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Deals with a study on the electrical properties of (barium (Ba),strontium (Sr))titanium oxide thin films deposited on (Ba,Sr)ruthenium oxide electrodes to demonstrate the advantageous use of tailored electrodes. Effect of structural similarity and chemical compatibility on the dielectric behavior of the films; Experimental procedure; Results and discussion; Conclusion.

Aluminum oxide (Al2O3) and titanium dioxide (TiO2) films deposited on flexible polyethersulfone substrates by plasma-enhanced atomic layer deposition have been investigated for transparent barrier applications. The effects of the induced plasma power on the passivation properties were investigated as function of film thickness and substrate temperature. The optimum plasma power and substrate temperature were investigated through measurements of the refractive index and packing density of the Al2O3 and TiO2 films. In this research, three different barrier structures were investigated for the purpose of improving water vapor barrier characteristics. A low water vapor transmission rate of approximately 5×10−3 g/m2·day or below was achieved with two pairs of Al2O3/TiO2 stacks with a total stack thickness of 40nm deposited at 80°C. The passivation performance of the multilayer film was investigated using an organic light-emitting diode. The coated device lifetime was 267h, which was 41 times longer than that of an uncoated sample. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the mobility enhancement in an Amorphous Oxide Semiconductor Thin Film Transistor (AOS TFT), particularly the effect of enhanced-mobility current path was investigated. In the TFT structure, the a-IGZO single active channel layer was replaced by double layers. Indium Tin Oxide (ITO) was employed as an enhanced-mobility current path material and was embedded in an amorphous Indium Gallium Zinc Oxide (a-IGZO) channel layer of a conventional bottom gate structure TFT. To analyze the effect of the length of an additional current path, the a-IGZO channel length was fixed at 80μm, and the length of the ITO enhanced-mobility current path was increased to 20, 40, and 60μm. As a result, the mobility increased monotonically with the length of the enhanced-mobility current path and was predictable from the rule of mixture. The maximum saturation mobility of 28.3cm2/Vs resulted when the length of the enhanced-mobility current path was 60μm. This value is more than double that of a single path TFT. Such enhancement in mobility is attributed to the high conductivity of ITO and a good conduction band match between a-IGZO and ITO. [Copyright &y& Elsevier]

Abstract: Rutile and anatase TiO2 nano particles with Ni doping were synthesized by mechanical alloying, and were characterized by XRD, TEM, UV-DRS and photoluminescence (PL) spectra. The relationships between crystal type and photocatalytic activity as well as the mechanisms of transition metal doping on TiO2 lattice were studied. The results showed that the rutile type TiO2 with Ni led to higher photocatalytic activities. [Copyright &y& Elsevier]

CO2 cluster ions are irradiated at the acceleration voltage of 25 kV to remove hillocks on indium tin oxide (ITO) surfaces and thus to attain highly smooth surfaces. CO2 monomer ions are also bombarded on the ITO surfaces at the same acceleration voltage to compare sputtering phenomena. From the atomic force microscope results, the irradiation of monomer ions makes the hillocks sharper and the surfaces rougher from 1.31 to 1.6 nm in roughness. On the other hand, the irradiation of CO2 cluster ions reduces the height of hillocks and planarize the ITO surfaces as smooth as 0.92 nm in roughness. This discrepancy could be explained by large lateral sputtering yield of the cluster ions and re-deposition of sputtered particles by the impact of the cluster ions on surfaces. [Copyright &y& Elsevier]

