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We have investigated the high quality p-type Cu2O thin films produced by the post vacuum annealing process of Cu2O thin films deposited on glass substrates at room temperature by facing target sputtering. As-deposited stoichiometric films show the high Cu2O (111)-axis orientation with the minimum value of electrical resistivity of 17 Ω cm. Furthermore, the XRD peaks intensities continuously decrease around the stoichiometric 2θ value of 36.4° with increasing the O2 partial pressure. With the vacuum annealing at 550 °C with optimized oxygen ambient, the high quality p-type Cu2O thin film could be obtained. The highest value of Hall mobility μH of 61 cm2/Vs is obtained for a vacuum annealed stoichiometric p-type Cu2O thin film. Such high value of μH in the described stoichiometric p-type Cu2O thin film is believed to be due to the minimized oxygen vacancies induced by optimized vacuum annealing of a stoichiometric as-deposited Cu2O thin film.

The properties of Cu-doped SnO thin films with various Cu contents (Sn 1 − x Cu x O) prepared by reactive co-sputtering using facing targets of Sn and Cu are investigated. The XRD patterns show the tetragonal SnO phases including the mixed phase of Cu 2 O (200) and metallic Cu (111). The XRD phase ratio of Cu 2 O/Cu increases from 0 to 41/59 for x = 3 to 22 at.%, which is compatible with the values of the content ratio of Cu 1 + /Cu 0 estimated from the XPS peaks. The decrease of the resistivity and the optical transmission with increasing Cu content in Sn 1 − x Cu x O thin films up to 17 at.% is mainly attributed to the Cu phase. Such behavior of results displays the n -type conduction, whereas the Sn 1 − x Cu x O thin film at x = 22 at.% shows the p -type conduction with Hall mobility of 1.1 cm 2 /Vs and the resistivity of 0.45 Ωcm.

Korean households' demand for food consumed away from home is on the steady increase. The ratio of eating-out expenditure of the household income, however, tends to decrease recently irrespective of income groups. This paper, therefore, aims to analyse the food-away-from-home expenditures of salary and wage earners' households by income decile group. The eating-out expenditure is modelled as a function of household income and then estimated using econometric methods such as regression, rolling regression, impulse response, and variance decomposition of forecast error. The regression results indicate that the higher the income decile group is, the lower the income elasticity of eating-out expenditure is, and the high income groups enjoy seasonal eating-out, the low groups do not. The coefficients of dynamic rolling regression are much smaller than those of static one, meaning that households tend to decrease the eating-out expenditure of their income. The impulse response analysis suggests that the eating-out expenditure increase of higher income groups lasts long relative to that of lower income groups. The variance decomposition, also, shows that household income plays much more important role in determining eating-out expenditure at the higher income groups than at the lower income groups.

Effective microorganism (EM) cultures have been applied in many research fields such as agriculture, environment and bioremediation. EM is a mixed culture of microorganisms including predominant populations of lactic acid bacteria and yeasts with smaller numbers of photosynthetic bacteria, actinomycetes and other types of microorganisms. Quantitative analysis of EM is requisite for the applications of EM, as its efficiency varies depending on the composition of its main genera of EM. In this study, Rhodobacter sphaeroides, Rhodopseudomonas palustris, Lactobacillus plantarum, and Saccharomyces cerevisiae, the main genera of EM were quantified by quantitative real time polymerase chain reaction, (qRT-PCR). By using selected specific primers, photosynthetic bacteria, lactic acid bacteria and yeast were quantified with high sensitivity and specificity. The ability of viable cell count by qRT-PCR was compared with agar plate cell count, showing linear relationship. Thus, PCR based quantification system is a rapid and highly specific and sensitive tool for the quantification of EM.

