Single Crystal Silicon Research Articles

Relative Strength of Polycation Adsorption on Oxide Surfaces.

Polyelectrolyte adsorption onto surfaces is widely employed in water treatment and mining. However, little is known of the relative interaction strengths between surfaces and polymer. This fundamental property is assumed to be dominated by electrostatics, i.e., attractive interactions between opposite charges, which are set by the overall ionic strength ("salt concentration") of the solution, and charge densities of the surface and the polymer. A common, counterintuitive finding is a range of salt concentrations over which the amount of adsorbed polyelectrolyte increases as electrostatic interactions are tempered by the addition of salt. After an adsorption maximum, higher salt concentrations then produce the expected gradual desorption of polyelectrolyte. In this work, the salt response of the adsorption of the same narrow molecular weight distribution polycation, poly(N-methyl-4-vinylpyridinium), PM4VP, to a variety of surfaces was explored. Oxide powders for adsorption included Al2O3, SiO2, Fe2O3, Fe3O4, TiO2, ZnO, and CuO. Planar surfaces included silicon wafers, mica, calcium carbonate, and CaF2 single crystals. The PM4VP was radiolabeled with 14C so that sensitive, submonolayer amounts could be detected. The position of the peak maximum, or the lack of a peak, in response to added salt was used to rank the electrostatic component of the interaction. The importance of charge regulation, a shift in the surface pKa in response to solution species, was highlighted as a mechanism for adsorption on the "wrong" side of the isoelectric point and also as a factor contributing to the difficulty of reaching the totally desorbed state even at the highest salt concentrations.

Study on high-shear and low-pressure grinding using a new BAAT with soft-hard combined substrate for single-crystal silicon

Study on high-shear and low-pressure grinding using a new BAAT with soft-hard combined substrate for single-crystal silicon

Adhesion of Electron-Irradiated Diazoquinone–Novolac Photoresist Films to Single-Crystal Silicon

Adhesion of Electron-Irradiated Diazoquinone–Novolac Photoresist Films to Single-Crystal Silicon

Polarization-Dependent Anisotropy of LIPSSs' Morphology Evolution on a Single-Crystal Silicon Surface.

Utilizing the principle of laser-induced periodic surface structures (LIPSSs), this research delves into the morphological evolution of single-crystal silicon surfaces irradiated by a near-infrared picosecond laser through a scanning mode. With the increase in laser energy density, the nanostructure morphology on single-crystal silicon surfaces induced by incident lasers with different polarization directions sequentially produces high spatial-frequency LIPSSs (HSFLs) with a period of 220 nm ± 10 nm parallel to the laser polarization, low spatial-frequency LIPSSs (LSFLs) with a period of 770 nm ± 85 nm perpendicular to the direction of the polarization, and groove structures. Furthermore, by varying the angle between the laser polarization and the scanning direction, the study examined the combined anisotropic effects of the laser polarization scanning direction angle and the laser polarization crystal orientation angle on the genesis of LIPSSs on single-crystal silicon (100) surfaces. The experiments revealed polarization-related anisotropic characteristics in the morphology of HSFLs. It was found that when the polarization angle approached 45°, the regularity of the LSFLs deteriorated, the modification width decreased, and the periodicity increased. This is critical for the precise control of the LSFLs' morphology.

The improvement in heat transfer performance of single crystal silicon carbide with diamond film

In order to reduce the temperature of SiC-based electronic power devices during operation, the diamond films of different thickness were grown on 4H-SiC substrates by microwave plasma chemical vapor deposition (MPCVD) method. The thermal conductivity of the composite with 92 μm thick diamond film was measured to be 429.97 W/(m·K) by laser flash method, which is 53.56 % higher than that of individual 4H-SiC. The diamond/SiC composite was heated on the heat stage to investigate its heat transfer characteristics. The heat spread performance was improved by more than 10 %, which benefits the reliability and the service life of the electronic power device. The solid heat transfer was also simulated by COMSOL software. It was found that the thicker diamond film, the higher thermal conductivity. The thermal resistance of the interface between diamond and single crystal SiC would lead to the decrease of thermal conductivity of the composite.

