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Showing papers in "Japanese Journal of Applied Physics in 2010"


Journal ArticleDOI
TL;DR: In this article, the authors review the radiation chemistry of materials related to chemically amplified resist materials and discuss the imaging mechanisms from energy deposition to proton migration in resist materials are discussed.
Abstract: Historically, in the mass production of semiconductor devices, exposure tools have been repeatedly replaced with those with a shorter wavelength to meet the resolution requirements projected in the International Technology Roadmap for Semiconductors issued by the Semiconductor Industry Association. After ArF immersion lithography, extreme ultraviolet (EUV; 92.5 eV) radiation is expected to be used as an exposure tool for the mass production at or below the 22 nm technology node. If realized, 92.5 eV EUV will be the first ionizing radiation used for the mass production of semiconductor devices. In EUV lithography, chemically amplified resists, which have been the standard resists for mass production since the use of KrF lithography, will be used to meet the sensitivity requirement. Above the ionization energy of resist materials, the fundamental science of imaging, however, changes from photochemistry to radiation chemistry. In this paper, we review the radiation chemistry of materials related to chemically amplified resists. The imaging mechanisms from energy deposition to proton migration in resist materials are discussed.

254 citations


Journal ArticleDOI
TL;DR: The effects of fabrication processes on the electrical properties of Al2O3/GaN structures prepared by atomic layer deposition were investigated in this paper, where the authors showed that the amorphous phase in the atomic configuration of Al 2O3 was maintained, leading to sufficient suppression of leakage current at the interface.
Abstract: The effects of fabrication processes on the electrical properties of Al2O3/GaN structures prepared by atomic layer deposition were investigated. The annealing process at 800 °C for the formation of ohmic electrodes brought a large number of microcrystallization regions into the Al2O3 layer, causing a marked leakage in the current–voltage characteristics of the Al2O3/GaN structure. The "ohmic-first" process with a SiN protection layer was thus applied to the GaN surface. In this process, the amorphous phase in the atomic configuration of Al2O3 was maintained, leading to the sufficient suppression of leakage current at the Al2O3/GaN interface. In addition, the Al2O3/GaN structures showed good capacitance–voltage characteristics, resulting in low interface state densities of less than 1×1012 cm-2 eV-1.

108 citations


Journal ArticleDOI
TL;DR: In this article, the intrinsic channel properties of monolayer and multilayer graphene were systematically investigated as a function of layer number by the exclusion of contact resistance using four-probe measurements.
Abstract: The intrinsic channel properties of monolayer and multilayer graphene were systematically investigated as a function of layer number by the exclusion of contact resistance using four-probe measurements. We show that the continuous change in normalized sheet resistivity from graphite to a bilayer graphene is governed by one unique property, i.e., the band overlap, which markedly increases from 1 meV for a bilayer graphene to 11 meV for eight layers and eventually reaches 40 meV for graphite. The monolayer graphene, however, showed a deviation in temperature dependence due to a peculiar linear dispersion. Additionally, contact resistivity was extracted for the case of typical Cr/Au electrodes. The observed high contact resistivity, which varies by three orders of magnitude (from ~103 to 106 Ω µm), might significantly mask the outstanding performance of the monolayer graphene channel, suggesting its importance in future research.

100 citations


Journal ArticleDOI
TL;DR: In this paper, the electrical characterization of complementary multiple-gate tunneling field effect transistors (MuGTFETs), implemented in a MuGFET technology compatible with standard complementary metal oxide semiconductor (CMOS) processing, is discussed.
Abstract: This paper discusses the electrical characterization of complementary multiple-gate tunneling field effect transistors (MuGTFETs), implemented in a MuGFET technology compatible with standard complementary metal oxide semiconductor (CMOS) processing, emphasizing the dependence of the tunneling current on the fin-width. A linear dependence of the tunneling current for narrow fins with the square root of the fin width is experimentally reported for the first time. The comparison between narrow fins and planar-like fins offers additional insights about the fin-width dependence. The output characteristic shows a perfect saturation, very attractive for analog circuits. The temperature dependence is measured indicating a weak dependence as expected for tunneling devices. Measured devices with a point slope of 46 mV/dec at low biases and an Ion/Ioff ratio of 106 at a supply voltage of 1.2 V for 25 nm wide fins are reported as best performing devices with a MuGFET technology using a high-k dielectric and a metal gate inserted gate stack.

