Load capacity prediction of monocrystalline silicon mirror based on multimodal coupling characterization

Monocrystalline silicon reflectors are widely used in infrared high energy laser systems. In order to ensure the system to achieve high precision and high stability of beam transmission, the reflector needs to have a good laser load capacity for high power density laser under long time irradiation. However, the evaluation of reflector laser load capacity is influenced by multiple factors, which is difficult to be decoupled one by one, and the multiple index systems are not perfect. In this paper, multi-modal characterization methods such as reflectivity, fluorescence detection and surface roughness detection are proposed to establish the influence model of multiple influencing factors on the laser load capacity of monocrystalline silicon reflector. Through quantitative analysis of these defects with specific types and different properties, the surface cleanliness and integrity of the monocrystalline silicon reflector were analyzed from different angles, and the influence trend of each influencing factor on the laser load capacity of the element was obtained. In this paper, a relatively completed characterization system of monocrystalline silicon and the influence model of the laser load capacity of the monocrystalline silicon reflector have been established effectively. The influencing factors of the laser load capacity on the surface of the monocrystalline silicon reflector are evaluated effectively, which lays a foundation for the efficient acquisition of the monocrystalline silicon reflector with high load capacity.

A Review of Hydrophilic Silicon Wafer Bonding

Thisreviewcoversthekeypapersrelatingtothetheory,techniques and quantification of hydrophilically activated silicon wafer bonding. This begins with a review of the history and development of the art. Bond strength characterization is then reviewed followed first by models of physical deformation and then by plasma and radical activation techniques. In the interests of clarity and succinctness this review is not an attempt to exhaustively catalog all direct bonding wafer literature. Excluded are hydrophobic and UHV bonding, and the many papers applying bonding techniques to differing combinations of wafer materials. This paper concludes with a summery of the state of the art of direct wafer bonding and a summation of the current wafer-bonding model derived from the papers reviewed.

Capturing Structural Dynamics in Crystalline Silicon Using Chirped Electrons from a Laser Wakefield Accelerator

Recent progress in laser wakefield acceleration has led to the emergence of a new generation of electron and X-ray sources that may have enormous benefits for ultrafast science. These novel sources promise to become indispensable tools for the investigation of structural dynamics on the femtosecond time scale, with spatial resolution on the atomic scale. Here, we demonstrate the use of laser-wakefield-accelerated electron bunches for time-resolved electron diffraction measurements of the structural dynamics of single-crystal silicon nano-membranes pumped by an ultrafast laser pulse. In our proof-of-concept study, we resolve the silicon lattice dynamics on a picosecond time scale by deflecting the momentum-time correlated electrons in the diffraction peaks with a static magnetic field to obtain the time-dependent diffraction efficiency. Further improvements may lead to femtosecond temporal resolution, with negligible pump-probe jitter being possible with future laser-wakefield-accelerator ultrafast-electron-diffraction schemes.

Optimization of fabrication process of high-efficiency and low-cost crystalline silicon solar cell for industrial applications

Abstract The process conditions for a high-efficiency and low cost crystalline silicon solar cell were optimized. Novel approaches such as wafer cleaning and saw -damage removal using 0.5 wt% of 2,4,6-trichloro-1,3,5-triazine, silicon surface texturing with optimized pyramid heights (∼5 μm), and a third step of drive-in after phosphosilicate glass (PSG) removal followed by oxide removal were investigated. A simple method of chemical etching adopted for edge isolation was optimized with edge etching of 5–10 μm, without any penetration of chemicals between the stacked wafers. The conversion efficiency, open-circuit voltage, short-circuit current, and fill factor of the cell fabricated with the optimized process were a maximum of 17.12%, 618.4 mV, 5.32 A, and 77% under AM1.5 conditions, respectively.

