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Sub ppm Gas Sensing Using a CNTFET-Based Sensor Array Fabricated Using Dierent Metals as Electrodes
Paolo Bondavalli,Pierre Legagneux,Didier Pribat 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1
This paper deals with the fabrication of carbon nanotube eld effect transistors (CNTFETs) for gas sensing applications. The aim of this study is to achieve a sort of fingerprinting of a specific gas by using an array of CNTFET-based sensors. The electronic ngerprinting will be obtained by exploiting the change of the metal electrode work function after gas exposure. This one strictly depends on the metal/gas interaction and consequently in uences univocally the transfer characteristics of each transistors. To demonstrate this original concept, we have fabricated different CNTFETs using different metal contacts: Au, Pt and Mo. Using these transistors, we have shown that a specific gas, in our case DiMethyl-Methyl-Phosphonate (DMMP, a sarin simulant), interacts specifically with each metal: exposure to 0.5 ppm of DMMP reduces the transistor ON current by 10 %, 60 % and 25 % after 5 minutes respectively for Au, Pt, Mo-based CNTFETs at V<SUB>GS</SUB> = -25 Volt. We think that this new approach can be applied for highly selective sensing of various gases using ultra-compact, room temperature and very low power devices. This paper deals with the fabrication of carbon nanotube eld effect transistors (CNTFETs) for gas sensing applications. The aim of this study is to achieve a sort of fingerprinting of a specific gas by using an array of CNTFET-based sensors. The electronic ngerprinting will be obtained by exploiting the change of the metal electrode work function after gas exposure. This one strictly depends on the metal/gas interaction and consequently in uences univocally the transfer characteristics of each transistors. To demonstrate this original concept, we have fabricated different CNTFETs using different metal contacts: Au, Pt and Mo. Using these transistors, we have shown that a specific gas, in our case DiMethyl-Methyl-Phosphonate (DMMP, a sarin simulant), interacts specifically with each metal: exposure to 0.5 ppm of DMMP reduces the transistor ON current by 10 %, 60 % and 25 % after 5 minutes respectively for Au, Pt, Mo-based CNTFETs at V<SUB>GS</SUB> = -25 Volt. We think that this new approach can be applied for highly selective sensing of various gases using ultra-compact, room temperature and very low power devices.
He, Zhanbing,Lee, Chang Seok,Maurice, Jean-Luc,Pribat, Didier,Haghi-Ashtiani, Paul,Cojocaru, Costel Sorin Elsevier 2011 Carbon Vol.49 No.14
<P><B>Abstract</B></P><P>Plasma-enhanced chemical vapor deposition, without a nickel-containing gaseous precursor, was used to synthesize continuous nickel (Ni) nanorods inside the hollow cavity of carbon nanofibers (CNFs), thus forming vertically aligned Ni/CNF core/shell structures. Scanning and transmission electron microscopic images indicate that the elongated Ni nanorods originate from the catalyst particles at the tips of the CNFs and that their formation is due to the effect of extrusion induced by the compressive force of the graphene layers during growth. Different from previous work, each vertically-aligned core/shell structure reported is totally isolated from its neighbors. Continuous Ni nanorods are found to separate into smaller ones with increasing growth time, which was ascribed to (i) the limited amount of Ni available in the tip of the CNF, (ii) the polycrystalline nature of the Ni nanorods and (iii) the combined effects of the compressive stresses on the side of the Ni nanorods and of the tensile stress along their axis.</P>
Singh, Swati,Hong, Seunghyun,Jeon, Wonjae,Lee, Dongmok,Hwang, Jae-Yeol,Lim, Seulky,Kwon, Gi Duk,Pribat, Didier,Shin, Hyunjung,Kim, Sung Wng,Baik, Seunghyun American Chemical Society 2015 Chemistry of materials Vol.27 No.7
<P>The successful mechanical exfoliation and chemical synthesis of graphene has attracted considerable attention for the synthesis of other two-dimensional materials on graphene template. Chalcogenide materials such as Sb2Te3 are of interest due to the rhombohedral lattice structure with two-dimensional hexagonally closed-packed atomic layers along the c-axis. Here we synthesized c-axis-oriented Sb2Te3 nanoplates (NPs) on graphene substrates by the microwave-assisted solvothermal method. The microwave irradiation resulted in a higher temperature of graphene, compared with the synthesis solution, which was revealed by the single-mode microwave experiments and an analytical model based on energy balance and convective heat transfer. Besides, the lattice mismatch between c-axis-oriented Sb2Te3 and bridge sites of graphene was only 4%, which is also favorable for the graphene-templated Sb2Te3 synthesis. c-Axis-oriented single-crystalline Sb2Te3 NPs as large as 7 mu m could be successfully synthesized on graphene with negligible damage of the graphene template. Larger surface coverage could be obtained by merging Sb2Te3 NPs. The merged Sb2Te3 NPs were polycrystalline with rotated grain boundaries. This work provides a facile, rapid, and low-cost synthesis route of c-axis-oriented Sb2Te3 NPs on graphene templates, which may be extended for the synthesis of various two-dimensional materials with hexagonally closed-packed atomic layers along the c-axis.</P>
Hot Electron Field Emission <i>via</i> Individually Transistor-Ballasted Carbon Nanotube Arrays
Li, Chi,Zhang, Yan,Cole, Matthew T.,Shivareddy, Sai G.,Barnard, Jon S.,Lei, Wei,Wang, Baoping,Pribat, Didier,Amaratunga, Gehan A. J.,Milne, William I. American Chemical Society 2012 ACS NANO Vol.6 No.4
<P>We present electronically controlled field emission characteristics of arrays of individually ballasted carbon nanotubes synthesized by plasma-enhanced chemical vapor deposition on silicon-on-insulator substrates. By adjusting the source–drain potential we have demonstrated the ability to controllable limit the emission current density by more than 1 order of magnitude. Dynamic control over both the turn-on electric field and field enhancement factor have been noted. A hot electron model is presented. The ballasted nanotubes are populated with hot electrons due to the highly crystalline Si channel and the high local electric field at the nanotube base. This positively shifts the Fermi level and results in a broad energy distribution about this mean, compared to the narrow spread, lower energy thermalized electron population in standard metallic emitters. The proposed vertically aligned carbon nanotube field-emitting electron source offers a viable platform for X-ray emitters and displays applications that require accurate and highly stable control over the emission characteristics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-4/nn300111t/production/images/medium/nn-2012-00111t_0006.gif'></P>
Lee, Dongmok,Kwon, Gi Duk,Kim, Jung Ho,Moyen, Eric,Lee, Young Hee,Baik, Seunghyun,Pribat, Didier The Royal Society of Chemistry 2014 Nanoscale Vol.6 No.21
<P>We have studied the influence of the surface roughness of copper foils on the sheet resistance of graphene sheets grown by chemical vapor deposition. The surface roughness of the copper foils was reproducibly controlled by electropolishing. We have found that the graphene sheet resistance monotonically decreases as the surface roughness of the copper foils decreases. We show that a pre-annealing treatment combined with an optimized electropolishing process of the Cu foils and a fast CVD growth prevents the evolution of the Cu surface roughness during graphene synthesis. This combination of fabrication conditions produces small grain polycrystalline graphene films with a sheet resistance of 210 Ω □<SUP>−1</SUP>and carrier mobility values as high as 5450 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP>after transfer onto SiO2/Si.</P>
Direct Synthesis and Integration of Individual, Diameter-Controlled Single-Walled Nanotubes (SWNTs)
Bouanis, Fatima Z.,Cojocaru, Costel S.,Huc, Vincent,Norman, Evgeny,Chaigneau, Marc,Maurice, Jean-Luc,Mallah, Talal,Pribat, Didier American Chemical Society 2014 Chemistry of materials Vol.26 No.17
<P>We present a robust and versatile approach for the reproducible and controllable growth of single-walled carbon nanotubes (SWNTs) through a self-assembled monolayer (SAM) technique coupled with an atomic hydrogen (H<SUB>at</SUB>) pretreatment to control the catalytic metallic nanoparticles size and density. The nanoparticles are obtained from a self-assembled monolayer of metal complexes or salts on a SiO<SUB>2</SUB> substrate using a two-step strategy. The oxide is first functionalized by silanization with a coordinating ligand leading to the formation of an anchoring SAM on the substrate. Then, metallic complexes such as ruthenium porphyrin (RuTPP) or metallic salts (FeCl<SUB>3</SUB>, RuCl<SUB>3</SUB>) are assembled by coordination bonds on the preformed organic SAM. Pyrolysis under radical hydrogen atmosphere of the as-prepared SAM yields metallic nanoparticles whose size and density are controlled and tuned. Using the as-formed nanoparticles as catalysts, SWNTs are grown by double hot-filament-assisted chemical vapor deposition (d-HFCVD). They exhibit a remarkably good crystalline quality, with a diameter (and type) strongly dependent on the nature of the initial catalyst precursor and its preparation. Field-effect transistors (FETs) with excellent characteristics were obtained using such in-place grown SWNTs. The electronic properties of the SWNTs can be tuned: the transistors obtained from Ru(TPP) and FeCl<SUB>3</SUB> exhibit <I>I</I><SUB>ON</SUB>/<I>I</I><SUB>OFF</SUB> current ratio up to ∼10<SUP>9</SUP>, indicative of the direct growth of a high proportion of semiconducting nanotubes over than 98%. Such elevated <I>I</I><SUB>ON</SUB>/<I>I</I><SUB>OFF</SUB> values have been reported essentially for CNT-FETs devices based on individual semiconducting SWNTs, so far. By contrast, devices obtained from the RuCl<SUB>3</SUB> salt display <I>I</I><SUB>ON</SUB>/<I>I</I><SUB>OFF</SUB> current ratio well below 10<SUP>2</SUP>, indicating the direct growth of SWNTs highly enriched in metallic specimens.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2014/cmatex.2014.26.issue-17/cm502282x/production/images/medium/cm-2014-02282x_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm502282x'>ACS Electronic Supporting Info</A></P>