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AIP Conference Proceedings [Author(s) SILICONPV 2018, THE 8TH INTERNATIONAL CONFERENCE ON CRYSTALLINE SILICON PHOTOVOLTAICS - Lausanne, Switzerland (19–21 March 2018)] - Atom probe Tomography of fast-diffusing impurities and the effect of gettering in multicrystalline silicon
摘要： This article demonstrates an approach for multiscale characterisation of individual defects, such as grain boundaries, in multicrystalline silicon. The analysis techniques range from macroscale characterisation of average bulk lifetime, through photoluminescence to resolve spatial recombination, and finally to nanoscale analysis of the crystallographic characteristics and impurity decoration of the grain boundary using Transmission Kikuchi Diffraction and Atom Probe Tomography. This method can be used to characterise defects and their response to processing, such as gettering and hydrogen passivation. In this paper it is applied to the test case of Saw Damage Gettering on Red Zone High Performance Multicrystalline Silicon. In both as-cast and gettered samples, copper and chromium were observed at a recombination active, random angle grain boundary. After gettering the copper excess was found to decrease. In contrast, the slower diffusing chromium was found to increase, potentially indicating internal gettering. At a recombination inactive Σ3 grain boundary only oxygen was observed at the boundary before gettering, with no transition metals detected.
关键词： multicrystalline silicon,grain boundaries,gettering,impurities,Atom Probe Tomography
更新于2025-11-21 11:20:48
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Optical Imaging of Charges with Atomically Thin Molybdenum Disulfide
摘要： Mapping local surface charge distribution is critical to the understanding of various surface processes and also allows the detection of molecules binding to the surface. We show here that the optical absorption of monolayer MoS2 is highly sensitive to charge and demonstrate optical imaging of local surface charge distribution with this atomically thin material. We validate the imaging principle and perform charge sensitivity calibration with an electrochemical gate. We further show that binding of charged molecules to the atomically thin material leads to a large change in the image contrast, allowing determination of the charge of the adsorbed molecules. This capability opens possibilities for characterizing impurities and defects in two dimensional materials and for label-free optical detection and charge analysis of molecules.
关键词： electrochemical gate,monolayer molybdenum disulfide,protein binding,local charge imaging,charged impurities
更新于2025-09-23 15:23:52
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Electronic Raman scattering as a probe for investigating interactions between impurities in silicon
摘要： Electronic Raman scattering (ERS) is investigated as a probe for interactions between impurities in silicon. We report ERS measurements of donors (P, Sb, and As) and acceptors (B) at various concentrations and measurements at various illumination wavelengths. The difference between above and below indirect band gap measurement is discussed in terms of the difficulties of using ERS as a localised probe. We extend the previous literature on impurity interactions of Si:P in the bulk to include Sb and B and demonstrate that the perturbation of the observed ERS transition energy resulting from wavefunction overlap of nearest neighbours is opposite for donors and acceptors. Finally, we model the magnitude of the shift to the first order as a function of the mean impurity atom separation.
关键词： silicon,electronic raman scattering,impurities
更新于2025-09-23 15:22:29
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Differential charging effects from impurities in pyrolytic graphite
摘要： This work reports differential charging effects in samples of pyrolytic graphite. Despite being considered a nuisance in XPS analyses, differential charging effects can be exploited for the identification and quantification of chemical species in heterogeneous materials. In this case, charging effects were useful to identify impurities at the surface of pyrolytic graphite. For these impurities, the analysis of the O 1s, Si 2p, and Al 2p core levels allowed distinguishing the contributions of SiO2 and Al2O3 from those of silicone/alumino-silicate oxides. Though both groups of compounds are insulators, a splitting of the above peaks was induced by the use of the flood gun device of the spectrometer when the samples were mounted on a conductive metallic sample holder. The shape and relative concentration of the chemical species ascribed to the split peaks served as a basis for the decomposition of the corresponding O 1s, Si 2p, and Al 2p peaks registered over a ceramic sample holder. The latter allowed for inducing a well controlled differential charging of the samples that led to the identification of true chemical shifts, i.e. those ascribed to variations on the chemical environment of the elements. A qualitative model for describing the observed charging effects was postulated. The model was based on an analogy between electrical circuits and the geometrical configuration of the impurity particles intercalated within the graphite particles.