The dependence of surface smoothing and sputtering phenomena of Si (1 0 0) solid surfaces irradiated by CO2 cluster ions on cluster-ion dosage was investigated using an atomic force microscope. The flux and total ion dosage of impinging cluster ions at the acceleration voltage of 50 kV were fixed at 109 ions/cm2 s and were scanned from 5×1010 to 5×1013 ions/cm2, respectively. The density of hillocks induced by cluster ion impact was gradually increased with the dosage up to 5×1011 ions/cm2, which caused that the irradiated surface became rough from 0.4 to 1.24 nm in root-mean-square roughness (σrms). At the boundary of the ion dosage of 1012 ions/cm2, the density of the induced hillocks was decreased and σrms was about 1.21 nm, not being deteriorated further. At the dosage of 5×1013 ions/cm2, the induced hillocks completely disappeared and the surface became very flat as much as σrms=0.7 nm. In addition, the irradiated region was sputtered as deep as 5.4 nm. From the experiment of isolated cluster ion impact on the Si surfaces, it was observed that the induced hillocks nm high had the surfaces embossed at the lower ion dosages. The surface roughness was slightly increased with the hillock density and the ion dosage. At higher than a critical ion dosage, the induced hillocks were sputtered and the sputtered particles migrated from the side of the hillocks to the valleys among the hillocks in order to fill. After prolonged irradiation of cluster ions, it was observed that the irradiated region was very flat and etched. A simple phenomenological model in terms of dosage-dependent sequential surface embossment, sputtering, smoothing and etching processes was suggested to explain these cluster-ion impact interactions with the Si surfaces at various dosages. [Copyright &y& Elsevier]

Crystallization behavior of amorphous silicon (a-Si) using the field aided lateral crystallization (FALC) process was investigated. The lateral crystallization of a-Si was remarkably enhanced at the negative electrode side with the aid of an electric field, while it was retarded at the positive electrode side. FALC velocity using Ni was as high as 11 μm/h at 500 °C with an electric field of 4 V/cm. In addition, the nickel silicide phase, known to be a mediator for low temperature crystallization, can be driven from either the drain to source or source to drain in the active layer, depending on the bias conditions during crystallization. Thus, the defects originating from residual nickel silicide can be driven out from the channel region. Due to such an asymmetric location of the residual nickel silicide, the leakage current of the polycrystalline silicon thin film transistor (poly-Si TFT) using the FALC process showed a leakage current of approximately one order of magnitude lower when we reversed the probing polarity. Therefore, it was judged that the judicious selection of the bias condition during the FALC process can be useful in improving the electrical properties of poly-Si TFT. [Copyright &y& Elsevier]

The authors investigated the field emission from vertically well-aligned zinc oxide (ZnO) nanoneedles grown on the Au/Ti/n-Si (100) substrate using metal organic chemical vapor deposition. The turn-on field of ZnO nanoneedles was about 0.85 V/μm at the current density of 0.1 μA/cm2, and the emission current density of 1 mA/cm2 was achieved at the applied electric field of 5.0 V/μm. The low turn-on field of the ZnO nanoneedles was attributed to very sharp tip morphology, and the high emission current density was mainly caused by the formation of the stable Ohmic contact between the ZnO nanoneedles and Au film. [ABSTRACT FROM AUTHOR]

In recent years, many researchers have attempted to improve the bias stability of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). In this study, the hydrogen cyanide (HCN) treatment was carried out to improve the positive bias stability of bottom-gate a-IGZO TFTs. The HCN treatment was performed using a 0.1 M HCN solution with a pH of 10 at room temperature. Before applying the positive bias stress, there were no differences in the major electrical properties, including the saturation mobility ( μ sat ), threshold voltage (V th ), and subthreshold swing (S/S), between HCN-treated and non-HCN-treated devices. However, after applying the positive bias stress, the HCN-treated device showed superior bias stability compared to the non-HCN-treated device. This difference is associated with the passivation of the defect states and the surface of the back-channel layer of the HCN-treated device by cyanide ions. [ABSTRACT FROM AUTHOR]

