Shigeyasu Uno

Preparation of organic nanoscrews from simple porphyrin derivatives

Twisted supramolecular assemblies nanoscrews, were prepared by using simple porphyrin derivatives and acetonitrile solvent. The electrical properties of the assemblies were measured by using microgap electrodes. The nanoscrew had conductivity and showed photo-current. By changing the solvent, the pitch of the screws and their aggregation shapes could be controlled.

Scaling consideration and compact model of electron scattering enhancement due to acoustic phonon modulation in an ultrafine free-standing cylindrical semiconductor nanowire

We theoretically investigate the interaction between modulated acoustic phonons and electrons in a free-standing cylindrical semiconductor nanowire and calculate the electron mobility limited by modulated acoustic phonons in a [001]-oriented silicon nanowire (SiNW) at room temperature. The mobility is smaller than that limited by bulk phonons because form factors increase due to acoustic phonon modulation. By expressing the form factor increase through an analytical formula, we derive a compact formula for mobility that is valid for a nanowire in which most electrons occupy the lowest subband, regardless of the wire material. The compact formula achieves excellent accuracy for a [001]-oriented SiNW with a radius of less than 2nm at an electron density of 2×109m−1, and its applicable radius increases with decreasing electron density

On-chip Microelectrode Capacitance Measurement for Biosensing Applications

Point-of-care testing (POCT) is a solution that is intensely studied to overcome the large size and high cost of geneticbased screening equipment for application at a hospital ward or patient’s home. Personalized medicine is attracting considerable attention as it can offer treatments based on the patient’s DNA profile. The availability of individual DNA data could lead to the prevention or early detection of fatal diseases such as cancer and could provide accurate information for medicine prescription to avoid side effects. To make it possible to do such a screening at a place that has a limited space, and as part of routine medical checkups, a low-cost, rapid, and portable biosensor is strongly demanded. Recently, label-free biosensing techniques have appeared as the most well-suited approach for the realization of POCT. A label-free and fully electrical biosensor could offer great advantages on such as lower cost, smaller instruments, and analysis time reduction since the fluorescent labeling, which is necessary in conventional optical biosensors, is eliminated. To date, published works on labelfree biosensors include amperometric, 1) voltammetric, 2,3) and impedance biosensors. 4–6) Among these, impedance biosensors are attracting increased attention owing to their simplicity, low-cost fabrication, and easy for array integration. In this work, we applied a nonfaradaic impedimetric measurement by implementing charge-based capacitance measurement (CBCM) to realize a label-free, fully integrated capacitance biosensor. The proposed sensor exploits the capacitance changes of electrical double-layer properties as a result of biorecognition events at the sensing electrode/ solution interface. In a previously reported capacitance biosensor, Stagni et al. reported DNA detection using 1 mm 2

Complementary Metal–Oxide–Semiconductor Ion-Sensitive Field-Effect Transistor Sensor Array with Silicon Nitride Film Formed by Catalytic Chemical Vapor Deposition as an Ion-Sensitive Membrane

Integration of 16 ×16 and 32 ×32 extended-gate ion-sensitive field-effect transistor (ISFET) arrays with a low-power consumption read-out circuitry has been reported. Si3N4 film used as a pH sensitive layer is deposited on the 4 ×4 µm2 extended-gate electrodes of ISFETs in the integrated circuit by catalytic chemical vapor deposition (Cat-CVD). The average pH sensitivity is 41 mV/pH, and the distribution obeys a Gaussian distribution with a standard deviation of 1.5–3.4 mV. The result is compared with that of pH sensitivity measurement using an Al2O3 layer formed by O2 plasma.