关键词： XPS,Inorganic impurities,O 1s,Pyrolytic graphite,Flood gun,Differential charging
更新于2025-09-23 15:22:29
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Synthesis, characterization and optical property study of BCNO and BCN related nanopowder
摘要： Boron carbon oxynitride (BCNO) and BCN nanocompounds are successfully synthesized by a solid state sintering method using boric acid, urea and dextrose as the sources of B, N and C respectively under inert atmosphere. X-ray diffraction (XRD) and infrared spectroscopy (FTIR) analysis show that nanomaterials are synthesized at the high temperature range of 1350 oC. Sufficient amount of oxygen impurities are present in the sample, which is manifested in their photoluminescence spectra. Increase in temperature to 1350 oC under N2 atmosphere causes elimination of significant amount of O-species from the system. The presence of ample amount of carbon in the system results in the formation of high amount of polycrystalline h-BCN with minor amount of h-BN. However, some residual oxygen in the sample, which is detected in the FTIR study, leads to the formation of BCNO compound. These semiconductor BCNO compounds act as the potential luminescence centers for the blue-green emissions of the particles. Thus, these materials may find potential application as a phosphor material in various opto-electronic devices.
关键词： optical properties,carbon,boron carbon nitride,Boron carbon oxynitride,impurities
更新于2025-09-23 15:22:29
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Granular Inhomogeneity Formation during Quartz Glass Melting
摘要： This paper examines the formation of fine-grain inhomogeneity in quartz glass. We demonstrate that this defect emerges during the melting of fine-particle crystalline raw materials and the formation of a three-dimensional intergranular network, which contains a high impurity concentration and has a disordered structure. The present results are inconsistent with the existing believe that incomplete melting of quartz grains is the main cause of the development of fine-grain inhomogeneity. In contrast, prolonged high-temperature heat treatment increases the intergranular impurity concentration and intensifies the effect.
关键词： quartz grit grains,grain boundaries,structural impurities,structure of quartz glass
更新于2025-09-23 15:22:29
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: A first-principles study
摘要： For environmental reasons there is a need for alternative Cd-free buffer materials in Cu(In,Ga)(S,Se)2 (CIGSSe) based thin film solar cells. In this context, β-In2S3 is one candidate material, whose optoelectronic properties can be affected by the presence of impurities. In this study, we investigate the impact of O and Cl impurities on the electronic and optical behavior of β-In2S3 by means of electronic structure calculations within density functional theory using hybrid functionals. We find that β-In2S3 is thermodynamically stable being in contact with both O and Cl reservoirs. Furthermore, we present evidence that O on interstitial sites (Oi) and Cl on 8c In sites (ClIn) cause low-temperature persistent electron photoconductivity. At room temperature, defect levels associated with Cl on S sites (ClS, ClS(cid:2) , and ClS(cid:2)(cid:2) ) get thermally ionized and release free electrons into the system. Thus, the n-type conductivity of the In2S3 buffer layer increases. O impurities on S sites, in contrast, are electrically inert. Hence, we conclude that intentional doping by Cl is a means to improve the properties of β-In2S3 serving as buffer material.
关键词： β-In2S3,hybrid functionals,O and Cl impurities,n-type conductivity,density functional theory,persistent electron photoconductivity,electronic structure calculations
更新于2025-09-23 15:21:21
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Realization of high efficiency and low damage machining of anisotropic KDP crystal by grinding
摘要： Potassium dihydrogen phosphate (KDP) is a non-linear material used in various opto-electronic applications including Q-switches, high-speed photography shutters, frequency harmonic generation lens and Pockels cells in the Inertial Confinement Fusion (ICF) devices. KDP belongs to the most difficult-to-cut material, due to its delicate and unique characteristics including the combination of softness with brittleness, anisotropic performances, tendency for deliquescence and sensitivity to temperature change. Single point diamond turning (SPDT) is considered to be the ideal method for machining KDP components. However, the process efficiency is rather low and often accompanied with severe tool wear issues. This paper studies the feasibility using grinding method to remove the surface material of KDP components with high process efficiency and low damage, fulfilling the task of re-aligning the surface orientation to the crystalline axis. The grinding tests were carried out on a common CNC grinder, using resin bonded diamond grinding wheel, whilst the diamond abrasives are coated with Ni-P alloy. The direction of precision grinding was determined by studying the anisotropy of KDP, including its elastic modulus E, Vickers hardness HV and fracture toughness KIC, to reduce the influence of material anisotropy on machining quality. The grinding process parameters were preliminarily determined based on the experimental results investigating the effects of peripheral speed of the grinding wheel, worktable feed rate and grinding depth on the ground surface roughness. The surface defects, surface morphology and sub-surface damage under different process parameters were investigated. Surface roughness Ra ≤ 0.3μm and sub-surface damage depth SSD ≤ 6μm were obtained. The machining efficiency can be improved by nearly ten times using the proposed precision grinding method, producing nearly the same surface quality (Ra ≤ 0.2μm, SSD ≤ 6μm) as that in the axis fixing phase in SPDT.