95 citations


Journal ArticleDOI
TL;DR: In this article, the authors demonstrated that resist parameters (namely, quencher concentration, acid diffusion constant, proportionality constant of line edge roughness, and dissolution point) can be extracted from the scanning electron microscopy (SEM) images of patterned resists without the knowledge on the details of resist contents using two types of latest EUV resist.
Abstract: The development of extreme ultraviolet (EUV) lithography has progressed owing to worldwide effort. As the development status of EUV lithography approaches the requirements for the high-volume production of semiconductor devices with a minimum line width of 22 nm, the extraction of resist parameters becomes increasingly important from the viewpoints of the accurate evaluation of resist materials for resist screening and the accurate process simulation for process and mask designs. In this study, we demonstrated that resist parameters (namely, quencher concentration, acid diffusion constant, proportionality constant of line edge roughness, and dissolution point) can be extracted from the scanning electron microscopy (SEM) images of patterned resists without the knowledge on the details of resist contents using two types of latest EUV resist.

82 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the behaviors of the carrier mobility and concentration of the undoped Ge1-xSnx layers epitaxially grown on silicon-on-insulator (SOI) substrates.
Abstract: We have investigated the behaviors of the carrier mobility and concentration of the undoped Ge1-xSnx layers epitaxially grown on silicon-on-insulator (SOI) substrates. Hall measurement revealed the conduction of holes excited from acceptor levels related to vacancy defects whose concentration was as high as 1018 cm-3 in Ge1-xSnx layers. The temperature dependences of the carrier mobility and concentration in the valence band was estimated by reducing the parallel conduction component in the impurity band. The incorporation of Sn at a content lower than 4.0% hardly degraded the hole mobility of heteroepitaxial Ge1-xSnx layers. In contrast, the mobility of the Ge1-xSnx layers was improved by reducing the carrier concentration of the Ge1-xSnx layers by Sn incorporation compared with that of the Ge layer formed under the same growth and annealing conditions. This result suggests that the incorporation of Sn into Ge leads to reducing the hole concentration of the electrically active vacancy defects due to the formation of Sn-vacancy pairs.

79 citations


Journal ArticleDOI
Yoshihisa Fujisaki1
TL;DR: An overview of the current status of nonvolatile semiconductor memory technology is presented and the possibility of phase-change random access memory (PRAM) or resistive-change RAM (ReRAM) replacing ultrahigh-density NAND flash memories has been discussed.
Abstract: In this report, an overview of the current status of nonvolatile semiconductor memory technology is presented. We are reaching the integration limit of flash memories, and many new types of memories to replace conventional flash memories have been proposed. Unlike flash memories, new nonvolatile memories do not require electric charge storing. The possibility of phase-change random access memory (PRAM) or resistive-change RAM (ReRAM) replacing ultrahigh-density NAND flash memories has been discussed; however, there are many issues to overcome, making the replacement difficult. Nonetheless, ferroelectric RAMs (FeRAMs) and MRAMs are gradually penetrating into fields where the shortcomings of flash memories, such as high operating voltage, slow rewriting speed, and limited number of rewrites, make their use inconvenient. For the successful application of new nonvolatile semiconductor memories, they must be practically utilized in new fields in which flash memories are not applicable, and the technology for them must be developed.