The effect of SiC on the growth habit of Fe-Ni-C system Ib gem grade diamond crystals

This article investigates the influence of different silicon carbide contents on the morphology and quality of diamond single crystals synthesized in the Fe-Ni-C-Si system under high temperature and pressure environments. It was found that silicon successfully entered the diamond lattice through bonding. As the doping concentration increases, the growth rate of diamond crystals decreases and defects appear on the crystal surface. The increase in internal stress in the lattice reduces the quality of diamond, as evidenced by the shift in Raman peak and half peak width of the diamond. Moreover, the infrared characterization results showed that the nitrogen element in the crystal exists as a single atom (C-center) in the diamond crystal, and the nitrogen content decreases with the increase of SiC content. This work provides insights for understanding the growth mechanism of natural diamonds and enriching the application of silicon doped diamond single crystals.

A Study on the Surface Quality and Damage Properties of Single-Crystal Silicon Using Different Post-Treatment Processes.

Detecting subsurface defects in optical components has always been challenging. This study utilizes laser scattering and photothermal weak absorption techniques to detect surface and subsurface nano-damage precursors of single-crystal silicon components. Based on laser scattering and photothermal weak absorption techniques, we successfully establish the relationship between damage precursors and laser damage resistance. The photothermal absorption level is used as an important parameter to measure the damage resistance threshold of optical elements. Single-crystal silicon elements are processed and post-processed optimally. This research employs dry etching and wet etching techniques to effectively eliminate damage precursors from optical components. Additionally, detection techniques are utilized to comprehensively characterize these components, resulting in the successful identification of optimal damage precursor removal methods for various polishing types of single-crystal silicon components. Consequently, this method efficiently enhances the damage thresholds of optical components.

Study on Plastic Deformation Removal Mechanism and Dislocation Change in Nanogrinding of Single Crystal Silicon Carbide with Random Rough Surface

This investigation centers on exploring the plastic deformation removal mechanism and dislocation dynamics in the nanogrinding of single‐crystal silicon carbide featuring a randomly rough surface. To simulate this, an approach combining the Weierstrass–Mandelbrot fractal surface function with molecular dynamics is employed. Randomly rough surface contours are generated using the Weierstrass–Mandelbrot fractal surface function. By adjusting the fractal dimension, an ideal representation of single‐crystal silicon carbide with randomly rough surfaces is obtained. By combining plastic deformation detection methods, the process of workpiece sliding, plowing, and chip removal is studied, and the plastic deformation removal mechanism of random rough surface grinding is explored. Combining postprocessing methods such as sheer strain and dislocation trajectory, the morphological changes and transformation mechanisms of dislocations are analyzed. Notably, at grinding depth of 33.18 nm, the activation of slip systems induces dislocation formation, enabling plastic deformation. Furthermore, at depths exceeding 144.00‐nm, the emergence of stacking faults on the random rough surface is observed. Throughout the grinding procedure, plastic deformation of debris occurs, leading to the formation of plastic bulges on both sides of the tool, and the debris generated during processing does not impact the defects encountered during secondary grinding of the rough surface.

Single-Crystal Silicon Nanotubes, Hollow Nanocones, and Branched Nanotube Networks.

We report a general approach for the synthesis of single-crystal silicon nanotubes, involving epitaxial deposition of silicon shells on germanium nanowire templates followed by removal of the germanium template by selective wet etching. By exploiting advances in the synthesis of germanium nanowires, we were able to rationally tune the nanotube internal diameters (5-80 nm), wall thicknesses (3-12 nm), and taper angles (0-9°) and additionally demonstrated branched silicon nanotube networks. Field effect transistors fabricated from p-type nanotubes exhibited a strong gate effect, and fluid transport experiments demonstrated that small molecules could be electrophoretically driven through the nanotubes. These results demonstrate the suitability of silicon nanotubes for the design of nanoelectrofluidic devices.