关键词： KDP crystal,Crystal axis fixing,Machining efficiency,Sub-surface damage,Grinding,Typical impurities embedded
更新于2025-09-23 15:21:01
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Terahertz shifted Fano resonance-induced plasmon-soliton in graphene-plasmonic waveguide with magnetic impurities
摘要： Fano resonance is a quantum effect particularly useful for determining the optical spectra of semiconductor heterostructures and radiation enhancement of semiconductor-based devices. We deal with the nonlinear amplitude equation to find the nonlinear plasmon modes and breather solutions in a magnetic impurities-added graphene-plasmonic waveguide at near and mid-IR frequency range. The results show that the coupling degree between the plamon modes and breather solutions in order to form plasmon-solitons is intensely influenced by the effective nonlinear refraction assigned to the waveguide and also by the Fermi energy; tunable plasmon-solitons can be formed with a lowly required bias voltage. We also deduce that the stable plasmon-solitons and subsequently the most condensed radiative feature with the largest effective propagation length can be obtained at interband transition edge if the resonance of the effective nonlinear refraction is of Fano type. The reason is inferred as the presence of a reversible mechanism caused by the optical doping which in turn bears a successive competition between the diffraction and nonlinearity. Accordingly, we indicate that the Fano resonance- induced plasmon-soliton modes supported by the Co-added graphene-plasmonic waveguide experience a frequency shift up to Δω ? 60 THz in contrast to the plasmon-soliton modes in the pristine graphene-based waveguide. This in turn, proposes a novel technique for the spectroscopy of magnetic impurities-added graphene-dielectric heterostructures. On the other hand, very sensi- tive modulation of the nonlinear response tunable with a low Fermi energy as presented in this study can delineate modern schemes for the next generation graphene plasmonic devices including the nanoscale radiation sources, modulators, biosensors and couplers.
关键词： Fano resonance,Graphene plasmonic waveguide,Plasmon-soliton,Nonlinear refraction,Breather solution,Magnetic impurities
更新于2025-09-23 15:19:57
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Laser-induced breakdown spectroscopy of uranium in the VUV range
摘要： Quantitative analysis of impurities in nuclear materials is necessary in a number of areas, including process control during manufacturing, quality control of products, or for nuclear forensics purposes. Due to the important handling constraints induced by the samples radioactivity and their containment inside airtight enclosures, optical analytical techniques have great advantages over standard ones that require sample preparation, like ICP-based techniques. Therefore, laser-induced breakdown spectroscopy (LIBS) is developed for fast quantitative analysis of impurities in uranium. Actinides are well-known to have a very large number of emission lines in the UV-visible spectral range, hence making the detection of trace or minor elements a real challenge. Therefore, in this study we explored the vacuum ultraviolet range (VUV), i.e. below 200 nm, in order to investigate if this spectral region is more favorable for elemental analysis of uranium by LIBS. As practically no data on VUV spectroscopy of uranium are available, we first analyzed the spectra obtained to assess the spectral density of uranium lines, both in the UV and VUV. Then, the detection limits of two elements, carbon and vanadium, were estimated. It was found that, in spite of a less dense and less intense uranium background in the VUV, this spectral region is not relevant for metal impurities whose spectra are marginally analytically useful in the VUV. Conversely, for non-metals having intense lines in the VUV, the detection limit can be significantly better than in the UV. This was already known for non-nuclear samples. This study extends that conclusion to nuclear materials and has important practical consequences on the implementation of a LIBS analyzer in a nuclear facility.
关键词： vanadium,uranium,Laser-induced breakdown spectroscopy,impurities detection,carbon,VUV range
更新于2025-09-23 15:19:57