N-type Single Crystalline Silicon Research Articles

A comparative study on piezoelectric and piezoresistive pressure sensor using COMSOL simulation

For system stability monitoring, pressure is one of the major and easy quantity to be measured among the many other physical quantities. A pressure sensor produces a signal as a function of the pressure imposed. These sensors became a vital part of our everyday life from devices we use at home to industrial equipment. In this paper, simulation, and comparative study of piezoresistive and piezoelectric pressure sensor is presented. All the simulations where made using COMSOL Multiphysics software of 5.5 version. Using this software, 3D models of sensors are simulated with different materials. From this simulation results, best materials for piezoelectric and piezoresistive pressure sensor are selected. This work follows the simulation, and analysis of a piezoresistive pressure sensor, done using four different sets of piezoresistive materials. Both p-type and n-type single crystalline silicon and polycrystalline silicon materials are used for the piezoresistive pressure sensor simulation. Pressure vs. displacement graphs of four set of piezoresistive materials are plotted. Displacement which is obtained in micrometer range increases with different input load from 100 KPa to 500 KPa. A piezoceramic tube, example for piezoelectric pressure sensor simulation also carried out using different piezoelectric materials like PZT 5A, PZT 5H, PVDF, BaTiO3, Lithium Tantalate, Cadmium Sulfide, Lithium Niobate, Aluminum Nitride and Barium Sodium Niobate. The modelling and simulation of Piezoceramic tube- Piezoelectric pressure sensor is done by giving different input pressure values. During the simulation of direct piezoelectric effect, voltage generation is obtained according to the input pressure. Output voltages of different piezoelectric materials are taken by giving different boundary load from 0.1 MPa to 1 MPa. Indirect piezoelectric effect simulation is also done, where piezoelectric materials become strained when the electric field is applied and this strain is directly proportional to the electric field. A Displacement table of indirect piezoelectric effect is measured by giving constant input pressure of 0.1 MPa. Here, analyses are done in MPa range of input pressures, obtained voltage in V and displacement in micrometers. Pressure vs. Voltage values for direct piezoelectric effect is plotted Efficiency and resolution of piezoresistive and piezoelectric pressure sensors are found out.

A comprehensive study on slicing processes optimization of silicon ingot for photovoltaic applications

Systematic cutting process design and optimization problems are studied for surface roughness minimization by stochastic algorithms. As the experimental background of the study, n-type single crystalline silicon (Si) ingot are cut into Si wafer with a thickness of 375 µm using a wire saw machine. In order to optimize the cutting parameters successfully, a two-step study has been organized as (i) a detailed study on multiple nonlinear regression analysis of the process parameters for predicting the feed rate and wire speed effects, (ii) design and optimization steps. Regression models include linear, quadratic, trigonometric, logarithmic and their rational forms for the same surface roughness problem. In design and optimization section, four distinct stochastic optimization algorithms (Differential Evaluation, Nelder-Mead, Random Search and Simulated Annealing) have been performed systematically to avoid inherent scattering of the stochastic processes. To investigate the advantages and disadvantages of the introduced mathematical processes for the similar cutting process problems, a review list are also given for the optimization on volumetric metal removal rate (VMRR), wear ratio (WR), material removal rate (MRR) and surface roughness (SR) by distinguishing the modeling methodology, model types, and optimization algorithms. It is also shown that different rational regression models can be utilized with the collaboration of stochastic optimization methods successfully to minimize the surface roughness of Si wafers.

