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This is the peer reviewed version of the following article: [Makoond, N, Pelà, L, Molins, C, Roca, P, Alarcón, D. Automated data analysis for static structural health monitoring of masonry heritage structures. Struct Control Health Monit. 2020; 27:e2581. https://doi.org/10.1002/stc.2581], which has been published in final form at https://onlinelibrary.wiley.com/doi/epdf/10.1002/stc.2581. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. Masonry heritage structures are often affected by slow irreversible deterioration mechanisms that can jeopardise structural stability in the foreseeable future. Static structural health monitoring (SHM), aimed at the continuous measurement of key slow-varying parameters, has the potential to identify such mechanisms at a very early stage. This can greatly facilitate the implementation of adequate preventive and remedial measures, which can be critical to ensure that such structures are preserved for generations to come. However, because monitored parameters usually experience reversible seasonal variations of the same order of magnitude as changes caused by active mechanisms, identification of the latter is often a difficult task. This paper presents a fully integrated automated data analysis procedure for complete static SHM systems utilising dynamic linear regression models to filter out the effects caused by environmental variations. The method does not only produce estimated evolution rates but also classifies monitored responses in predefined evolution states. The procedure has successfully been used to identify vulnerable areas in two important medieval heritage structures in Spain, namely, the cathedral of Mallorca and the church of the monastery of Sant Cugat. Ajuntament de Sant Cugat through a project aimed at monitoring the Monastery of Sant Cugat, ref. num. C-10764. Ministry of Education, Culture and Sports of the Spanish Government through a project aimed at studying the structural condition of Mallorca Cathedral, ref. num. 2/131400106ca - 5/030300592 EF. AGAUR agency of the Generalitat de Catalunya and European Social Fund, through a predoctoral grant awarded to the corresponding author. Ministry of Science, Innovation and Universities of the Spanish Government and European Regional Development Fund through the SEVERUS project, ref. num. RTI2018-099589-B-100.

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Crystalline Si nanowire (SiNW) springs, produced via a low temperature (

We report on the decrease in photoluminescence (PL) intensity with the increase of the sample temperature (thermal quenching) in crystalline silicon and its suppression after ion irradiation. The crystalline silicon surface was passivated with intrinsic and doped hydrogenated amorphous silicon (a-Si:H) layer stacks as for making silicon heterojunction solar cell precursors. Low energy argon ion irradiation, in the range between 5 and 17 keV, was used for controlled defect formation either in the thin a-Si:H top layer or at the interface with the crystalline silicon beneath. The irradiation defects introduce radiative recombination centers in the a-Si:H as can be measured from PL at low temperature. Moreover, the irradiation and annealing result in a strong modification of the thermal quenching of the PL intensity up to 500 K, showing evidence for the strong reduction of thermally activated non-radiative recombinations at the amorphous-crystalline interface. This result can have implications in the field of crystalline silicon surface passivation.

We evaluate the use of p-type silicon oxide (p-SiOx) dielectric layers as a boron diffusion source for n-type crystalline silicon (c-Si) substrates. The p-SiOx layers grown on n-type c-Si substrates by plasma enhanced chemical vapor deposition using a gas mixture of He/hexamethyldisiloxane/CO2/B2H6 are thermally stable and do not peel off during annealing up to 1050 °C, making them effective diffusion sources. The layers were examined before and after annealing with characterization techniques including spectroscopic ellipsometry and secondary ion mass spectrometry. We observe that there is a reduction in the thickness of the p-SiOx layer after annealing by about 50%, and that boron diffuses into the n-type c-Si substrate, forming a p+ layer, limited by the formation of a carbon-rich layer above the c-Si surface. The concentration of holes in the diffused region was measured by the electrochemical capacitance–voltage technique, and it was found that essentially all the boron that diffused into the n-type c-Si was active, unaffected by the presence of carbon and oxygen atoms. The concentration of carriers can be controlled by the initial thickness of the p-SiOx layers and the depth of the p+/n junction can be controlled by the time of annealing. A surface carrier concentration of 3 × 1019 at cm−3 and a sheet resistance of the order of 120 Ω sq−1 was obtained upon annealing at 1050 °C for 30 min.

Fabrication of high-quality ultrathin monocrystalline silicon layers and their transfer to low-cost substrates are key steps for flexible electronics and photovoltaics. In this work, we demonstrate a low-temperature and low-cost process for ultrathin silicon solar cells. By using standard plasma-enhanced chemical vapor deposition (PECVD), we grow high-quality epitaxial silicon layers (epi-PECVD) from SiH4/H2 gas mixtures at 175 °C. Using secondary ion mass spectrometry and transmission electron microscopy, we show that the porosity of the epi-PECVD/crystalline silicon interface can be tuned by controlling the hydrogen accumulation there. Moreover, we demonstrate that 13–14% porosity is a threshold above which the interface becomes fragile and can easily be cleaved. Taking advantage of the H-rich interface fragility, we demonstrate the transfer of large areas (∽10 cm2) ultrathin epi-PECVD layers (0.5–5.5 µm) onto glass substrates by anodic bonding and moderate annealing (275–350 °C). The structural properties of transferred layers are assessed, and the first PECVD epitaxial silicon solar cells transferred on glass are characterized. Copyright © 2016 John Wiley & Sons, Ltd.

