Search

Bulk heterojunction organic solar cells based on active layer of PTB7-Fx (x = 0–100), conjugated block copolymer incorporating benzo[1,2-b:4,5-b′]dithiophene and partly fluorinated thieno[3,4-b]thiophene units, and fullerene derivatives as phenyl C61 and phenyl C71 butyric acid methyl esters sandwiched between a transparent anode of indium tin oxide, a hole conducting layer of either poly(ethylene dioxythiophene) : polystyrene sulfonate or magnetron-sputtered molybdenum oxide and evaporated aluminum cathodes were fabricated. Polymer-organic thin films were prepared at 1:1.5 mass ratio of the donor:acceptor mixture and deposited from dichlorobenzene solution of different concentrations by spin coating in ambient conditions. To control the active layer morphology, the films were subjected either to post-deposition treatments (annealing) at different temperatures or incorporation of an additive such as diiodooctane. Optical transmission, film surface topography and thickness measurements were used to characterize the active layer. Test devices with the architecture described above were prepared and their current–voltage characteristics, quantum efficiency and impedance spectra were measured and used to compare the different active layers, architectures and deposition sequences.

LiFe1−xMnxPO4 solid solutions in the whole concentration range (0 ≤ x ≤ 1) are obtained at 500 °C by a phosphate–formate precursor method. The method is based on the formation of homogeneous lithium–iron–manganese phosphate–formate precursors by freeze-drying of aqueous solutions containing Li(I), Fe(II), Mn(II), phosphate, and formate ions. Thermal treatment of the phosphate–formate precursors at temperatures at 500 °C yields nano-sized LiFe1−xMnxPO4 coated with carbon. The structure and the morphology of the LiFe1−xMnxPO4 compositions are studied by XRD, IR spectroscopy, and SEM analysis. The in situ formed carbon is analyzed by Raman spectroscopy. The electrochemical performance of LiFe1−xMnxPO4 is tested in model lithium cells using a galvanostatic mode. All LiFe1−xMnxPO4 compositions are characterized with an ordered olivine-type structure with a homogeneous Fe2+ and Mn2+ distribution in the 4c olivine sites. The morphology of LiFe1−xMnxPO4 consists of plate-like aggregates which are covered by in situ formed carbon. Inside the aggregates nano-sized isometric particles with narrow particles size distribution (between 60 and 100 nm) are visible. The structure of the deposited carbon presents a considerable disordered graphitic phase and does not depend on the Fe-to-Mn ratio. The solid solutions LiFe1−xMnxPO4 deliver a good reversible capacity due to the Fe2+/Fe3+ and Mn2+/Mn3+ redox-couples at 3.5 and 4.1 V, respectively.

International audience; Sodium manganates with nominal composition Na2/3MnO2 were prepared by solid state reaction between Na2CO3 and MnCO3 at 1000 °C. The composition and structure of NaxMnO2 were controlled by the rate of cooling from the temperature of preparation. This is a consequence of the capability of Na2/3MnO2 to accommodate over-stoichiometric Mn4+ ions up to 12.5%. Structural characterization was carried out by XRD powder diffractions, TEM analysis and Raman spectroscopy. The composition and oxidation state of manganese were determined by chemical analysis and magnetic susceptibility measurements. The manganese distribution in the layers was analysed using electron paramagnetic resonance (EPR) spectroscopy. By quenching from 1000 °C, the orthorhombic distorted modification is stabilized. A phase separation into orthorhombic and hexagonal modifications takes place when Na2/3MnO2 is slow cooled. The structure changes are concomitant with an increase in the oxidation state of Mn. The over-stoichiometric Mn4+ ions are accommodated in the hexagonal modification by creation of vacancies in the MnO2-layers.