A large deflection translatory actuator for optical path length modulation

A novel translational micro mirror with a circular shape of 3 mm diameter and oscillation frequencies of 500 Hz and 1000 Hz is presented including a design study based on analytical and numerical calculations. The study takes mechanical limits like stress and shock resistivity into account as well as fabrication issues resulting in the design points presented. Considerations and results of this study including stress limits for single crystalline silicon and a FE analysis of the main oscillation mode of the resonant structure will be illustrated. Based on an SOI process with 30 μm thick and highly doped single crystalline silicon several devices were fabricated. For the characterization of the devices a Michelson interferometer set-up was used which allows determining the voltage-deflection curves as a function of the air pressure. Deflections of more than ± 50 μm for the 500 Hz device and ± 85 μm for the 1000 Hz have been achieved at a pressure of 10 Pa. The target is at ± 250 μm and ± 180 μm amplitude. In the outlook packaging requirements and approaches will be shown.

Variability on Raman Shift to Stress Coefficient of Porous Silicon

Porous silicon film is a capillary-like medium, which is able to reveal different meso-elastic modulus with porosity. During the preparation of porous silicon samples, the capillary force is a non-classic force related to the liquid evaporation which directly influences the evolution of residual stress. In this study, a non-linear relation of Raman shift to stress coefficient and the porosity is obtained from the elastic modulus measured with nano-indentation by Bellet et al. [J. Appl. Phys. 60 (1996) 3772] Dynamic capillarity during the drying process of porous silicon is investigated using micro-Raman spectroscopy, and the results reveal that the residual stress resulted from the capillarity increased rapidly. Indeed, the dynamic capillarity has a close relationship with a great deal of micro-pore structures of the porous silicon.

Design, fabrication, and analysis of double-layer antireflection coatings (ARC) for industrial bifacial n-type crystalline silicon solar cells.

Monocrystalline silicon-based, n-type front and back contact (nFAB) solar cells are gradually attracting more interest from the photovoltaic industry, due to their good bifaciality and high efficiency potentials. To further improve the conversion efficiency, nFAB solar cells need to make better use of the solar spectrum. Conventional single-layer SiNx antireflection coating (ARC) tends to have a high reflection loss for ultraviolet photons. Thus, in this work, we prepare a double-layer ARC structure made of SiNx/SiOx stack, deposited by the plasma-enhanced chemical vapor deposition method. We investigate the effects of double-layer ARC through simulation and experimental studies by fabricating bifacial nFAB cells. The results show that the implementation of a double-layer ARC helps to greatly reduce front reflection in short wavelength, and thus allow for improvement of the photocurrent by up to 0.3  mA/cm2. As a result, the average cell efficiency of nFAB solar cells increases by absolute ∼0.2%.

3D characterisation of tool wear whilst diamond turning silicon

Abstract Nanometrically smooth infrared silicon optics can be manufactured by the diamond turning process. Due to its relatively low density, silicon is an ideal optical material for weight sensitive infrared (IR) applications. However, rapid diamond tool edge degradation and the effect on the achieved surface have prevented significant exploitation. With the aim of developing a process model to optimise the diamond turning of silicon optics, a series of experimental trials were devised using two ultra-precision diamond turning machines. Single crystal silicon specimens (1 1 1) were repeatedly machined using diamond tools of the same specification until the onset of surface brittle fracture. Two cutting fluids were tested. The cutting forces were monitored and the wear morphology of the tool edge was studied by scanning electron microscopy (SEM). The most significant result showed the performance of one particular tool was consistently superior when compared with other diamond tools of the same specification. This remarkable tool performance resulted in doubling the cutting distance exhibited by the other diamond tools. Another significant result was associated with coolant type. In all cases, tool life was prolonged by as much as 300% by using a specific fluid type. Further testing led to the development of a novel method for assessing the progression of diamond tool wear. In this technique, the diamond tools gradual recession profile is measured by performing a series of plunging cuts. Tool shape changes used in conjunction with flank wear SEM measurements enable the calculation of the volumetric tool wear rate.