Contemporary externally bonded structural upgrading schemes for masonry structures employ Fiber Reinforced Polymer (FRP) systems (a technique that was extended from concrete to masonry structures) and technical textiles (structural fiber grids) embedded in inorganic matrices. The latter account for a multitude of systems depending on the type of grid – fiber material, bundle treatment (dry, coated or even impregnated), grid geometry, manufacturing method etc. – and matrix – binder (e.g. cement or lime), rheology etc. – resulting in the derivation of many different acronyms (FRCM, TRM, CMG, IMG or other – see for definitions below). The mechanical behavior of such systems and their interaction with different substrates may vary significantly (e.g. dry vs. impregnated fiber grids embedded in mortars). This paper aims to summarize all reported efforts to increase the load-carrying and/or deformation capacity of unreinforced masonry walls against in-plane loading and second-order phenomena (eccentric compressive loading). Zeitgemase externe Verbundstrukturen zur Verbesserung der Mauerwerkstrukturen sind zum Beispiel faserbewehrter Kunststoff (GFK), eine Methode, die vom Beton ubernommen wurde, und technische Textilien (Fasernetze), die in anorganischen Matrices eingebunden werden. So hat sich eine Vielzahl von Systemen in Abhangigkeit des Netztyps – Fasermaterial, Garnbehandlung (trocken, beschichtet oder impragniert), Netzgeometrie, Herstellungsmethode etc. – und der Matrix-Bindemittel (z. B. Zement oder Kalk) Rheologie etc. – entwickelt, mit der Folge diverser Kurzbezeichnungen (FRCM, TRM, CMG, IMG und andere), die im Folgenden noch erklart werden. Das mechanische Verhalten solcher Systeme und die Interaktion mit dem Untergrund kann sehr stark variieren (z. B. trockene im Vergleich zu impragnierten Fasernetzen, in Mortel eingebettet). Der Beitrag fasst die Masnahmen zur Erhohung der Tragfahigkeit und/oder der Verformbarkeit von in der Wandebene belasteten unbewehrten Mauerwerkswanden unter Berucksichtigung von Effekten zweiter Ordnung (exzentrische Druckbelastung) zusammen.

We report on the fabrication, integration, and simulation, both optical and optoelectrical, of two-dimensional photonic nanostructures for advanced light trapping in thin crystalline silicon (c-Si) solar cells. The photonic nanostructures are fabricated by the combination of various lithography (nanoimprint, laser interference, and hole mask colloidal) and etching (dry plasma and wet chemical) techniques. The nanopatterning possibilities thus range from periodic to random corrugations and from inverted nanopyramids to high aspect ratio profiles. Optically, the nanopatterning results in better performance than the standard pyramid texturing, showing a more robust behavior with respect to light incidence angle. Electrically, wet etching results in higher minority carrier lifetimes compared to dry etching. From the integration of the photonic nanostructures into a micron-thin c-Si solar cell certain factors limiting the efficiencies are identified. More precisely: (a) the parasitic absorption is limiting the short circuit current, (b) the conformality of thin-film coatings on the nanopatterned surface is limiting the fill factor, and (c) the material damage from dry etching is limiting the open circuit voltage. From optical simulations, the optimal pattern parameters are identified. From optoelectrical simulations, cell design considerations are discussed, suggesting to position the junction on the opposite side of the nanopattern.

We present a single pump-down process to texture hydrogenated amorphous silicon solar cells. Mats of p-type crystalline silicon nanowires were grown to lengths of 1mm on glass covered with flat ZnO using a plasma-assisted Sn-catalyzed vapor-liquid-solid process. The nanowires were covered with conformal layers of intrinsic and n-type hydrogenated amorphous silicon and a sputtered layer of indium tin oxide. Each cell connects in excess of 10 7 radial junctions over areas of 0.126 cm². Devices reach open-circuit voltages of 0.8 V and short-circuit current densities of 12.4 mA cm 2 ,m atching those of hydrogenated amorphous silicon cells deposited on textured substrates. Copyright © 2012 John Wiley & Sons, Ltd.