Thin films of poly-Si on low cost substrates such as glass are attractive for thin film solar cells and other large-area electronic devices. The controlled and reproducible preparation of polycrystalline silicon thin films by aluminium-induced crystallisation (AIC) needs optimization of both the process of crystallisation and the deposition conditions of the precursor silicon and aluminium layers. In this work, the influence of the hydrogen concentration in the precursor amorphous silicon layer and the deposition temperature of the aluminium layer on the structural properties of poly-Si thin films obtained by AIC of un-hydrogenated (a-Si) and hydrogenated amorphous silicon films (a-Si:H) are studied. Stacks of glass/a-Si:H/Al were prepared for performing the AIC process. The aluminium and amorphous silicon films are deposited by rf magnetron sputtering. The hydrogen concentration in the a-Si:H films is varied from 0 to 18 at.%. The substrate temperature during a-Si (a-Si:H) deposition is kept constant at 250 °C. The Al film is deposited on top of the a-Si (a-Si:H). The deposition temperature of the aluminium films (T S Al ) is varied from room temperature (RT) to 500 °C. The samples are isothermally annealed in air at T an = 530 °C for 7 h. The structural properties of the poly-Si films are studied by Raman spectroscopy and optical microscopy. The results indicate that the hydrogen concentration in the precursor a-Si:H is a very important parameter. It is also observed that T S Al influences the structural properties of the poly-Si films. It is found that films with better crystalline structure are obtained when the a-Si:H precursor layers contain 9 at.% hydrogen and the aluminium deposition temperature is about 350 °C.

Thin films of silica containing 0.15 at.% Eu and 3.5 to 7 at.% Na were prepared by sol–gel chemistry and annealed at 600 ° C in air, then submitted to ion–exchange treatments in NaNO3 : AgNO3 for studying the effect of the plasmon resonance of Ag nanoparticles on the excitation of Eu3+ ions. When excited at other wavelengths in the UV other than that corresponding to the 7F0–5L6 transitions of the Eu3+ ions, the yield of the 5D0–7F2 emission is increased by a factor of the order of 10 in films containing Ag particles with respect to that in non-exchanged films.

We have investigated the various types of instability phenomena in μc-Si:H solar cells prepared by HWCVD under conditions close to the transition to amorphous growth, resulting in compact material, and other cells containing a high crystalline volume fraction of material with a pronounced porosity. It was found that light-induced degradation is most pronounced for material with some amorphous volume fraction while highly crystalline material is stable under illumination. On the other hand, we have observed a strong degradation of the current–voltage (J–V) parameters after treatment in de-ionized water of the cells with highly crystalline i-layers, while cells with compact i-layer material show very little changes.

The formation of high-quality polycrystalline silicon (poly-Si) on low cost substrates has important applications in the development of thin film solar cells, transistors, image sensors, etc. In this study, we present the results of an investigation of poly-Si and poly-SiGe films on glass, formed by aluminum induced crystallization (AIC). The process is based on the isothermal annealing at temperatures between 500 and 540 °C of co-sputtered Si+Al, Si+Ge or sputtered a-Si films on glass, with and without thermally evaporated or sputtered Al film. The crystallized films were investigated by Raman spectroscopy, optical microscopy, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Raman spectra demonstrate the crystalline structure of the poly-Si and poly-SiGe films prepared by AIC. The grain sizes of the poly-Si films estimated from the SEM and optical microscopy images are up to 25 μm for the different annealing conditions.

Thin films (d∼200 nm) of hydrogenated amorphous silicon carbide (a-SiC:H), deposited by RF reactive magnetron sputtering, have been ion implanted with high doses (D=1016–1017 cm−2) of Ga+ as the implant species. The increased disorder and additional structural modification of a-SiC:H, induced by the implantation of Ga+, results in a considerable change of the optical properties, best manifested by a significant shift of the optical absorption edge to lower photon energies in the results obtained by optical transmission and reflection measurements and as derived from photo-thermal-deflection spectroscopy results. This shift may be attributed both to additional defect introduction and to accompanying structural modification effects, as confirmed by optical absorption measurements in the infra-red region and by Raman spectroscopy results.

The sensitization of the infrared luminescence of Er ions by Si clusters is studied in oxide films derived from tetraethoxysilane and triethoxysilane gels, doped chemically or by ion implantation with Er and/or Si. No quenching of the luminescence by impurities and structural defects is observed with respect to ion-implanted silica, and a maximum enhancement is observed in the SiO1.5 suboxide formed from triethoxysilane. The segregation of erbium silicide or oxide, depending on the synthesis procedure, deactivates the Er ions when their concentration exceeds 1 at % or the temperature of annealing is above 1050 °C.

The transformations induced by ion irradiation in films of polycarbosilane and gels derived from tetraethoxysilane, methyltriethoxysilane and triethoxysilane have been studied. Hydrogen is released selectively under the effect of electronic excitations at a rate depending on the probability of H radicals to combine for forming molecules inside the film. The radiolysis efficiency of C—H bonds is the lowest and that of Si—H bonds the highest. Beside the conversion of the polymeric structure into an amorphous ceramic, ion irradiation induces the precipitation of C or Si clusters, according to the precursor, leading to a noticeable luminescence in the visible. This precipitation has been put into evidence for the first time by energy filtered electron microscopy.

