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David B. Janes

Bio: David B. Janes is an academic researcher from Purdue University. The author has contributed to research in topics: Nanowire & Field-effect transistor. The author has an hindex of 30, co-authored 165 publications receiving 4434 citations. Previous affiliations of David B. Janes include University of Illinois at Urbana–Champaign.


Papers
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Journal ArticleDOI
20 Sep 1996-Science
TL;DR: In this article, a planar array of nanometer-diameter metal clusters that are covalently linked to each other by rigid, double-ended organic molecules have been self-assembled.
Abstract: Close-packed planar arrays of nanometer-diameter metal clusters that are covalently linked to each other by rigid, double-ended organic molecules have been self-assembled. Gold nanocrystals, each encapsulated by a monolayer of alkyl thiol molecules, were cast froma colloidal solution onto a flat substrate to form a close-packed cluster monolayer. Organic interconnects (aryl dithiols or aryl di-isonitriles) displaced the alkyl thiol molecules and covalently linked adjacent clusters in the monolayer to form a two-dimensional superlattice of metal quantum dots coupled by uniform tunnel junctions. Electrical conductance through such a superlattice of 3.7-nanometer-diameter gold clusters, deposited on a SiO2 substrate in the gap between two gold contacts and linked by an aryl di-isonitrile [1,4-di(4-isocyanophenylethynyl)-2-ethylbenzene], exhibited nonlinear Coulomb charging behavior.

1,081 citations

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TL;DR: Half transparent In(2)O(3) and ZnO NWTs fabricated on both glass and flexible plastic substrates, exhibiting high-performance n-type transistor characteristics with approximately 82% optical transparency are reported.
Abstract: The development of optically transparent and mechanically flexible electronic circuitry is an essential step in the effort to develop next-generation display technologies, including 'see-through' and conformable products. Nanowire transistors (NWTs) are of particular interest for future display devices because of their high carrier mobilities compared with bulk or thin-film transistors made from the same materials, the prospect of processing at low temperatures compatible with plastic substrates, as well as their optical transparency and inherent mechanical flexibility. Here we report fully transparent In(2)O(3) and ZnO NWTs fabricated on both glass and flexible plastic substrates, exhibiting high-performance n-type transistor characteristics with approximately 82% optical transparency. These NWTs should be attractive as pixel-switching and driving transistors in active-matrix organic light-emitting diode (AMOLED) displays. The transparency of the entire pixel area should significantly enhance aperture ratio efficiency in active-matrix arrays and thus substantially decrease power consumption.

533 citations

Journal ArticleDOI
TL;DR: In this article, the authors reported a hybrid structure employing a CVD SLG film and a network of silver nanowires (AgNWs), achieving a sheet resistance as low as 22 Ω/□ (stabilized to 13 Ω /□ after 4 months).
Abstract: Transparent conducting electrodes (TCEs) require high transparency and low sheet resistance for applications in photovoltaics, photodetectors, flat panel displays, touch screen devices and imagers. Indium tin oxide (ITO), or other transparent conductive oxides, have typically been used, and provide a baseline sheet resistance (RS) vs. transparency (T) relationship. However, ITO is relatively expensive (due to limited abundance of Indium), brittle, unstable, and inflexible; moreover, ITO transparency drops rapidly for wavelengths above 1000 nm. Motivated by a need for transparent conductors with comparable (or better) RS at a given T, as well as flexible structures, several alternative material systems have been investigated. Single-layer graphene (SLG) or few-layer graphene provide sufficiently high transparency (≈97% per layer) to be a potential replacement for ITO. However, large-area synthesis approaches, including chemical vapor deposition (CVD), typically yield films with relatively high sheet resistance due to small grain sizes and high-resistance grain boundaries (HGBs). In this paper, we report a hybrid structure employing a CVD SLG film and a network of silver nanowires (AgNWs): RS as low as 22 Ω/□ (stabilized to 13 Ω/□ after 4 months) have been observed at high transparency (88% at λ = 550 nm) in hybrid structures employing relatively low-cost commercial graphene with a starting RS of 770 Ω/□. This sheet resistance is superior to typical reported values for ITO, comparable to the best reported TCEs employing graphene and/or random nanowire networks, and the film properties exhibit impressive stability under mechanical pressure, mechanical bending and over time. The design is inspired by the theory of a co-percolating network where conduction bottlenecks of a 2D film (e.g., SLG, MoS2) are circumvented by a 1D network (e.g., AgNWs, CNTs) and vice versa. The development of these high-performance hybrid structures provides a route towards robust, scalable and low-cost approaches for realizing high-performance TCE.

