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Kagome silicene: a novel exotic form of two-dimensional epitaxial silicon
Authors:
Y. Sassa,
F. O. L. Johansson,
A. Lindblad,
M. G. Yazdi,
K. Simonov,
J. Weissenrieder,
M. Muntwiler,
F. Iyikanat,
H. Sahin,
T. Angot,
E. Salomon,
G. Le Lay
Abstract:
Since the discovery of graphene, intensive efforts have been made in search of novel two-dimensional (2D) materials. Decreasing the materials dimensionality to their ultimate thinness is a promising route to unveil new physical phenomena, and potentially improve the performance of devices. Among recent 2D materials, analogs of graphene, the group IV elements have attracted much attention for their…
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Since the discovery of graphene, intensive efforts have been made in search of novel two-dimensional (2D) materials. Decreasing the materials dimensionality to their ultimate thinness is a promising route to unveil new physical phenomena, and potentially improve the performance of devices. Among recent 2D materials, analogs of graphene, the group IV elements have attracted much attention for their unexpected and tunable physical properties. Depending on the growth conditions and substrates, several structures of silicene, germanene, and stanene can be formed. Here, we report the synthesis of a Kagome lattice of silicene on aluminum (111) substrates. We provide evidence of such an exotic 2D Si allotrope through scanning tunneling microscopy (STM) observations, high-resolution core-level (CL) and angle-resolved photoelectron spectroscopy (ARPES) measurements, along with Density Functional Theory calculations.
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Submitted 30 January, 2020;
originally announced January 2020.
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Multilayer Silicene: a clear evidence
Authors:
Paola De Padova,
Amanda Generosi,
Barbara Paci,
Carlo Ottaviani,
Claudio Quaresima,
Bruno Olivieri,
Eric Salomon,
Thierry Angot,
Guy Le Lay
Abstract:
One year after the publication of the seminal paper on monolayer 3 by 3 reconstructed silicene grown on a silver (111) substrate, evidence of the synthesis of epitaxial root3 by root3 reconstructed multilayer silicene hosting Dirac fermions was presented. Although a general consensus was immediately reached in the former case, in the latter one, the mere existence of multilayer silicene was questi…
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One year after the publication of the seminal paper on monolayer 3 by 3 reconstructed silicene grown on a silver (111) substrate, evidence of the synthesis of epitaxial root3 by root3 reconstructed multilayer silicene hosting Dirac fermions was presented. Although a general consensus was immediately reached in the former case, in the latter one, the mere existence of multilayer silicene was questioned and strongly debated. Here, we demonstrate by means of a comprehensive x-ray crystallographic study, that multilayer silicene is effectively realized upon growth at rather low growth temperatures (~200°C), while, instead, 3D growth of silicon crystallites takes place at higher temperatures, (~300°C). This transition to bulk like silicon perfectly explains the various data presented and discussed in the literature and solves their conflicting interpretations.
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Submitted 21 June, 2016; v1 submitted 19 June, 2016;
originally announced June 2016.
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Raman micro-spectroscopy as a tool to measure the absorption coefficient and the erosion rate of hydrogenated amorphous carbon films heat-treated under hydrogen bombardment
Authors:
Cedric Pardanaud,
E. Aréou,
C. Martin,
R. Ruffe,
T. Angot,
P. Roubin,
C. Hopf,
T. Schwarz-Selinger,
W. Jacob
Abstract:
We present a fast and simple way to determine the erosion rate and absorption coefficient of hydrogenated amorphous carbon films exposed to a hydrogen atomic source based on ex-situ Raman micro-spectroscopy. Results are compared to ellipsometry measurement. The method is applied to films eroded at different temperatures. A maximum of the erosion rate is found at ~ 450 {\degree}C in agreement with…
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We present a fast and simple way to determine the erosion rate and absorption coefficient of hydrogenated amorphous carbon films exposed to a hydrogen atomic source based on ex-situ Raman micro-spectroscopy. Results are compared to ellipsometry measurement. The method is applied to films eroded at different temperatures. A maximum of the erosion rate is found at ~ 450 {\degree}C in agreement with previous results. This technique is suitable for future quantitative studies on the erosion of thin carbonaceous films, especially of interest for plasma wall interactions occurring in thermonuclear fusion devices.
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Submitted 21 August, 2013;
originally announced August 2013.
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Raman study of CFC tiles extracted from the toroidal pump limiter of Tore Supra
Authors:
Cedric Pardanaud,
G. Giacometti,
C. Martin,
R. Ruffe,
T. Angot,
E. Aréou,
B. Pégourié,
E. Tsitrone,
T. Dittmar,
C. Hopf,
W. Jacob,
T. Schwarz-Selinger,
P. Roubin
Abstract:
The structure of six tiles extracted from the erosion and deposition zones (thin and thick deposition) of the Tore Supra toroidal pump limiter (TPL) have been analysed in the framework of the DITS campaign using micro-Raman spectroscopy. This post-mortem analysis gives information on both carbon structure and D content. We have found that the carbon structure is most often similar to that of plasm…
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The structure of six tiles extracted from the erosion and deposition zones (thin and thick deposition) of the Tore Supra toroidal pump limiter (TPL) have been analysed in the framework of the DITS campaign using micro-Raman spectroscopy. This post-mortem analysis gives information on both carbon structure and D content. We have found that the carbon structure is most often similar to that of plasma-deposited hard amorphous carbon layers. The role of the surface temperature during the discharge in the D content is investigated: in all locations where the temperature does not reach more than 500{\degree}C the D content seems to be roughly uniform with D/D+C \approx 20%.
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Submitted 21 August, 2013;
originally announced August 2013.
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On the interpretation of valence band photoemission spectra at organic-metal interfaces
Authors:
L. Giovanelli,
F. C. Bocquet,
P. Amsalem,
H. -L. Lee,
M. Abel,
S. Clair,
M. Koudia,
T. Faury,
L. Petaccia,
D. Topwal,
E. Salomon,
T. Angot,
A. A. Cafolla,
N. Koch,
L. Porte,
A. Goldoni,
J. -M. Themlin
Abstract:
Adsorption of organic molecules on well-oriented single crystal coinage metal surfaces fundamentally affects the energy distribution curve of ultra-violet photoelectron spectroscopy spectra. New features not present in the spectrum of the pristine metal can be assigned as "interface states" having some degree of molecule-substrate hybridization. Here it is shown that interface states having molecu…
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Adsorption of organic molecules on well-oriented single crystal coinage metal surfaces fundamentally affects the energy distribution curve of ultra-violet photoelectron spectroscopy spectra. New features not present in the spectrum of the pristine metal can be assigned as "interface states" having some degree of molecule-substrate hybridization. Here it is shown that interface states having molecular orbital character can easily be identified at low binding energy as isolated features above the featureless substrate sp-plateau. On the other hand much care must be taken in assigning adsorbate-induced features when these lie within the d-band spectral region of the substrate. In fact, features often interpreted as characteristic of the molecule-substrate interaction may actually arise from substrate photoelectrons scattered by the adsorbates. This phenomenon is illustrated through a series of examples of noble-metal single-crystal surfaces covered by monolayers of large pi-conjugated organic molecules.
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Submitted 18 September, 2012;
originally announced September 2012.