Performance Evaluation and Comparison between Direct and Chemical-Assisted Picosecond Laser Micro-Trepanning of Single Crystalline Silicon

The fabrication of micro-holes in silicon substrates that have a proper taper, higher depth-to-diameter ratio, and better surface quality has been attracting intense interest for a long time due to its importance in the semiconductor and MEMS (Micro-Electro-Mechanical System) industry. In this paper, an experimental investigation of the machining performance of the direct and chemical-assisted picosecond laser trepanning of single crystalline silicon is conducted, with a view to assess the two machining methods. The relevant parameters affecting the trepanning process are considered, employing the orthogonal experimental design scheme. It is found that the direct laser trepanning results are associated with evident thermal defects, while the chemical-assisted method is capable of machining micro-holes with negligible thermal damage. Range analysis is then carried out, and the effects of the processing parameters on the hole characteristics are amply discussed to obtain the recommended parameters. Finally, the material removal mechanisms that are involved in the two machining methods are adequately analyzed. For the chemical-assisted trepanning case, the enhanced material removal rate may be attributed to the serious mechanical effects caused by the liquid-confined plasma and cavitation bubbles, and the chemical etching effect provided by NaOH solution.

Modeling Microdefect Formation in Czochralski Silicon

An internally consistent model is presented for the dynamic formation of microdefects in single‐crystal silicon. The model is built on the dynamics of point defects, vacancies and self‐interstitials, and is extended to include the growth of clusters of these point defects into microdefects. A hybrid finite‐element/finite‐difference numerical method is used to solve the coupled system of partial differential equations, which includes sets of discrete rate equations for small clusters and Fokker‐Planck equations for larger ones. As described previously by a point defect dynamics model [J. Electrochem. Soc., 145, 303 (1998)], the oxidation‐induced stacking fault (OSF)‐ring position delineates the vacancy‐rich region inside from the external interstitial‐rich crystal. In Czochralski silicon, the radial position of the OSF‐ring correlates well with the expression . Simulations are used to explore the formation of voids in the vacancy‐rich region inside the OSF‐ring. Predictions of the total concentration of observable voids and the dependence of this concentration on the cooling rate agree with experiments and point to the importance of the axial temperature profile in the crystal from the melting point (1685 K) down to about 1150 K in setting the number and size of voids. The total number of voids correlates with V 〈G〉 where 〈G〉 is a measure of the temperature gradient in the temperature range 1173 K ≤ T ≤ 1685 K. The appearance of the OSF‐ring is explained qualitatively in terms of the residual vacancy concentration remaining in the crystal after aggregation has ceased. © 1999 The Electrochemical Society. All rights reserved.

Towards a deeper understanding of plastic deformation in mono-crystalline silicon

Evaluation and comparison of crystalline silicon and thin-film photovoltaic solar cells technologies using data envelopment analysis

In the recent years, electricity production from renewable energy sources especially solar energy has progressed a great deal. Solar energy is a locally available renewable resource which is the most plentiful, unfailing and clean of all the renewable energy resources till date. A solar cell also called photovoltaic cell or PV is the technology used to convert energy from sunlight directly into electricity. As the PV market grows, it is becoming increasingly important to understand the energy performance of photovoltaic solar cells technologies. The purpose of this paper is to evaluate and compare the performance of crystalline silicon and thin film PV technologies with the DEA (data envelopment analysis) method in four states (considering payback period factor, total factors, technical and economic factors). The results indicate that in the three states where in “total factors”, “technical factors” and “economic factors” have been considered as performance factors, the mean of efficiency scores for crystalline silicon is higher than the mean of efficiency scores for thin-film. But in the state where in “payback period factor” has been considered as performance factor, the mean of efficiency score for Thin-film is higher than the mean of efficiency score for crystalline Silicon.