77 citations


Journal ArticleDOI
TL;DR: In this paper, the authors modified the conventional Rayleigh-Plesset theory in the following two points to reproduce the experimental observation theoretically: the effect of the contact angle among the water, the cavitation bubble, and the ablation target.
Abstract: The solution of the conventional Rayleigh–Plesset equation did not agree with the experimental results on the temporal variations of the sizes of cavitation bubbles produced by laser ablation in water. In this work, we modified the conventional Rayleigh–Plesset theory in the following two points to reproduce the experimental observation theoretically. One was to introduce the effect of the contact angle among the water, the cavitation bubble, and the ablation target. The other was to treat the surface tension and the kinematic viscosity coefficient of water as additional adjusting parameters to fit the theoretical result with the experimental observation. The latter modification was effective especially for laser ablation in the pressurized water. Better agreement between the theoretical and the experimental results was realized with the help of these modifications, but anomalous thermodynamic parameters were necessary to obtain the best fitting. We evaluated the pressures and the temperatures inside the cavitation bubbles.

69 citations


Journal ArticleDOI
Ali Hussain, Chang Won Ahn, Aman Ullah1, Jae-Shin Lee, Ill Won Kim1 
TL;DR: In this article, the effects of Hf substitution on the crystal structure and electromechanical properties of the BNKTH-100x ceramics were investigated by the conventional solid-state reaction method.
Abstract: Lead-free piezoelectric Bi0.5(Na0.78K0.22)0.5(Ti1-xHfx)O3 ceramics (abbreviated as BNKTH-100x, x=0–0.05) were prepared by the conventional solid-state reaction method. The effects of Hf substitution on the crystal structure and electromechanical properties were investigated. The X-ray diffraction patterns of the BNKTH-100x ceramics revealed a single-phase perovskite structure with no evidence of secondary phases. The temperature-dependent dielectric curves of the BNKTH-100x ceramics were found to broaden with increasing Hf concentration. The electric-field-induced strain of the BNKTH-100x ceramics increased up to x=0.03 and then decreased. An enhanced electric-field-induced strain of 0.38% is observed for the BNKTH-3 ceramic. The corresponding normalized strain (Smax/Emax=d33*) for this composition was 475 pm/V at an applied electric field of 80 kV/cm. The BNKTH-3 ceramic can be considered as a promising candidate material for lead-free electromechanical applications.

68 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used density functional theory to analyze the THz spectra of polylactide and showed that the 50 cm-1 absorption peak is due to normal-mode molecular vibrations parallel to the molecular helix.
Abstract: Terahertz (THz) spectra were obtained for polylactide, and they were analyzed by numerical calculations based on density functional theory. An absorption band was observed at approximately 50 cm-1, which becomes larger when the THz electric field is parallel to the sample drawing direction. An absorption peak with a similar directional dependence appears at approximately 40 cm-1 in the simulation, which is due to normal-mode molecular vibrations parallel to the molecular helix. Since the 50 cm-1 absorption decreases with an increase in crystallinity and the permittivity shows a step-like decrease, the molecular vibrations responsible for the 50 cm-1 band seem to be subjected to strong damping in amorphous regions. On the other hand, another absorption peak at 65 cm-1 with a positive absorption dependence on the sample's crystallinity is likely to be due to lattice vibration, since it does not appear in the calculations, which only deal with intramolecular vibration.

