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- 2019
- polycrystalline ferrite-garnet
- magnetoplasmonic crystals
- magnetooptical effects
- deposition
- ion-beam methods
- sputtering
- plasmon resonance
- Physics
- Moscow Technological University
- Moscow State University
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Origin of milky optical features in type IaB diamonds: Dislocations, nano-inclusions, and polycrystalline diamond
摘要： The milky appearance shown by certain type IaB diamonds has been subjected to several recent studies, but the origin of this feature is not fully understood. Here several type IaB diamonds with a milky appearance have been studied by cathodoluminescence (CL), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). CL of several hazy type IaB diamonds shows scattered or orientated micro-sized spots or short linear luminescence features. TEM observation revealed that those spots and linear features are caused by dislocation loops that are likely responsible for the hazy appearance of the host diamonds. It is also shown that type IaB diamonds with a cloudy appearance contain nano-sized inclusions with negative crystals of octahedral shape. Some of these negative crystals contain a precipitate that can be explained by a compressed disordered cubic δ-N2 phase observed by high-resolution TEM. In one of the milky IaB diamonds with platelet defects, polycrystalline areas composed of columnar diamond crystals elongated radially in [110], similar to ballas diamond, were revealed by EBSD. Taking into account these observations, it is suggested that the dislocation loops, nano-sized inclusions (negative crystals) and/or characteristic grain boundaries of the radiating fibrous crystals would be the origins for the milky appearance of the type IaB diamonds studied here. Those results add a complementary explanation that accounts for the milkiness of type IaB diamonds studied before.
关键词： Type IaB diamonds,Nanominerals and Mineral Nanoparticles,milky,voidites,dislocations,polycrystalline diamond
更新于2025-11-21 11:18:25
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The current-voltage characteristics of the ferroelectric p-YMnO3 thin film/bulk p-Si heterojunction over a broad measurement temperature range
摘要： The reverse and forward bias I-V characteristics of the Al/p-YMO/p-Si/Al heterojunction were measured at room temperature (RT) and over temperature range, from 50 to 320 K, and the I-V curves showed Schottky diode-like characteristics. The ideality factor and barrier height values were calculated as 0.81 and 2.62 from the forward bias I-V curve at room temperature (300 K), respectively. The YMO powder was prepared via solid state reaction technique. YMO thin films were grown on front surface of p-Si substrate by radio frequency (rf) magnetron sputtering using a polycrystalline YMO single target. The YMO thin film thickness on Si substrate was measured as ~70 nm via Dektak XT surface profilometer. The XRD, SEM, UV-Vis and XPS measurements of the YMO thin film were also performed. The bandgap energy of YMnO3 thin films was determined as 2.10 eV by UV-vis. The temperature-dependent reverse and forward bias I-V curves were evaluated in terms of thermionic emission (TE), Schottky emission, Fowler-Nordheim (F-N) tunneling and space charge-limited current (SCLC) current theories. Furthermore, it has been seen that the forward bias conduction in the junction at each temperature obeys F-N tunneling because of the linearity in the ln (I/V2) versus V-1 curves.
关键词： Polycrystalline,Heterojunction,Ferroelectric,Al/p-YMO/p-Si/Al,Schottky barrier,YMnO3,Temperature dependent current characteristics
更新于2025-09-23 15:23:52
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The effect of cut depth and distribution for abrasives on wafer surface morphology in diamond wire sawing of PV polycrystalline silicon
摘要： Due to the existence of an acid etch resistant thin amorphous silicon layer over the smooth grooves of the diamond wire sawing polycrystalline silicon wafer surface, the anti-re?ection e?ect is usually not ideal using the mature acidic texturization. The amorphous silicon layer will be produced on the machined surface by material ductile removal. Therefore, during the process of cutting photovoltaic polycrystalline silicon wafers, the material removed in the brittle way is expected and the surface topography of the wafers formed with the brittle fracture is better for the texture fabricating. In this paper, a mathematical model considering the in?uences of process parameters and wire saw parameters was developed based on indentation fracture mechanics. The variations of cutting groove pro?le formed by di?erent material removal modes were also included. The e?ect of abrasives distributed on the wire saw on material removal and surface formation of polysilicon was analyzed. The results showed that most of abrasives removed material with ductile removal mode, however, the volume of the material removed by abrasive in ductile mode is less than 10% of the total removal volume. Brittle fracture removal mode was still the major way of material removal in diamond wire sawing. With the same ratio of the feed rate and wire speed, the faster feed rate and wire speed will not only improve the cutting e?ciency, but also is easier to obtain a brittle fracture surface. There is a critical angle θc for the distribution of abrasives on the wire saw surface. Only when the position angle of the abrasive removing material in brittle mode is less than θc, the brittle fracture can be formed on the wafers surface.