Full Three-Dimensional Simulation of Ion-Sensitive Field-Effect Transistor Flatband Voltage Shifts Due to DNA Immobilization and Hybridization

A full three-dimensional simulation of the ion-sensitive field-effect transistor flatband voltage shifts due to DNA immobilization and hybridization is presented. Poissons equation is solved for a domain consisting of an electrolyte, DNA, Stern layer, linker molecular layer, and nitride layer. DNA is modeled as an insulating cylinder with discrete negative charges at the coordinates of phosphate groups. The site binding on the nitride surface significantly suppresses the flatband voltage shift due to DNA charge, while switching off the site binding gives results close to experimentally reported values. Increasing DNA density or decreasing salt concentration leads to increasing flatband voltage shifts for both immobilization and hybridization. The flatband voltage shift due to DNA hybridization is proportional to DNA density at a high salt concentration or a low DNA density. At a low salt concentration and a high DNA density, however, the flatband voltage dependence on DNA density deviates from this proportional relationship.

Universality in electron-modulated-acoustic-phonon interactions in a free-standing semiconductor nanowire

Modulated acoustic phonons and their interactions with electrons in a free-standing cylindrical semiconductor nanowire are investigated theoretically. It is shown that the form factor is a key quantity in discussing the impact of acoustic phonons on electron transport. The form factor calculated using modulated acoustic phonons is identical to that calculated using bulk phonons for a large phonon wave vector along the wire, whereas it is larger for a small phonon wave vector. This increase directly leads to an increase in the electron scattering rate and a reduction in mobility. In addition, the form factor increase has a universality independent of the wire material and radius.

Form factor increase and its physical origins in electron-modulated acoustic phonon interaction in a free-standing semiconductor plate

Impacts of acoustic phonon modulation on the electron-acoustic phonon interaction in a free-standing semiconductor plate are theoretically investigated. In formulating the electron-phonon interaction, the differences between bulk and modulated acoustic phonons are encapsulated into the form factor. The form factors calculated using modulated acoustic phonons are larger than those obtained using bulk phonons, regardless of electronic states, plate thickness, or plate material. The form factor explains the behavior of the momentum relaxation rate and electron mobility qualitatively, but consistently. When properly normalized, the form factors show an universality. The form factor increase can be attributed to an increase in the number of phonon modes having longitudinal vibration due to surface mode generation and mode conversion.

Electron–Modulated-Acoustic-Phonon Interactions in a Coated Silicon Nanowire

Modulated acoustic phonons and their interactions with electrons in a coated cylindrical silicon nanowire (SiNW) are investigated theoretically. The impact of acoustic phonons on the interactions is encapsulated in the form factor. The form factor for a SiO2-coated SiNW is larger than that calculated using bulk phonons while that for a HfO2-coated SiNW is smaller, when the coating shell thickness is sufficiently large. This result can be qualitatively explained by the relationship of acoustic impedance between the nanowire core and shell. The form factor reduction directly weakens the interactions, and thereby provides higher electron mobility than that limited by bulk phonons.

Integrated Bio-Imaging Sensor Array with Complementary Metal–Oxide–Semiconductor Cascode Source–Drain Follower

A new bio-imaging sensor with photosystem I (PSI) of Thermosynechococcus elongatus and complementary metal–oxide–semiconductor (CMOS) circuits is demonstrated. Photons are converted into electrons by PSI, and electrons are detected as an electric signal by a CMOS integrated circuit. For a sensor circuit, a 4 ×4 sensor array with a CMOS source–drain follower is designed and fabricated by a standard CMOS process. An extended-gate electrode and an SU-8 passivation layer are formed on a CMOS chip by a post-CMOS process, and PSI is electrostatically fixed on the electrode. A 3×4 image of the pattern of light illuminated on a chip is taken with the sensor array, where four cells are used as reference cells.

An Analytical Compact Model of Ballistic Cylindrical Nanowire MOSFET

Tatsuhiro Numata , Shigeyasu Uno , Kazuo Nakazato , Yoshinari Kamakura and Nobuya Mori a) Department of Electrical and Computer Science, Graduate School of Engineering, Nagoya University Furo-Cho, Chikusa-ku, Nagoya 464-8603, Japan b) Department of Electronic Engineering, Osaka University 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan Phone: +81-52-789-2794, Fax: +81-52-789-3139, E-mail: t_numata@echo.nuee.nagoya-u.ac.jp , uno@nuee.nagoya-u.ac.jp