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We present the design, fabrication, and characterization of high quality factor and small mode volume planar photonic crystal cavities from cubic (3C) thin films (thickness ~ 200 nm) of silicon carbide (SiC) grown epitaxially on a silicon substrate. We demonstrate cavity resonances across the telecommunications band, with wavelengths from 1,250 - 1,600 nm. Finally, we discuss possible applications in nonlinear optics, optical interconnects, and quantum information science., Comment: 7 pages, 6 figures

Similar to the field of application of traditionally used fibers based on plastic scintillators, there is a growing interest to replace the materials by inorganic crystalline materials. They will provide significantly higher light yield, an efficient interaction with electromagnetic probes due to the content of high-Z elements, a wider range of emission wavelength to adapt to the appropriate photo sensors and remain more resistant to radiation damage for long-term applications in highly radioactive environments. The HP3-WP22 collaboration has focused on the optimization of the micro-pulling-down technique and the quality inspection of fibers made of LuAG:Ce and LYSO:Ce, respectively. In spite of the more challenging growing conditions, the ongoing R&D program has been directed towards fibers based on LYSO:Ce. The very radiation hard and bright scintillator material appears to be attractive for many applications in particular due to its very short radiation length. Fibers up to 2 mm in diameter and more than 100 mm in length were successfully produced and show a very promising performance. The paper will discuss in detail measurements of the achieved light output and attenuation in the fiber as well as the homogeneity of the produced samples. For further optimization of the technology, a comparison of the fiber quality and the growth parameters is given.

International audience; We report on the electrical characteristics of Ni/4H-SiC Schottky contacts fabricated on a Ge-doped 4H-SiC epilayer. The morphology and the current mapping carried out by conductive atomic force microscopy on the epilayer allowed observing nanoscale preferential conductive paths on the sample surface. The electrical characteristics of Ni contacts have been studied before and after a rapid thermal annealing process. A highly inhomogeneous Schottky barrier was observed in as-deposited diodes, probably related to the surface electrical inhomogeneities of the 4H-SiC epilayer. A significant improvement of the Schottky diodes characteristics was achieved after annealing at 700°C, leading to the consumption of the near surface epilayer region by Ni/4H-SiC reaction. After this treatment, the temperature behavior of the ideality factor and Schottky barrier height was comparable to that observed on commercial 4H-SiC material.

In this work, we report on the addition of GeH4 gas during homoepitaxial growth of 4H-SiC by chemical vapour deposition. Ge introduction does not affect dramatically the surface morphology and defect density though it is accompanied with Ge droplets accumulation at the surface. The Ge incorporation level inside the 4H-SiC matrix, ranging from few 1017 to few 1018 at.cm-3, was found to be mainly affected by the growth temperature and GeH4 flux. Other growth parameters like C/Si ratio, polarity, or off-orientation did not show any significant influence. On the other hand, adding GeH4 led to the increase of the intentional n type doping level by a factor of 2 to 5 depending on the C/Si ratio in the gas phase., 8 pages

We have investigated the electrical properties of n-type 4H-SiC in-situ germanium-doped homoepitaxial layers grown by chemical vapor deposition. Germanium is an isoelectronic impurity and, therefore, not expected to contribute to the conductivity. However, Hall effect measurements taken on samples with and without germanium revealed an enhanced mobility by a factor of ≈2 at T ≈ 55 K in the germanium-doped sample despite equal free electron concentration and equal compensation. Deep level transient spectroscopy (DLTS) measurements taken on germanium-doped samples reveal negative peaks indicating the presence of charged extended defects.

Growth of cubic P-Sic crystals from a C-saturated Al-Si melt under atmospheric pressure has been investigated at temperatures ranging from 700 to 120OoC and for silicon contents in the melt varying from 12.5 to 40 at%. Under favourable conditions (1 100°C, 30 at%Si), crystals with (1 11) faces up to 100pm wide have been produced. Thermo-kinetic considerations based on an optimum deviation to the A14C3-Sic-L monovariant equilibrium in the Al-C-Si ternary system are proposed for modelling the experimental results.

Chemical Vapour Transport is a well known process widely used for the growth of monocrystals. This paper is a thermodynamic overview of different heterogeneous chemical systems, promising for the growth of silicon carbide by means of chemical transport reactions. The systems are Si-C-Y where Y is oxygen or a chalcogen (S, Se) and Si-C-H-X where X is an halogen (Cl, Br, I). We studied in a first step the gas phase composition obtained from SiC etching with the transporting agent as a function of temperature. In a second step, we report the conditions for the formation of silicon carbide from such a vapour at a different temperature. Finally we discuss optimal conditions of temperatures and thermal gradients required for SiC transport with each systems.

International audience; We present the first demonstration of pL-scale analyte index sensing based on surface phonon polaritons in the midinfrared, which are excited at the silicon carbide/analyte interface in the Otto configuration. Attenuated total reflectance measurements reveal analyte index specificity through a double-scan of wavelength and incidence angle for analyte volumes as small as 100 pL. Midinfrared sensing tuned to surface phonon polariton resonance paves the way for index sensing of analytes beyond current volume−resolution limits.

^aObjective: To assess quality of life before and after thoracoscopic sympathectomy for treatment of primary hyperhidrosis.Methods: we conducted an observational, analytical, cross-sectional and quantitative study. We evaluated patients undergoing thoracoscopic sympathectomy for primary axillary hyperhidrosis, primary palmar hyperhidrosis, and axillary hyperhidrosis associated with palmar one. We applied a questionnaire on quality of life related to hyperhidrosis before and after the operation.Results: The questionnaire was administered to 51 patients with a mean age of 32.4 years, 45 women and six men. The average quality of life related to hyperhidrosis in a score of 0-100 before sympathectomy was 34.6 and after the operation it was 77.1. Compensatory hyperhidrosis occurred in 84.3% of patients.Conclusion: thoracoscopic sympathectomy improves the quality of life of patients with primary hyperhidrosis, with results supported over time. Compensatory hyperhidrosis occurred in most patients, but did not significantly influence the improved quality of life.^len^aObjetivo: avaliar a qualidade de vida antes e apos a realizacao de simpatectomia por videotoracoscopia para tratamento de hiperidrose primaria.Metodos: estudo observacional, analitico, transversal e quantitativo. Foram avaliados os pacientes submetidos a simpatectomia por videotoracoscopia para tratamento de hiperidrose primaria axilar, palmar e a hiperidrose axilar associada a palmar. Foi aplicado um questionario sobre qualidade de vida relacionada a hiperidrose, antes e apos a operacao.Resultados: O questionario foi aplicado em 51 pacientes com media de idade de 32,4 anos, sendo 45 mulheres e seis homens. A qualidade de vida media relacionada a hiperidrose, em um escore de 0 a 100, antes da simpatectomia foi 34,6 e depois da operacao foi 77,1. A hiperidrose compensatoria ocorreu em 84,3% dos pacientes.Conclusao: a simpatectomia videotoracica melhora a qualidade de vida dos pacientes com hiperidrose primaria, sustentando-se ao longo do tempo. A hiperidrose compensatoria ocorreu na maioria dos pacientes, todavia nao influenciou de maneira significativa a melhora da qualidade de vida.^lpt

We have studied the epitaxial growth of AlN layers by plasma-assisted molecular beam epitaxy (MBE) on 6H–SiC substrate. Reflection high-energy electron diffraction (RHEED) was used to monitor the growth by the observation of the 2D–3D growth transition, respectively, in Al- and N-rich conditions. Special attention was given to the elimination of the Al droplets which often form in Al-rich conditions. Different growth procedures are proposed to avoid the appearance of these droplets while keeping a 2D growth. Each of the procedure gives AlN epilayers with identical crystalline quality and low surface roughness as measured, respectively, by X-ray diffraction and atomic force microscopy.

AlN layers were grown on 3.5° off 6H-SiC substrate by plasma-assisted molecular beam epitaxy (MBE). A study of the growth mechanism has been carried out by varying the growth time and the III/V ratio, at a constant growth temperature of 800°C. The layers were characterized by means of Reflection high-energy electron diffraction (RHEED), atomic force microscopy (AFM) and X-ray diffraction (XRD). It is shown that nitrogen-rich conditions always give rise to a three-dimensional growth with spotty RHEED patterns and rough surface. In Al-rich conditions, the growth is much more two dimensional like with streaky RHEED patterns. By AFM, step bunching growth is observed. The size of the steps depends on the thickness of the layer as well as on the III/V ratio. All the samples grown in Al-rich conditions showed better crystalline quality than those grown in N-rich conditions.