The effect of adding of silicon tetrafluoride (SiF4) to silane (SiH4) hydrogen gas mixture on the properties of highly crystallized microcrystalline silicon (μc-Si:H) films was studied. We found that the addition of a small amount of SiF4, with a ratio to SiH4 not exceeding 1/10, has almost no effect on deposition rate and does not affect the structure of the μc-Si:H films, but strongly reduces oxygen incorporation into the films. Reduction of oxygen content to values below 1019 cm-3 results in intrinsic character of the films with ratio of photo to dark conductivity about 103 in whole studied range of deposition temperatures from 175 to 250 °C in contrast to films, deposited without SiF4 addition, which show strong decrease of photosensitivity with increase of deposition temperature above 200 °C (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The structural and optoelectronic properties of undoped hydrogenated microcrystalline silicon (μ c-Si:H) films deposited in a matrix distributed electron cyclotron resonance (MDECR) plasma CVD system using pure silane were studied as a function of microwave power (PMW) and gas pressure (Pgas). The analysis of the silane plasma optical emission spectra (OES) shows the effect of the deposition conditions on the plasma chemistry and resulting film microstructure as studied by spectroscopic ellipsometry and atomic force microscopy. The use of the PMW and Pgas as tunable parameters to achieve μ c-Si:H films with desired microstructure is discussed. Intrinsic μ c-Si:H films with good phototransport properties were realized at high deposition rate. Our study shows the usefulness of OES as a fast diagnostic tool for controlling and optimizing the μ c-Si:H deposition process in MDECR reactor. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The latest results obtained in a new promising Matrix Distributed Electron Cyclotron Resonance (MDECR) reactor for the deposition of microcrystalline silicon (μc-Si:H) films and cells are reported in this article. The reactor is presented with a focus on the importance and the difficulties of temperature measurements. The unique properties of this high density plasma allowed us to demonstrate high deposition rates of 28 A/s. The chemical composition of the MDECR material has been compared to a standard material and in particular, the effect of the oxygen level will be discussed. The installation of a load-lock allowed a reduction of the oxygen con-tamination by a factor of 10. Lower microwave powers helped to improve the electrical properties of the material. So far, the cell performance unfortunately seems decoupled from these successive optimizations of the film quality, and stayed limited (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Low temperature plasma deposition of a-Si:H thin films has emerged as a promising alternative for high efficiency hetero junction (HJ) solar cells. In this work we study plasma processes for texturing and cleaning c-Si wafers pursuing a low cost dry fabrication process of HJ solar cells. We have studied two independent plasma processes: i) Texturing of c-Si wafers using SF6 - O2 plasmas in a RIE system, in order to reduce the surface reflectance and therefore improve the light trapping. The effects of the RF power and gas ratio on the c-Si surface texture have been studied in detail. Highly textured surfaces, with very low reflectance values (around 6% in the range of 300 – 1000 nm) have been achieved. ii) Etching of the native oxide and passivation of the c-Si surface by plasma, in a standard RF PECVD system. We used SiF4 plasma with optimized conditions for an efficient native oxide removal, and without breaking the vacuum, 40 nm of a-Si:H were deposited in order to passivate the c-Si surface. High effective lifetime values were obtained (τeff ≈ 1.5 ms), providing high implicit open circuit voltages (Voc ≈ 0.713 V) and low surface recombination velocities (Seff < 9 cm s-1). (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Microcrystalline silicon films were deposited in a matrix distributed electron cyclotron resonance (MDECR) plasma enhanced chemical vapor deposition (PECVD) system using pure silane, under varying substrate bias conditions. Microstructural characterization of the films shows a lower void fraction and a preponderance of nanograins in films deposited at negative bias, while in positive bias a thin incubation layer is seen with a higher void fraction. Plasma emission studies reveal higher electron temperature and more atomic H at positive bias, which lead to early onset of crystallization. The microstructural properties of the films are correlated with the dark and phototransport properties. Our study demonstrates the importance of substrate bias in controlling the ion energy and properties of films deposited in the MDECR reactor.

The crucial influence of the interface between the gate dielectric and intrinsic layer has been studied in detail for amorphous silicon, polymorphous silicon and microcrystalline silicon bottom gate thin-film transistors. We show that the electrical parameters of the TFTs depend directly on the quality of this interface, which can be strongly degraded by a vacuum break. A hydrogen plasma pretreatment of this interface greatly improves the electrical characterstics of polymorphous silicon TFTs, the mobility increases from 0.4 to 0.75 cm2/V s while their subthreshold slope decreases from 1 to 0.7 V/dec. Moreover, we show that these improvements also translate into more stable TFT characteristics. Finally, microcrystalline silicon TFTs show the best stability and a nitrogen-plasma treatment of the dielectric improves their stability.

