High hole mobility (≥500 cm2 V−1 s−1) polycrystalline Ge films on GeO2-coated glass and plastic substrates

The highest recorded hole mobility in semiconductor films on insulators has been updated significantly. We investigate the solid-phase crystallization of a densified amorphous Ge layer formed on GeO2-coated insulating substrates. The resulting polycrystalline Ge layer with a glass substrate consists of large grains (~10 μm) and exhibits a hole mobility as high as 620 cm2 V−1 s−1, despite a low process temperature (500 °C). Even for the Ge layer formed on a flexible polyimide substrate at 375 °C, the hole mobility reaches 500 cm2 V−1 s−1. These achievements will aid in realizing advanced electronics, simultaneously allowing for high performance, inexpensiveness, and flexibility

Polycrystalline thin-film transistors fabricated on high-mobility solid-phase-crystallized Ge on glass

Low-temperature formation of Ge thin-film transistors (TFTs) on insulators has been widely investigated to improve the performance of Si large-scale integrated circuits and mobile terminals. Here, we studied the relationship between the electrical properties of polycrystalline Ge and its TFT performance using high-mobility Ge formed on glass using our recently developed solid-phase crystallization technique. The field-effect mobility μFE and on/off currents of the accumulation-mode TFTs directly reflected the Hall hole mobility μHall, hole concentration, and film thickness of Ge. By thinning the 100-nm thick Ge layer with a large grain size (3.7 μm), we achieved a high μHall (190 cm2/Vs) in a 55-nm thick film that was almost thin enough to fully deplete the channel. The TFT using this Ge layer exhibited both high μFE (170 cm2/Vs) and on/off current ratios (∼102). This is the highest μFE among low-temperature (<500 °C) polycrystalline Ge TFTs without minimizing the channel region (<1 μm)

Noninvasive prediction of shunt operation outcome in idiopathic normal pressure hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is a syndrome characterized by gait disturbance, cognitive deterioration and urinary incontinence in elderly individuals. These symptoms can be improved by shunt operation in some but not all patients. Therefore, discovering predictive factors for the surgical outcome is of great clinical importance. We used normalized power variance (NPV) of electroencephalography (EEG) waves, a sensitive measure of the instability of cortical electrical activity, and found significantly higher NPV in beta frequency band at the right fronto-temporo-occipital electrodes (Fp2, T4 and O2) in shunt responders compared to non-responders. By utilizing these differences, we were able to correctly identify responders and non-responders to shunt operation with a positive predictive value of 80% and a negative predictive value of 88%. Our findings indicate that NPV can be useful in noninvasively predicting the clinical outcome of shunt operation in patients with iNPH

Fundamental physics activities with pulsed neutron at J-PARC(BL05)

"Neutron Optics and Physics (NOP/ BL05)" at MLF in J-PARC is a beamline for studies of fundamental physics. The beamline is divided into three branches so that different experiments can be performed in parallel. These beam branches are being used to develop a variety of new projects. We are developing an experimental project to measure the neutron lifetime with total uncertainty of 1 s (0.1%). The neutron lifetime is an important parameter in elementary particle and astrophysics. Thus far, the neutron lifetime has been measured by several groups; however, different values are obtained from different measurement methods. This experiment is using a method with different sources of systematic uncertainty than measurements conducted to date. We are also developing a source of pulsed ultra-cold neutrons (UCNs) produced from a Doppler shifter are available at the unpolarized beam branch. We are developing a time focusing device for UCNs, a so called "rebuncher", which can increase UCN density from a pulsed UCN source. At the low divergence beam branch, an experiment to search an unknown intermediate force with nanometer range is performed by measuring the angular dependence of neutron scattering by noble gases. Finally the beamline is also used for the research and development of optical elements and detectors. For example, a position sensitive neutron detector that uses emulsion to achieve sub-micrometer resolution is currently under development. We have succeeded in detecting cold and ultra-cold neutrons using the emulsion detector.Comment: 9 pages, 5 figures, Proceedings of International Conference on Neutron Optics (NOP2017

Machine learning of fake micrographs for automated analysis of crystal growth process

Material informatics is being applied to crystal engineering, which is a core technology in electronics. Micrographs particularly provide important insights; however, they have not benefited significantly from material informatics because of the efforts required to acquire huge numbers of data. Herein, we propose a fast and automated analysis technique for micrographs showing the crystallization process of semiconductor thin films. We automatically generated fake micrographs and trained the crystal domain recognition capability on 10 different machine learning models. Experimentally obtained micrographs were analyzed using the developed model, which correctly determined the domain size and nuclei density. The activation energies required for growth and nucleation were determined from the lateral growth velocity and nucleation frequency, the variations of which were smaller than those measured by humans. Therefore, the proposed analysis framework not only reduces the time required to derive the crystal growth properties, but also enables a high accuracy without human subjectivity