Si/GaAs(001): влияние толщины эпитаксиального слоя Si на строение массива

Structures with arrays of planar and tilted quasi-one-dimensional GaAs nanocrystals have been grown on GaAs(001) substrates. An epitaxial silicon layer oxidized in air was used as a passivation coating. The amount of silicon deposited varied from structure to structure and was equivalent to 1, 2, 4, and 6 atomic layers. It has been found that in the case of a passivation layer based on silicon with a thickness of 1 atomic layer, an array of planar nanocrystals is formed, and in other cases, inclined quasi-one-dimensional nanocrystals. Nanocrystals are surrounded by crystallites, the shape, size, orientation, and distribution density of which change with the amount of silicon. The lowest density of crystallites was achieved with a silicon layer 6 atomic layers thick.

Liquid Metal-Based Flexible Sensor for Perception of Force Magnitude, Location, and Contacting Orientation

Flexible sensors have the advantage to enable intelligent systems to interact with the environment with high safety and versatility. Liquid metal is a useful element for flexible sensors due to its stretchable, reconfigurable, and healing characteristics. However, it is difficult to decode the stimuli position using uniform liquid metal because of its homogeneity and fluidity. Current sensing systems for the perception of force magnitude and contact location mostly rely on sensing arrays and massive crossover electrodes. In this paper, we proposed a novel method for simultaneously sensing the force magnitude and contact location without crossover electrodes. In the new design, we encapsulate the liquid metal electrodes with varying cross-sections in two silicon layers that function as protective skin and govern the geometry of liquid metals. When a force is applied to the flexible sensor, the change of resistance is dependent on both location and stimuli magnitude. Three liquid metal channels with different gradient resistance are embedded in the prototypes with parallel distributions. Combining the signals collected from the three channels, we can simultaneously measure the force magnitude, stimuli location, and contacting orientation. The overall force resolution is sub-Newton in the range from 0.5 N to 20 N. The position can also be determined with a 100% success rate for the segmented sensor and a position resolution of 2 mm for the continuous sensor. The error for contact orientation measurement is 4.58° when the orientation ranges from 45° to 135°. The proposed multifunctional sensing device with high accuracy and wide sensing range has significant potential for developing interactive interfaces for human-machine interactions and industrial applications.

Управление морфологией и поверхностной энергией электрода для создания этанольных топливных элементов на основе пористого кремния, сформированного Pd-стимулированным травлением

The evolution of macro- and mesoporous layers of porous silicon formed by Pd-assisted etching with different duration of formation and temperature of the etching solution from 25 to 75 °С, which have the property of ethanol electrooxidation, has been studied. High values of the dissolution rate of porous silicon at a temperature of 75 °С are shown, leading to a significant loss of thickness and specific surface area of the macro- and mesoporous layer, respectively. The obtained porous layers with different surface energy and surface area, show different rates of ethanol dehydrogenation and the number of dehydrogenated ethanol molecules, which allows you to control the activity of the electrode material for ethanol fuel cells.

Changes in the electronic structure of the Si surface as a result of ion implantation

The composition, structure, and physicochemical properties of the surface and near-surface layers of silicon doped with low-energy (E0<5 keV) Ba+ and O2+ ions have been studied using a set of photoelectron and secondary electron spectroscopy methods. It has been established that in the process of ion implantation, chemical bonds are formed between the atoms of the alloying element and the matrix, the width of the energy bands and the density of electronic states in the bands change.

Analyzing the ZnO and CH3NH3PbI3 as Emitter Layer for Silicon Based Heterojunction Solar Cells

Today, it has become an important task to modify existing traditional silicon-based solar cell factory to produce high-efficiency silicon-based heterojunction solar cells, at a lower cost. Therefore, the aim of this paper is to analyze CH3NH3PbI3 and ZnO materials as an emitter layer for p-type silicon wafer-based heterojunction solar cells. CH3NH3PbI3 and ZnO can be synthesized using the cheap Sol-Gel method and can form n-type semiconductor. We propose to combine these two materials since CH3NH3PbI3 is a great light absorber and ZnO has an optimal complex refractive index which can be used as antireflection material. The photoelectric parameters of n-CH3NH3PbI3/p-Si, n-ZnO/p-Si, and n-Si/p-Si solar cells have been studied in the range of 20–200 nm of emitter layer thickness. It has been found that the short circuit current for CH3NH3PbI3/p-Si and n-ZnO/p-Si solar cells is almost the same when the emitter layer thickness is in the range of 20–100 nm. Additionally, when the emitter layer thickness is greater than 100 nm, the short circuit current of CH3NH3PbI3/p-Si exceeds that of n-ZnO/p-Si. The optimal emitter layer thickness for n-CH3NH3PbI3/p-Si and n-ZnO/p-Si was found equal to 80 nm. Using this value, the short-circuit current and the fill factor were estimated around 18.27 mA/cm2 and 0.77 for n-CH3NH3PbI3/p-Si and 18.06 mA/cm2 and 0.73 for n-ZnO/p-Si. Results show that the efficiency of n-CH3NH3PbI3/p-Si and n-ZnO/p-Si solar cells with an emitter layer thickness of 80 nm are 1.314 and 1.298 times greater than efficiency of traditional n-Si/p-Si for the same sizes. These findings will help perovskites materials to be more appealing in the PV industry and accelerate their development to become a viable alternative in the renewable energy sector.

Modeling and Simulation Analysis of Junctionless Transistors with Double Gates

A simple analytical model for the drain current and threshold voltage for junctionless transistors with double gates is presented. This model provides a relatively exact and continuous description of junctionless transistor behaviour in all operating regions. Besides, the influence of different structure parameters such as the channel length, silicon layer thickness, gate oxide thickness, and the doping density on the drain current and threshold voltage is discussed. The analytical model solutions are compared with the numerical results obtained by using the COMSOL Multiphysics simulator. In addition, the influences of the channel length on the sub-threshold swing, threshold voltage, and Drain Induced Barrier Lowing are investigated in the simulation model. Moreover, by adding interface traps to the gate in the model, the effects of interface traps on transferring characteristics and the threshold voltage of junctionless transistor are studied.

A self-consistent hybrid model connects empirical and optical models for fast, non-destructive inline characterization of thin, porous silicon layers

Epitaxially-grown wafers on top of sintered porous silicon are a material-efficient wafer production process, that is now being launched into mass production. This production process makes the material-expensive sawing procedure obsolete since the wafer can be easily detached from its seed substrate. With high-throughput inline production processes, fast and reliable evaluation processes are crucial. The quality of the porous layers plays an important role regarding a successful detachment. Therefore, we present a fast and non-destructive investigation algorithm of thin, porous silicon layers. We predict the layer parameters directly from inline reflectance data by using a convolutional neural network (CNN), which is inspired by a comprehensive optical modelling approach from literature. There, a numerical fitting approach on reflection curves calculated with a physical model is performed. By adding the physical model to the CNN, we create a hybrid model, that not only predicts layer parameters, but also recalculates reflection curves. This allows a consistency check for a self-supervised network optimization. Evaluation on experimental data shows a high similarity with Scanning Electron Microscopy (SEM) measurements. Since parallel computation is possible with the CNN, 30.000 samples can be evaluated in roughly 100 ms.

Fabrication of N-Type Nanocrystalline Silicon Thin-Film by Magnetron Sputtering and Antimony Induced Crystallization

The fabrication of n-type nanocrystalline silicon thin films using magnetron sputtering and crystallization by adding antimony and thermal treatment is presented in this article. Firstly, a short overview about thin film deposition methods, along with the advantages and disadvantages of the magnetron sputtering, is provided. Then, the technique of adding metals for recrystallization of amorphous silicon is described, and the necessity of using antimony for obtaining n-type nanocrystalline silicon along with its characteristics is discussed. Next, the process of thin film deposition using magnetron sputtering and the production of n-type nanocrystalline silicon on a quartz substrate, by antimony induced crystallization, is explained. Subsequently, the characterization process and necessary measurements to confirm the crystallization of the nanocrystalline silicon layer and determine its crystalline properties are presented. For ease of electrical characterization, a simple n/p junction Schottky solar cell is fabricated using the produced nanocrystalline silicon layer on a p-type monocrystalline silicon wafer. In addition to nanocrystalline properties, the optical and electrical characteristics of this cell are also investigated. The measurements show that with the proposed method, a fine grains nanocrystalline silicon layer with an average grain size of 20 nm was formed in the <111> direction. J-V characteristic measurement shows the creation of a solar cell with conversion efficiency of 1.39%, open circuit voltage of 265mV and current density of 16.32mA/cm2. These results confirm that antimony can be used in the process of crystallizing amorphous thin film silicon obtained from magnetron sputtering and converting it into n-type nanocrystalline silicon.

Smart Mattress Based on Multipoint Fiber Bragg Gratings for Respiratory Rate Monitoring

Long-term monitoring of respiratory rate (RR) is of great importance in people suffering from sleep-related breathing disorders (SBDs). Instrumented mattresses are gaining the attention of several research groups to monitor this vital sign. Among the existing sensing techniques, fiber Bragg grating sensors (FBGs) show promise in this arena. In this article, we presented a novel FBG-based smart mattress to monitor RR over time. The proposed measuring system consisted of 13 sensing elements (SEs) based on FBGs encapsulated in soft biocompatible rubber, totally embedded in multiple silicone layers. Compactness, robustness, and user comfort are the main advantages of our solution. The mattress size and the arrangement of the 13 SEs were chosen to allow monitoring subjects with different anthropometric parameters and taking up different sleeping postures. Before the overall system integration, each SE was subjected to static and dynamic metrological characterization, a process often overlooked in fiber-optic-based mattresses. Results showed a mean sensitivity to force equal to 14 pm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot \,\,\text{N}^{-1}$ </tex-math></inline-formula> and a mean percentage hysteresis error always lower than 18%. The feasibility assessment of the system in RR monitoring was carried out on five healthy volunteers taking up common sleeping postures (i.e., supine -S-, right side -RS-, left side -LS-, and prone -P-) under two breathing conditions (i.e., quiet breathing -QB-, and tachypnea -T-). RR estimation showed a mean absolute error (MAE) always lower than 0.65 breaths/min. The promising findings proved the capability of our smart mattress in monitoring RR over time, encouraging the investigation of its performance in real-world scenarios.

Influence of highly doped layers on hydrogen in-diffusion into crystalline silicon

In this work, the influence of highly doped layers on the hydrogen in-diffusion into silicon from hydrogen-rich silicon nitride is investigated. Hydrogen in the crystalline silicon bulk of wafers with and without highly doped layers present was examined in solar cell-like structures by resistivity measurements for quantification of BH-pair dynamics. Hydrogen diffusion through phosphorus- and boron-doped Float-Zone samples without highly doped layers and with p + - respectively n + -layers was determined via secondary ion mass spectrometry. Therefore, deuterium concentration in an amorphous silicon layer on the backside was measured. This experiment shows an up to threefold increase of deuterium concentration in the amorphous layer for samples with highly doped layers present. A possible explanation of this observation is given by simulations. • Influence of highly doped layers on H in-diffusion. • BH-pair dynamics in samples with and without highly doped layers. • SIMS data of D diffusing through highly doped layers and bulk c-Si. • Simulations of H-species in samples with n + -p-n + structure after firing.