Toshiki Sugimoto

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Charge carrier trapping plays a vital role in heterogeneous photocatalytic water splitting because it strongly affects the dynamics of photogenerated charges and hence the photoconversion efficiency. Although hole trapping by water at water/photocatalyst interface is the first step of oxygen evolution in water splitting, little has been known on how water(More)
We have studied the effect of RE substitution on the structure and the local atomic disorder in REO0.5F0.5BiS2 (RE = rare-earth) to understand their correlation with the bulk superconductivity in these materials. The mean RE size, affecting the chemical pressure, has been varied in two series namely Ce1-xNdxO0.5F0.5BiS2 and Nd1-ySmyO0.5F0.5BiS2. The lattice(More)
We have used Bi and Ce L3-edges extended x-ray absorption fine structure measurements to study local structure of CeO(1-x)F(x)BiS2 system as a function of F-substitution. The local structure of both BiS2 active layer and CeO1-xFx spacer layer changes systematically. The in-plane Bi-S1 distance decreases (ΔRmax ∼ 0.08 Å) and the out-of-plane Bi-S2 distance(More)
Ultrafast dynamics of excitons in organic semiconductors is essential for a deep understanding of the working mechanism of plastic opto-electronic devices. In this work, excited state dynamics in dinaphtho[2,3-b:2'3'-f]thieno[3,2-b]-thiophene thin films has been studied with femtosecond transient absorption and time-resolved photoluminescence spectroscopy.(More)
This paper discusses and compares the effects of dynamic element matching (DEM) methods applied to the stochastic flash A-to-D converter (SFADC) to improve its linearity and noise behavior. Simulation results have shown that the application of DEM greatly improves linearity and SNDR behavior, and a simple random barrel-shift type of DEM is enough for 6-bit(More)
We report a hardware implementation of stochastic flash A-to-D converter (SFADC) with dynamic element matching (DEM) technique. For fast prototyping, the SFADC hardware was implemented on an FPGA board with 64 on-chip inverters using as comparators. The DEM circuit is implemented by analog multiplexer, which is put in front of the main SFADC. Measured(More)
We proposed a linearization technique with dynamic element matching for stochastic flash A-to-D converters (SFADCs), and estimated that 6-bit SFADC can be realized by using about 1,000 comparators through system level simulations. In this paper, we present circuit level design of the linearized SFADC. First, we discuss the difference between requirements of(More)
Hot carriers at metal surfaces can drive nonthermal reactions of adsorbates. Characterizing nonequilibrium statistics among various degrees of freedom in an ultrafast time scale is crucial to understand and develop hot carrier-driven chemistry. Here we demonstrate multidimensional vibrational dynamics of carbon monoxide (CO) on Cu(100) along hot-carrier(More)
Singlet fission, in which a singlet exciton is converted to two triplet excitons, is a process that could be beneficial in photovoltaic applications. A full understanding of the dynamics of singlet fission in molecular systems requires detailed knowledge of the relevant potential energy surfaces and their (conical) intersections. However, obtaining such(More)
Crystalline ice formation requires water molecules to be sufficiently mobile to find and settle on the thermodynamically most stable site. Upon cooling, however, diffusion and rearrangement become increasingly kinetically difficult. Water ice grown by the condensation of water vapor in laboratory is thus generally assumed to be in a metastable amorphous(More)
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