The development of the technology for the growth of inorganic scintillating fibers has initiated a significant progress in the production of compact inorganic scintillators during the last years. Triggered by the traditional applications of fibers based on plastic scintillators, there are strong arguments for replacing those fibers by inorganic crystals. One can rely on a significantly higher light yield, an efficient interaction with electromagnetic probes due to the content of high-Z elements, a wider range of emission wavelength to adapt to the appropriate photo sensors and remain more resistant to radiation damage for long-term applications in a highly ionizing environment. The HP3-WP22 collaboration has focused on the optimization of the micro-pulling down technique and the quality inspection of fibres based on LuAG:Ce and LYSO:Ce. There has been first progress in the variation of the geometry, pulling several fibres in parallel, the optimization of the crucibles and the requirements for an increased efficiency being mandatory for future mass production. In spite of the more challenging growing conditions the final goal of the R&D program has been directed towards fibers made of LYSO:Ce. The very radiation hard and bright scintillator material appears to be very attractive for many applications in particular due to its very short radiation length and high light yield. Fibers up to 1 mm diameter and more than 100 mm length have been successfully produced and show a very promising performance. The paper will discuss in detail measurements of the achieved light output and light attenuation in the fiber, as well as the homogeneity of the produced samples. In addition, the studies are performed and compared to the achievements manufacturing fibers based on LuAG:Ce.

This paper presents the results obtained after chemical vapor deposition of SiC with the addition of GeH4gas to the classical SiH4+C3H8precursor system. Epitaxial growth was performed either on 8°off-axis or on-axis 4H-SiC substrate in the temperature range 1500-1600°C. In the off-axis case, the layer quality (surface morphology and defect density) does not change though accompanied with Ge droplets accumulation at the surface. The Ge incorporation level was found to increase with temperature in the 10171018cm-3ranges. It was observed that adding GeH4leads to the increase of the n type doping level by a factor from 2 to 5 depending on the C/Si ratio. In the on-axis case, GeH4was only added to the gas phase before starting the SiC growth. It was found that there is a conditions window (temperature and GeH4flux) for which 3C-SiC twin free layers can be grown. Adding this foreign element before SiC growth clearly modifies SiC nucleation on on-axis substrate.

International audience; This works deals with the localized growth of SiC on monocrystalline (100) diamond surface. It describes an attempt of selective epitaxy using vapor–liquid–solid (VLS) transport. Patterns of Al–Si stacking were melted and fed by propane. Morphology, structure and doping type of the SiC deposit were evaluated. The deposit was found to be successfully selective but polycrystalline, with the 3C-SiC polytype. Study of the initial step of growth showed that SiC nucleation occurs without any propane addition but just through the interaction of liquid Al–Si and diamond via a dissolution/precipitation process. The VLS transport mainly assists the growth of these nuclei by providing a secondary carbon source. This explains the random nucleation and the polycrystalline growth. Despite this, the deposit was dense enough to perform some preliminary electrical measurements which show encouraging results.

International audience; This work reports on the performances of ohmic contacts fabricated on highly p-type doped 4H-SiC epitaxial layer selectively grown by vapor-liquid-solid transport. Due to the very high doping level obtained, the contacts have an ohmic behavior even without any annealing process. Upon variation of annealing temperatures, it was shown that both 500 and 800 °C annealing temperature lead to a minimum value of the Specific Contact Resistance (SCR) down to 1.3×10−6 Ω⋅cm2. However, a large variation of the minimum SCR values has been observed (up to 4×10−4 Ω⋅cm2). Possible sources of this fluctuation have been also discussed in this paper.The authors thank the Agence Nationale pour la Recherche, ANR, for its financial support in the framework of the Very High Voltage Devices SiC project (VHVD-SiC, ANR-08-BLAN-0191).

International audience; This work focuses on the Transmission Electron Microscopy investigation of p‐type doped 3C‐SiC layers grown by Vapor‐Liquid‐Solid mechanism using Si‐Ga melts on 4H‐SiC substrates. Ga concentration strongly influences the appearance of defects in the grown layers. Ga inclusions are observed only in the layer grown at the highest temperature and lowest Ga content in the melt. At the highest concentration of Ga in the melt main defects are dislocations forming periodic bands along 〈equation image〉 and 〈equation image〉 directions. The most appropriate conditions (in terms of defect density) for VLS growth using SiGa melts, as defined from the current study, should be growth in Si25Ga75 alloy at T = 1200 ºC.

