Effect of post-implantation annealing on the current-voltage characteristics of IR photodiodes based on <Emphasis Type="Italic">p</Emphasis>-HgCdTe

Current-voltage characteristics of IR photodiodes and distributions of charge carriers in n ⁺-n ⁻-p-structures based on vacancy p-doped Hg_{1 − x} Cd _x Te films with x = 0.22 are examined. Three-dimensional numerical modeling of the distribution of charge carriers and current-voltage characteristics during photodiode annealing is performed. The calculations predict that large tunnel currents in diodes after implantation can result from an elevated (more than 10¹⁵ cm⁻³) concentration of donors in the n ⁻-layer, which enhances tunneling by decreasing the thickness of the space charged region of the n-p-junction, and also from a small (less than 3 μm) depth of the p-n-junction.     

射频CO2激光陶瓷基板划片机光路设计及分析

介绍了RFCO₂激光陶瓷基板划片的特点.分析了导光系统的设计原则,着重讨论了圆偏振镜和伽利略离焦望远镜的作用和特点.对导光系统进行了优化和模拟,给出了导光系统的光路图及成像质量图.试验结果和理论相符,系统划片速度可达10m/min,划缝宽度<0.1mm,划缝深度>0.3mm.利用所设计的陶瓷划片机加工的氧化铝陶瓷基片可与国外同类划片机相媲美.     

碳纤维增强复合材料水导激光加工实验研究

为了研究水导激光加工关键工艺参数对碳纤维增强复合材料(CFRP)沟槽截面形貌与热影响区的影响,利用水导激光加工设备设计单因素实验探究了激光功率、水射流压力、进给速度及激光重复频率四个关键工艺参数对沟槽截面形貌以及热影响区的影响规律,分析了沟槽截面形貌和热影响区形成机理。实验结果表明：激光功率对沟槽烧蚀深度和热影响区的影响最大,水射流压力对沟槽烧蚀宽度的影响最大,进给速度和激光重复频率对沟槽烧蚀深度和宽度的影响不大,对热影响区有较大影响。此外,发现沟槽截面去除区呈V字形,热影响区呈锯齿形状。通过单因素方法分析得到了较好的沟槽截面形貌,其沟槽截面烧蚀深度为772.8μm,烧蚀宽度为897.7μm,铺设方向为90°的碳纤维层热影响区为326.5μm,铺设方向为0°的碳纤维层热影响区为102.4μm。     

A comparative study of switching possibilities of silicon diodes with different axial distribution shapes of recombination centers

Three groups of silicon p ⁺-n-n ⁺ diodes with a small turn-off time ensured by charged particle irradiation were studied in the high-power (3 kA) and short (50 μs) current pulse switching modes. The diodes of the first group were irradiated by electrons with a 550-keV energy, those of the second group were irradiated by protons with a 2.5-MeV energy and then by electrons with a 6-MeV energy, and those of the third group were irradiated by electrons with a 6-MeV energy. The studied diodes have a 16-mm semiconductor element diameter and 3-kV maximum permissible disabled voltage. The radiation doses were selected in such a way as to obtain an approximately equal current carrier lifetime near the p ⁺-n junction (4 μs), measured by the Lacks method, when the forward current density is 1 A/cm². It was determined that, when diodes of the first group change to the OFF position, the peak power of energy losses is two and more times smaller than that of diodes of the second and third groups, when they are switched off. The diodes of the first group also feature a substantially smaller voltage, when the forward current is at maximum (by two times as compared with diodes of the second group and by seven times as compared with diodes of the third group) and significantly smaller (by several times) voltage spike at a sharp forward current increase instant.     

Registration of picosecond CO<Subscript>2</Subscript> laser pulses by means of two-stage parametric transformation in nonlinear crystals

A technique for registering the temporal structure of picosecond pulses of CO₂ laser radiation with an energy of 1.5–4.5 μJ at a wavelength of 10.27 μm using two-stage parametric transformation of IR radiation frequency into visible light under pumping of nonlinear crystals by Nd:YAG-laser radiation in a Q-switched mode is described. A GaSe nonlinear crystal was used at the first stage of transformation (10.27 μm + 1.064 μm → 0.964 μm). Radiation was further transformed (1.064 μm + 0.960 μm → 0.506 μm) by using the same pumping in an α-HIO₃ nonlinear crystal. For the first time, no additional optical elements were present between the stages of the frequency transformer in the proposed optical scheme. The transformed radiation was registered with a Hamamatsu Temporal Disperser C1587 streak camera in a region of the photocathode maximum spectral sensitivity of ～0.5 μm with a temporal resolution of up to 2 ps. The minimum recorded pulse duration of the CO₂ laser was ～45 ps.     