Ag nanoclusters in a SiO2 matrix prepared by RF magnetron co-sputtering and subsequent irradiation with heavy 4.5 MeV Au+ ions were formed. The refractive index and optical absorption spectra of the films were studied. The method of the disappearing diffraction pattern was used for the refractive index determination. The refractive index enhances with increasing Ag concentration, as expected from the light scattering theory. SiO2:Ag thin films exhibit a plasmon resonance in the visible region. In the as-deposited films the Ag nanoclusters are less than 1 nm and are formed during the deposition. The intensity of the plasmon peak is low. After irradiation with 4.5 MeV Au+ ions the intensity of the peak increases and the peak becomes narrower. The TEM study shows that this is related to the change in the size of the Ag nanoclusters.

The luminescence properties of erbium-doped silicon offer exciting potential applications in optoelectronics. Although the optical and structural properties of this material have been studied extensively, there have been no prior examinations of the transport properties. In this paper, results from photo-thermal deflection spectroscopy (PDS) and from the study of transient photocurrents (TPC) in rf sputtered a-Si:H films doped with different concentrations of Er are presented. It is shown that films with and without Er feature a broad distribution of localised states. Incorporation of Er does not significantly influence the concentration or energy distribution of shallow states, but increases the sub-gap optical absorption associated with deeper states. The transient photocurrent remains detectable to times of at least 0.1 s, without evidence of significant carrier losses by recombination. This suggests that the transport properties are adequate for electroluminescent device applications.

Thin amorphous and polycrystalline tungsten oxide films were prepared by chemical vapour deposition at atmospheric pressure from a metalorganic precursor - tungsten hexacarbonyl. The dependence of the structural and optical properties of tungsten oxide films on the technological conditions has been investigated by XRD, Raman spectroscopy and spectroscopic ellipsometry.

Porous silicon (PS) is studied by stepwise peeling of the surface layer to clarify the non-uniformity in the photoluminescence (PL) and correlate it with the in-depth chemical bonding and structure of the 30 μm thick layer. The PL intensity grows by an order of magnitude after the peeling off of the first 10 μm and decreases five times in the next 5 μm while the peak maximum position shifts from 730 to 800 nm. X-ray photoelectron spectroscopy (XPS) measurements show that Si–Si and Si–O bonds are present both on the surface and below, and the preferential oxidation state of silicon changes from 3+ and 4+ on the surface to 1+ and 2+ below 10 μm. Using Raman spectroscopy silicon nanocrystals are shown to exist. Their mean size can be estimated at about 3 nm. These results show that the strongest PL comes from a region in the PS layer where silicon nanocrystallites are surrounded by oxides with a low level of oxidation and not from the strongly oxidized surface layer.

Thin films of polysiloxanes and polycarbosilanes with various substituents were converted into SiOC and SiC ceramics by irradiation with ions of increasing masses. The transformation kinetics as a function of the ion dose was assessed by means of ion beam analyses (RBS, NRA, ERDA), compaction measurements, spectroscopies of infrared absorption and Raman scattering. The kinetics depends strongly on the linear density of electronic excitations. The formed radicals tend to react with the atmosphere after irradiations when this density is too low for permitting their combination into crosslinks. Part of the C atoms segregate into clusters with a noticeable degree of tetragonal hybridization, varying with the nature of side groups in the polymeric precursor. This precipitation affords to the films interesting properties: (1) a strong yellow photoluminescence, within a given range of ion doses where the quantum dots of C are not too coarse or too numerous; (2) at higher doses, a hardness reaching that of amorphous SiC and three times that of films converted by heat treatment at 1000–1200°C (as evidenced by nanoindentation tests); (3) a greatly improved thermochemical stability.

A method of preparation of thin (1000 A) porous silicon layers by chemical etching of c-Si in HF:HNO 3 :H 2 O=1:3:5 solution is reported wherein a thin Al film is deposited by evaporation on the silicon surface prior to etching. The method is characterized by no “incubation” period to the onset of the stain etching. The reaction between Al and HNO 3 produces the required holes for the very fast start of the chemical etching of Si. Using Al patterns deposited through a mask or prepared by photolithography it is possible to achieve selective formation of porous silicon. The porous silicon layers exhibit visible photoluminescence and when prepared on p-type c-Si and a shallow p–n c-Si homojunction the resulting heterostructures also display electroluminescence and photovoltaic properties. © 1997 Elsevier Science S.A.