68 citations


Journal ArticleDOI
TL;DR: In this article, the phase stability and electronic structure of Cu2ZnSiSe4 and CZnGeSe4 were theoretically evaluated and compared with those of CZTSe4.
Abstract: We have theoretically evaluated phase stability and electronic structure of Cu2ZnSiSe4 and Cu2ZnGeSe4 and compared the results with those of Cu2ZnSnSe4. The enthalpies of formation for kesterite (KS), stannite (ST), and wurtz-stannite (WST) phases of Cu2ZnSiSe4, Cu2ZnGeSe4, and Cu2ZnSnSe4 (CZTSe) were calculated by first-principles calculations. In these three compounds, the KS phase is more stable than the ST and WST phases. The theoretical band gaps of KS-type Cu2ZnSiSe4 (1.48 eV) and Cu2ZnGeSe4 (1.10 eV) are wider than that of KS-type Cu2ZnSnSe4 (0.63 eV). The valence band maximum (VBM) of KS-type Cu2ZnIVSe4 consists of antibonding orbital of Cu 3d and Se 4p, while the conduction band minimum (CBM) consist of antibonding orbital of IV ns and Se 4p. The VBMs of Cu 3d + Se 4p in Cu2ZnSiSe4 and Cu2ZnGeSe4 are similar to that in Cu2ZnSnSe4. Therefore, the energy levels of VBMs in Cu2ZnIVSe4 (IV = Si, Ge) do not change so much compared with that of CZTSe. On the other hand, the energy levels of CBMs of IV ns + Se 4p in Cu2ZnSiSe4 and Cu2ZnGeSe4 become higher than that in Cu2ZnSnSe4. These trends in the electronic structures are explained by the schematic molecular orbital diagrams of tetrahedral CuSe47-, ZnSe46-, and IVSe44- (IV = Si, Ge, Sn) clusters.

Journal ArticleDOI
TL;DR: In this article, the size effect of nanograined BaTiO3 ceramics with various grain sizes from 24 to 170 nm was demonstrated. But, the grain size was controlled by reannealing treatment at various temperatures.
Abstract: We demonstrated the size effect of nanograined BaTiO3 ceramics using freestanding BaTiO3 thick films fabricated by the aerosol deposition (AD) method. Dense BaTiO3 thick films fabricated by the AD method were crystallized and detached from the SrTiO3 substrate by annealing treatment at 600 °C, and then the grain size was controlled by reannealing treatment at various temperatures. As a result, freestanding BaTiO3 thick films with various grain sizes from 24 to 170 nm were successfully obtained. Polarization–electric field (P–E) measurement revealed that BaTiO3 ceramics with grain sizes of more than 58 nm showed ferroelectricity, whereas BaTiO3 ceramics with an average grain size of 24 nm showed paraelectricity at room temperature. Dielectric measurement indicated that the permittivity decreased with decreasing grain size in the range from 170 to 24 nm. The decrease in permittivity was due to the decreases in ferroelectricity and domain-wall contributions with decreasing grain size.

Journal ArticleDOI
TL;DR: In this article, the crystal structure of metastable LuFeO3 synthesized by containerless processing has been revealed to be a non-centrosymmetric structure (space group P63cm) by analyzing the high-energy synchrotron-radiation powder-diffraction data using the maximum entropy method (MEM)/Rietveld method.
Abstract: The crystal structure of metastable LuFeO3 synthesized by containerless processing has been revealed to be a non-centrosymmetric structure (space group P63cm) by analyzing the high-energy synchrotron-radiation powder-diffraction data using the maximum entropy method (MEM)/Rietveld method. The structural characteristics are found in the FeO5 trigonal bipyramid distorted and tilted from the c-axis, which is cause by the hybridization of atomic orbitals between the O atom constituent of the polyhedron and the neighboring Lu atom. The spontaneous polarization expected from the polar structure is estimated at about 5 µC/cm2.

Journal ArticleDOI
TL;DR: The line width and line edge roughness (LER) of resist patterns are related to the concentration and its gradient of chemical compounds that determine the solubility of the resist, respectively as discussed by the authors.
Abstract: The line width and line edge roughness (LER) of resist patterns are related to the concentration and its gradient of chemical compounds that determine the solubility of the resist, respectively. Therefore, latent images can be obtained from the line width and LER of resist patterns. In this study, two-dimensional (exposure dose and half-pitch) matrices of resist line width and LER were analyzed on the basis of the sensitization mechanisms of chemically amplified resists used for extreme ultraviolet (EUV) lithography. In the reconstruction of latent images, the effective reaction radius for catalytic chain reaction is an important parameter. The probable range of effective reaction radius was from 0.05 to 0.2 nm. In this range, latent images were successfully reconstructed. The finding that the effective reaction radius is smaller than the typical size of a counteranion suggests that the resist performance can be improved by increasing the effective reaction radius.