Method of reducing the gap between chips in mosaic photodetector modules

A method is proposed to shape the edges of chips in order to reduce the gap between chips in infrared-sensitive mosaic photodetectors modules. The method involves laser scribing of asymmetric grooves, splitting-off of the edge of the chip surface going under the chip, and the subsequent vertical alignment of the edges using laser radiation. The width of the gap between chips is 1–3 μm.     

Buried amorphous-layer impact on dislocation densities in silicon

The impact of amorphous layers on dislocation densities in silicon piezoresistors was investigated by means of transmission electron microscopy and chemical etching. Mechanical bevel polishing at a shallow angle and selective etching were applied to assess the dislocation depth distributions. It was found that, despite the presence of additional defects after recrystallization, the initial presence of a buried amorphous layer reduced, after annealing, the dislocation density in the depletion region of a p–n junction, compared with the case of a shallower, surface amorphous layer.     

The use of an Er:YAG laser to remove demineralized dentin and its influence on dentin permeability

The purpose of this study was to analyze, correlate, and compare the demineralization and permeability of dentin remaining after caries removal with either an Er:YAG laser, a bur, or a curette. Thirty human dentin fragments were immersed in a demineralizing solution for 20 days and were randomly divided into three groups (n = 10) for the removal of the demineralized lesion. The groups were G1—Er:YAG laser (200 mJ/6 Hz; noncontact at 12 mm; spot: 0.63 mm), G2—Bur, and G3—Curette. The specimens were then immersed in a 10% copper sulfate solution, then in a 1% dithiooxamide alcoholic solution for 30 min and kept in ammonia vapor for 7 days. Next, the specimens were examined with optical microscopy. The amount of demineralized dentin and the level of copper ion infiltration in the dentin were quantified in μm using Axion Vision software. Data were analyzed with the Kruskal‐Wallis test (p < 0.05) and Pearson's Correlation test. The analysis revealed no significant differences between the three caries removal methods in terms of their capacity to remove demineralized tissue (G1: 10.6 μm; G2: 8.4 μm; G3: 11 μm), although the laser removal generated more tissue permeability than the others methods (G1: 17.6 μm; G2: 6.6 μm; G3: 5.5 μm). The correlation between the remaining demineralized dentin and the dentin permeability was moderate for the conventional methods and higher for the Er:YAG laser. It can therefore be concluded that the laser produced an increase in permeability that was directly proportional to the amount of demineralized tissue removal. Microsc. Res. Tech. 76:225–230, 2013. © 2012 Wiley Periodicals, Inc.     

A compensation method for measuring the junction temperature of a p +-p-n + silicon structure

The principle of determining the temperature of an active junction is considered. The method is based on measuring the temperature dependence of the forward bias voltage using the compensation method that provides the direct calibration of the junction temperature as a function of the bias voltage. An example of a microwave diode on a p ⁺-p-n ⁺ silicon structure is used to determine the dependences of the junction temperature on the magnitude of the flowing direct current and applied pulsed power with a variable frequency.     

EBIC microscopy of double-heterostructure laser materials and devices

The electron beam induced current (EBIC) mode of the scanning electron microscope (SEM) has been used to characterize double heterostructure laser materials and devices in GaAs/Ga_1–xAl_xAs. Scanning the electron probe across the cleaved face of the laser structure shows that displacement of the p-n junction with respect to the heterojunctions is not uncommon with displacements ～ 1 μm occurring. Concurrent measurement of the minority carrier diffusion length gives very short lengths of 0·3–0·4 μm, differing from those in much thicker layers. Scanning the electron probe in the contact plane indicates clearly that long-lived lasers exhibit marked heterogeneity during degradation. Considerable complexity and variation is recorded depending upon the fabrication details and degradation conditions adopted.     

A Nanographite Film-Based Fast Response Detector for Intense Laser Radiation

A simple high-speed photodetector of high-power laser radiation, based on the optical rectification effect, is described. It operates without an external power source. A nanographite film deposited onto a silicon substrate using the plasmochemical deposition technique and having two conducting surface electrodes is used as the photodetector’s photosensitive element. The performance of this device was demonstrated by detecting pulsed laser radiation in a spectral range of 0.266–1.9 µm using the second, third, and fourth harmonics of radiation from an YAG : Nd³⁺ laser with passive Q-switching and radiation from light oscillators based on stimulated Raman scattering in compressed hydrogen. It was shown that the photodetector sensitivity is proportional to the optical radiation frequency and its response time is shorter than 0.5 ns.__________Translated from Pribory i Tekhnika Eksperimenta, No. 3, 2005, pp. 84–89.Original Russian Text Copyright © 2005 by Mikheev, Zonov, Obraztsov, Svirko, Volkov.     