A correlation between the photoluminescence, chemical bonds and structure of c-Si subjected to electrochemical and laser induced chemical etching has been obtained by X-ray photoelectron spectroscopy, IR spectroscopy and Raman scattering. Photoluminescence is very strongly related to the chemical bonding and depends on the Si, O and C content and the presence of different oxidized states of Si which are different for porous silicon prepared on Si substrates of different electrical resistivity. Porous silicon having Si oxidized states typical for Si suboxides exhibits very intensive photoluminescence. The influence of the doping level of c-Si on the process of electrochemical etching as well as the influence of the laser power on the process of stain etching are discussed.

The changes in the visible photoluminescence and Raman spectra of n-type porous silicon as a result of rapid thermal annealing and chemical treatment have been studied. Modification of the chemical bonds due to these treatments has been observed by X-ray photoemission spectroscopy. Our results show that the change in the luminescence spectra of porous silicon is related to the modification of the chemical bonds and that complexes such as the terminations in siloxene as well as silicate molecules play a role in determining the optical properties of this new photonic material. The surface containing siloxene-like bonding exhibits very intensive photoluminescence. The presence of silicates leads to a decrease in luminescence intensity and to the appearance of a weak high energy band in the photoluminescence spectra.

Luminescent a-Si:O:C layers were obtained by magnetron co-sputtering and annealing. The maximum photoluminescence intensity is comparable with that of porous silicon. The luminescence maximum is between 1.8 eV and 2.2 eV. X-ray photoelectron spectroscopy finds both CSi and CC bonding and maximum luminescence is obtained when the amount of the two kinds of bonding is comparable.

A solution based deposition method to form nano-sized thin films of molybdenum oxide suitable for photovoltaic device applications is presented. The samples were deposited by spin-coating from molybdenum metal organic precursor solution on soda lime glass substrates. The influence of the process parameters such as spinning regime and concentration of the precursor solutions on the thickness and morphology of the films were investigated. The thermal decomposition of the molybdenum precursor and oxide formation were investigated by differential scanning calorimetry and characteristic patterns showed transitions up to 300oC followed by a zone of stability. Optical spectroscopy measurements in the wavelength range from 300 to 1800 nm presented an increase in transparency when temperature of annealing was raised up to 400oC. Raman scattering analysis revealed the presence of mixed molybdenum oxides. Measurements of the electrical conductivity were performed by the 4-point method.

Two types of polymer solar cells with active layers of P3HT:PCBM and PCDTBT:PCBM in a standard configuration were deposited by spin-coating the polymer layers and sputtering the Ag back contacts. After encapsulation, they were subjected to post-deposition annealing and were studied by measuring their current-voltage characteristics and quantum efficiency spectra. Their stability was examined by exposing them to solar radiation in open-circuit conditions for several hours every day for a total of 80 hours. Their characteristics were measured regularly throughout this period. The performance of the two types of cells are compared and discussed.

We report on the photoluminescence (PL) spectra of porous silicon excited resonantly by laser lines within the luminescence band. Measurements have been performed for different excitation energies, temperatures and delay times. At low temperatures, the known step-like phonon structure in the PL spectra of porous silicon and a gap of the few millielectronvolts between the laser line and the onset of the luminescence are observed. As the temperature is increased, the onsets of both the PL spectra and the step features shift towards higher energies whereas the peak of the spectrum moves towards lower energies by an amount which depends on the delay time after excitation. Furthermore, the gap disappears and simultaneously an exponential tail of the spectrum occurs on the high energy side of the laser line, which broadens proportionally to kT . These results are discussed in light of the existing theories for the luminescence mechanism in porous silicon and for the origin of the step features in the PL spectra.