Reduction of multiple scattering of positively charged ultra relativistic particles channeling in planar fields of single crystals

Based on the theory of multiple scattering of positively charged particles channeled in the planes of a single crystal of silicon, calculations of the rms angle of scattering have been made for particles in the range of momenta 100–7000 GeV/c. As a result of the analysis, we find that the rms angle of multiple particle scattering can be represented by in the form of (Cl)1/w/ph, where p is the particle momentum, l is the crystal thickness and C,w,h are the constant coefficients. We show that these calculation results can be represented in a unified way using the found universal function. This function is shown to be in a good agreement with the experimental data. Furthermore, our analysis is consistent with the effect (predicted by Luboshits and Podgoretsky) of reducing multiple scattering of above-barrier particles moving at small angles to the planes of the crystal. In general, the obtained results give a simple and clear description of the scattering process under consideration.

Dynamic magnetic field magnetorheological finishing with constant load and variable gap

Magnetorheological finishing is limited by weak polishing forces and small polishing areas, resulting in a low polishing efficiency. This study formulates a method for dynamic magnetic field magnetorheological finishing in compression-shear mode with a constant load and variable gap, which can remodel the magnetic particle string using a dynamic magnetic field and enhance the polishing force by a constant load and variable gap. To investigate the impact of process parameters on macro and micro machining processes, as well as their effects, a series of experiments were conducted to investigate the polishing force, machining clearance, and machining effect of single-crystal silicon wafers under four different conditions: static magnetic field magnetorheological finishing (T1), dynamic magnetic field magnetorheological finishing (T2) at a constant gap, static magnetic field magnetorheological finishing (T3), and dynamic magnetic field magnetorheological finishing (T4) with a constant load and variable gap. The results indicated that the shearing force and processing quality significantly improved in the constant-load and variable-gap modes, and the process of machining clearance reduction involved two stages: fast and slow compression. The shearing force of T3 increased by 35 % compared to T1, and T4 increased by 20 % compared to T2. The material removal rate of T3 and T4 increased over time, in contrast to those of T1 and T2. The key parameters of the T4 single-factor shear and machining gap testing experiments show that the constant load variable gap compression process adaptively adjusts the machining gap such that the chain string structure is in a body-centered cubic structure (BCT), increasing the number of abrasive contacts and the depth of pressure into the workpiece to achieve a significant increase in the polishing shear constant load.

Ultrahigh-mobility semiconducting epitaxial graphene on silicon carbide.

Semiconducting graphene plays an important part in graphene nanoelectronics because of the lack of an intrinsic bandgap in graphene1. In the past two decades, attempts to modify the bandgap either by quantum confinement or by chemical functionalization failed to produce viable semiconducting graphene. Here we demonstrate that semiconducting epigraphene (SEG) on single-crystal silicon carbide substrates has a band gap of 0.6 eV and room temperature mobilities exceeding 5,000 cm2 V-1 s-1, which is 10 times larger than that of silicon and 20 times larger than that of the other two-dimensional semiconductors. It is well known that when silicon evaporates from silicon carbide crystal surfaces, the carbon-rich surface crystallizes to produce graphene multilayers2. The first graphitic layer to form on the silicon-terminated face of SiC is an insulating epigraphene layer that is partially covalently bonded to the SiC surface3. Spectroscopic measurements of this buffer layer4 demonstrated semiconducting signatures4, but the mobilities of this layer were limited because of disorder5. Here we demonstrate a quasi-equilibrium annealing method that produces SEG (that is, a well-ordered buffer layer) on macroscopic atomically flat terraces. The SEG lattice is aligned with the SiC substrate. It is chemically, mechanically and thermally robust and can be patterned and seamlessly connected to semimetallic epigraphene using conventional semiconductor fabrication techniques. These essential properties make SEG suitable for nanoelectronics.

Substrate effects on structural and optoelectronic properties of quasi-2D perovskite films

This work presents a comprehensive investigation into the impact of different substrates—both rigid (glass and single-crystal silicon) and flexible (PEN and PDMS)—on the structural and optoelectronic behavior of quasi-2D perovskite films.