Currently, much work has focused on the engineering of bone using adipose-derived stem cells (ADSCs), which differentiate into osteogenic cells. This study was conducted to assess the bone-regenerating capacity of ADSCs with genetic modification.ADSCs were cultured and transduced with recombinant adenovirus-expressing bone morphogenetic protein-2 (rAd/BMP-2). Two 5-mm full-thickness bone defects were created on the parietal bones of 24 rats. The defects were left empty (n = 12), restored with a scaffold alone (n = 12), transplanted with ADSCs in osteogenic media (n = 12), or transplanted with rAd/BMP-2-transduced ADSCs (n = 12). Six defects from each group were assessed by histologic observation, histomorphometric analysis, and microcomputed tomography (micro-CT) imaging at 4 and 8 weeks after transplantation.Increased new bone formation was observed in the rAd/BMP-2-transduced ADSC groups, compared with the other groups. On micro-CT, significant differences were noted in bone volume-to-tissue volume ratios between rAd/BMP-2-transduced ADSCs group and the other groups at both time points (P0.05).The result demonstrates that transferring BMP-2 promotes the osteogenic differentiation of ADSCs and enhances bone regeneration. Under limitation of this study, genetic modification of ADSCs with BMP-2 could be adopted in clinical application.

We investigate the controllability of the threshold voltage (Vth) by varying the O2 partial pressure in sputter-deposited of InGaZnO4 thin-film transistors (IGZO TFTs). We showed that the Vth values could be linearly controlled from a depletion-type of Vth ∼ −6 V to an enhancement-type of Vth ∼ 2 V, without any abrupt change in µsat, Ion/off, and S, by only changing the O2 partial pressure in a fixed region of the Ar partial pressure. Such Vth controllability is thought to be due to the proper reduction of defect states and, in turn, to the preservation of high-performance TFT behavior.

We investigate the feasibility of a 10-nm-thick semitransparent layer of Al as gate electrodes, instead of a conducting oxide, for bottom-gate-type amorphous iridium gallium zinc oxide thin-film transistors (a-IGZO TFTs). Good adhesion with glass and plastic substrates is reported for 10-nm-thick Al-gate electrodes, with a sheet resistance of 32 Omega/square. The described semitransparent a-IGZO TFT also shows about a 70%-transmittance. A device operating at low voltage, a saturation mobility of 4.45 cm(2)/V s, a subthreshold swing of 1.06 V/decade, an off-current of about 10(-11) A, and an on-off ratio of 10(7) at an operating gate voltage of 5 V are reported.

The optical properties and an X-ray photoelectron spectroscopy (XPS) analysis of amorphous TaN thin films were investigated. Ta-N thin films reactively sputtered at N2 partial pressures (P(N2)) < 0.2 mTorr had the [111]-axis preferred orientation with a cubic δ-TaN phase while amorphous TaN thin films were obtained for P(N2) = 0.2 mTorr. The band gap of the amorphous Ta-N thin films increased from 1.4 eV to 3.6 eV with increasing P(N2) from 0.3 mTorr to 5.0 mTorr. For P(N2) < 0.3 mTorr, the chemical binding states of Ta-N are predominant as the TaN compound. Otherwise, in the chemical states of Ta-N, N-rich metastable phases similar to those of Ta2O5 increase up to a 50% fraction of Ta-N bonding states with increasing P(N2) and are closely related to the optical transparency of amorphous Ta-N thin films.

We have investigated the feasibility of the deposition of ferroelectric PZT films on transparent conducting Ga-doped ZnO (GZO) films, for transparent ferroelectric thin-film transistors. Low resistive and high c-axis oriented GZO films are prepared at the substrate temperature of 250°C using the dc magnetron sputtering method. PZT films are deposited at low substrate temperature and subsequently crystallized by means of the rapid annealing process in a high vacuum to minimize the reaction of PZT with GZO films. Various vacuum-annealing conditions are investigated to get high-quality PZT films, which show single perovskite phase with a random orientation. The optimized PZT/GZO capacitors have somewhat unsaturated P-E hysteresis loops with the values of remanent polarization and coercive field of about 4.5 μC/cm2 and 145 kV/cm, respectively.