关键词： Diamond wire sawing,Depth of cut,Material removal mode,Photovoltaic polycrystalline silicon
更新于2025-09-23 15:23:52
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Effect of substrate temperature on the physical properties of SnS <sub/>2</sub> :Cu thin films deposited by spray pyrolysis
摘要： The main impetus of the present study is to investigate thin films of tin disulfide that have been doped with copper impurities and prepared on glass substrates by using the spray pyrolysis technique. Also, the influence of the substrate temperature on the structural, optical, and electrical properties of these films are investigated. The thin films have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical absorption (UV–vis) analyses. The XRD patterns clarify that the thin films possess polycrystalline structures, having a peak associated with the (001) plane of the SnS2 phase. The average crystalline grain sizes were estimated to be within the range 5.7–7.1 nm. The SEM images indicate that the grain size increases from 53 to 114 nm with an increment in the substrate temperature, resulting in an increasing–decreasing trend in the band gap of the thin films. However, the films’ resistance decreases from 92.5 to 0.174 Ω·cm as the substrate temperature increases from 400 to 450 °C. Also, their optical energy band gap depicts an increasing–decreasing trend with the estimated values of 2.81, 3.21, and 3.06 eV at 400, 425, and 450 °C, respectively. The thin films exhibit n-type conductivity.
关键词： polycrystalline,spray pyrolysis,thin film
更新于2025-09-23 15:23:52
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Research on Micro-Size Electrical Discharge Machining Polycrystalline Diamond
摘要： With the demand of modern cutting technology for ‘high efficiency, precise, flexibility and green manufacturing’, polycrystalline diamond materials as cutting tools have been widely used in automobile, aerospace and non-metal processing. Electro-spark erosion is one of the most effective ways to machine polycrystalline diamond materials. Single pulse discharge is one of the research foundations of micro-EDM. Using 2 micron granularity polycrystalline diamond as experiment material, the influence of single pulse discharge technology on the removal efficiency of materials was studied, such as pit radius, pit depth and radius-depth ratio, etc. The experimental results show that, with the extension of the pulse duration, the radius of the discharge pit begins to increase rapidly, then slowly increases, and finally to slow down; while the radius of thermal influence zone increases rapidly and then continues to increase slowly. With the extension of pulse duration, the ratio of pit depth to radius changes within the range of 0.05 ~ 0.25, which shows a downward trend basically.
关键词： Single pulse,Micro-size,Polycrystalline diamond (PCD),Electrical Discharge Machining (EDM),Corrosion pit size
更新于2025-09-23 15:22:29
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The effect of grain-size on fracture of polycrystalline silicon carbide: A multiscale analysis using a molecular dynamics-peridynamics framework
摘要： A robust atomistic to mesoscale computational multiscale/multiphysics modeling framework that explicitly takes into account atomic-scale descriptions of grain-boundaries, is implemented to examine the interplay between grain-size and fracture of polycrystalline cubic silicon carbide (3C-SiC). A salient feature of the developed framework is the establishment of scale-parity between the chosen atomistic and the mesoscale methods namely molecular dynamics (MD) and peridynamics (PD) respectively, which enables the ability to model the effect of the underlying microstructure as well as obtain relevant new insights into the role of grain-size on the ensuing mechanical response of 3C-SiC. Material properties such as elastic modulus, and fracture toughness of single crystals and bicrystals of various orientations are obtained from MD simulations, and using appropriate statistical analysis, MD derived properties are interfaced with PD simulations, resulting in mesoscale simulations that accurately predict the role of grain-size on failure strength, fracture energy, elastic modulus, fracture toughness, and tensile toughness of polycrystalline 3C-SiC. In particular, it is seen that the fracture strength follows a Hall-Petch law with respect to grain-size variations, while mode-I fracture toughness increases with increasing grain-size, consistent with available literature on brittle fracture of polycrystalline materials. Equally importantly, the developed MD-PD multiscale/multiphysics framework represents an important step towards developing materials modeling paradigms that can provide a comprehensive and predictive description of the microstructure-property-performance interplay in solid-state materials.
