Masayuki Kanehara

Large‐Scale Synthesis of High‐Quality Metal Sulfide Semiconductor Quantum Dots with Tunable Surface‐Plasmon Resonance Frequencies

High-quality CdS and Cu(7)S(4) quantum dots (QDs) were synthesized with N,N-dibutylthiourea (DBTU) as an organic sulfur source. In this method, nucleation and growth reactions were controlled simply by the heating rate of the reaction. The mild oxidation conditions gave monodisperse CdS QDs exhibiting pure band-edge emission with relatively high photoluminescence quantum yield. During the synthesis of Cu(7)S(4) QDs, the addition of dodecanethiol to the reaction system controlled the reaction rate to give monodisperse spherical or disk-shaped QDs. A hundred-gram scale of copper precursor could be used to generate the high-quality Cu(7)S(4) QDs, indicating that an industrial-scale reaction is achievable with our method. As observed in anisotropic noble-metal nanocrystals, larger disk-shaped Cu(7)S(4) QDs showed lower localized-surface-plasmon resonance energy in the near-infrared region. The disk-shaped Cu(7)S(4) QDs could be used effectively as templates to form cation-exchanged monodisperse disk-shaped CdS QDs.

Spontaneous Patterning of High‐Resolution Electronics via Parallel Vacuum Ultraviolet

A spontaneous patterning technique via parallel vacuum ultraviolet is developed for fabricating large-scale, complex electronic circuits with 1 μm resolution. The prepared organic thin-film transistors exhibit a low contact resistance of 1.5 kΩ cm, and high mobilities of 0.3 and 1.5 cm(2) V(-1) s(-1) in the devices with channel lengths of 1 and 5 μm, respectively.

Covalent assembly of silver nanoparticles on hydrogen-terminated silicon surface

Synthesis of ω-alkenyl-terminated silver nanoparticles (AgNPs) and then their immobilization on a hydrogen-terminated silicon surface in two-dimensional arrangement through covalent interaction are demonstrated. The thermal-induced hydrosilylation at mild conditions facilitate nanoparticles assembly through interaction between terminal alkenyl (CH(2)=CH-) groups of AgNPs and hydrogen-terminated silicon surface. The assembly of AgNPs on a silicon surface is characterized by FESEM and XPS. Adequate coating of 10-undecene-1-thiol (UDT) on AgNPs and mild temperature hydrosilylation impede the fusion or aggregation of nanoparticles, while they immobilized on a silicon surface, which is very crucial to preserve the discrete entities of nanoparticles. This elegant and facile approach provides stable monolayer of AgNPs with very good coverage area and promises potential to fabricate electronic devices and solar cells, where nanoparticles needs to be directly attached to the silicon surface without an interfacial oxide thin film.

Ultra-high-resolution printing of flexible organic thin-film transistors

ABSTRACT Fully printed electronics on plastic have attracted considerable interest owing to their high compatibility and ease of integration. Here, an ultra-high-resolution printing technique based on parallel vacuum ultraviolet patterning that can produce high-contrast wettability regions on flexible substrates was developed. This technique was used to selectively deposit a functional ink with a 1 µm feature size, thereby allowing the large-scale fabrication of organic thin-film transistors with channels as short as 1 µm under an ambient atmosphere. Moreover, in short-channel devices, hole injection barriers can be tuned by printing the optimum gate overlaps associated with selectively doping semiconductor/electrode interfaces, resulting in a marked reduction in contact resistance from 20 to 1.5 kΩ cm, and an elevation of the charge carrier mobility to a record high of 0.3 cm2 V−1 s−1 in a 1-µm-channel device. The results indicate that the developed technique is promising for the fabrication of large-area, high-resolution, low-cost electronics.

High-Resolution Electronics: Spontaneous Patterning of High-Resolution Electronics via Parallel Vacuum Ultraviolet (Adv. Mater. 31/2016).