Journal ArticleDOI
TL;DR: In this article, variable capacitors (VCs) connected to SAW/BAW resonators in the ladder-type filter configuration are used to tune the frequency and width of a passband.
Abstract: In this paper, we describe possible configurations for tunable filters based on RF surface or bulk acoustic wave (SAW/BAW) technologies. The frequency tuning is made possible by variable capacitors (VCs) connected to SAW/BAW resonators in the ladder-type filter configuration. First, it is shown that the passband edges can be controlled by one VC connected to each resonator. Second, it is discussed that the width and location of a passband can be controlled flexibly by two VCs connected to each resonator both in parallel and in series. Finally, the SAW filters with the proposed configuration are fabricated on a Cu-grating/15°YX-LiNbO3 substrate structure, and the tuning capability is demonstrated.

Journal ArticleDOI
Hirokazu Fukidome1, Yu Miyamoto1, Hiroyuki Handa1, Eiji Saito1, Maki Suemitsu1 
TL;DR: In this article, a detailed structural characterization of this graphene-on-silicon (GOS) material by Raman spectroscopy and transmission-electron microscopy was conducted to obtain insights into the impacts of process parameters on defect formation.
Abstract: Few-layers graphene is epitaxially grown on silicon substrates via SiC thin films inserted in between. We have conducted a detailed structural characterization of this graphene-on-silicon (GOS) material by Raman spectroscopy and transmission-electron microscopy, to obtain insights into the impacts of process parameters on defect formation. Results suggest that defects in graphene preferentially dwell at steps. Future flattening of the SiC surface, prior to graphene growth, is thus expected to contribute to the improvement of GOS quality.

Journal ArticleDOI
TL;DR: In this article, an inverted-staggered amorphous In-Ga-Zn-oxide (a-IGZO) thin-film transistor (TFT) was fabricated and measured the temperature dependence of its characteristics.
Abstract: We fabricated an inverted-staggered amorphous In–Ga–Zn-oxide (a-IGZO) thin film transistor (TFT) and measured the temperature dependence of its characteristics. A threshold voltage (Vth) shift between 120 and 180 °C was as large as 4 V. In an analysis with two-dimensional (2D) numerical simulation, we reproduced the measured result by assuming two types of donor-like states as carrier generation sources. Furthermore, by ab initio molecular dynamics (MD) simulation, we determined the electronic structures of three types of a-IGZO structures, namely, "stoichiometric a-IGZO", "oxygen deficiency", and "hydrogen doping".

Journal ArticleDOI
TL;DR: In this paper, the performance of the remote-phosphor scattered photon extraction (SPE) white light-emitting diode (LED) was investigated with commercial yellow and red phosphors in equal amounts, and the highest light output was obtained when the longer wavelength red phosphor was placed as the second layer.
Abstract: To understand how multiple phosphors in a mixture or stacked layers affect the performance of the remote-phosphor "scattered photon extraction (SPE)" white light-emitting diode (LED), a laboratory study was conducted with commercial yellow [quantum efficiency (QE)=0.91] and red (QE=0.59) phosphors in equal amounts. The highest light output was obtained when the longer-wavelength red phosphor was placed as the second layer. Experiments showed that when using two phosphors in an SPE package, several factors influence the performance: mixture or stacked layers; specific layer order; phosphor densities; phosphor external QE; overall spectral power distribution (SPD); phosphor excitation and emission spectra and efficiencies.

Journal ArticleDOI
TL;DR: In this paper, a first-principles density functional theory (DFT) study of H2O molecular adsorption on the tri-s-triazine-based structure is presented.
Abstract: As an initial step towards understanding the mechanism behind photocatalysis in graphitic carbon nitride (g-C3N4), we present a first-principles density functional theory (DFT) study of H2O molecular adsorption on the tri-s-triazine-based structure. The optimization of the system determined that the most stable configuration would be on top of the two-coordinated nitrogen atom in an orientation where one O–H bond is parallel to the surface and the other one is pointing to the surface. The adsorption energy at the most stable configuration was found to be 0.82 eV with a barrier energy of ~0.02 eV. Partial density of states (PDOS) and charge density distribution analysis show that, primarily, the bonding occurs between the hydrogen atom of the water molecule and the two-coordinated nitrogen atom of g-C3N4. Results of this study would be useful not only to better understand the mechanism behind H2O molecule adsorption but also to give insight into the role of the catalyst in the photocatalytic process.