International audience; The formation of gold islands on a transparent conductive oxide by annealing a thin evaporated layer is studied by SEM. The droplets of metal formed this way may catalyze the growth of nanowires or nanotubes to be used in optoelectronic devices. The effect of the initial thickness (between 1 nm and 4 nm) and the annealing temperature (between 70 °C and 650 °C) is investigated. A qualitative description of the evolution is given and quantitative data are obtained by automated image analysis. Number density, area and effective diameter of the aggregates depend heavily on the initial thickness but very slightly on the annealing temperature. Three phenomena are considered to explain the evolution: interfacial stress due to mismatch in the linear expansion coefficient, Ostwald ripening and kinetic aggregation. By comparing the experimental size distributions to the theoretical ones, the relevance of the last two is discussed. As an application, the gold catalyzed CVD growth of silicon nanowires on zinc oxide is demonstrated.

Spectroscopic ellipsometric measurements showed that amorphous silicon thin films made by very high frequency plasma enhanced chemical vapour deposition at 100 °C using an optimum H2 dilution has denseness (A parameter) and structural order (C parameter) that are comparable to the sample made at 200 °C. The materials made by hot wire chemical vapour deposition (HWCVD) at low hydrogen dilution conditions have a less dense structure and higher roughness compared to the plasma deposited samples. The C parameter reaches the lowest value (C=1.67) for the HWCVD sample made at an optimum H2/SiH4 ratio of 20, even though it was made only at 100 °C. The importance of filament to substrate distance in HWCVD process in suppressing the undesirable species reaching at the growing surface has been put forward to achieve materials with very small structural disorder and fabrication of thin film silicon solar cells with high stability

The exact role of hydrogen in the crystallization process is still a subject of broad controversies due to the complexity of the overall plasma enhanced chemical vapor deposition (PECVD) process. We have investigated by ellipsometry the amorphous-to-microcrystalline the phase transition in intrinsic and doped hydrogenated amorphous silicon (a-Si:H) thin films during their exposure to a hydrogen plasma in conditions of chemical transport. The whole ellipsometry diagnostics reveal that, while intrinsic and phosphorus-doped a-Si:H present a similar trend during the plasma treatment, boron-doped a-Si:H differs by special features such as a rapid formation of the hydrogen–rich subsurface layer and an early amorphous-to-microcrystalline phase transition. The particular behavior of boron-doped material is also pointed out through the time-evolution of the self-bias voltage on the radio-frequency electrode during the hydrogen plasma treatment (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Just after their deposition by plasma enhanced chemical vapor deposition (PECVD) process, we have exposed Cr/I/N, Cr/I/P, Cr/N/I and Cr/P/I a-Si:H based junctions to H2 plasma and followed in situ, by ellipsometry, the modifications induced by hydrogen diffusion. In the case of Cr/N/I and Cr/P/I junctions, no significant effects of the junction on the hydrogen diffusion were observed since the time-evolution of the thickness of the H-modified layer is similar to that of a single intrinsic layer. However, Cr/I/N, Cr/I/P structures present an attenuated thickness of the H-modified layer in the first few minutes of hydrogen plasma exposure. This effect should be attributed to the charges in the field regions of I/N or I/P junctions which increase the hydrogen trap concentration and restrain the hydrogen diffusion. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Imitating natural rod or cone cells in human eyes can inspire a biomimetic design of filter-free color sensing photodetector with the aid of three-dimensional (3D) nanophotonic engineering. Here, a novel radial tandem junction (RTJ) super-rod structure is proposed and demonstrated, which consists of coaxially stacking hydrogenated amorphous silicon PIN junctions upon silicon nanowires, resembling to the live retinal cells in terms of both geometry and dimension. As a consequence, these RTJ units enjoy a unique wavelength-selective and cavity-mode-assisted light absorption/responses in the inner and the outer radial PIN junctions, which are readily tunable to achieve natural RGB color discrimination in the RTJ rod-cells without the need of any filter system. This unique RTJ design can indicate a new 3D implementation of color sensing photodetectors enabled by advanced nanophotonic structuring and engineering.

Microcrystalline silicone (μ-Si:H) TFTs were fabricated using a conventional bottom gate amorphous Si (a-Si:H) process. A unique μc-Si:H deposition technique and TFT architecture was proposed to enhance the reliability of the TFTs. This three-mask TFT fabrication process is comparable with existing a-Si:H TFT process. In order to suppress nucleation at the bottom interface, a N2 plasma passivation was conducted before the deposition of the μc-Si:H. A typical transfer characteristic of the TFTs shows a low off-current with a value of less than 1 pA and a sub-threshold slope of 0.7 V/dec. DC bias stress was applied to verify the use of μc-Si:H TFTs for AMOLED displays. After 10,000 s of stress application time, the off-current was even lowered and sub-threshold slope variation was less than 5%. For AMOLED displays, OLED pixel simulation was performed. A pixel current of 13 μA was achieved with a Vdata of 10 V. After the simulation, a linear equation for the pixel current was derived. We also present the simulation tests of simple logical electronics. At last, for Active matrix Display back-plane, a row driver with no shift compensation is simulated with good results in terms of reproducibility and reliability.