International audience; This work deals with the study of the Selective Epitaxial Growth (SEG) of SiC using Vapour-Liquid-Solid (VLS) transport at temperature ≤ 1100°C. Focus was made on the nucleation step by observing the evolution of the growth as a function of growth duration with variable Si-content of the Al-Si liquid phase. Addition of propane during the initial heating ramping-up not only avoids liquid de-wetting but also allows good starting of the epitaxial growth. Additionally, it was observed that, by increasing the silicon content in the liquid, the morphology of the grown SiC is improved, and no parasitic Al4C3 inclusions are formed. Limiting the growth rate is found to be essential for getting controlled smooth growth process.

The effect of various growth conditions has been studied in order to modelize and optimize the SiC buffer layers obtained by reactive chemical‐vapor deposition (RCVD) on Si(100) substrates. First, thermodynamic calculations have been carried out on the Si–H2–CxHyClz system to simulate the RCVD process and to foresee the nature and the evolution of the deposit with varying parameters. The experiments have confirmed some of the thermodynamic results, such as the carbon deposition in specific conditions, and brought out complementary information on the kinetics point of view. Due to our low heating up rate, no SiC island formation was characterized at the early stage of growth. The obtained SiC layers are ultrathin with a very particular morphology. We propose a new model of growth based on atomic force microscopy observations to explain the resulting morphology. The optimal conditions have been deduced to elaborate ultrathin, smooth, and monocrystalline β‐SiC buffer layers.

A kinetic study was carried out on the growth of an SiC buffer layer on Si(100) by reactive chemical vapour deposition. Experiments were performed at temperatures in the range 1150–1300 °C for 1 to 45 min using C 3 H 8 and H 2 as gas reactants. Infrared transmittance spectrometry was used for accurate film thickness determination (down to 1.2 nm). The growth profiles as a function of time show a four-step mechanism involving the rapid formation of an SiC “thermal layer” by coalescence of SiC islands. The thickness increases by Si out-diffusion through this layer until a critical thickness, controlled by the temperature and Si etching, is reached. Only the initial values of the diffusion profiles can be fitted by Fick's second law. The hypothesis of silicon etching by H 2 is confirmed by thermodynamic calculations. The etching activation energy is E e = 4.4 eV. The temperature dependence of the resulting diffusion coefficients gives an apparent diffusion activation energy of E d = 4.5 eV. The close agreement between these two activation energies illustrates the competition between the two mechanisms deduced from the growth profiles.

This work addresses the process of ageing in Al-4wt.% Cu at two temperatures (150 °C, 180°C) and in conditions of secondary ageing at temperatures up to 60°C, after artificial ageing treatment at 150°C. Positron lifetime and coincidence Doppler broadening measurements are reported. The analysis shows an initial association of positron trapping sites with Cu (about 9 at. % Cu at the annihilation site) that decreases to 7÷6 % in the initial stages of ageing, but then increases sharply (up to 25 at. % Cu after 300 hours at 180°C). The positron lifetime also displays an initial decrease followed by a final increase. The results confirm the hypothesis that positrons are not trapped in GP[1] zones, but show that trapping occurs in GP[2] zones formed at 150°C. During secondary ageing, the vacancy-Cu association as well as the positron lifetime decrease with the ageing time. This is attributed to the formation of GP[1] zones due to residual supersaturation.

In this paper, conditions for obtaining high growth rate during epitaxial growth of SiC by vapor-liquid-solid mechanism are investigated. The alloys studied were Ge-Si, Al-Si and Al-Ge-Si with various compositions. Temperature was varied between 1100 and 1300°C and the carbon precursor was either propane or methane. The variation of layers thickness was studied at low and high precursor partial pressure. It was found that growth rates obtained with both methane and propane are rather similar at low precursor partial pressures. However, when using Ge based melts, the use of high propane flux leads to the formation of a SiC crust on top of the liquid, which limits the growth by VLS. But when methane is used, even at extremely high flux (up to 100 sccm), no crust could be detected on top of the liquid while the deposit thickness was still rather small (between 1.12 μm and 1.30 μm). When using Al-Si alloys, no crust was also observed under 100 sccm methane but the thickness was as high as 11.5 µm after 30 min growth. It is proposed that the upper limitation of VLS growth rate depends mainly on C solubility of the liquid phase.

