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Dependence of Mechanical Stresses in Silicon Nitride Films on the Mode of Plasma-Enhanced Chemical Vapor Deposition
摘要： Films of silicon nitride SiNx, obtained by plasma-enhanced chemical vapor deposition from the monosilane SiH4 and ammonia NH3 gases, are widely used in microelectronics and micro- and nanoelectromechanical systems. Residual mechanical stresses and film composition are important characteristics for many applications. The properties of SiNx films, particularly mechanical stresses and composition, depend largely on the conditions of production, e.g., the ratio of the reacting gas flow rates, the composition of the gas mixture, the power and frequency of the plasma generator, and the temperature and pressure during deposition. Despite the great volume of works on the subject, data regarding the dependence of the properties and composition of SiNx films on the conditions of production remain sparse. This work considers the effect the ratio of the reacting gas flow rates has on the mechanical stresses and composition of silicon nitride films SiNx obtained by plasma-enhanced chemical vapor deposition from gaseous mixtures of SiH4 monosilane and NH3 ammonia using low-frequency plasma. It is found that when the ratio of the gas flow rates of SiH4 and NH3 is raised from 0.016 to 0.25, the compressive mechanical stresses are reduced by 31%, the stoichiometric coefficient falls from 1.40 to 1.20, the refractive index rises from 1.91 to 2.08, the concentration of N–H bonds is reduced by a factor of 7.4, the concentration of Si–H bonds grows by a factor of 8.7, and the concentration of hydrogen atoms is reduced by a factor of 1.5. These results can be used for the controlled production of SiNx films with such specified characteristics as residual mechanical stresses, refractive index, stoichiometric coefficient, and the concentration of hydrogen-containing bonds.
关键词： mechanical stresses,optical profilometry,films of PECVD silicon nitride SiNx,IR Fourier spectroscopy
更新于2025-11-14 15:18:02
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[IEEE 2017 International Renewable and Sustainable Energy Conference (IRSEC) - Tangier (2017.12.4-2017.12.7)] 2017 International Renewable and Sustainable Energy Conference (IRSEC) - Thermomechanical Investigation of PV Panels Behaviour under NOCT Conditions
摘要： Numerous works on the enhancement of photovoltaic cells’ efficiency can been found in the literature. However, studies related to its durability are limited. For instance, solar radiation induced internal thermal stresses on the structure of photovoltaic (PV) panels has received little attention. These effects cannot be ignored when analyzing the panel’s durability. The internal stresses are difficult to measure since a PV panel is a complex structure composed by different layers, which causes a non-uniform distribution of the temperature inside the panel. In this work, fully coupled thermo-mechanical finite element simulations were performed with the commercial code ABAQUS/CAE to estimate these stresses. Temperature variations and local stress states are estimated throughout the PV panel thickness under nominal operating conditions.
关键词： thermo-mechanical stresses,FE simulation,silicon solar cells,PV panels
更新于2025-09-23 15:22:29
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Nondestructive monitoring of damage caused by accelerated ageing in photovoltaic modules
摘要： Accelerated ageing tests of photovoltaic laminates are requested by the IEC standards for quality control, which require the assessment of the electrical power losses after a prescribed amount of temperature and/or humidity cycles inside a climatic chamber (thermal cycling, humidity freeze, and damp heat tests). Since electric damage is measured only at the end of such tests, its kinetics induced by thermo-elastic stresses and the related degradation phenomena are reported in few cases. The aim of this study is to investigate the progress of damage, reporting the results of an unprecedented experimental campaign on a photovoltaic mini-module composed of nine multi-crystalline silicon solar cells, one of them containing a cracked cell, subject to a revised thermal cycling test including moisture. Every 40 cycles, and up to 460 (corresponding to 1840 h of testing), the progress of electric damage is assessed by monitoring the evolution of the overall electric resistance of the module. Moreover, electroluminescence images are taken with the same time interval, to assess local damage phenomena responsible for electric power-losses. Cracks are found to significantly accelerate the progress of damage as compared to what happens in intact solar cells, inducing progressive gridline failure and the spread of electrically inactive zones.
关键词： thermo-mechanical stresses,electroluminescence,accelerated ageing tests,Photovoltaics,nondestructive monitoring
更新于2025-09-12 10:27:22
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Modeling of crystal growth in heteroepitaxial systems
摘要： This paper investigates the elastic deformation of the structure containing InAs nanoclusters in a pyramid, grown on the substrate GaAs. So far the data have not been grown quantum dots (QDs), one of the reasons is significant difference of periods, which reaches 7%. Ideally atomic plane on the border of QDs and substrate must continuously sews. Due to the difference in lattice periods crosslinking occurring deformations and mechanical stresses, the magnitude of which is proportional to the number of atomic planes, the size of base of the pyramid. Therefore, when you reach a certain size islands (quantum dots), they may experience mechanical stresses sufficient for the appearance of structural defects - dislocations, fractures.
关键词： mechanical stresses,crystal growth,quantum dots,heteroepitaxial systems,elastic deformation
更新于2025-09-09 09:28:46
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Influence of the Conditions of the Chemical Bath Deposition of Thin ZnSe Films on Their Morphology and Internal Mechanical Stresses
摘要： ZnSe films up to 2300 nm thick on glass-ceramic supports were prepared by chemical bath deposition in the ZnCl2–Na2EDTA–NaOH–NH2OH·HCl system using sodium selenosulfate as a chalcogenizer. The reflections observed in the X-ray diffraction patterns correspond to the ZnSe (stilleite) phase of cubic (space group F43m) structure with a = 5.610 ± 0.002 ?. As shown by electron-microscopic examination, ZnSe films consist of globular formations tightly adjoining to each other with the mean size of 250–400 nm depending on the deposition conditions. Elemental EDX analysis shows that the films contain, on the average, 43.68 at. % Zn, 30.50 at. % Se, and 25.82 at. % O, with the oxygen concentration somewhat decreasing at a depth of 30 nm. The internal mechanical compression stresses caused by the difference in the thermal expansion coefficients of the ZnSe film and glass-ceramic support were calculated; these stresses depend on the film thickness and at ~1040 nm reach –30.62 kN m–2. The results obtained make it possible to exclude film discontinuities, which can appear with increasing film thickness in preparation of precursor layers, and to choose the optimum support material.
关键词： chemical bath deposition,microstructure,internal mechanical stresses,film morphology,zinc selenide,films,sodium selenosulfate
更新于2025-09-04 15:30:14