State of Art of Solar Photovoltaic Technology

Solar electricity is more expensive than that produced by traditional sources. But over the past two decades, the cost gap has been closing. Solar photovoltaic (SPV) technology has emerged as a useful power source of applications such as lightning, meeting the electricity needs of villages, hospitals, telecommunications, and houses. The long and increasing dominance of crystalline silicon in photovoltaic (PV) market is perhaps surprising given the wide variety of materials capable of producing the photovoltaic effect. PV based on silicon wafers has captured more than 90% market share because it is more reliable and generally more efficient than competing technologies. The crystalline silicon PV is reliable as far as long term stability in real field but it is not economically viable due to starting material silicon itself costly. But still, research continues on developing a diverse set of alternative photovoltaic technology. Now PV technology is being increasingly recognized as a part of the solution to the growing energy challenge and an essential component of future global energy production. In this paper, we give a brief review about PV technology particularly crystalline silicon PV including the world and Indian PV scenarios.

Amorphous silicon waveguides for microphotonics

Amorphous silicon a-Si was made by ion irradiation of crystalline silicon with 1×1015 Xe ions cm−2 at 77 K in the 1–4 MeV energy range. Thermal relaxation of the amorphous network at 500 °C for 1 h leads to an amorphous layer with a refractive index of n=3.73, significantly higher than that of crystalline silicon (n=3.45 at λ=1.55 μm). a-Si can thus serve as a waveguide core in Si based optical waveguides. Channel waveguides were made by anisotropic etching of a 1.5 μm silicon-on-insulator structure that was partly amorphized. Transmission measurements of these waveguides as function of the amorphous silicon length show that the a-Si part of the waveguides exhibit a modal propagation loss of 70 cm−1 (0.03 dB μm−1) and a bulk propagation loss of 115 cm−1 (0.05 dB μm−1). Losses due to sidewall roughness are estimated, and are negligible compared to the modal loss.

Comparative study of the reliability of MPPT algorithms for the crystalline silicon photovoltaic modules in variable weather conditions

Abstract The crystalline silicon photovoltaic modules are widely used as power supply sources in the tropical areas where the weather conditions change abruptly. Fortunately, many MPPT algorithms are implemented to improve their performance. In the other hand, it is well known that these power supply sources are nonlinear dipoles and so, their intrinsic parameters may vary with the irradiance and the temperature. In this paper, the MPPT algorithms widely used, i.e. Perturb and Observe (P&O), Incremental Conductance (INC), Hill-Climbing (HC), are implemented using Matlab ® /Simulink ® model of a crystalline silicon photovoltaic module whose intrinsic parameters were extracted by fitting the I(V) characteristic to experimental points. Comparing the simulation results, it is obvious that the variable step size INC algorithm has the best reliability than both HC and P&O algorithms for the near to real Simulink ® model of photovoltaic modules. With a 60 Wp photovoltaic module, the daily maximum power reaches 50.76 W against 34.40 W when the photovoltaic parameters are fixed. Meanwhile, the daily average energy is 263 Wh/day against 195 Wh/day.

Thin-film crystalline silicon solar cells

A photoelectric conversion efficiency of over 10% has been achieved in thin-film polycrystalline silicon solar cells which consists of a 2 μm thick layer of polycrystalline silicon with a very small grain size (microcrystalline silicon) formed by low-temperature plasma CVD. This has shown that if the recombination velocity at grain boundaries can be made very small, then it is not necessarily important to increase the size of the crystal grains, and that an adequate current can be extracted even from a thin film due to the light trapping effect of silicon with a low absorption coefficient. As a result, this technology may eventually lead to the development of lowcost solar cells. Also, an initial efficiency as high as 12% has been achieved with a tandem solar cell module of microcrystalline silicon and amorphous silicon, which has now started to be produced commercially. An even greater initial efficiency of 14.5% has been achieved in devices with a small size area, and further increases of efficiency can be expected.

Inscription of optical waveguides in crystalline silicon by mid-infrared femtosecond laser pulses.