International audience; In this work we report on SiC epitaxial growth by vapour-liquid-solid (VLS) mechanism on on-axis 4H-SiC(0001) substrates which were previously patterned to form mesa structures. The liquid phase was set to Al 70Si 30. At 1100°C, it led to very high homoepitaxial lateral growth (140 μm/h) with pronounced spiral growth and in plane anisotropy of growth rate. Upon temperature increase to 1200 °C, this spiral growth was suppressed and the lateral growth was further increased up to 180 μm/h. The in-plane versus out-of-plane anisotropy of growth rate was found to be as high as 60 at this temperature and 46 at 1100°C.

A compact, solid-state accelerating structure based on surface waves is proposed and experimentally characterized. The structure, consisting of two SiC layers epitaxially grown on Si slabs and separated from each other by a subwavelength acceleration channel, is shown to support both longitudinal (accelerating) and transverse (deflecting) surface modes. Both modes are experimentally excited and characterized by performing angle-resolved spectroscopy with a wavelength-tunable carbon dioxide laser. Phase velocities of superluminous and subluminous modes are experimentally demonstrated, paving the way for tabletop charged particle acceleration. The same structure can be used for optical characterization of ultrashort electron bunches that generate longitudinal and transverse Cherenkov radiation.

Since a few years, VLS transport is studied not only for homoepitaxial SiC growth but also for SiC selective epitaxial growth (SEG). In this approach, a stacking of silicon and aluminum layers is deposited on the substrate and patterns are created by photolithography. Upon melting, the Al-Si liquid droplets are fed by propane to obtain the SEG of p-doped SiC. In this work, the growth mechanisms were deeper investigated, in particular the influence of the carrier gas (H2 or Ar) and the growth temperature. SEG experiments showed higher growth rates than those measured in the standard configuration (nonselective growth). Moreover, the SiC layers exhibited step-bunched areas characteristic of liquid phase growth but also areas with morphological features due to a disruption of the step-bunching growth mode.

International audience; The objective of this study is to grow Si-SiC core-shell nanowires (NWs) for bio-nano-sensors. The idea is to benefit from the electronic transport into the Si core NW and from the biocompatibility of the SiC shell all around the Si NW. Silicon nanowires (NWs) have been first obtained by a top-down approach. Before carburization, in situ deoxidation under H-2 allowed significant smoothening and faceting of the Si NWs sidewalls. Then, Si NWs have been carburized under methane or propane at atmospheric pressure and at temperatures >= 1000 degrees C. Carburization of Si NWs leads to Si-SiC core-shell NWs with a thin (similar to 3 nm), continuous and single crystalline cubic SiC shell. The 3C-SiC shell has been further thickened by chemical vapor deposition and preferential growth of 3C-SiC has been observed on the sidewalls of NWs. Based both on the electronic transport properties of silicon and on the biocompatibility of SiC, these new 1D-nanostructures could be an ideal object for nano-bio-sensors.

International audience; Chemical vapour deposition in a cold wall reactor working at atmospheric pressure was used to study the homoeptaxial growth of 4H-SiC on 4°ff misoriented substrates from silane and propane precursors. The effect of various growth parameters (temperature 1450-1650°C, C/Si ratio 1-7, thickness 2.5-10 µm) were studied in order to determine the best conditions for obtaining smooth surfaces after epitaxy. It is shown that the main source of roughness is surface undulation which easily appears during growth, especially at low C/Si ratios and high temperature (up to 1600°C). Temperatures above 1600°C and C/Si ratio of 1 give the best results. When reducing temperature, a trade-off has to be found between defects formation and surface undulation.

VLS mechanism was used for growing boron doped homoepitaxial SiC layers on 4H-SiC(0 0 0 1) 8° off substrate. Si-based melts were fed by propane in the temperature range 1450–1500 °C. Two main approaches were studied to incorporate boron during growth: (1) adding elemental B in the initial melt, with two different compositions: Si 90 B 10 and Si 27 Ge 68 B 5 ; the growth was performed at 1500 °C; (2) adding B 2 H 6 to the gas phase during growth with a melt composition of Si 25 Ge 75 ; the growth was performed at 1450 °C. In most cases, the growth time was limited by liquid loss. The longest growth duration (1 h) was obtained when adding B 2 H 6 to the gas phase. In the case of Si 90 B 10 melt, the surface morphology exhibits large and parallel terraces whereas the step front is more undulated when adding Ge. Raman and photoluminescence characterizations performed on these layers confirmed the 4H polytype of the layers in addition to the presence of B, which results in a strong B–N donor–acceptor band. The thickness and the growth rate were determined by micro-Infrared spectroscopy. Particle Induced γ-ray Emission (PIGE) was tentatively used to detect B incorporation inside the grown layers. These results were compared to SIMS measurements from which B concentration was found to vary from 10 18 to 10 19 at cm −3 .

In this work we report on the study of twin boundary (TB) evolution during heteroepitaxial growth of 3C-SiC on patterned 4H-SiC(0001) substrate by vapour-liquid-solid (VLS) mechanism. Ge50Si50 melt was used at a temperature of 1450°C. 3C-SiC deposit was obtained on top and outside the mesas. Some lateral enlargement of these mesas was observed but it was systematically homoepitaxial. Elimination of TBs inside the 3C-SiC deposit on top of the mesas was observed for specific mesa shape and/or orientation of the sidewalls. Though three–fold or six-fold symmetry mesas are recommended for TB elimination, originally circular mesas lead also to the same result due to initial faceting toward hexagonal shape.

The crystal growth of 3C-SiC onto silicon substrate by Vapour-Liquid-Solid (VLS) transport has been investigated. In the studied growth configuration, propane feeds a SiGe liquid phase contained in 10 µm-deep etched trenches on the Si substrate. Before SiGe deposition, the substrate surface and the trench walls were coated with a thin (100 - 200 nm) CVD-grown 3C-SiC seeding layer. For the VLS growth, the temperature was increased up to 1280°C, above the SiGe alloy melting point, at which point propane was added to start VLS growth. X-ray diffraction shows that some SiC is grown epitaxially onto the CVD seeding layer. However, cross-section SEM observations have evidenced that SiC has grown as trapezoidal islands and not as an uniform layer. Backscattered electron images also clearly show a deep penetration of germanium into the substrate through the SiC seeding layer. This penetration was found to be strongly reduced when increasing the seeding layer thickness from 100 to 200 nm.

International audience; This work reports on the stabilization of 3C–SiC polytype during heteroepitaxial growth by vapor–liquid–solid (VLS) on on-axis and 2° off-axis 6H–SiC(0001) substrates using Si–Ge as liquid phase. It was found that, depending on growth conditions (mainly temperature or nitrogen amount in the reactor), the deposit could be either a complete 3C or 6H–SiC layer or even a mixture of both polytypes. The proportion of 3C inside the deposit increases when 1) nitrogen amount in the reactor increases or 2) temperature is decreased. Though the effect of temperature could be explained in terms of 3C–SiC initial island dissolution, the influence of nitrogen is less obvious but it is shown to be effective at the early stage of growth. Several hypotheses are proposed such as SiC lattice modification by N incorporation or surface effects during the early stage of growth.

Silane was successfully used to grow SiO x nanowires by vapor-liquid-solid at low temperature ( < 600 °C) using in-situ reduced tin oxide catalyst. The temperature of catalyst reduction was found to have a significant impact on the morphology, which was mainly composed of nanowires cocoons and bamboo-like microtubes. Experimental results suggest that the catalyst drop size is probably at the origin of the morphology selection. Growth mechanisms are proposed to explain these results. For long growth time, partial etching of the nanowires was observed due to SiO formation. Growing at very low temperature ( < 400 °C) was found to significantly reduce the growth rate while improving the shape and size control. PL measurements evidenced defects in SiO x nanowires coming from oxygen deficiency.

International audience; In this work, we present and compare the results obtained from different Si-based melts (Ge–Si, Al–Si and Al–Ge–Si) for growing SiC layers on α-SiC substrate by vapour–liquid–solid (VLS) mechanism. It was found that, depending on melt composition, the deposit could be either a complete 3C or α-SiC layer or even a mixture of these polytypes. The binary Al–Si melt leads systematically to a highly p-type homoepitaxial α-SiC deposit while Ge–Si melt gives a non-intentional n-type doped layers of either 3C or 6H polytypes depending on growth conditions. However, highly p-type doped 3C heteroepitaxial deposit can be obtained if a small amount of Al is added to the Ge–Si binary liquid phase. This means that the VLS mechanism is very flexible and allows growing either n- or p-type SiC layers of 3C or 6H polytypes.

Highly confined “spoof” surface plasmons (SSPs) are predicted and observed in a perforated metal film coated with a thin dielectric layer. They are better confined than conventional guided modes and conventional SSPs and are controllable by the perforations geometry.

