Sumio Hosaka

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We present the first measurement of the planet frequency beyond the “snow line”, for the planet-to-star mass-ratio interval −4.5 < log q < −2, corresponding to the range of ice giants to gas giants. We find dNpl d log q d log s = (0.36± 0.15) dex at mean mass ratio q = 5×10−4 with no discernible deviation from a flat (Öpik’s Law) distribution in log(More)
Phase change memory (PCM), which exploits the phase change behavior of chalcogenide materials, affords tremendous advantages over conventional solid-state memory due to its nonvolatility, high speed, and scalability. However, high power consumption of PCM poses a critical challenge and has been the most significant obstacle to its widespread(More)
Although synaptic behaviours of memristors have been widely demonstrated, implementation of an even simple artificial neural network is still a great challenge. In this work, we demonstrate the associative memory on the basis of a memristive Hopfield network. Different patterns can be stored into the memristive Hopfield network by tuning the resistance of(More)
We have studied graphoepitaxy to make nanodots or nanolines ordered along electron beam (EB)-drawn resist guide using block copolymers (BCPs) of polystyrene-polydimethylsiloxane (PS-PDMS). We found out that the number n of ordered molecular dot arrays in the line gap increases stepwise with the gap between guide lines. The n self-assembled dot arrays were(More)
We studied the possibility of achieving very fine-pitch dot arrays with a pitch of 20 nm × 20 nm using 30 keV electron beam (EB) drawing on negative calixarene resist. In order to form such patterns, we studied the dependence on resist thickness of the dot size and the packing. We propose EB drawing on an extremely thin film for very highly packed dot-array(More)
We have investigated electrical properties of a chalcogenide-based device with naturally oxidized Al electrodes. Intermediate-resistance (IR) states exhibited by current–voltage (I–V) characteristics, dynamic resistance change as a function of pulse height and decay behavior from a low-resistance state of such a device make multi-state storage feasible.(More)
We have proposed an illumination-collection-type scanning near-field Raman spectroscopy (SNRS) with a completely gold metal-inside-coated (MIC) pyramidal probe without an optical aperture in order to detect the Raman spectra of fine Si devices for local stress measurements. The gold MIC pyramidal probe has been studied to act as a plasmon resonance(More)
In this work, we studied the advanced nanofabrication technologies including electron beam lithography, blockcopolymer-based self assembly fabrication and their combination lithography, that is, directed self assembly (DSA). Nanostructures with a size of 10 nm order were successfully fabricated using these technologies. We attempted to further incorporate(More)
Lateral single-channel (SC) and multi-channel (MC) phase-change memory (PCM) cell structures are numerically analyzed for multi-state storage based on their temperature distributions and their programming characteristics. As studied by finite element modeling (FEM), shorter pulses lead to more gradual transition from the set to the reset state of these(More)