Papers by Keyword: RAMAN

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Authors: Kazukuni Hara, Hiroaki Fujibayashi, Yuuichi Takeuchi, Shoichiro Omae
Abstract: In this work, we have developed a selective embedded epitaxial growth process on 150-mm-diameter wafer by vertical type hot wall CVD reactor with the aim to realize the all-epitaxial 4H-SiC MOSFETs [1, 2, 3, 4, 5]. We found that at elevated temperature and adding HCl, the epitaxial growth rate at the bottom of trench is greatly enhanced compare to growth on the mesa top. And we obtain high growth rate 7.6μm/h at trench bottom on 150mm-diameter-wafer uniformly with high speed rotation (1000rpm).
Authors: P. Dupel, Thierry Chassagne, Didier Chaussende, Yves Monteil, François Cauwet, Etienne Bustarret, A. Deneuville, G. Bentoumi, Eugénie Martinez, B. Daudin, G. Feuillet
Authors: Kazukuni Hara, Masami Naito, Hiroaki Fujibayashi, Atsuya Akiba, Yuuichi Takeuchi, Olga Milikofu, Tomomi Kozu
Abstract: In this report we were able to successfully identify and localize in 3D 3C and 6H foreign polytypes and stress in the embedded epilayer by high resolution 3D Raman spectroscopy, that were otherwise invisible under the microscope or SEM, in non-contact and non-destructive way. Stripe patterned deep trenches with aspect ratio about 2 (depth=3.0μm; width=1.5μm) were formed on 4H-SiC substrate by ICP. The epitaxial layer was embedded in these trenches by SiC CVD. Poly type defects and stress in the embedded epilayer were mapped by curve-fitting of spectra obtained from Raman measurement of the embedded SiC epilayer. The location of the foreign polytypes and the stress inside the stripe pattern allows speculating on the origin of the defects and correlating it to the manufacturing process.
Authors: Michael J. Uren, Martin Kuball
Abstract: Recent work on the thermal and electrical challenges in realizing AlGaN/GaN microwave heterojunction field effect transistors grown on SiC substrates is discussed. Raman thermography has been used to directly measure the self-heating induced lattice temperature rise with dramatically improved resolution and accuracy compared to traditional infrared techniques. It is demonstrated that defects in the SiC substrate can influence the temperature distribution within the active device with potential consequences for reliability. Microwave devices require an insulating GaN substrate material for device isolation. It is shown that the net deep level acceptor concentration has to be accurately controlled to suppress short-channel effects and to achieve radio frequency power efficient operation.
Authors: Alessia Le Donne, Simona Binetti, Giovanni Isella, Bernard Pichaud, Michael Texier, Maurizio Acciarri, Sergio Pizzini
Abstract: The knowledge and control of the structural and morphological properties of nanocrystalline silicon is a fundamental requisite for its proper application in photovoltaics. To this purpose, nanocrystalline silicon films grown by Low Energy Plasma Enhanced Chemical Vapour Deposition (LEPECVD) technique on different kinds of substrates were submitted to a systematic characterization using Raman spectroscopy, X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The results showed that the nature of the film substrate induces deep changes in the structural properties of the deposited films. The importance of a Raman in–depth analysis for an accurate determination of the sample structure has been also demonstrated.
Authors: Antoine Tiberj, Marta Martin, Nicolas Camara, P. Poncharal, T. Michel, J.L. Sauvajol, Phillippe Godignon, Jean Camassel
Abstract: We report an investigation of few layers graphene exfoliated on SiC. Using AFM and Raman spectroscopy, we find that the graphene thickness determined from the normalized intensity of Raman lines significantly depart from the one obtained using XPS.
Authors: G.R. Ahmed Jamal, M. Asraf Siddique, Sawon, Khalid Hasan, M. Jane Alam
Abstract: In this work, an improved technique for chirality assignment of single wall carbon nanotubes (SWCNT) is proposed which work for both isolated and bundles SWCNTs. The technique exploits the (2n+m) family pattern both in optical transitions vs diameter plot and Raman G-mode frequency vs diameter plot of SWCNTs. Using two different plots can give accurate value of the family of unknown SWCNTs that can be used to find chiral index (n, m) of unknown SWCNT unambiguously in most of the cases. Unlike existing methods, graphical comparison or pattern recognition with an existing Kataura plot is not required here. Chirality of 13 SWCNTs are assigned here using this technique. Validity of assigned chirality is cross checked from previous experimental reports. The technique is especially useful for determining chirality of isolated SWCNT.
Authors: Narcis Mestres, M. Ben El Mekki, F.J. Campos, Jordi Pascual, Erwan Morvan, Phillippe Godignon, José Millan, Giorgio Lulli
Authors: M. Holla, Tzanimir Arguirov, Winfried Seifert, Martin Kittler
Abstract: We report on the optical and mechanical properties of Si3N4 inclusions, formed in the upper part of mc-Si blocks during the crystallization process. Those inclusions usually appear as crystalline hexagonal tubes or rods. Here we show that in many cases the Si3N4 inclusions contain crystalline Si in their core. The presence of the Si phase in the centre was proven by means of cathodoluminescence spectroscopy and imaging, electron beam induced current measurements and Raman spectroscopy. The crystalline Si3N4 phase was identified as β-Si3N4. Residual stress was revealed at the particles. While the stress is compressive in the Si material surrounding the Si3N4 particles tensile stress is found in the Si core. We assume that the stress is formed during cool down of the Si block and is a consequence of the larger thermal expansion coefficient of Si in comparison to that of β-Si3N4. Iron assisted nitridation of Si at temperatures below 1400 °C is considered a possible mechanism of Si3N4 formation.
Authors: Felix Fromm, Martin Hundhausen, Michl Kaiser, Thomas Seyller
Abstract: Raman spectroscopy is commonly applied for studying the properties of epitaxial graphene on silicon carbide (SiC). In principle, the Raman intensity of a single graphene layer is rather low compared to the signal of SiC. In this work we follow an approach to improve the Raman intensity of epitaxial graphene on SiC by recording Raman spectra in a top-down geometry, i.e. a geometry in which the graphene layer is probed with the excitation through the SiC substrate [1]. This technique takes advantage of the fact, that most of the Raman scattered light of the graphene is emitted into the SiC substrate. We analyze in detail the top-down measurement geometry regarding the graphene and SiC Raman intensity, as well as the influence of aberration effects caused by the refraction at the air/SiC interface.
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