On page 6568, T. Minari and co-workers describe spontaneous patterning based on the parallel vacuum ultraviolet (PVUV) technique, enabling the homogeneous integration of complex, high-resolution electronic circuits, even on large-scale, flexible, transparent substrates. Irradiation of PVUV to the hydrophobic polymer surface precisely renders the selected surface into highly wettable regions with sharply defined boundaries, which spontaneously guides a metal nanoparticle ink into a series of circuit lines and gaps with the widths down to a resolution of 1 μm.

Printable electronic circuits based on metal nanoparticles and organic semiconductors

We propose a large-scale fabrication method of electronic devices based on solution-processed coating and printing. This method relies on bottom-up printing processes using soluble metal nanoparticles and organic semiconductors, resulting in thin-film electronic devices to be printed at room temperature without application of heat. We successfully fabricated high-performance organic thin-film transistors on plastic and paper substrates. In addition, the printing technique with 1-micron line width and space was also achieved. Our fabrication method is very promising for low-cost fabrication of high-resolution flexible electronics.

Organic thin-film transistors with over 10 cm2/Vs mobility through low-temperature solution coating

ABSTRACT Recent studies on organic thin-film transistors (OTFTs) have reported high mobility values, but many of them showed non-ideal current–voltage characteristics that could lead to the overestimation of the mobility values. In this study, the non-ideal transistor behavior was briefly investigated by considering the effect of charge injection, and a method of overcoming the effect was developed. Correspondingly, various charge injection layers were developed, and their effects on the modification of metal contacts, including work function tuning and interfacial doping, were studied. The materials that had been coated formed a good metal-semiconductor interface through fine manipulation in the wetting and dewetting of the selected liquid. With such electrodes, the OTFTs were fabricated at room temperature and exhibited almost ideal transistor behavior in terms of the current–voltage characteristics, featuring high (over 10 cm2/Vs) field-effect mobility.

Metal Nanoparticle/Porphyrinoid Hybrids

In this chapter, electronic properties of Au/porphyrin or phthalocyanine (porphin) hybrid nanostructure are mentioned. The coordination ability of porphin onto metal nanostructure is relatively strong exploiting orbital hybridization between π-orbitals of porphin. The orbital hybridization gives some useful properties which cannot be obtained from isolated metal nanostructure or porphin.

Electrode fabrication using conductive nano-ink and microfluidic technology for bio-applications

Printed electronics technology, which is used to economically prepare printing conductive patterns onto flexible materials, is both fundamental and crucial for the successful integration of electronics with textiles or fluidics. Conductive channels can be prepared using conventional printing technologies and conductive inks. These preparation methods would cost less, and they are convenient for prototyping of microdevices. The use of hydrophilic organic-inorganic hybrid nanoparticles (NPs), dispersed in water, enables the simplification of the electrode preparation process at room temperature. In this study, we developed a transparent breadboard and NP microelectrodes in the microfluidic channel to measure the number of particles. The electrode fabrication in the microfluidic channel can be acquired using conventional laboratory equipment without the need for expensive ultra-vacuum deposition instruments. We integrated the equipment with electrical measurement systems to count cells and/or microparticles. By using a parallel electric-circuit model (diluted case) or Langmuir isotherm model (saturated case), the particle concentration between two NP electrodes can be analyzed by measuring the capacitance of the total circuit. The microfluidic fabrication of electrodes and electrical measurement technologies may be potentially applied to the technology for micro-nano fluidics and bio-applications such as cell counting or ion sensing.

Coulomb Blockade Electron Shuttle with Chemisorbed Au Nanodot

Yasuo Azuma, Norihiro Kobayashi, Masayuki Kanehara, Toshiharu Teranishi, Simon Chorley, Jonathan Prance, Charles G. Smith, and Yutaka Majima Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552, Japan, Phone: +81-3-5734-2673, E-mail: azuma@nanoele.pe.titech.ac.jp CREST-JST, 5 Sanban-cho, Chiyoda-ku, Tokyo 102-0075, Japan Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom