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Bismuth telluride nanostructures: preparation, thermoelectric properties and topological insulating effect
Eric ASHALLEY,Haiyuan CHEN,Xin TONG,Handong LI,Zhiming M. WANG
Front. Mater. Sci.. 2015, 9 (2 ): 103-125.
https://doi.org/10.1007/s11706-015-0285-9
Bismuth telluride is known to wield unique properties for a wide range of device applications. However, as devices migrate to the nanometer scale, significant amount of studies are being conducted to keep up with the rapidly growing nanotechnological field. Bi2 Te3 possesses distinctive properties at the nanometer level from its bulk material. Therefore, varying synthesis and characterization techniques are being employed for the realization of various Bi2 Te3 nanostructures in the past years. A considerable number of these works have aimed at improving the thermoelectric (TE) figure-of-merit (ZT) of the Bi2 Te3 nanostructures and drawing from their topological insulating properties. This paper reviews the various Bi2 Te3 and Bi2 Te3 -based nanostructures realized via theoretical and experimental procedures. The study probes the preparation techniques, TE properties and the topological insulating effects of 0D, 1D, 2D and Bi2 Te3 nanocomposites. With several applications as a topological insulator (TI), the topological insulating effect of the Bi2 Te3 is reviewed in detail with the time reversal symmetry (TRS) and surface state spins which characterize TIs. Schematics and preparation methods for the various nanostructural dimensions are accordingly categorized.
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Synthesis, crystal structure and thermal analysis of a new stilbazolium salt crystal
Bing TENG,Weijin KONG,Ke FENG,Fei YOU,Lifeng CAO,Degao ZHONG,Lun HAO,Qing SUN,Sander van SMAALEN,Wenhui GONG
Front. Mater. Sci.. 2015, 9 (2 ): 147-150.
https://doi.org/10.1007/s11706-015-0284-x
A new organic crystal of 4-N, N-dimethylamino-4′-N′-methyl-stilbazolium benzene sulfonate (DASBS) was synthesized and characterized for the first time. It is a derivative of 4-N, N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) with the benzene sulfonate replacing p-toluenesulfonate. Single crystal XRD demonstrated that the crystal structure of DASBS·H2 O was triclinic. The thermal analysis of this new crystal was also conducted, and the melting point was obtained to be 232°C.
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2.45 GHz 0.8 mW voltage-controlled ring oscillator (VCRO) in 28 nm fully depleted silicon-on-insulator (FDSOI) technology
Gilles JACQUEMOD,Alexandre FONSECA,Emeric de FOUCAULD,Yves LEDUC,Philippe LORENZINI
Front. Mater. Sci.. 2015, 9 (2 ): 156-162.
https://doi.org/10.1007/s11706-015-0288-6
MOS bulk transistor is reaching its limits: sub-threshold slope (SS), drain induced barrier lowering (DIBL), threshold voltage (VT) and VDD scaling slowing down, more power dissipation, less speed gain, less accuracy, variability and reliability issues. Fully depleted devices are mandatory to continue the technology roadmap. FDSOI technology relies on a thin layer of silicon that is over a buried oxide (BOx). Called ultra thin body and buried oxide (UTBB) transistor, FDSOI transistors correspond to a simple evolution from conventional MOS bulk transistor. The capability to bias the back-gate allows us to implement calibration techniques without adding transistors in critical blocks. We have illustrated this technique on a very low power voltage-controlled oscillator (VCO) based on a ring oscillator (RO) designed in 28 nm FDSOI technology. Despite the fact that such VCO topology exhibits a larger phase noise, this design will address aggressively the size and power consumption reduction. Indeed we are using the efficient back-gate biasing offered by the FDSOI MOS transistor to compensate the mismatches between the different inverters of the ring oscillator to decrease jitter and phase noise. We will present the reasons which led us to use the FDSOI technology to reach the specifications of this PLL. The VCRO exhibits a 0.8 mW power consumption, with a phase noise about --94 dBc/Hz@1 MHz.
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Effects of different magnetic flux densities on microstructure and magnetic properties of molecular-beam-vapor-deposited nanocrystalline Fe64 Ni36 thin films
Yongze CAO,Qiang WANG,Guojian LI,Yonghui MA,Jiaojiao DU,Jicheng HE
Front. Mater. Sci.. 2015, 9 (2 ): 163-169.
https://doi.org/10.1007/s11706-015-0289-5
The nanocrystalline Fe64 Ni36 thin films were prepared by molecular-beam-vapor deposition under different magnetic flux densities. The microstructure and magnetic properties of thin films were examined by AFM, TEM, HRTEM and VSM. The results show that with the increase of magnetic flux densities, the changing trend of the average particle size is the same as the coercive force except 6 T. Under 6 T condition, the thin film became the mixture of bcc and fcc phases, which leads to slight increase of the coercive force. In addition, the HRTEM result shows the short-range ordered clusters (embryos) or nucleation rate of thin films increase with increasing magnetic flux densities.
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The beginnings of plasmomechanics: towards plasmonic strain sensors
Thomas MAURER,Joseph MARAE-DJOUDA,Ugo CATALDI,Arthur GONTIER,Guillaume MONTAY,Yazid MADI,Benoît PANICAUD,Demetrio MACIAS,Pierre-Michel ADAM,Gaëtan LÉVÊQUE,Thomas BÜRGI,Roberto CAPUTO
Front. Mater. Sci.. 2015, 9 (2 ): 170-177.
https://doi.org/10.1007/s11706-015-0290-z
This article exposes the beginnings of a new field which could be named as “plasmomechanics”. Plasmomechanics comes from the convergence between mechanics and plasmonics. Here we discuss a relatively recent topic whose technological aim is the development of plasmonic strain sensors. The idea is based on the ability to deduce Au nanoparticles (NPs) distance distributions from polarized optical extinction spectroscopy which could thus give access to material strains. Variations of interparticle distances distributions can indeed lead to variations of plasmonic coupling and thus to material color change as shown here experimentally and numerically for random Au NP assemblies deposited onto elastomer films.
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