In this investigation, the carrier concentration gradient between channel and contact region is achieved to improve the Thin film Transistors (TFT) performance by employing annealing at 350 °C in forming gas (N 2 + 5% H 2 ). The contact region is covered with Mo metal and the channel region is only exposed to forming gas to facilitate the diffusion controlled reaction. The TFT using a-IGZO active layer is fabricated in ambient of Ar:O 2 in ratio 60:40 and the conductivity of the order of 10 −3 S/cm is measured for as-deposited sample. The electrical conductivity of an annealed sample is of the order of 10 2 S/cm. The device performance is determined by measuring merit factors of TFT. The saturation mobility of magnitude 18.5 cm 2 V −1 s −1 has been determined for W/L (20/10) device at 15 V drain bias. The extrapolated field effect mobility for a device with channel width (W) 10 μm is 19.3 cm 2 V −1 s −1 . The on/off current ratio is 10 9 and threshold voltage is in the range between 2 and 3 V. The role of annealing on the electronic property of a-IGZO is carried out using X-ray photoelectron spectroscopy (XPS). The valance band cut-off has been approximately shifted to higher binding energy by 1 eV relative to as-deposited sample. [ABSTRACT FROM AUTHOR]

Abstract: We have developed transparent organic light-emitting devices (TOLEDs) with CsCl capping layers deposited on top of semitransparent Ca/Ag cathodes. The CsCl layer was deposited by the thermal evaporation method which does not result in any damage to the underlying organic layers. The transmittance was enhanced by depositing the CsCl layer on the Ca/Ag cathode. The current efficiency measured at the cathode side increased by the enhanced transmittance of the cathode, whereas the anode-side current efficiency was determined by the reflectance of the cathode. In a TOLED with semitransparent Ca/Ag/CsCl layer, the microcavity effect was not profound so that the electroluminescence spectrum was not seriously changed by the CsCl capping layer. [Copyright &y& Elsevier]

We introduce a transparent diode that consists of a coupled junction of amorphous indium tin zinc oxide and Al2O3. In addition, the photo-sensing behavior under visible light was investigated. In the initial dark state, the diode exhibited maximum on current density of 10 A/cm2 and off current density of 10−9 A/cm2–10−10 A/cm2. Because of the extremely low off current level, it exhibited an excellent on/off ratio of 1010–1011. The light sensibility of the diode started from as low as 250 lux, and the off current density increased about three orders of magnitude under the exposure of 3000 lux. Such an off current density increase turned out to be mainly due to the short wavelength (400 nm) visible light, which has enough energy to generate photo-electrons from the valence band or deep level trap site to the conduction band. Meanwhile, a square pulse type dynamic light sensing test resulted in residual current at the dark state. The residual current was electrically removed by applying a forward bias, and the identical light sensing reproducibility was confirmed by repetitive trials. [ABSTRACT FROM AUTHOR]

We studied hydrogen (H) behavior in amorphous In-Ga-Zn-O (a-IGZO) films under X-ray irradiation by evaluating the threshold voltage (VTH) shift in a-IGZO thin film transistors (TFTs) with different H concentrations in the active layers. We fabricated three types of a-IGZO TFTs: (i) one without a buffer layer and postannealed in N2, (ii) one with a H-resolved buffer layer and postannealed in N2, and (iii) one with a H-resolved buffer layer and postannealed in a mixture of N2 and H2. All three TFTs showed a negative VTH shift after 100 Gy of X-ray exposure. The degree of VTH shift correlated with an increase in conductivity, which, in turn, corresponds to the H concentration in the active layer of the as-fabricated TFTs. Based on spectroscopic ellipsometry analysis, we confirmed a large increase in the donorlike H related D1 state after X-ray irradiation in high-H concentration a-IGZO films. In addition, an increase in the number of H2 molecules in a-IGZO films after X-ray irradiation was observed via thermal desorption spectroscopy analysis. Therefore, we conclude that the increase in conductivity and/or the resulting negative VTH shift in a-IGZO TFTs during X-ray irradiation can be attributed not only to the state transition from acceptorlike to donorlike H in the as-prepared a-IGZO but also to the incorporation of additional H radicals generated by X-ray irradiation. [ABSTRACT FROM AUTHOR]