International audience; Si nanowires (NWs), with diameters of about 800 nm and lengths of about 10 lm, previously synthesized by the VLS method with gold catalyst, were carburized at 1,100 C under methane for conversion into SiC nanostructures. These experiments have shown that Si NWs have been transformed into SiC nanotubes (NTs) with approximately the same sizes. Nanotubes’ sidewall thickness varies from 20 to 150 nm depending on the NTs’ height. These SiC nanotubes are hexagonal in shape and polycrystalline. A model of growth based on the outdiffusion of Si through the SiC layer was proposed toexplain the transformation from Si nanowires to SiC nanotubes. This model was completed with thermodynamic calculations on the Si–H2–CH4–O2 system and with results from complementary experiment using propane precursor. Routes for obtaining crystalline SiC NTs using this reaction are proposed.

International audience; The current communication focuses on the influence of a post-growth annealing on the evolution of defects inside (111) 3C-SiC layers grown by the Vapour Liquid Solid (VLS) mechanism in SiGe melts on Si-face on- and off axis 6H-SiC substrates. The layers are studied by Transmission Electron Microscopy (TEM) and Low Temperature Photoluminescence (LTPL). It was found that the growth on off-axis substrates results in a 3C-SiC layer containing mainly stacking faults (SFs) and microtwins (MT). The density of MT lamellae and SFs reduces in the layers grown on the on-axis substrate compared to off-axis substrate. In the layers grown on off-axis substrates the annealing strongly reduces the density of SFs inclined to the 3C/6H-SiC interface. Additionally, 3C to 6H polytypic transformation appears only at the interface, most probably starting from substrate step edges. This was only seen on off-axis seed since the step edges are more.

An indefinite permittivity medium (IPM) has been fabricated and optically characterized in mid-infrared spectral range (10.7 µm−11.3 µm). Phase and amplitude transmission measurements reveal two remarkable properties of IPMs: (i) transmission of sub-diffraction waves (as short as λ/4) can exceed those of diffraction-limited ones, and (ii) sub-diffraction waves can propagate with negative refractive index. We describe a novel double-detector optical technique relying on the interference between sub-diffraction and diffraction-limited waves for accurate measurement of the transmission amplitude and phase of the former.

International audience; The study reports on structural and optical investigations of (111) 3C‐SiC layers grown homoepitaxially by Chemical Vapour Deposition (CVD) at different C/Si ratios. The seeds were 3C‐SiC layers grown on on‐axis Si‐face (0001) 6H‐SiC substrates by Vapour‐Liquid‐Solid (VLS) mechanism in Si‐Ge or Si‐Sn melt. Transmission Electron Microscopy (TEM) investigation showed that the main defects reaching the VLS seed surface are dislocations, stacking faults (SFs) and twin boundaries. In the CVD layer the defect density is reduced compared to the VLS layer at low C/Si ratio (in the range of 1–3). The low‐temperature Photoluminescence (LTPL) spectra of all the layers display a defect related peak at 1.98 eV attributed to DI defect, while G bands are observed in the range of 1.82–1.92 eV range at C/Si ratio of 7 and 10. Common defect in CVD layers was multiple twin complex, which appears as a rule at the vicinity of the twinned domains. This multiple twin complex consists of four twins bound by two fully symmetrical (1̄11) twin boundaries and one (2̄11) interface.

International audience; The present work reports on the tentative growth of p‐type 3C‐SiC layers deposited by vapour‐liquid‐solid (VLS) mechanism using Si‐Ga and Si‐Ge‐Al melts with different compositions and temperatures. It was found that 3C‐SiC polytype was always recorded when both liquid phases were used. However, from Raman characterizations, only the layers grown from Al‐based melts show evidence of p‐type doping, with pronounced Fano interferences. For the layers grown using Ga‐based melts, the layers are n type due to higher (non intentional) incorporation of nitrogen compared to gallium one. A simple mechanism is proposed to explain these differences.