ВПЛИВ ТЕХНОЛОГІЧНИХ ЧИННИКІВ НА ЯКІСТЬ ПРИЛАДОВИХ СТРУКТУР

n the modern production of semiconductor devices and integrated circuits, epitaxial compositions are widely used: sili-con single-layer epitaxial structures, silicon inverted epitaxial structures and silicon structures with dielectric insulation. An urgent task is a thorough study of the defects of such structures and technological factors that significantly affect their quality at various stages of the manufacturing process.The purpose of the work is to study the dependence of the density of defects in the substrate and the built-up layer of silicon epitaxial compositions on technological factors and to develop a system that has increased resistance to electromigra-tion and at the same time prevents erosion of silicon in the contact windows.Substrates with a thickness of 260 μm with a crystallographic surface orientation made of single crystals of dislocation-free silicon with a resistivity of 10-50 Оm∙m were taken for the study. Defects in the structure were detected by selective etching and investigated using metallographic and scanning electron microscopes. Processing of the working side of the surface was also carried out: chemical-mechanical polishing with removal of a layer 1-2 microns and 20 microns thick; mechanical pol-ishing with diamond paste with a grain size of 1.0 μm and 5 μm. The processing of the non-working side of the substrates was also different: chemical-mechanical polishing, grinding, hetering -grinding with a free abrasive followed by shallow mechan-ical polishing. After growth, the epitaxial compositions were polished and grinded by chemical-mechanical polishing on both sides to a thickness of 80 μm on the substrate side and 170-180 μm on the side of the built-up layer.During research, the substrates were exposed to various technological factors. The obtained experimental results allow us to conclude that to produce semiconductor device structures based on epitaxial compositions with a low density of disloca-tions, it is necessary to use dislocation-free substrates that do not contain bands of A-type microdefects. All other things being equal, the best quality of epitaxial compositions is achieved by applying thorough chemical-mechanical polishing of the sub-strate on its working side and heterogenization on the reverse side.

A Review on the Third-Generation Solar Cells: Model, Materials, and Performance.

The present solar cells – first and second generation solar cells are very expensive. They are formed from single crystal and poly-crystal silicon (Si) and Si base, CIGS, CdTe and III-V thin films respectively. This led to the idea of third generation photovoltaic modules. This paper presents works on different types of third generation solar cells. This includes organic photovoltaics (OPVs), copper zinc tin sulfide (CZTS), perovskite solar cells, dye-sensitized solar cells (DSSCs), and quantum dot solar cells.

Surface morphology analysis of silicon doped with erbium atoms

This scientific work presents an analysis of the structural and electrical properties of light-emitting structures based on a single crystal of silicon doped with the rare earth element. As a result of thermal treatment of the initial samples at a temperature of 1200 ºC, it was found that the surface relief width of the sample decreased by 1.5÷2 times and the surface height increased by 3 times. According to the atomic force microscope analysis, it was found that n-Si<Er> samples have nanostructured surface defects with a surface relief width of 20÷300 nm and a height of 9÷42 nm. It was found that impurity atoms have a significant effect on the quantitative parameters of the initial sample atoms. As a result of the introduction of Er atoms into the control sample, it was determined that the number of technological impurities (O, C) increased by 10-15% by introducing one of the rare-earth elements (Er).

Effects of different compositional ratios on physical structure and optical properties of thin films during alloying of Zn<sup>2+</sup> and TiO<sub>2</sub>

A batch of TiO<sub>2</sub> films with different Zn<sup>2+</sup> compositions are prepared on a single crystal silicon substrate by using sol-gel method to observe the changes in optical and photocatalytic properties in the alloying process of Zn<sup>2+</sup> and TiO<sub>2</sub>. X-ray diffractometer (XRD) is used to observe the changes in the crystal structures of the films in the alloying process and to track the formation of ZnTiO<sub>3</sub> compounds. Scanning electron microscope (SEM) and atomic force microscope (AFM) are used to observe the phenomena of a large number of holes on the surfaces of the films due to the limited solubility of the crystal lattice for Zn<sup>2+</sup> in the alloying process. X-ray photoelectron spectroscopy (XPS) and optical bandgap are used to observe the changes at a level of the electronic structure of the films in the alloying process of Zn<sup>2+</sup> with TiO<sub>2</sub>. Finally, by degrading the methylene blue solution, it is shown that a small amount of Zn<sup>2+</sup> doping is completely dissolved in TiO<sub>2</sub>, destroying the TiO<sub>2</sub> crystalline quality. As the compositional share of Zn<sup>2+</sup> continues to increase to 15%, the limited solubility of TiO<sub>2</sub> for Zn<sup>2+</sup> is verified in the XPS peak fitting, resulting in a large number of hole structures in the film, and the active specific surface area of the film is enhanced, while Zn<sup>2+</sup> effectively traps the photogenerated e<sup>–</sup>/h<sup>+</sup>. In order to continue to observe the effect of Zn<sup>2+</sup> concentration on TiO<sub>2</sub>, we increase the concentration of Zn<sup>2+</sup> to 40% and observe the phenomenon in the alloying process of Zn<sup>2+</sup> with TiO<sub>2</sub>. It is shown that the appearance of the compound ZnTiO<sub>3</sub> can act as a complex center for e<sup>–</sup>/h<sup>+</sup> and a significant decrease in the percentage of TiO<sub>2</sub> leads to a gradual decrease in the photocatalytic efficiency of the films after alloying.