Determination of micro sized texturing and nano sized etching procedure to enhance optical properties of n-type single crystalline silicon wafer

Crystalline silicon (c–Si) wafer was manufactured by applying micro texture and nano etching process without lapping and polishing for solar cell applications. Before micro texture and nano etching, wafers were exposed to chemical polishing process in high concentrated alkaline solution to remove saw damages and obtain a surface with low surface roughness (Ra). Uniform pyramidal structures were formed in alkaline solution. On pyramidal structures, nano sized porous shapes were formed by using Ag nano particles via wet chemical etching method. Micro textured and nano etched surface formed without any chemical mechanical (CM) lapping and polishing step, examined by Scanning Electron Microscope (SEM) for surface structure and UV–visible spectrometer for reflectance and absorbance measurements. Considerably good uniform porous surface with low reflectance was formed and compared with usual solar wafers produced with CM lapping and polishing. Furthermore, present process for preparing solar cell provides low cost, short time and less material consumption by removing lapping and polishing steps from overall process. Reflectance values were measured between 7 and 10% for best micro textured and nano etched c-Si wafers, respectively. Absorbance values were measured 0.4 and 1.2% for best micro textured and nano etched c–Si wafers, respectively. Curves of \({\text{h}}{\upnu }\) versus \({\left({\upalpha }{\text{h}}{\upnu }\right)}^{2}\) indicated the optical band gaps almost 1.12 e.V. for all wafers cut from same n-type single c-Si ingot.

Progression of rapid potential-induced degradation of n-type single-crystalline silicon photovoltaic modules

This study addresses progression of potential-induced degradation (PID) of photovoltaic modules using n-type single-crystalline silicon cells. In a PID test in which a voltage of −1000 V was applied to the cells, the modules started to degrade within 10 s and the degradation saturated within 120 s, suggesting that PID is caused by positive charge accumulation in the front passivation films. We propose that these positive charges originate from positively charged K centers formed by extracting electrons from the K centers, which explains the rapid degradation and its saturation behavior. We obtain simulated and experimental results supporting this hypothesis.

Changes in the current density–voltage and external quantum efficiency characteristics of n-type single-crystalline silicon photovoltaic modules with a rear-side emitter undergoing potential-induced degradation

This study addresses the potential-induced degradation (PID) of n-type single-crystalline silicon (sc-Si) photovoltaic (PV) modules with a rear-side emitter. The n-type rear-emitter module configurations were fabricated using n-type bifacial sc-Si solar cells by module lamination with the p+ emitter side down. After the PID tests applying −1000V, the modules show a rapid decrease in the open-circuit voltage (Voc), followed by relatively slower reductions in the fill factor and the short-circuit current density (Jsc). Their dark current density–voltage (J–V) data and external quantum efficiencies (EQEs) indicate that the drop in Voc is caused by an increase in the saturation current density due to the enhanced surface recombination of minority carriers. In contrast, the modules exhibit slight degradation under +1000V, which is characterized by only slight decreases in Voc and Jsc. The EQE measurement reveals that these decreases are also attributed to the enhanced surface recombination of minority carriers. This behavior is almost identical to that of the polarization effect in n-type interdigitated back contact PV modules reported in a previous study. By comparing the PID resistance with that of other types of modules, the n-type rear-emitter PV modules are relatively resistant to PID. This may become an advantage of the n-type rear-emitter PV modules.

Hard breakdown mechanisms of compensated p-type and n-type single-crystalline silicon solar cells

The hard breakdown behaviors of boron–phosphorus compensated p-type and n-type Czochralski silicon solar cells were studied as functions of the type of conductivity, the net doping concentration and the temperature. We showed as expected from previous studies that the hard breakdown was governed by avalanche mechanisms (impact ionization) and that for a given net doping concentration the hard breakdown voltage was almost the same for both p-type and n-type solar cells, despite the different reported values for the electron and hole impact ionization coefficients. The studied compensated materials offered the opportunity to determine the hard breakdown voltages for samples with the same net doping concentration but different total amount of doping species. However no major effects of the dopant compensation were observed, the experimental data being described by the empirical expressions used for uncompensated silicon samples.