Journal ArticleDOI
TL;DR: In this article, an electrically tunable pico-projector adopting a liquid crystal (LC) lens as an active optical element is demonstrated, where the focal length of this picoprojector is electrically tuned from 350 to 14 cm and the tunable range is even wider than that of a manually focused pico projector.
Abstract: An electrically tunable pico-projector adopting a liquid crystal (LC) lens as an active optical element is demonstrated. The focal length of this pico-projector is electrically tunable from 350 to 14 cm and the tunable range is even wider than that of a manually focused pico-projector. The response times of turn-on and turn-off are approximately 313 and 880 ms, respectively. In addition, the location of the projection lens can affect the electrically tunable range of the system. A small shift of the projection lens results in the large tunable focusing range of the pico-projector and a tunable focusing range is determined by the LC lens. The optical analysis is also discussed. This concept can even be applied to design other electrically auto focusing pico-projectors based on other optical elements such as liquid lenses and spatial light modulators.

Journal ArticleDOI
TL;DR: In this paper, a PbO-type structure was successfully grown on MgO(100) and LaSrAlO4(001) substrates from FeSe0.5Te0.75 polycrystalline targets by pulsed laser deposition.
Abstract: FeSe0.5Te0.5 thin films with a PbO-type structure are successfully grown on MgO(100) and LaSrAlO4(001) substrates from FeSe0.5Te0.5 or FeSe0.5Te0.75 polycrystalline targets by pulsed laser deposition. The film deposited on the MgO substrate (film thickness: ~55 nm) shows superconductivity at 10.6 K (onset) and 9.2 K (zero resistivity). On the other hand, the film deposited on the LaSrAlO4 substrate (film thickness: ~250 nm) exhibits superconductivity at 5.4 K (onset) and 2.7 K (zero resistivity). This suggests the strong effect of substrate materials and/or the c-axis length on the superconducting properties of FeSe0.5Te0.5 thin films.

Journal ArticleDOI
TL;DR: In this article, a 4.0-in. quarter video graphics array (QVGA) active-matrix organic light-emitting diode (AMOLED) display integrated with gate and source driver circuits using amorphous In-Ga-Zn-oxide (IGZO) thin-film transistors (TFTs).
Abstract: We have newly developed a 4.0-in. quarter video graphics array (QVGA) active-matrix organic light-emitting diode (AMOLED) display integrated with gate and source driver circuits using amorphous In–Ga–Zn-oxide (IGZO) thin-film transistors (TFTs). Focusing on a passivation layer in an inverted staggered bottom gate structure, the threshold voltage of the TFTs can be controlled to have "normally-off" characteristics with suppressed variation by using a SiOx layer formed by sputtering with a low hydrogen content. In addition, small subthreshold swing S/S of 0.19 V/decade, high field-effect mobility µFE of 11.5 cm2 V-1 s-1, and threshold voltage Vth of 1.27 V are achieved. The deposition conditions of the passivation layer and other processes are optimized, and variation in TFT characteristics is suppressed, whereby high-speed operation in gate and source driver circuits can be achieved. Using these driver circuits, the 4.0-in. QVGA AMOLED display integrated with driver circuits can be realized.