1% Ni-doped barium strontium titanate (BST) thin film deposited at room temperature reveals the significantly enhanced leakage current performance which is extraordinarily effective for low temperature applications. Significant leakage current suppression of >2 orders was achieved for electric fields from 0.25 to 2 MV/cm in Pt/Ni-doped BST/Pt metal-insulator-metal (MIM) capacitor cells compared to undoped BST. For Ni doping at the 1% level, the spectral dependence of (i) the imaginary part of the complex dielectric constant, [variant_greek_epsilon]2, obtained from the rotating compensator enhanced spectroscopic ellipsometry and (ii) OK1 absorption spectra obtained from synchrotron x-ray absorption spectroscopy shows significant differences (0.26±0.15 eV) in the conduction band edge trap depth relative to undoped BST. The valence band (VB) edge x-ray photoelectron spectroscopy analysis reveals the Fermi energy level downshift of 0.4 eV for Ni-doped BST toward the VB edge. There is a direct correlation between these changes in band edge states of BST thin films with Ni doping and the improved electrical performance in MIM capacitors led by the qualitatively different charge injection mechanism. The proposed transition metal doping process and analysis approach provide a pathway for charge injection control driven by band edge state changes in other perovskite oxides for low temperature (i.e., room temperature) applications. [ABSTRACT FROM AUTHOR]

Degradation of (Ba,Sr)TiO[sub 3] during a forming gas anneal was examined and the effect of a SiO[sub 2] capped (Ba,Sr)RuO[sub 3] electrode was studied. All the samples were prepared by a rf magnetron sputtering technique and the forming gas (10% H[sub 2]+90% N[sub 2]) anneal was carried out at 400 °C for 30 min. The (Ba,Sr)RuO[sub 3] film directly exposed to H[sub 2] ambient was damaged severely, which resulted in the reduction and phase separation into BaO and Ru. On the other hand, the SiO[sub 2] capped (Ba,Sr)RuO[sub 3] film was not damaged during H[sub 2] annealing. By adopting the SiO[sub 2] capped (Ba,Sr)RuO[sub 3] as an electrode of (Ba,Sr)TiO[sub 3], the degradation of (Ba,Sr)TiO[sub 3] could be inhibited. SiO[sub 2] capping also decreased the extent of the reduction of a Pt/(Ba,Sr)TiO[sub 3]/Pt structured capacitor, which is known to degrade dramatically. It is believed that the major cause of the tolerance to the forming gas anneal is the blocking capability of SiO[sub 2] against the diffusion of reaction products such as H[sub 2]O. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The (Ba,Sr)RuO[sub 3] (BSR) oxide electrode which can enhance electrical properties of (Ba,Sr)TiO[sub 3] (BST) dielectric film due to structural and chemical matches with BST, was evaluated as an oxygen diffusion barrier. It was possible to restrain the oxidation of TiN layer under BSR to TiO[sub 2] by sequential depositions of amorphous BSR and crystalline BSR, in which the amorphous BSR eventually crystallized into crystalline BSR during the deposition of crystalline BSR. When two-step BSR layers on TiN, however, were annealed in oxygen ambient at 700 °C, oxygen atoms diffused and oxidized TiN layer to TiO[sub 2]. On the other hand, oxygen could be effectively blocked by the BSR/Ru bilayer. In this system, the Ru sublayer plays a role as an oxygen getter and the bilayer tends to block oxygen diffusion. The blocking effect was more obvious when the thickness of BSR in the bilayer increased. The BST/bilayer showed higher dielectric constant due to the suppression of formation of a low dielectric layer between BST and the bilayer. Although the BST/bilayer showed a slightly higher leakage current density, it was possible to reduce the leakage current density to 10[sup -8] order A/cm² at 1 V by increasing the BSR thickness in the bilayer. [ABSTRACT FROM AUTHOR]