Single-layered PtRhO y thin films were investigated as electrode barriers for ferroelectric Pb(Zr x Ti 1-x )O 3 (PZT) (x = 0.2-0.8) thin film capacitors. PtRhO y thin films were deposited directly on n+ Si wafers by means of the reactive sputtering method. PtRho y /PZT/PtRhO y /n+ Si capacitors showed well-defined P-E hysteresis loops. The remanent polarizations, as well as the polarization loss after the switching repetitions, were varied with the ratio of Zr/Ti. Especially, Pb(Zr 0.4 Ti 0.6 )O 3 thin film capacitor showed the superior ferroelectric properties, such as the P-E hysteresis characteristics and the polarization fatigue. The typical remanent polarization and the coercive field of this capacitor were 22 μC/cm 2 and 87 kV/cm, respectively, and the polarization loss was only less than 5% after 10 11 switching repetitions. From the measurement of the depth profile and the microstructure of this capacitor, it could be convinced that single-layered PtRhO y films behaved as high quality electrode barriers for PZT thin film capacitors.

We have investigated the high quality electrode-barriers for Pb(Zr0.35Ti0.65)O3 (PZT) thin film capacitors to contact directly on W-plug for COB (capacitor-over-bit line) structured high density ferroelectric memories (FRAM). A conducting oxide of 40-nm-thickness PtRhOx was used as a fatigue free electrode for PZT capacitors. Various materials, such as Ta, NiCr (Ni with 20 wt% Cr), Cr and PtRh (Pt with 10 wt% Rh), were investigated as conducting oxygen diffusion barriers between PtRhOx bottom electrode and W-plug. It was found that PZT capacitors with Ta-barriers of 30-nm-thickness showed superior thermal stability up to 630°C, whose remanent polarization and coercive field were typically 30 μ C/cm2 and 86 kV/cm, respectively. However, their polarization fatigue behaviors are associated with the oxygen content in PtRhOx electrodes.

We have tried to improve the Ir electrode-barrier for Pb(Zr,Ti)O3 (PZT)-based non-volatile ferroelectric memories (NvFRAMs). Ir layer of 150-nm thickness was deposited on poly-Si substrates by means of the rf-sputtering method. Although Ir in itself acted as an oxygen barrier and a IrO2/PZT/Ir/poly-Si capacitor showed device-worth ferroelectric properties, whose remanent polarization, coercive field, fatigue loss after 1011 switching repetitions were 25 μ C/cm2, 48 kV/cm and 12%, respectively, the high leakage current at the field of larger than 80 kV/cm was found, which might be caused by the reaction of PbO with bottom-Ir. Such poor leakage current behaviors could be successively improved by the insertion of vacuum-annealed thin IrO2 (or IrOx) layer of 20-nm thickness between PZT/Ir. We suggest that such improvements in the microstructures and the ferroelectric properties including the leakage current behaviors are attributed to the reduction of the reaction between PbO and Ir in bottom electrode by inserting the IrOx interlayer.

In this paper, two electrode-barrier structures based on Pt-Rh and Pt-Ir alloys and their oxides are proposed for high-density ferroelectric memory applications. These electrode-barriers are multi-layered, comprising a diffusion barrier (PtRhOx or PtIrOx), metal alloy (PtRh or PtIr) and another PtRhOx or PtIrOx layer for fatigue reduction in the case of PZT capacitors. Both lead zirconate titanate (PZT) and strontium bismuth tantalate (SBT) capacitors based on the electrode-barriers were used in the present study. The electrode-barrier structure acts as a conducting electrode as well as an excellent diffusion barrier for lead, bismuth, oxygen and silicon. The PZT test capacitors fabricated on these electrode-barriers showed excellent fatigue resistance with other ferroelectric properties being similar to those on Pt. Also, these electrode-barriers are stable, and remain conductive even up to the processing temperatures of SBT (750 °C). This makes direct integration of both PZT and SBT capacitors on to a poly-Si plug attainable. In addition, the conducting electrode-barrier structures can be deposited in situ, directly over n+polycrystalline Si, thereby significantly improving the density of the device.

Thin TiO2 layers were sputter-deposited on Pt/Ti/SiO2/Si wafers, as buffer layers for PZT thin film capacitors. It was found that TiO2 buffers of less than 4-nm-thickness could assist in obtaining ...

