Applied Physics Express (APEX) is a letters journal devoted solely to rapid dissemination of up-to-date and concise reports on new findings in applied physics. It is published daily online and monthly for the printed version. The motto of APEX is high scientific quality and prompt publication. APEX is a sister journal of the Japanese Journal of Applied Physics (JJAP) and is published by IOP Publishing Ltd on behalf of the Japan Society of Applied Physics (JSAP).
This publication is partially supported by a Grant-in-Aid for Publication of Scientific Research Results from the Japan Society for the Promotion of Science.
Number 12, December 2015 (121101-126602)
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In the last 30 days
Akihiro Nakamura et al 2015 Appl. Phys. Express 8 107101
The highest efficiency of 24.4% for the solar-to-hydrogen (STH) energy conversion was obtained in an outdoor field test by combining concentrator photovoltaic (CPV) modules with InGaP/GaAs/Ge three-junction cells and polymer-electrolyte electrochemical (EC) cells. The high efficiency was obtained by using the high-efficiency CPV modules (∼31% under the present operation conditions) and the direct connection between the CPV modules and the EC cells with an almost optimized number of elements in series. The STH efficiency bottleneck was clarified to be the efficiency of the CPV modules, the over-potential of the EC cells, and matching of the operation point to the maximal-power point of the CPV modules.
Amir Reuveny et al 2015 Appl. Phys. Express 8 091601
We fabricated extremely flexible short-channel (2 µm channel length) organic thin-film transistors in a bottom-contact architecture. The transistors demonstrated excellent mechanical stability under systematic bending tests at a bending radius as small as 600 µm and were durable against severe device crumpling. The mechanical stability benefited from the thinness of the base film (1-µm-thick parylene diX-SR) and encapsulation as well as the utilization of a self-assembled-layer contact-modified staggered structure with a polymeric gate dielectric. The proposed approach is an important step in realizing flexible large-area sensors and high-frequency ultra-flexible circuits.
Sho Okubo et al 2015 Appl. Phys. Express 8 122701
We present an all-optically stabilized, erbium-doped mode-locked fiber laser with an optically pumped ytterbium-doped fiber. The mode-locked fiber laser has two frequency-control actuators that are pump laser powers for erbium-doped and ytterbium-doped fibers. We investigate the frequency-control characteristics of the mode-locked laser and find that the fixed points for the two actuators are sufficiently apart from each other, realizing the simultaneous phase locking of the repetition and carrier envelope offset frequencies. We describe a long-term frequency measurement of an acetylene-stabilized laser at 1542 nm using an all-optically stabilized frequency comb.
Sho Okubo et al 2015 Appl. Phys. Express 8 082402
We have carried out dual-comb spectroscopy and observed in a simultaneous acquisition a 140-THz-wide spectrum from 1.0 to 1.9 µm using two fiber-based frequency combs phase-locked to each other. This ultrabroad-wavelength bandwidth is realized by setting the difference between the repetition rates of the two combs to 7.6 Hz using the sub-Hz-linewidth fiber combs. The recorded spectrum contains five vibration-rotation bands of C 2H 2, CH 4, and H 2O at different wavelengths across the whole spectrum. The determined transition frequencies of C 2H 2 agree with those from the previous sub-Doppler resolution measurement of individual lines using CW lasers within 2 MHz.
Yuki Hibino et al 2015 Appl. Phys. Express 8 113002
We investigated the electric field effect on magnetic anisotropy in a perpendicularly magnetized Pt/Co system with a top ultrathin layer of nonmagnetic Pd. By applying an electric field to the surface of the ferromagnetic Pd layer, we observed a clear modulation of the perpendicular magnetic anisotropy of the system. This result shows that the magnetic anisotropy can be modulated by an electric field even when nonmagnetic Pd is inserted at the interface formed by the magnetic layer and insulator. The electric field effect of the proximity-induced moment in Pd might contribute to the anisotropy modulation.