Investigation of P3HT/n-Si heterojunction using surface photovoltage spectroscopy

Surface photovoltage spectroscopy (SPS) was used to investigate the interactions of the interface between regioregular poly(3-hexylthiophene) (P3HT) and n-type single crystalline silicon. The SPS responses of silicon and the P3HT/n-Si heterojunction caused by band to band transition of silicon are 30 mV and 160 mV respectively. The band-bending in the silicon side of the P3HT/n-Si structure is larger than that of bare n-Si. The density of the interface states of the P3HT/n-Si heterojunction increased significantly after the deposition of P3HT. Based on the contact potential difference (CPD) transient results, charge transport and separation processes are fast in the silicon substrate and slow in the P3HT layer respectively.

Electronic structure and formation mechanism of complex Ti–Nb oxide

Two-layer thin film specimens of Nb2O5 and TiO2 were deposited on optical-grade quartz and n-type single crystalline silicon substrates with (100) crystallographic orientation by a magnetron deposition source under high vacuum. All samples were subjected to 1–5h of resistive heating at ultra high vacuum, and in situ X-ray diffraction measurements (XRD) were made in the temperature range of 300–1373K. Analysis of the XRD data confirmed the growth of TiNbO4 during cooling of the two-layered specimens which had been previously heated to 1373K. Optical measurements revealed a band gap value of 3.78eV for the direct transition and 3.29eV for the indirect one. The samples had a transmittance of 85% in the visible range. Electrophysical measurements in high vacuum established the electroresistivity vs. temperature dependence in the range of 300–773K, from 7.3⁎10−1 to 3.9⁎10−2Ω cm, respectively. X-ray photoelectron spectroscopy measurements were used to examine the chemical shift for Nb 3d, with a value of −1.1eV in comparison with Nb5+ and matched to Nb4+[1], while the Ti lines correspond to Ti4+[2].

Preparation of Hydrogenated Amorphous Silicon Carbon Nitride Films by Hot-Wire Chemical Vapor Deposition Using Hexamethyldisilazane for Silicon Solar Cell Applications

We propose hydrogenated amorphous silicon carbon nitride (a-SiCN:H) films prepared by hot-wire chemical vapor deposition (HWCVD) using hexamethyldisilazane (HMDS) as a new passivation layer of silicon solar cells. The films deposited at various deposition conditions were characterized focusing on optical properties and passivation quality. We found that the effective lifetime of the samples depended on the amount of Si–H bond and had strong correlation with the interface trap densities. After the optimization, the effective surface recombination velocity of n-type single crystalline silicon (c-Si) (1–10 Ω cm) with a-SiCN:H films has become lower than 60 cm/s and that of p-type was approximately 300 cm/s. The efficiency of a cast polycrystalline silicon solar cell using a-SiCN:H as a passivation layer reached 13.7% (2×2 cm2). Experimental results indicate that a-SiCN:H films are promising low-cost antireflection and passivation layers for silicon solar cells.

Growth of Silicon Nanoclusters on Different Substrates by Plasma Enhanced Chemical Vapor Deposition

We report an atomic force microscopy study of the early stages of growth of silicon nanoclusters formed on different substrates by plasma-enhanced chemical vapor deposition, using dichlorosilane (SiH2CI2) and hydrogen (H2) as reactive gases. (100) n-type single crystalline silicon, fused silica, amorphous silicon nitride and corning glass, were used as substrates for the growth of the nanoclusters, which were formed at low substrate temperature (200 degrees C). The diameter, height and number density of the clusters were controlled by the deposition time and pressure. It was found that not only the plasma conditions but also the surface characteristics of the substrate influence the cluster density, shape, and size. For the ordered silicon surface and the amorphous fused silica, the nanoclusters result oval in shape and exhibit preferential growth along the surface. When deposited over amorphous silicon nitride and corning glass, the density of nanoclusters increases and there is a tendency toward columnar growth since the diameter of the nanoclusters tends to decrease. We conclude that although the specific features of the nanoclusters originate from the chlorine chemistry introduced by the SiHxCly deposition precursor and the chemical stability of chlorine-terminated surfaces under hydrogen plasma, the surface quality and roughness also plays an important role on the nucleation and mobility of the species. The combination of both effects gives rise to the different nanostructured growths observed.