Perovskite type conducting materials (Ca, Sr)RuO[sub 3] and (Ba, Sr)RuO[sub 3] were prepared by rf magnetron sputtering as bottom electrodes for (Ba, Sr)TiO[sub 3] thin film capacitors. The crystallinity, interface property, and electrical properties of the (Ba, Sr)TiO[sub 3] capacitor applying the perovskite oxide electrodes were investigated. The interface between the dielectric and the electrode were analyzed by high-resolution electron microscopy and Auger electron spectroscopy. The interface had a marked effect on the electrical properties of the (Ba, Sr)TiO[sub 3] thin films. Dielectric constant for the (Ba, Sr)TiO[sub 3] had considerable dependence on the thickness of interfacial layer. The leakage current density of the capacitor was sensitive not only to the structural match but also to the chemical match between (Ba, Sr)TiO[sub 3] and the electrode. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Self-aligned coplanar top gate indium–gallium–zinc-oxide thin-film transistors (TFTs), with source/drain (S/D) regions that were heavily doped by various deep-ultraviolet (DUV) irradiation energies at dual wavelengths of 185 and 254 nm, were investigated. The electrical performances of TFTs improved as the DUV irradiation energy increased. The proposed TFTs, with DUV irradiation of 20 J/cm2, have a field-effect mobility of 22.0 cm2/ \text V\cdot \text s , a threshold voltage of 2.2 V, a subthreshold swing value of 0.24 V/decade, and an on/off current ratio of 1.34 \times 10^6 . In addition, the channel length modulation ( \Delta L ) and the width-normalized contact resistance ( R_{\mathrm {SD}}W ) were 1.04 \mu \text{m} and 60.5 \Omega \cdot \text cm , respectively. Such short \Delta L and low R\mathrm {\mathbf {SD}}W values indicate that the S/D regions were properly formed by the DUV irradiation. This simple and cost-effective doping technique can be useful for the fabrication of self-aligned TFTs. [ABSTRACT FROM PUBLISHER]

In the current study, dual-active layer amorphous indium-gallium-zinc-oxide (a-IGZO) TFT has been fabricated by sequential deposition of oxygen-rich layer on a top of oxygen-poor layer in the active layer through oxygen partial pressure control in order to improve reliability under negative bias illumination stress (NBIS) condition. The method is very simple as it is performed in situ without any post treatment. Reliability of a TFT that had a thickness of oxygen-poor layer and oxygen-rich active layer in the ratio of 6:4, quite improved with the threshold voltage shift Δ of a-IGZO TFT at around 3.2 V under NBIS condition of 1000 s in comparison with a TFT (8.5 V) that comprised only oxygen-poor active layer. The increased reliability is attributed to decrease interaction with ambient and the reduction in the total neutral oxygen vacancy concentration due to the oxygen rich layer at the back-channel region, which was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. [ABSTRACT FROM AUTHOR]

In our previous studies, vanadium (V)-based self-formed barriers were found at the interface between Cu–V alloy films and low-k/Si substrates after annealing at elevated temperatures. In the present work, the diffusion barrier properties of the V-based self-formed interlayer on low-k dielectrics were investigated with and without UV curing treatment. A V-based interlayer on a low-k substrate with UV curing exhibited lower electrical resistivity and higher thermal stability than on a low-k substrate without UV curing. Transmission electron microscopy (TEM) images and energy-dispersive X-ray spectroscopy (EDS) showed that an approximately 4-nm V-based interlayer was found only on the low-k substrates with UV curing after annealing at 300 °C for 1 h. Based on these results, UV curing may play an important role in the formation of a V-based interlayer due to changes in the chemical composition and porosity of the dielectric layer. [ABSTRACT FROM AUTHOR]