Ultraprecision machining for single-crystal silicon carbide wafers: State-of-the-art and prospectives

Ultraprecision machining for single-crystal silicon carbide wafers: State-of-the-art and prospectives

In English

In mini-review, deals with the theory of exciton quasimolecules in a nanosystem consisting of double quantum dots of germanium synthesized in a silicon matrix. An exciton quasimolecule was formed as a result of the interaction of two spatially indirect excitons. It is shown that, depending on the distance D between the surfaces of the quantum dots, spatially indirect excitons and of exciton quasimolecules was formedin the nanosystem.The binding energy of the singlet ground state of the exciton quasimolecule has been gigantic exceeding the binding energy of the biexciton in a silicon single crystal by almost two orders of magnitude. The emergence of a band of localized electron states in the band gap of the silicon matrix was found. This band of localized electron states appeared as a result of the splitting of electron levels in the chain of germanium quantum dots. The nature of formation in the Ge/Si heterostructures was analyzed depending on the distance D between the surfaces of QDs SIEs and of exciton quasimolecules.It was shown that the binding energy of the ground singlet state of an exciton quasimolecule was gigantic, exceeding the binding energy of a biexciton in a silicon single crystal by almost two orders of magnitude.The possibility of using quasimolecules of excitons to create elements of silicon infrared nanooptoelectronics, including new infrared sensors, was established. The emergence of a band of localized electron states in the band gap of the silicon matrix was found.In this case, the band of localized electron states appeared as a result of the splitting of electron levels in the chain of germanium QDs.It was shown that the movement of an electron along the zone of localized electron states in the linear chain of germanium QDs caused an increase in photoconductivity.The effect of increasing photoconductivity can make a significant contribution in the process of converting the energy of the optical range in photosynthesizing nanosystems.

Ultra-Smooth Polishing of Single-Crystal Silicon Carbide by Pulsed-Ion-Beam Sputtering of Quantum-Dot Sacrificial Layers.

Single-crystal silicon carbide has excellent electrical, mechanical, and chemical properties. However, due to its high hardness material properties, achieving high-precision manufacturing of single-crystal silicon carbide with an ultra-smooth surface is difficult. In this work, quantum dots were introduced as a sacrificial layer in polishing for pulsed-ion-beam sputtering of single-crystal SiC. The surface of single-crystal silicon carbide with a quantum-dot sacrificial layer was sputtered using a pulsed-ion beam and compared with the surface of single-crystal silicon carbide sputtered directly. The surface roughness evolution of single-crystal silicon carbide etched using a pulsed ion beam was studied, and the mechanism of sacrificial layer sputtering was analyzed theoretically. The results show that direct sputtering of single-crystal silicon carbide will deteriorate the surface quality. On the contrary, the surface roughness of single-crystal silicon carbide with a quantum-dot sacrificial layer added using pulsed-ion-beam sputtering was effectively suppressed, the surface shape accuracy of the Ø120 mm sample was converged to 7.63 nm RMS, and the roughness was reduced to 0.21 nm RMS. Therefore, the single-crystal silicon carbide with the quantum-dot sacrificial layer added via pulsed-ion-beam sputtering can effectively reduce the micro-morphology roughness phenomenon caused by ion-beam sputtering, and it is expected to realize the manufacture of a high-precision ultra-smooth surface of single-crystal silicon carbide.