Optimization of the structure of a GaInP/GaAs/Ge triple-junction solar cell with an Al0.1Ga0.9As/Al0.8Ga0.2As integrated bragg reflector

The structure of a GaInP/GaAs/Ge triple-junction solar cell (SC) with an integrated Bragg reflector (BR) is optimized, resulting in reduction of losses of transmitted (reflected) radiation in tunnel diode layers. The optimized structure of the SC with a BR is obtained by means of metalorganic chemical vapor deposition. 20 × 30-mm SC samples are manufactured. The samples of SCs with and without BRs are tested under the action of electron fluxes with the energies of 1 MeV. It is shown that the SC radiation resistance can be increased by integrating a Bragg reflector into the SC structure and decreasing the thickness of the middle p-n junction base..     

Studying the statistical distribution of single-photon pulses from avalanche photodetectors

The statistical distributions of pulses from silicon avalanche photodetectors with p ⁺ n-v-n ⁺ and n ⁺ p-π-p ⁺ structures have been investigated in the photon-counting mode. Comparative analysis of the statistical distributions for these avalanche photodetectors is presented.     

Effect of formation of grooves in sapphire and filling them with indium under the action of laser radiation

A groove coated with a layer of indium that fills the groove during its formation is generated on the lower surface of sapphire in a single process under the action of laser pulses. The process is performed by using a pulsed gas laser with a wavelength of 0.337 µm. The laser beam is focused through sapphire onto a surface coated with indium. The sapphire motion velocity is uniform, and the sapphire displacement during the time between two pulses is 10% of the light spot diameter. The groove is formed by using the scanning mode (multiple passes of laser radiation through the groove). The pulse energy density in a single pass is sufficiently large. The process is carried out in air. It is found that the optimal option is two passes when the specific resistance of indium in the groove is only 3.8 times greater than the resistance of pure (99.999%) indium bars..     

An X-ray Backlighting Technique Based on Using X-Pinch Radiation for Probing the Plasma of Multiwire Imploding Liners at the Angara-5-1 Facility

A method for determining the substance density distribution in the plasma produced by a current-driven implosion of multiwire tungsten liners at the Angara-5-1 facility is described. This method is based on the X-ray probing of plasma with radiation from a point source. As a source of this radiation, an X pinch is used. The time resolution (<2 ns) was determined by the X pinch. The probing of both the liner peripheral and near-axial regions is considered. The plasma-attenuated X-pinch radiation was detected using photographic film and p–i–n diodes in the first and second approach, respectively. The spatial resolutions (over the object) in both cases were determined by the sizes of the X pinch and p–i–n diodes and amounted to 4 and 44 m, respectively. The design of the X-pinch and the dependence of its radiation characteristics (the burst time moment and the radiation-pulse power and duration) on the electric and design parameters of the circuit and load are described. The experimental data on the X-pinch radiation spectrum in the range of photon energies of 1–20 keV and the results of studying the substance-density distribution inside liners during the current-driven implosion at the Angara-5-1 facility are presented.     

Tight junctions in Gerbil von Ebner's Gland: Horseradish peroxidase and freeze‐fracture studies

The permeability of tight junctions to horseradish peroxidase (HRP) and the freeze‐fracture appearance of junctional structures were investigated in the von Ebner's gland of gerbils. In the tracing study, HRP was either administered topically on the dorsal surface of tongues or injected subepithelially into the connective tissue of vallate papillae for 5–30 min. Lingual tissues containing the von Ebner's gland were sectioned and examined by light and electron microscopy. In von Ebner's glands, the reaction product for HRP was found in the intercellular and interstitial spaces, whereas HRP appeared to penetrate the tight junctions and the reaction product was localized in the lumina of serous acini. In contrast, the staining for HRP that delineated the boundary of epithelial cells was frequently observed in the superficial layers of the lingual epithelium but not the underlying tissues while applying HRP topically. Freeze‐fracture replicas of acinar cells revealed that the tight junction had a depth of 0.815 ± 0.023 μm, and 4–6 parallel strands on the protoplasmic fracture face, with a branching network of joining strands with interruptions, interconnections and high linear strand density apically, and corresponding grooves on the extracellular face. Quantitative analyses showed a greater number of strands (7.217 ± 0.326) in gerbils compared to those of acinar cells (3.86 ± 0.22) in mice. These results demonstrate that the tight junctions in the gerbil von Ebner's gland is permeable, and that specific species differences in tight junction structures may be associated with the mechanism for survival in an extremely dry environment. Microsc. Res. Tech. 78:213–219, 2015. © 2015 Wiley Periodicals, Inc.     