Luminescence from stain-etched and electrochemically etched germanium samples was observed in the blue part of the visible spectrum. Although it is weaker than the luminescence of porous silicon, its origin is of scientific interest as a parallel to the luminescence of porous silicon. Stain-etched germanium was studied in more detail. Under visible laser excitation the luminescence band is located around 525 nm. Another luminescence band around 400 nm is observed with UV excitation. The luminescence lifetime in the UV-excited band is of the order of 1 ms, compared with about 100 ns in the band excited in the visible. The luminescence intensity either passes through a maximum or slowly decreases as the temperature is increased from 8 to 300 K. This behaviour is similar to that observed in porous silicon. The IR spectra of stain-etched Ge show the presence of GeO2, -OH groups and water. In the Raman spectra the unmistakable bands of trigonal crystal GeO2 are observed. A band at 760 cm−1 in the Raman spectra and 752 cm−1 in the IR spectra could be assigned to substoichiometric regions and oxygen-vacancy complexes in GeO2. The chemical composition of the samples is characterized by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The XP spectra give evidence for GeO2 and GeO. SIMS data show the presence of both hydrogen and -OH groups. On the basis of these data we propose that the luminescence of stain-etched and electrochemically etched germanium is due to defects in GeO2.

International audience; In this contribution, new data on the reversible Li+ intercalation in iron substituted sodium manganates are provided. Novel Na2/3Mn1−yFeyO2 (y = 0, 1/3 and 2/3) compounds with a P′3-type structure are prepared from freeze-dried citrate precursors at 500 °C. A new structural element is the development of three-layer oxygen stacking contrary to the well-known P2-type Na2/3MnO2 with a two-layer sequence. The effect of Fe additives on the structure of Na2/3MnO2 was examined by XRD powder diffraction and TEM analysis. The oxidation state and the distribution of transition metal ions in Na2/3Mn1−yFeyO2 were analysed using electron paramagnetic resonance spectroscopy. The lithium intercalation in Na2/3Mn1−yFeyO2 was investigated in two-electrode lithium cells of the type Li|LiPF6 (EC:DMC)|Na2/3Mn1−yFeyO2. The stability of the layered phases during lithium intercalation was studied by ex situ Raman spectroscopy. It was found that the intermediate Na2/3Mn2/3Fe1/3O2 composition is able to intercalate Li+ reversibly in high amounts. Details of the structure and its stability during the Li+ intercalation are discussed.

The structural properties of sodium manganates and iron substituted sodium manganates with compositions Na2/3Mn1-xFexO2 (x=0, 1/3 and 2/3) were studied by Raman spectroscopy. The Raman spectroscopy allows distinguishing between layered phases with orthorhombic (Cmcm space group) and hexagonal (P63/mmc space group) distortion. It has been found that the crystal structure and the composition of Na2/3MnO2 display a strong dependence on the history of the thermal treatment. The orthorhombic distorted modification is stabilized at high temperatures (1000 oC). At lower quenching temperature, there is a phase separation into an orthorhombic and a hexagonal modification, concomitant with an increase in the oxidation state of Mn. When Fe substitutes for Mn, the hexagonal modification is stabilized. In order to understand the origin of the Raman spectra of Na2/3Mn1-xFexO2, we have used Na2/3Co2/3Mn1/3O2 as a standard for hexagonal structure, where Co3+ and Mn4+ are statistically distributed in the transition metal layers.

Thin transparent dielectric films containing Tb3+ are developed for application as spectral converters of the solar spectrum in thin film silicon solar cells. The results on the deposition and characterization of thin SiO2 and Al2O3 films containing Tb3+ ions are presented. The films are prepared by RF magnetron co‐sputtering, a well established technique for large area coatings. Photoluminescence (PL) is measured at room temperature, using the 488 nm line of an Ar laser and a nitrogen‐cooled CCD camera attached to a monochromator. The dependence of the PL intensity on the concentration of Tb in the film is studied. It is found that the intensity exhibits a maximum at about 1 at.%. Annealing studies are performed on SiO2:Tb with two different methods to improve the PL intensity. In both regimes of annealing, the best results for thin SiO2:Tb films are obtained in the temperature range of 650–700° C. After treatment at this temperature the Tb PL increases 2.5–3 times.

The laser excited luminescence of CaF2:Ho has been studied between 17 and 300 K using various Ar+ and He-Ne laser lines. The dependence of the effectiveness of excitation on the laser photon energy finds explanation if one-phonon assisted processes are taken into account. The adiabatic model and the model of phonon relaxation has been applied to the experimental linewidth temperature dependence of the A-sites of Ho3+ (transition 5F4, 5S2 to 5I7) and Er3+ (transition 4S3/2 to 4I15/2) and the results are discussed.