243 citations

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TL;DR: In this article, a self-assembled superlattice (SAS) was used as the gate insulator for the 15-nm SAS-based ZnO field effect transistors (NW-FETs).
Abstract: The development of nanowire transistors enabled by appropriate dielectrics is of great interest for flexible electronic and display applications. In this study, nanowire field-effect transistors (NW-FETs) composed of individual ZnO nanowires are fabricated using a self-assembled superlattice (SAS) as the gate insulator. The 15-nm SAS film used in this study consists of four interlinked layer-by-layer self-assembled organic monolayers and exhibits excellent insulating properties with a large specific capacitance, 180 nF/cm2, and a low leakage current density, 1 × 10-8 A/cm2. SAS-based ZnO NW-FETs display excellent drain current saturation at Vds = 0.5 V, a threshold voltage (Vth) of −0.4 V, a channel mobility of ∼196 cm2/V s, an on−off current ratio of ∼104, and a subthreshold slope of 400 mV/dec. For comparison, ZnO NW-FETs are also fabricated using 70-nm SiO2 as the gate insulator. Implementation of the SAS gate dielectric reduces the NW-FET operating voltage dramatically with more than 1 order of magnit...

159 citations

Journal ArticleDOI
TL;DR: Simulations using a two-dimensional device simulator (MEDICI) show that the improvements in device performance after ODT passivation can be quantified in terms of a decrease of interface trap electron donor states, shifts in fixed interfacial charge, and changes in body and surface mobilities.
Abstract: The existence of large densities of surface states on InAs pins the surface Fermi level above the conduction band and also degrades the electron mobility in thin films and nanowires. Field effect transistors have been fabricated and characterized in the “as fabricated” state and after surface passivation with 1-octadecanethiol (ODT). Electrical characterization of the transistors shows that the subthreshold slope and electron mobility in devices passivated with ODT are superior to the respective values in unpassivated devices. An X-ray photoelectron spectroscopy study of ODT passivated undoped InAs nanowires indicates that sulfur from ODT is bonded to In on the InAs nanowires. Simulations using a two-dimensional device simulator (MEDICI) show that the improvements in device performance after ODT passivation can be quantified in terms of a decrease of interface trap electron donor states, shifts in fixed interfacial charge, and changes in body and surface mobilities.

122 citations


Cited by
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TL;DR: A review of gold nanoparticles can be found in this article, where the most stable metal nanoparticles, called gold colloids (AuNPs), have been used for catalysis and biology applications.
Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

11,752 citations

Journal ArticleDOI
TL;DR: In this article, solution phase syntheses and size-selective separation methods to prepare semiconductor and metal nanocrystals, tunable in size from ∼1 to 20 nm and monodisperse to ≤ 5%, are presented.
Abstract: ▪ Abstract Solution phase syntheses and size-selective separation methods to prepare semiconductor and metal nanocrystals, tunable in size from ∼1 to 20 nm and monodisperse to ≤5%, are presented. Preparation of monodisperse samples enables systematic characterization of the structural, electronic, and optical properties of materials as they evolve from molecular to bulk in the nanometer size range. Sample uniformity makes it possible to manipulate nanocrystals into close-packed, glassy, and ordered nanocrystal assemblies (superlattices, colloidal crystals, supercrystals). Rigorous structural characterization is critical to understanding the electronic and optical properties of both nanocrystals and their assemblies. At inter-particle separations 5–100 A, dipole-dipole interactions lead to energy transfer between neighboring nanocrystals, and electronic tunneling between proximal nanocrystals gives rise to dark and photoconductivity. At separations <5 A, exchange interactions cause otherwise insulating ass...

4,116 citations

Journal ArticleDOI
TL;DR: The Review presents the recent developments and the use of NP catalysis in organic synthesis, for example, in hydrogenation and C--C coupling reactions, and the heterogeneous oxidation of CO on gold NPs.
Abstract: Interest in catalysis by metal nanoparticles (NPs) is increasing dramatically, as reflected by the large number of publications in the last five years. This field, "semi-heterogeneous catalysis", is at the frontier between homogeneous and heterogeneous catalysis, and progress has been made in the efficiency and selectivity of reactions and recovery and recyclability of the catalytic materials. Usually NP catalysts are prepared from a metal salt, a reducing agent, and a stabilizer and are supported on an oxide, charcoal, or a zeolite. Besides the polymers and oxides that used to be employed as standard, innovative stabilizers, media, and supports have appeared, such as dendrimers, specific ligands, ionic liquids, surfactants, membranes, carbon nanotubes, and a variety of oxides. Ligand-free procedures have provided remarkable results with extremely low metal loading. The Review presents the recent developments and the use of NP catalysis in organic synthesis, for example, in hydrogenation and C--C coupling reactions, and the heterogeneous oxidation of CO on gold NPs.

2,790 citations

Journal ArticleDOI
TL;DR: The development of novel materials is a fundamental focal point of chemical research; and this interest is mandated by advancements in all areas of industry and technology.
Abstract: The development of novel materials is a fundamental focal point of chemical research; and this interest is mandated by advancements in all areas of industry and technology. A good example of the synergism between scientific discovery and technological development is the electronics industry, where discoveries of new semiconducting materials resulted in the evolution from vacuum tubes to diodes and transistors, and eventually to miniature chips. The progression of this technology led to the development * To whom correspondence should be addressed. B.L.C.: (504) 2801385 (phone); (504) 280-3185 (fax); bcushing@uno.edu (e-mail). C.J.O.: (504)280-6846(phone);(504)280-3185(fax);coconnor@uno.edu (e-mail). 3893 Chem. Rev. 2004, 104, 3893−3946

2,621 citations