Manufacturing process of copper microgrooves utilizing a novel optical fiber-based laser-induced etching technique

A new approach for the fabrication of copper microgrooves with near triangular cross-sectional profile is introduced. For manufacturing the microgrooves, a laser-induced thermochemical etching technique based on an optical fiber as an optical waveguide and machining tool is proposed, which significantly reduced the complexity of a conventional laser etching set up. It is explained that the possible problem of fiber damage during laser etching with the proposed method can be solved by appropriately controlling the gap between the sample surface and fiber tip. The fabrication of copper microgrooves with 100 ∼ 300 μm in depth and 100 ∼ 150 μm in width is accomplished with the proposed technique. The grooves fabricated in the optimal process condition have smooth surfaces and clear edge. The angle of triangular groove is measured to be in the range of 30 ∼ 50 degree and the aspect ratio of grooves is about 1 ∼ 2. The overall etching results such as etch width, depth, and aspect ratio variation are reported in detail with respect to process variables.     

A pulsed two-channel Nd:YAG laser with an improved spatial structure of IR radiation for prompt recording and development of photothermoplastic holograms

A two-channel Nd:YAG laser for high-speed recording and development of photothermoplastic holograms has been created. In two independent channels, the laser generates monopulse radiation of nanosecond duration (30 ns) at the second harmonic frequency (λ ₂ = 0.532 μm) and IR radiation (λ ₁ = 1.064 μm) produced by quasi-stationary free-running lasing of millisecond duration (4 ms). The radiations with wavelengths λ ₂ and λ ₁ are used, respectively, for exposure and development of photothermoplastic holograms. A method based on the use of a passive resonator is proposed to improve the spatial structure of IR radiation during lasing.     

Histomorphological,immunohistochemical, and ultrastructural study on ontogeny of ileocaecal lymphoglandular complexes in prenatal and postnatal Indian buffalo: An innate mucosal immune barrier

The present study was conducted on prenatal and postnatal development of lymphoglandular complexes (LGCs) in ileocaecal region of buffalo fetuses (n = 15) ranging from 11.5 cm curved crown rump length (CVRL) (80 days) to 100 cm CVRL (299 days) and neonatal buffalo calves (n = 10). The fetuses were categorized into three groups based on their CVRL. LGC formation was not evident in ileocaecal junction up to 32 cm CVRL (145 days). At 35 cm CVRL (152 days), diffuse lymphocytes were scattered around the base of glands that encircled them. At 54 cm CVRL (195 days), lymphoid aggregates were present in submucosa around deep submucosal glands and formed primordia of LGCs in ileocaeccal orifice region. At 100 cm CVRL (299 days), these complexes were completely visible grossly. The distinguished lymphoid nodules in submucosa were invaded by submucosal extensions of overlying mucosal glands to form a large clear complex of glands and lymphoid nodules called as “Lymphoglandular complex” at this stage. It is the first report of prenatal development of LGCs in large intestine of buffaloes. Abundant CD3⁺ T cells were observed towards periphery of LGC. In neonates, these complexes were uniform, few with demarcation into dark and light zones that is, germinal center formation. Lymphocytes interspersed in lamina propria were mainly CD3⁺ T lymphocytes. In conclusion, the development of LGCs in ileocaecal region started prenatally in terms of all its cellular components into completely developed and immunocompetent to generate mucosal immunity.     

Influence of glass substrate thickness in laser scribing of glass

The thickness of the glass substrate used in liquid crystal displays continues to be decreased from its original thickness of 1.1 mm for the purpose reducing size and weight. The aim of this study was to clarify the influence of the glass substrate thickness during laser scribing with crack propagation caused by laser heating followed by quick quenching. The laser scribe conditions for soda-lime glass substrates with thickness equal to or less than 1.1 mm were obtained in laser irradiation experiments. Two-dimensional thermal elasticity analysis was conducted with a finite element method based on the scribable conditions obtained in the experiment. The laser scribable conditions can then be estimated by the upper limit of the maximum surface temperature, T_max, and the lower limit of the maximum tensile stress, σ_tmax, in the cooling area, regardless of the glass substrate thickness. There is a substrate thickness with which the maximum tensile stress σ_tmax becomes the largest under each scribe condition. The substrate thickness with which σ_tmax becomes the largest is obtained at a faster scribe velocity for thinner glass substrate and at slower scribe velocity for thicker glass substrate. Owing to these relations, the crack depth also has almost the same tendency as σ_tmax.