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the temperature-dependent characteristics of amorphous indium-gallium-zincoxide (a-IGZO) thin-film transistors (TFTs).
Abstract: In this study, we analyzed the temperature-dependent characteristics of amorphous indium–gallium–zinc-oxide (a-IGZO) thin-film transistors (TFTs). We observed that a-IGZO TFTs obey the Meyer–Neldel rule (MN rule) at low gate-to-source voltage (VGS) and the inverse MN rule at high VGS, both of which can be explained by the statistical shift of Fermi level and electrostatic potential. Large Fermi level movement for small VGS change and the inverse MN rule, which are hardly observed for conventional amorphous TFTs, indicate that there is a very low density of state (DOS) in the sub-bandgap region for a-IGZO TFTs and the performance of TFTs is not affected by contact characteristics, respectively. By using the field-effect method and considering surface band bending, we extracted the DOS in the sub-bandgap region, the distribution of which is clearly distinguished by deep and tail states. The calculated parameters for tail and deep states were Nta = 3.5 ×1017 cm-3 eV-1, Eta = 0.18 eV, Nda = 1.6×1016 cm-3 eV-1, and σda = 0.21 eV.

Journal ArticleDOI
TL;DR: In this paper, the grain boundary properties of polycrystalline Cu(In1-x,Gax)Se2 (CIGS) have been characterized using electron beam-induced current (EBIC) measurements, electron backscatter diffraction (EBSD) patterns, and scanning spreading resistance microscopy (SSRM) measurements.
Abstract: The grain boundary (GB) properties of polycrystalline Cu(In1-x,Gax)Se2 (CIGS) have been characterized using electron beam-induced current (EBIC) measurements, electron backscatter diffraction (EBSD) patterns, and scanning spreading resistance microscopy (SSRM) measurements. The polished cross section of CIGS solar cells was evaluated by these three methods, and the surface EBIC image was obtained by scanning electron microscopy (SEM). A combination of the EBIC and EBSD techniques makes it possible to investigate the effect of the GBs on the minority carrier collection. Furthermore, the SSRM mapping enables the analysis of grain-by-grain carrier profiling by measuring the spreading resistance of CIGS solar cells. It was found from these results that the twin boundaries of CIGS grains do not contribute to carrier recombination. Furthermore, the brighter EBIC signals were observed at the GBs of CIGS, which showed that the produced electron–hole pairs easily separate from each other and that the minority carriers are repelled from the GBs. This remarkable property of the GBs is suitable for application of CIGS to solar cells.

Journal ArticleDOI
TL;DR: In this article, a first step for a novel fabrication method of a flexible display, nanomaterial based laser processing schemes to demonstrate organic light emitting diode (OLED) pixel transfer and organic field effect transistor (OFET) fabrication on a polymer substrate without using any conventional vacuum or photolithography processes were developed.
Abstract: To demonstrate a first step for a novel fabrication method of a flexible display, nanomaterial based laser processing schemes to demonstrate organic light emitting diode (OLED) pixel transfer and organic field effect transistor (OFET) fabrication on a polymer substrate without using any conventional vacuum or photolithography processes were developed. The unique properties of nanomaterials allow laser induced forward transfer of organic light emitting material at low laser energy while maintaining good fluorescence and also allow high resolution transistor electrode patterning at plastic compatible low temperature. These novel processes enable an environmentally friendly and cost effective process as well as a low temperature manufacturing sequence to realize inexpensive, large area, flexible electronics on polymer substrates.

Journal ArticleDOI
TL;DR: The merit of the proposed modulation codes is that their trellis structure allows error correcting capability and they have better performance than the conventional 6/8 and 4/6 modulation codes overall.
Abstract: We introduce error correcting 4/6 modulation codes for holographic data storage. Above all, the merit of the proposed modulation codes is that their trellis structure allows error correcting capability. The proposed codes also do not have any fatal (i.e., isolated pixels) two-dimensional intersymbol interference (2D ISI) patterns. The decoding scheme uses the Viterbi algorithm. As a result, the proposed codes have better performance than the conventional 6/8 and 4/6 modulation codes overall.