Yasuhiro Yamada et al 2014 Appl. Phys. Express 7 032302
We studied the near-band-edge optical responses of solution-processed CH 3NH 3PbI 3 on mesoporous TiO 2 electrodes, which is utilized in mesoscopic heterojunction solar cells. Photoluminescence (PL) and PL excitation spectra peaks appear at 1.60 and 1.64 eV, respectively. The transient absorption spectrum shows a negative peak at 1.61 eV owing to photobleaching at the band-gap energy, indicating a direct band-gap semiconductor. On the basis of the temperature-dependent PL and diffuse reflectance spectra, we clarified that the absorption tail at room temperature is explained in terms of an Urbach tail and consistently determined the band-gap energy to be ∼1.61 eV at room temperature.
Yoshiya Sakai et al 2015 Appl. Phys. Express 8 096601
Molecular orientation in organic light-emitting diodes (OLEDs) is now regarded as an important factor that affects device efficiency. However, methods to quantitatively estimate the degree of molecular orientation in OLEDs are currently limited, and they require constructing a model of an optical structure. Here, we propose a simple model-free method to estimate the orientation order parameters ( S) of molecules in amorphous OLED films from their absorption spectra using the randomization of molecular orientation induced by heating. This method is used to quantitatively estimate the S values of vacuum-deposited and spin-coated films and clearly demonstrate the random orientation in the latter.
Takayuki Tahara et al 2015 Appl. Phys. Express 8 113004
We experimentally demonstrate a Si spin metal–oxide–semiconductor field-effect transistor (MOSFET) that exhibits a high on/off ratio of source–drain current and spin signals at room temperature. The spin channel is nondegenerate n-type Si, and an effective application of gate voltage in the back-gated structure allows the spin MOSFET operation. This achievement can pave the way for the practical use of the Si spin MOSFET.
Hiroki Shioya et al 2015 Appl. Phys. Express 8 121101
We report a molecular adsorption effect on the first-order metal–insulator transition of vanadium dioxide (VO 2) thin films. The phase transition temperature is shifted higher by the adsorption of particular polar and rigid tripodal molecules on the film surfaces. The shift becomes larger with increasing dipole moment magnitude, which ranges from 0 to 20 D. The orientation of polar molecules aligned on the surface is most likely responsible for the higher shift of the transition temperature. Coating the surfaces with polar molecules, as demonstrated in this work, might provide a unique way of controlling the phase transition of materials.
Tohru Oka et al 2015 Appl. Phys. Express 8 054101
In this paper, we report on 1.2-kV-class vertical GaN-based trench metal–oxide–semiconductor field-effect transistors (MOSFETs) on a free-standing GaN substrate with a low specific on-resistance. A redesigned epitaxial layer structure following our previous work with a regular hexagonal trench gate layout enables us to reduce the specific on-resistance to as low as 1.8 mΩ·cm 2 while obtaining a sufficient blocking voltage for 1.2-kV-class operation. Normally-off operation with a threshold voltage of 3.5 V is also demonstrated. To the best of our knowledge, this is the first report on vertical GaN-based MOSFETs with a specific on-resistance of less than 2 mΩ·cm 2.
This cloud represents the 50 most popular PACS codes from the latest 250 coded articles for this journal. The larger the code the more times it occurs in those 250 articles. Click on a code to link to the articles in that category.
42.55.Px 42.65.Ky 42.60.Pk 42.82.-m 42.60.Lh 42.65.Pc 02.50.Fz 42.79.Sz 41.75.Fr 42.70.Hj 42.55.Lt 42.65.Jx 03.67.Lx 07.20.Dt 42.81.Dp 37.10.De 42.79.Bh 42.70.Mp 42.55.Sa 42.30.Wb 42.25.Bs 33.50.Dq 42.81.Qb 42.50.Gy 42.81.Ht 42.60.Fc 42.55.Rz 41.20.Jb 42.70.Qs 42.55.Wd 42.60.Jf 42.65.Re 07.57.Kp 42.70.Jk 42.79.Dj 37.30.+i 42.25.Ja 42.81.Pa 07.07.Df 42.55.Xi 42.72.Ai 42.79.Kr 42.25.Lc 42.79.Gn 42.60.Da 42.79.Wc 42.79.Ci 07.85.Qe 42.40.Lx 07.57.-c