For the first time to the authors' knowledge, optical waveguides have been inscribed in bulk crystalline silicon by ultrafast laser radiation. Femtosecond laser pulses of 40-nm spectral bandwidth, 1-kHz repetition rate, and 1.7-microJ on-target energy were applied at a mid-infrared wavelength of 2.4 microm to induce nonlinear absorption in the focal volume of the beam. By scanning the laser beam with respect to the sample, buried optical waveguides have been created that were single mode at 1550 and 1320 nm and guided light only with its polarization perpendicular to the sample's surface. Propagation losses with an upper limit of 1.2 dB/cm or less were observed throughout the optical telecommunications band.

Plasmon-enhanced high-harmonic generation from silicon

High-harmonic emission from crystalline silicon can be made ten times brighter by exploiting local plasmonic fields in arrays of nano-antennas. Plasmonic antennas can enhance the intensity of a nanojoule laser pulse by localizing the electric field in their proximity1. It has been proposed that the field can become strong enough to convert the fundamental laser frequency into high-order harmonics through an extremely nonlinear interaction with gas atoms that occupy the nanoscopic volume surrounding the antennas2,3,4. However, the small number of gas atoms that can occupy this volume limits the generation of high harmonics5,6,7. Here we use an array of monopole nano-antennas to demonstrate plasmon-assisted high-harmonic generation directly from the supporting crystalline silicon substrate. The high density of the substrate compared with a gas allows macroscopic buildup of harmonic emission. Despite the sparse coverage of antennas on the surface, harmonic emission is ten times brighter than without antennas. Imaging the high-harmonic radiation will allow nanometre and attosecond measurement of the plasmonic field8 thereby enabling more sensitive plasmon sensors9 while opening a new path to extreme-ultraviolet-frequency combs10.

Crystalline silicon photovoltaics: the hurdle for thin films

The dominant photovoltaic (PV) technology today is crystalline silicon, used in 85% of the terrestrial modules shipped in 1996. Thin-film PV technologies promise to allow significant reductions in the cost per watt of electricity generated by PV modules. However, thin films must meet or exceed the standards for performance, reliability, and cost set by crystalline silicon in order to successfully penetrate the market. This paper reports the results of a detailed economic analysis done for a 25 MW year−1 multi-crystalline silicon production facility, including crystal growth, water slicing, solar cell fabrication and module assembly. The module manufacturing cost is projected to be $1·78 W−1. The sensitivity of module cost to polysilicon cost and cell efficiency were determined. This analysis provides a near-term (1998–2000) cost/performance benchmark against which thin-film technologies can be compared. © 1997 John Wiley & Sons, Ltd.

Silicon processing: from quartz to crystalline silicon solar cells

Silicon has been the dominant material in the photovoltaic (PV) industry since its application in the space industry in 1958. This review focuses on crystalline silicon solar cells, primarily due to their dominance in the photovoltaic industry, omitting other photovoltaic cell technologies such as second generation (e.g. thin films) and third generation (e.g. nano-structured solar cells). The value chain for the production of crystalline silicon solar cells has been reviewed. The primary processing steps for the production of silicon solar cells from quartz are as follows: bulk production of metallurgical -grade silicon via carbothermic reduction in a submerged furnace, refining of metallurgical -grade silicon via the chemical means to polycrystalline silicon, or through the metallurgical route to solar-grade silicon, wafer manufacturing, and, lastly, silicon solar cell manufacturing. During downstream processing, solar cells are interconnected and encapsulated into solar modules (panels), which can be used individually or incorporated into a photovoltaic system for electricity generation and supply. The cost for crystalline silicon based solar cells is approaching one US dollar per watt peak ($1/Wp), while the most cost-effective solar modules in industry have reported costs below $1/Wp, and are based on CdTe thin films. Solar cell energy conversion efficiencies as high as 22% have been reported in industry for crystalline silicon solar cells.