Room temperature electroluminescence from a nanocrystalline diamond/Si heterojunction

We report on the fabrication and characterization of the room temperature electroluminescence of heterojunction between nanocrystalline diamond film (NDF) and heavily doped n-type single crystalline silicon (n +-Si) substrate. The current–voltage characteristics ( I– V) of the NDF/n +-Si heterojunction show clear rectification properties. Importantly, with sufficiently high forward bias applied on the NDF/n +-Si heterojunction, fairly strong visible electroluminescence (EL) was obtained at room temperature. The EL occurred as the consequence of the electrons tunneling from the n +-Si into the NDF. An energy-band model has been proposed to understand the mechanism of the I– V characteristics and the EL for the NDF/n +-Si heterojunction.

Electrical properties of B-doped polycrystalline silicon thin films prepared by rapid thermal chemical vapour deposition

In this paper, about 30 μm thick B-doped polycrystalline silicon (poly-Si) thin films were deposited on quartz substrates, n-type single crystalline silicon wafers and p++-type poly-Si ribbons by a rapid thermal chemical vapour deposition system in a temperature range from 1000 to 1150 °C. Activation energy measurement and room temperature/temperature dependent Hall effect measurement were performed on the poly-Si thin films prepared on the former two kinds of substrates, respectively. It seems that the electrical properties of as-prepared poly-Si thin films could be qualitatively explained by Seto's grain boundary (GB) trapping theory although there is a big difference between our samples and Seto's in grain size and film thickness etc. The experimental results reconfirm that GB itself is a kind of most effective recombination center with trapping level near the midgap and trapping state density in the order of 1012 cm−2 magnitude. Electron beam induced current measurements on the poly-Si thin films prepared on the poly-Si ribbons also show that severe recombination occurs at the positions of GBs.

Photoluminescence from nano porous silicon prepared by photoelectrochemical etching of n-type single crystalline silicon

AbstractThe influence of operating parameters in producing light-emitting porous silicon materials was investigated in ethanolic solutions of hydrofluoric acid. Photoluminescence spectra depended on applied potential, the intensity and wavelength of illumination, and electrolyte concentration. When the applied potential and the illumination wavelength increased, the photoluminescence shifted to longer wavelength. Change in HF concentration resulted in different intensity in photoluminescence.

Improvgement of Voc for μc-Si: H/poly-Si p—n junction solar cells

The p-n junction solar cells consisting of p-type hydrogenerated microcrystalline suilicon (p-μc-Si:H) and n-type single crystalline silicon (n-c-Si) or cast polycrystalline silicon (n-poly-Si) have been investiagated. By inseerting a thin oxide layer (SiO x) between p-μcSi:H and n-c-Si or n-poly-Si and by optimizing fabrication processes. V oc as high as 648 was obtained for the p-μc-Si/SiO x/n-c-Si cell, and 623 mV for the p-μc-Si:H/SiO x/n-poly-Si cell. The effects and role of the inserted oxide layer in the p-μc-Si:H/n-c-Si cell are discussed.

Time Resolved Transmission and Reflectivity of Pulsed Ruby Laser Irradiated Silicon

ABSTRACTThe time resolved optical transmission, T (atλ = 1152 nm), and reflectivity, R (at 633 nm and 1152 nm), have been measured for n-type single crystalline silicon (c-Si) during and immediately after pulsed ruby laser irradiation (λ = 693 nm, FWHM pulse duration 14 nsec), for a range of pulsed laser energy densities, El. The T is found to go to zero, and to remain at zero, for a period of time that increases with increasing El, in apparent disagreement with earlier measurements elsewhere that used semi-insulating Si and a different pulsed laser wavelength. Measured reflectivities during the high R phase agree within experimental error with reflectivities calculated from the optical constants of molten Si. Quantitative agreement is also found between both our T and R measurements and detailed time– and El-dependent results of thermal melting model calculations.