International audience; In today's nanoelectronics devices, thermal management is a major issue to miniaturization. Because of its high thermal conductivity, diamond is an extremely interesting material for heat spreading. SOI (Silicon-On-Insulator) technology suffers of the poor thermal dissipation due to the silicon oxide buried layer. Thus, SOD (Silicon-On-Diamond) based on dielectrical diamond layer is seen as a promising candidate for future bulk solution. Polycrystalline diamond layers of extreme insulating properties (>10 14 Ω.cm) are successfully synthesis with thickness under 150 nm on 2 inches silicon wafer. However, defects due to the growth and the polycrystal structure are responsible for the detrimental current stimulate by alternative electrical field. The defects activation energies were measured on columnar nanostructured diamond grown under different conditions. Values of 0.56 to 1.56 eV were found for defects in these films and were correlated to the growth parameters as well as the diamond morphology.

Highly confined "spoof" surface plasmon-like (SSP) modes are theoretically predicted to exist in a perforated metal film coated with a thin dielectric layer. Strong modes confinement results from the additional waveguiding by the layer. Spectral characteristics, field distribution, and lifetime of these SSPs are tunable by the holes' size and shape. SSPs exist both above and below the light line, offering two classes of applications: "perfect" far-field absorption and to efficient emission into guided modes. It is experimentally shown that these plasmon-like modes can turn thin, weakly-absorbing semiconductor films into perfect absorbers., 5 pages; 5 figures

International audience; Stacking faults (SFs) and the 3C-6H polytypic transition in thick (001)-oriented 3C-SiC crystals are studied by means of diffuse X-ray scattering. The presence of SFs lying in the {111} planes gives rise to streaked reciprocal lattice points with the streaks being parallel to the directions. In the case of low SF densities the defects are uncorrelated and the simulation of the diffuse intensity distribution allows to derive the SF density. In partially transformed crystals, the SFs are spatially correlated which gives rise to an intense and asymmetric diffuse scattering distribution. Its simulation allows to determine both the transformation mechanism and the transformation level.

International audience; The influence of nitrogen impurity on the stabilization of 3C-SiC polytype has been studied during vapour-liquid-solid (VLS) growth on 6H-SiC(0001) seed with Si-Ge melt. By changing the partial pressure of N2 during growth, it was found that the proportion of 3C-SiC inside the grown material increases with N2 partial pressure. 6H inclusions are only found for high purity (low N2 content) conditions. The possible interactions proposed to explain this effect are divided in two effects: i) lattice parameter modification and ii) surface induced lateral enlargement variation. A combination of both effects is suspected.

In this work we investigated the influence of the Si substrate misorientation and 3C‐SiC film thickness on the density of Anti‐Phase Boundaries, in order to better understand the mechanism of antiphase domain annihilation. The two highlights in our work are the utilization of [001] orientated Si on‐axis wafer with spherical dimples, which gave us access to a continuum of off‐cut angles (0° to ∼11°) and directions, and the deposition of elongated silicon islands on the surface of 3C‐SiC epilayers, which improved the detection of APDs by analysis of Scanning Electron Microscopy images. We found that for a given layer thickness the relative surface occupation of one domain increases with the off‐cut angle value, leading to single domain film up to a certain angle. This critical value is reduced as the film is thickened.

Zinc‐blende GaN quantum dots were grown on 3C‐AlN(001) by two different methods in a molecular beam epitaxy system. The quantum dots in method A were fabricated by the Stranski‐Krastanov growth process. The quantum dots in method B were fabricated by droplet epitaxy, a vapor‐liquid‐solid process. The density of the quantum dots was controllable in a range of 108 cm−2 to 1012 cm−2. Reflection high energy electron diffraction analysis confirmed the zinc‐blende crystal structure of the QDs. Photoluminescence spectroscopy revealed the optical activity of the QDs, the emission energy was in agreement with the exciton ground state transition energy of theoretical calculations.

By the analysis of intra‐ and intersubband transitions in GaN/AlN superlattices the band offset is determined experimentally. Superlattice structures with different period lengths were fabricated by plasma‐assisted molecular beam epitaxy 3C‐SiC substrates. The structural properties were studied by high resolution X‐ray diffraction, revealing a high structural perfection of the superlattice region with several peaks in the X‐ray spectra. Infrared absorbance spectroscopy revealed clear intrasubband transitions in the spectral region of 1.55 μm measured at room temperature. Clear intersubband transitions were observed by photoluminescence at room temperature. These transition energies were compared to calculated energies using a 1D Poisson Schrodinger solver. For the calculations standard parameters for cubic GaN and AlN were used, while the band offset between GaN and AlN was varied. Optimal agreement between experimental and theoretical data was obtained for a band offset ΔEC:Δ EV of 55:45.