关键词： Peridynamics,Polycrystalline,Multiscale modeling,3C-SiC,Grain boundaries,Molecular dynamics
更新于2025-09-23 15:22:29
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Investigation of hydrogen effect on phosphorus-doped polysilicon thin films
摘要： Polycrystalline silicon is widely used in microelectronic and photovoltaic applications. The main problem of this material is the recombination of charge carriers at the grain boundaries which affects the efficiency of the polycrystalline silicon solar cells. In order to improve the crystalline quality and the electrical properties of phosphorus-doped poly-silicon thin films, heat treatments under hydrogen were carried out. This allowed the occupation of the dangling bonds at the grain boundaries and made them inactive, which resulted in improved optoelectronic properties of the treated samples. It has been shown that the effect of hydrogen on the electrical characteristics is more pronounced for low doping concentrations where a 20% improvement of the free carrier concentration was obtained. In addition, the results have shown that the introduction of hydrogen in poly-silicon thin films reduces the density of trap states at the grain boundaries.
关键词： hydrogen,passivation,solar cells,grain boundaries,Polycrystalline silicon
更新于2025-09-23 15:21:21
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Study of solar irradiance and performance analysis of submerged monocrystalline and polycrystalline solar cells
摘要： Underwater photovoltaic (PV) systems supported with modern-day technology can lead to possible solutions for the lack of long-term power sources in marine electronics, navy corps, and many other remotely operated underwater power systems. Currently, most of these systems are powered by conventional batteries, which are bulky, costly, and require periodic maintenance and replacement. Harnessing the underwater Solar energy by using Solar PV cells is simple, reliable, and leads to tremendous advantageous as water itself provides cooling, cleaning, and avoid challenges due to land constraints. The present work encompasses an experimental study on Solar radiation in water and its changes with varying water conditions. Accordingly, the performance of monocrystalline and polycrystalline silicon solar cells with different submerged water conditions and water depths up to 20 cm has been studied. Most importantly, these studies have been carried out with different types of water conditions, consisting of salinity, bacteria, algae, and other water impurities. These investigation results manifest that the percentage decrease of maximum power output in monocrystalline and polycrystalline Solar cells is 65.85% and 62.55%, respectively, in the case of ocean water conditions, whereas in deionized (DI) water conditions, it is 63.06% and 60.72% up to 20 cm. Such results conclude that valuable amount of Solar energy is can be explored underwater. These experimental studies pave the way to explore further to utilize Solar PV cells efficiently in underwater conditions.
关键词： monocrystalline Solar cell,underwater Solar radiation,photovoltaic (PV) technology,PDMS (polydimethylsiloxane),water salinity,polycrystalline Solar cell
更新于2025-09-23 15:21:01
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The impacts of LPCVD wrap-around on the performance of n-type tunnel oxide passivated contact c-Si solar cell
摘要： In this paper, Tunnel Oxide Passivated Contact (TOPCon) silicon solar cells with the industrial area (244.32cm2) are fabricated on N-type silicon substrates. Both the ultra-thin tunnel oxide layer and phosphorus doped polycrystalline silicon (polysilicon) thin film are prepared by the LPCVD system. The wrap-around of polysilicon is observed on the surface of borosilicate glass (BSG). The polysilicon wrap-around can form a leakage current path, thus degrades the shunt resistance of solar cells, and leads to the degradation of solar cell efficiency. Different methods are adopted to treat the polysilicon wrap-around and improve shunt resistance of solar cells. The experimental results indicate that a chemical etching method can effectively solve the problem of polysilicon wrap-around and improve the performance of solar cells. Finally, a conversion efficiency of 22.81% has been achieved by our bifacial TOPCon solar cells, with Voc of 702.6 mV, Jsc of 39.78 mA/cm2 and FF of 81.62 %.
关键词： LPCVD,wrap-around,Tunnel oxide passivated contact,polycrystalline silicon thin film
更新于2025-09-23 15:21:01
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Influence of Film Morphology on Transient Photocurrent Pulse Shape in Organic Thin Films: A Monte Carlo Study
摘要： The in?uence of ?lm morphology on the broadening of the time-of-?ight transient photo-current pulse is investigated using Monte Carlo simulation. Simulation of the time-of-?ight transient photo-current pulse shape is carried out for homogeneous and inhomogeneous organic thin ?lms by varying the overall energetic disorder. In homogeneous system, the value of the tail broadening parameter (W) of the photocurrent pulse is found to decrease upon decreasing the energetic disorder, which can be attributed to the variation in the non-thermal ?eld assisted diffusion. Interestingly, in the case of inhomogeneous system, upon decreasing the overall energetic disorder of the system the value of W initially attains a maximum value before it starts decreasing. This observation is explained in terms of the morphology dependent carrier diffusion. This study asserts the importance of the in?uence of the morphology dependent carrier diffusion on the charge transport in disordered systems and the related experimental measurements.
关键词： Polycrystalline organic thin ?lms,Charge transport,Tail broadening,Diffusion,Time of ?ight photoconductivity,Film Morphology
更新于2025-09-23 15:21:01