This paper presents a study of the anodic bonding technique using a hydrophilic surface. Our method differs from conventional processes in the pre-treatment of the wafer. Hydrophilic surfaces were achieved from dipping in H2O/H2O2/NH4OH solution. The hydrophilic surface has a large number of -OH groups, which can form hydrogen bonds when two wafers are in contact. This induces a higher electrostatic force, because of the decreasing gap between the glass and silicon wafer. We achieved improved properties, such as a wider bonded area and a higher bond strength than those of conventional methods. Also, the fabricated pressure sensors on the 5-inch silicon wafer were bonded to Pyrex #7740 glass of 3 mm thickness. In order to investigate the migration of the sodium ions, the depth profile at the glass surface by secondary-ion mass spectroscopy and the bonding current were compared with that of conventional methods.

A lateral force microscope (LFM) was used for studying the surface morphologies of SrBi2Ta2O9 thin films with varying post-annealing temperature. Specimens were prepared onto platinized silicon wafers by the sol–gel method and post-annealed at 600–800°C. Non-ferroelectric matrix phases were found for specimens annealed below 700°C, which were confirmed by the measurement of X-ray diffraction (XRD) patterns. The friction coefficients between the surface of ferroelectric grain and non-ferroelectric matrix, and the silicon nitride tip, were determined from the line profile of the LFM images. The measured coefficients of friction for a tip on grain and matrix are 0.19±0.08 and 0.28±0.08, respectively. In the LFM images, the matrix phases decreased with increasing post-anneal temperature and the surfaces of the specimens annealed above 700°C were filled with SBT grains which were consistent with the XRD results. Ferroelectricities of these specimens were confirmed by the measurement of polarization field hysteresis loops.

We have studied the structural and electrical properties of bismuth-modified lead zirconate titanate thin films. Specimens with various Bi contents, (Pb1−3/2xBix) (Zr0.52 Ti0.48) O3 (PBZT) thin films, were prepared on a Pt-coated Si wafer by the sol–gel method. Ferroelectricity confirmed by the measurement of dielectric constant and P–E hysteresis loop was found for specimens below x = 0.25, in which the values of both dielectric constant and remanent polarization were decreased with increasing Bi contents. The behaviors of the electrical properties with Bi content corresponded to the structural changes by increasing non-ferroelectric cubic phase with increasing Bi contents, which was thought to be due to the vacancies in Pb-sites created by the substitution of Bi into Pb.

The changes in the gap state distributions produced by light soaking in undoped a-Si:H prepared by remote-plasma chemical vapour deposition were determined from the simultaneous measurement of thermally stimulated conductivity and low-intensity photoconductivity. The temperature dependence and the changes of the product of the microscopic mobility and the recombination lifetime, μ m τ r , produced by light soaking were also determined. In the gap profiles in the energy interval between 0.2 and 0.8 eV below the conduction band edge, at least two electron traps are found at 0.30 ± 0.02 and 0.54 ± 0.02 eV. The density of the trap located at 0.54 eV due to the doubly occupied dangling bond, D − , is increased by light soaking together with a simultaneous decrease of traps located at 0.30 eV due to the weak bonds. These effects are interpreted as defect creation and annealing, respectively. The temperature dependence of the μ m τ r product is found to be due to that of μ m , and thermal quenching and light quenching of μ m τ r are mainly due to those of τ r .

本報は, すでに公表されている各種繊維の応カ―歪曲線を用いて求めた引張タフネスについて報告する.それらの引張タフネスについて引張速度, 温度および湿度のような引張試験条件の影響を解析した.その結果, 試験環境並びに引張速度が引張タフネスに著しく影響することを結論づけた.各種繊維の引張タフネスを用いる諸性質の評価は, 繊維の引張強伸度のそれとは異なることが分かった.それゆえに, 繊維の引張性質は強伸度のみで評価するのでなく, タフネスについても評価しなければならないことを提案した.

