Si Nanocrystals Embedded in a Silicon Oxynitride Matrix

We investigated the morphological and structural change in silicon nanostructures embedded in the silicon oxynitride matrix. The study has been carried out on thin films thermally annealed at high temperature, after deposition at 400°C by Electron Cyclotron Resonance Plasma Enhanced Chemical Vapour Deposition (ECR‐ PECVD), under different deposition parameters. Our study evidenced the existence of a well defined threshold for the silicon content in the film (around 47%), to get Si nano‐crystallization in the silicon oxynitride matrix. Both Si nano‐crystals and Si nano‐columns have been observed by TEM analysis in two samples having a similar Si content but deposited under different condition

Effect of annealing treatments on photoluminescence and charge storage mechanism in silicon-rich SiNx:H films

In this study, a wide range of a-SiNx:H films with an excess of silicon (20 to 50%) were prepared with an electron-cyclotron resonance plasma-enhanced chemical vapor deposition system under the flows of NH3 and SiH4. The silicon-rich a-SiNx:H films (SRSN) were sandwiched between a bottom thermal SiO2 and a top Si3N4 layer, and subsequently annealed within the temperature range of 500-1100°C in N2 to study the effect of annealing temperature on light-emitting and charge storage properties. A strong visible photoluminescence (PL) at room temperature has been observed for the as-deposited SRSN films as well as for films annealed up to 1100°C. The possible origins of the PL are briefly discussed. The authors have succeeded in the formation of amorphous Si quantum dots with an average size of about 3 to 3.6 nm by varying excess amount of Si and annealing temperature. Electrical properties have been investigated on Al/Si3N4/SRSN/SiO2/Si structures by capacitance-voltage and conductance-voltage analysis techniques. A significant memory window of 4.45 V was obtained at a low operating voltage of ± 8 V for the sample containing 25% excess silicon and annealed at 1000°C, indicating its utility in low-power memory devices

Optical and structural properties of Nd doped SnO2 powder fabricated by the sol-gel method

We report on the structural and optical properties of undoped and neodymium doped SnO2 powders (0, 1, 3, and 5 at% of Nd) synthesized by the sol-gel method. SEM and TEM microscopy techniques reveal a nanometric scale of the powders. We show that the tetragonal rutile phase is achieved after annealing at 700 degrees C. The crystallite size of the doped SnO2 is found to decrease gradually with the increase of Nd content without changing the SnO2 structure. A strong decrease in the intensity of the Raman peaks is noted for doped powders, which can be attributed to the location of Nd3+ ions at the Sn sites indicating Nd incorporation into the host matrix. For the first time the optical properties were studied by UV-VisNIR spectroscopy and revealed Nd related absorption bands in the SnO2 matrix. The investigation of the photoluminescence properties shows broad emission centred around 550-650 nm originating from defects present in the SnO2 host matrix. Under 325 nm laser excitation, a strong photoluminescence of trivalent Nd is observed in the infrared region and shows Nd related emission peaks at 885, 1065, and 1336 nm. Such a strong PL signal under laser excitation indicates that Nd3+ is optically active. The excitation dependent PL (PLE) recorded in the 450-700 nm range confirms the presence of active Nd3+ successfully inserted into the SnO2 host matrix

Photoluminescence of Nd-doped SnO2 thin films

Structural, optical, and electrical properties of Nd-doped SnOx thin films are reported. The atomic structure was characterized by x-ray diffraction and infrared absorption spectrometry. Investigation of the photoluminescence properties revealed Nd-related bands at 920 and 1100 nm for samples annealed at 700 degrees C, which present the tetragonal structure of the SnO2 rutile phase. Nd3+ ions can be indirectly excited and no concentration quenching was observed up to 3 at. %. It is concluded that Nd3+ ions are efficient optically active dopants in addition to be responsible of the observed electric conductivity improvement. These materials are then interesting for solar cell applications

Etude et réalisation de capteurs d'humidité (Capteur à détection optique, capteur piézoélectrique à base de couche d'oxyde de zinc)

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Evaluation of the effective quantum efficiency of photon conversion layers placed on solar cells

Équipe 104 : NanomatériauxInternational audiencePhoton conversion layers are a possible way of improving the efficiency of existing solar cells, even above the Shockley-Queisser limit. The related concepts are often called downshifting, downconversion, and upconversion. Despite the variety of photon conversion systems proposed in the literature, understanding their real impact is often difficult due to joint effects. Here, a new methodology is provided to analyse the efficiency of such conversion layers and to be able to compare the different systems proposed

Deposition of thin layers of zinc oxide and characterization of resonators

International audienc

Local inspection of refractive index and thickness of thick transparent layers using spectral reflectance measurements in low coherence scanning interferometry

International audienceFor a long time, obtaining the optical and morphological properties of a transparent sample with high accuracy without degrading the layer has been challenging. To achieve these expectations, contactless techniques are used and have not only been proven well-suitable but have also brought optical methods to the forefront. Over recent years white light scanning interferometry has been increasingly used for studying and characterizing transparent materials with thicknesses ranging from a few hundred nanometers to several micrometers. Then, multiple techniques have been developed to retrieve the transparent layer properties from interferometric data. The more recent techniques, based on the use of an error function which defines the best fit between the experimental and theoretical data, allow the determination of the thickness of very thin films (<1 μm). We show here that a method based on this principle can be applied to thicker layers (>1 μm) for simultaneously measuring their optical and morphological properties, provided that a crucial step is carefully considered during the data acquisition process. This enables the simultaneous measurements of both the thickness and the refractive index (dispersion) without any prior assumptions about one of the two parameters. We demonstrate the proposed method by accurate measurements on a few micrometers thick PMMA layer as well as on a SnO2 layer, which is a much more dispersive sample

Preparation of ZnO thin films by reactive e-beam evaporation technique

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