Journal ArticleDOI
TL;DR: In this article, a combination of two-dimensional and one-dimensional printing was used for high resolution printing on a large area using silver nanoparticle ink and poly(3-hexylthiophene) ink.
Abstract: We have developed a new printing method based on microcontact printing, where an image of dried ink is transferred from a stamp to a substrate via two steps. Combination of two-dimensional press and one-dimensional press enables high resolution printing on a large area using silver nanoparticle ink and poly(3-hexylthiophene) ink. A channel length below 10 µm was successfully obtained. Furthermore, we have succeeded in fabricating organic thin-film-transistor arrays with large area and high precision, 150 mm square area and 200 ppi, respectively, entirely by solution and printing processes.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a simplified model introducing a stopping power Sd(Eion) with a power-law dependence on the energy of incident ions (Eion), and applied this model to damaged-layer formation in plasma with an rf bias, where various energies of incident ion are expected.
Abstract: Bias frequency effects on damaged-layer formation during plasma processing were investigated. High-energy ion bombardment on Si substrates and subsequent damaged-layer formation are modeled on the basis of range theory. We propose a simplified model introducing a stopping power Sd(Eion) with a power-law dependence on the energy of incident ions (Eion). We applied this model to damaged-layer formation in plasma with an rf bias, where various energies of incident ions are expected. The ion energy distribution function (IEDF) was considered, and the distribution profile of defect sites was estimated. We found that, owing to the characteristic ion-energy-dependent stopping power Sd(Eion) and the straggling, the bias frequency effect was subject to suppression, i.e., the thickness of the damaged layer is a weak function of bias frequency. These predicted features were compared with experimental data on the damage created using an inductively coupled plasma reactor with two different bias frequencies; 13.56 MHz and 400 kHz. The model prediction showed good agreement with experimental observations of the samples exposed to plasmas with various bias configurations.

Journal ArticleDOI
TL;DR: In this paper, a p-channel oxide semiconductor thin film transistors were fabricated with a bottom-gate and bottom-contact structure, and the resulting on-current/off-current ratio was more than 102 and the field effect mobility was approximately 4×10-5 cm2 V-1 s-1.
Abstract: By using tin monoxide films, p-channel oxide semiconductor thin film transistors were fabricated with a bottom-gate and bottom-contact structure. A p-type tin monoxide semiconductor thin film was obtained from tin monoxide powder by vacuum thermal evaporation. The as-deposited film showed an amorphous phase, and a polycrystalline tin monoxide was obtained by thermal annealing after the deposition. The hole concentration was on the order of 1017 cm-3, and the Hall mobility was 2.83 cm2 V-1 s-1. The resulting on-current/off-current ratio was more than 102, and the field-effect mobility was approximately 4×10-5 cm2 V-1 s-1.

Journal ArticleDOI
TL;DR: In this article, a two-layer (SiO2/Si) optical model was revised for in-line monitoring of H2-plasma damage, showing that the interface layer plays an important role in the optical assessment of the plasma-damage layer.
Abstract: Si surface damage induced by H2 plasmas was studied in detail by optical and electrical analyses. Spectroscopic ellipsometry (SE) revealed a decrease in the pseudo-extinction coefficient in the region of photon energy higher than ~3.4 eV upon H2-plasma exposure, which is attributed to the disordering of crystalline silicon (c-Si). The increase in in the lower energy region indicates the presence of trap sites for photogenerated carriers in the energy band gap in the E–k space of Si. The current–voltage (I–V) measurement of metal-contacted structures was performed, revealing the following characteristic structures: thinner surface (SiO2) and thicker interface (SiO2:c-Si) layers on the Si substrate in the case of H2-plasma exposure than those with Ar- and/or O2-plasma exposure. The structure assigned on the basis of both SE and I–V was further analyzed by a layer-by-layer wet-etching technique focusing on the removability of SiO2 and its etch rate. The residual damage-layer thickness for the H2-plasma process was thicker (~10 nm) than those for other plasma processes (<2 nm). Since the interface layer plays an important role in the optical assessment of the plasma-damage layer, the present findings imply that a conventional two-layer (SiO2/Si) optical model should be revised for in-line monitoring of H2-plasma damage.