We have investigated the feasibility of the Pt/PtOx multilayer as an electrode barrier for Pb(Zr,Ti)O3 (PZT)-based ferroelectric random access memories. PtOx and Pt layers were prepared on polycrystalline-Si/SiO2/Si substrates by means of the sputtering method in Ar and O2 ambience, and the Pb(Zr0.53Ti0.47)O3 layer was prepared by the sol-gel method. A capacitor consisting of Pt/PtOx/PZT/PtOx/Pt/PtOx/poly-Si had a remanent polarization of 18 μC/cm2 and a low coercive field of 32 kV/cm. The polarization fatigue behavior of test capacitors was improved as compared with that of Pt/PZT/Pt, which showed negligible fatigue loss of 15% after 1011 switching repetitions with a frequency of 1 MHz.

We present the feasibility of single-layer PtRhO/sub y/ thin films as electrode barriers for ferroelectric Pb(Zr/sub 1-x/Ti/sub x/)O/sub 3/ (PZT) (x = 0.2 to 0.8) thin film capacitors. PtRhO/sub y/ thin films were deposited directly on n+ Si wafers by means of the reactive sputtering method. PtRhO/sub y//PZT/PtRhO/sub y//n+ Si capacitors showed well-saturated P-E hysteresis loops. The remanent polarizations, as well as the polarization loss after the switching repetitions, were varied with the ratio of Zr/Ti. Especially, Pb(Zr/sub 0.4/Ti/sub 0.6/)O/sub 3/ thin film capacitor showed the superior ferroelectric properties, such as the shape of P-E hysteresis loops and the behaviors of the polarization fatigue. The typical remanent polarization and the coercive field of this capacitor were 22 /spl mu/C/cm/sup 2/ and 87 kV/cm, respectively, and the polarization loss was only less than 5 % after 10/sup 11/ switching repetitions. The chemical binding states of PtRhO/sub y/ films affected mainly the shape of P-E hysteresis loops. From the measurement of the depth profile and the microstructure of this capacitor, it could be convinced that single-layer PtRhO/sub x/ films behaved as high quality electrode barriers for PZT thin film capacitors.

The influences of ambient gases on the packaging of Spindt-type Mo-field emitter arrays (FEAs) in the atmoshere were studied through electrical field emission characteristics and Mo surface analysis according to various ambient gases (N/sub 2/, Ar and air). Also electrical field emission characteristics in an ultra high vacuum chamber and Mo surface analysis were performed after breaking the sealing lines to expose the FEAs. We can obtain increased electron emission current for each pixel by using Ar gas when compared with other gases during frit process.

We have investigated the structural and electrical properties of sol-gel derived Pb(Zr, Ti)O-3 (PZT) thin films deposited on Ir electrode barrier (Ir/poly-Si/SiO2/Si). Owing to the interface-controlled growth, highly c-axis oriented perovskite PZT thin films were obtained for the postdeposition annealing temperature of 580 degrees C. Additionally, we found that the ferroelectric properties of IrO2/PZT/Ir/poly-Si capacitors were remarkably changed by the partial pressure of oxygen during the deposition of IrO2 top electrodes, which could be due to the enhanced reaction of IrO2 with PZT by the oxygen ion bombardments. Remanent polarization and coercive field of IrO2/PZT/Ir/poly-Si capacitor with the top electrodes deposited at P-O2 = 1 mTorr was 20 mu C/cm(2) and 30 kV/cm, respectively, and showed negligible polarization fatigue up to 10(11) switching repetitions. The leakage current density at a field of 80 kV was 5 X 10(-8) A/ cm(2). (C) 1999 American Institute of Physics. [S0003-6951(99)01510-7].

We have investigated the structural and electrical properties of Sr-modified Pb(Zr,Ti)O3, i.e., (Pb1-xSrx)(Zr0.53Ti0.47)O3 (PSZT), thin films. Sol-gel derived PSZT films were deposited by spin casting onto Pt/Ti/SiO2/Si substrates. Ferroelectric perovskite phases were found for all specimens (x ≤ 0.6), which implied the successful substitution of Sr for Pb. The values of dielectric constant (εr) as well as remanent polarization (Pr) of PSZT capacitors decreases monotonically with increasing Sr for x ≥ 0.1. PSZT (x=0.4) thin film was found to be applicable to high permittivity films for high density dynamic random access memories, whose Pr and εr are 5 μC/cm2 and 350, respectively, and leakage current density is low as 1×10−7 A/cm2 at a electric field of 100 kV/cm. In this paper, we also discuss the characteristics of Sr-modified PbTiO3 thin films.