The efficiencies of three methods based on a combination of sol-gel chemistry and ion implantation for obtaining an optical activation of Er atoms via the transfer of excitons energy are compared. A better coupling is observed in silica-gel containing Er prepared by addition of Er nitrate to the tetraethoxysilane sol and embedding Si nanocrystals formed by ion implantation or in a silicon suboxide derived from triethoxysilane and implanted with Er ions than in silica-gel implanted sequentially with Si then Er. The infrared emission of Er ions is reduced by the segregation of erbium oxide or the precipitation of Er5Si3, depending on the matrix, in films containing more than 1 at.% Er annealed at temperatures over 1000°C. © 2002 Elsevier Science B.V. All rights reserved.

Thin films containing iron silicides are prepared by two methods. The first one consists in depositing a-Si:H:Fe thin films by magnetron co-sputtering followed by rapid thermal annealing (RTA). The second one is ion implantation of Fe in a-Si:H thin films and RTA treatment. The samples are characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Rutherford back-scattering (RBS). FTIR spectra show absorption bands typical for β-FeSi2 at 263, 293, 308, 345 and 425 cm−1. It is shown that the optimal concentration of Fe in the co-sputtered films to obtain β-FeSi2 is 35–40% and the optimal RTA temperature is 900°C. XPS spectra show that β-FeSi2 is formed in as-deposited and annealed co-sputtered a-Si:H:Fe and implanted a-Si:H thin films.

The laser excited photoluminescence (PL) of SiO 2 and a-SiC:H thin films doped with Tb deposited by co-sputtering has been studied. In the case of SiO 2 :Tb the PL is due to 4f-4f transitions of Tb 3 + ions starting from the 5 D 4 level which is resonantly excited by the 488 nm Ar + laser line. The PL in this case has no temperature quenching from 18 K up to room temperature. The inhomogeneous broadening of the PL bands predominates over the homogeneous one. In the case of a-SiC:H:Tb a broad band covering the whole visible spectrum is observed. It is tentatively assigned to a recombination centre created by the Tb impurity.

Thin films of SiO2 containing Sm were deposited by magnetron co-sputtering. The concentration of Sm in the films was varied by changing the amount of Sm placed on the fused silica target. The samarium content in the films was established by Rutherford back-scattering measurements. Photoluminescence (PL) was excited with the 488-nm line of an Ar ion laser. It consists of several lines in the visible, which are assigned to transitions between multiplets of Sm3+. The concentration dependence of the PL intensity was studied. It passes through a maximum and decreases at higher Sm content. The films were annealed in vacuum at temperatures between 300 and 1000 °C. There was a strong increase in the PL intensity after annealing at 600 °C, and then it fell again after annealing at 1000 °C. The data are compared to spectra of Sm3+ in other matrices. The mechanisms of PL excitation and quenching are discussed.

The I–V characteristics of diode structures containing sputtered a-Si : H : Er films for potential LED applications have been studied. The a-Si : H : Er films were deposited on p+ Si substrates. On top of the film, ZnO : Al transparent conductive layers, 3 mm in diameter, were deposited. The back contacts were made of Al. The Er concentration in the films was varied between 0.05 and 0.16 at %, and the hydrogen concentration between 14 and 24 at %. It was found that the log–log plot of the forward I–V characteristic of a typical sample consisted of several regions with different slopes. On the basis of models put forward in the literature, it is proposed that the electron transport in the studied structure is governed by unipolar carrier injection, and the space charge limited currents are controled by two types of electron trap. The first are probably deep acceptor traps formed by dangling bonds, and the second are donor-like levels created by Er–O complexes. The energy positions of these traps are estimated.

The formation of high-quality polycrystalline silicon (poly-Si) on different substrates has important applications in the development of thin-film transistors, solar cells, image sensors, etc. In this study, we present the results of an investigation of poly-Si films on glass, formed by aluminum-induced crystallization. The process is based on the isothermal annealing for 3 h at 500 °C of co-sputtered Al+Si or sputtered a-Si films on glass, with and without thermally evaporated Al. The poly-Si films were investigated by Raman spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy.

We report studies of the shape of the photoluminescence (PL) band in a-Si:H and its alloys with carbon and nitrogen, made in order to learn more about the broadening mechanism and to test models in which the distribution of initial states results from thermalisation down band tails. The central region and the high energy side of the band shows a double Gaussian form which becomes more symmetric with increasing alloying. The low energy side at intensities