This paper presents the process and experimental results for the improved silicon-to-glass bonding using silicon direct bonding (SDB) followed by anodic bonding. The initial bonding between glass and silicon was caused by the hydrophilic surfaces of silicon-glass ensemble using SDB method. Then the initially bonded specimen had to be strongly bonded by anodic bonding process. The effects of the bonding process parameters on the interface energy were investigated as functions of the bonding temperature and voltage. We found that the specimen which was bonded using SDB process followed by anodic bonding process had higher interface energy than one using anodic bonding process only. The main factor contributing to the higher interface energy in the glass-to-silicon assemble bonded by SDB followed by anodic bonding was investigated by secondary ion mass spectroscopy analysis.

We have studied the optimum conditions of the deposition of NiCr-bottom electrode for preparing the ferroelectric PZT(50/50) thin film capacitor. The NiCr(80/20) layer of about 300nm in thickness was deposited on bare Si(111) wafer by rf magnetron sputtering. The surface morphology and crystallinity were investigated by using Atomic force microscope (AFM) and X-ray diffractormeter (XRD). It is found that the size and crystallinity of grains of NiCr or Ni-silicide depend mainly on the rf power. The PZT(50/50) thin films were prepared on NiCr/Si substates by spin-casting of PZT coating sol and then annealing at 520°C in air for crystallization. The undesirable Pb-silicate is found to be grown during post-annealing in case that substrates having NiCr layer deposited by high power above 80 W are used. We suggest that the formation of Pb-silicate is due to the thermal diffusion of Pb or PbO through crystalline NiCr-grain boundaries. The ferroelectric PZT thin films having the perovskite structure can be obtained by using the NiCr-bottom electrodes whose morphologies are in the amorphous-crystalline boundaries, in which the surface roughness and grain size of NiCr layer is minimum. The values of the dielectric constant, εn, were measured in the range 300˜500, the remanent polarization, Pr, in the range 10˜13 C/cm2 and the coercive field, Ec, around 160 kV/cm, depending on the deposition conditions of NiCr layers.

We have investigated the changes in the temperature dependence of the dc conductivity and the optical gap with nitrogen content in amorphous carbon nitride (a-C:N) films, in order to find the effect of nitrogen doping on the electrical and optical properties of amorphous carbon films. Specimens were deposited onto borosilicate glass substrates by the rf magnetron sputtering method using Ar and N2 as a sputtering gas and a reactive one, respectively. The values of the activation energy of the dc conductivity, Ea, of these films are 0.3∼0.8 eV and those of the optical gap, Eg, are 0.8∼ 1.4 eV. Both values decrease with increasing nitrogen content, which is due to the increase of the concentration or average size of sp islands segregated into the sp matrix by nitrogen doping. From the investigation of the behavior of both Ea and Eg in accordance with the nitrogen content, we discuss the three subsequent shifts of band edge and Fermi level, accompanied with the subsequent changes of microstructure in a-CN films by nitrogen doping.

We have prepared Pb(Zr0.35Ti0.65)O3 (PZT) films on various transparent conductive oxides (TCO), such as Sn-doped In2O3 (ITO), Zn-doped In2O3 (IZO), and Ga-doped ZnO (GZO), in order to investigate the feasibility of transparent thin-film transistors (TTFTs) using a ferroelectric PZT insulator in the bottom-gated TFTs. GZO films deposited at a substrate temperature of 250 ◦C show high crystalline properties while ITO and IZO films have low crystalline and amorphous natures, respectively. Vacuum annealing of the TCO films followed by rapid annealing of the PZT films is performed in order to diminish the interface states between PZT and TCO. Optimized-PZT films with device-worth qualities of P-E hysteresis characteristics and leakage current behaviors are believed to be suitable for ferroelectric gate insulators in transparent TFTs.