Hf–Sn–Zn–O (HTZO) thin films were prepared on SiO 2 /SiN x substrates at room temperature by the direct current (DC) magnetron sputtering of Hf-doped Sn–Zn–O targets. The characteristics of films with different amounts of Hf were analyzed. Amorphous HTZO films were obtained by increasing the Hf content, while polycrystalline films have not shown with Hf doping. With the proper Hf concentration in the HTZO films (∼2.0 atomic % Hf/(Hf + Sn + Zn + O)), HTZO films demonstrated good performance as an oxide semiconductor channel material in thin film transistors (TFTs) with a field effect mobility (μ FE ) of 10.9 cm 2 V −1 s −1 , an on/off current ratio of 10 9 , and a subthreshold voltage swing of 0.71 V/decade. [ABSTRACT FROM AUTHOR]

As an alternative to indium–tin oxide (ITO), MTO/Ag/MTO (MAM) multilayer transparent electrodes with a nano-sized Ag thin film embedded between Mn-doped tin oxide (MTO) layers were prepared. The MTO/Ag/MTO thin films were deposited on a glass substrate by RF sputtering at room temperature to evaluate their characteristics as transparent electrodes for organic photovoltaic cells (OPVs). Optical and electrical properties of the single layer MTO were investigated at various working pressures and oxygen partial pressures. Based on the optimal condition, the MTO/Ag/MTO multilayer electrode showed a sheet resistance of 10.1–10.6 Ω/sq and transmittance of 80.1–85.4% in the visible range ( λ =380–780 nm). Their values are compatible with commercial indium–tin oxide (ITO). Conventional-type bulk hetero-junction organic photovoltaic cells (BHJ-OPVs) using the MTO/Ag/MTO multilayer electrode show an open circuit voltage ( V OC ) of 0.62 V, a short circuit current ( J SC ) of 7.12 mA/cm 2 , a fill factor (FF) of 0.62, and a power conversion efficiency (PCE) of 2.73%. This PCE is comparable with a commercial ITO electrode (3.17%). This suggests that the MTO/Ag/MTO multilayer electrode is a new promising transparent conducting electrode for BHJ-OPVs. [ABSTRACT FROM AUTHOR]

Highlights: [•] We investigated current hysteresis mechanism in Pt/a-IGZO/TaO x /W structure that shows rectifying characteristics. [•] In order to understand the role of each layer and the origin of memory effect, we designed and performed two model experiments on the basis of preliminary experimental results and analysis. [•] Current hysteresis (memory effect) is attributed to the bias dependent resistance change in TaO x layer due to positively charged oxygen vacancy exchange between two oxides. [ABSTRACT FROM AUTHOR]

Abstract: A non-volatile nanocrystal floating gate MOS capacitor with multi-level function is achieved by engineering the electric field within the tunneling oxide via a stepped control oxide. A MOS capacitor containing Au nanocrystals in a stepped HfO2 and SiO2 tunneling oxide matrix was fabricated in order to demonstrate this concept. The flatband voltage shift, measured from the C–V hysteresis curves, exhibited a saturated region within a programming mode that is not observed in the conventional step free MOS capacitor. The values of the flatband voltage shift measured at the first and second saturation were slightly higher than the values predicted from the Coulomb blockade theory. However, there is a strong consensus with the flatband voltage ratios between experimental results and the predicted values, which supports successful operation. More obvious evidence of multi-level storage function was confirmed by turnaround voltage measurement. [Copyright &y& Elsevier]

Abstract: The measurements of the photoluminescence (PL) spectra have been performed on GaAs, GaMnAs, GaAs:Be, and GaMnAs:Be samples to study the effect of Be codoping on the PL spectra of GaMnAs layers grown via low temperature molecular beam epitaxy. Based on the temperature dependence of the exciton-related transitions energy, it was shown that doping GaAs with Mn and Be leads to modification of the temperature dependence of the band gap. It was shown that although Be itself weakly affected the PL spectra of GaAs, codoping with Be significantly modified the PL spectra of GaMnAs. [Copyright &y& Elsevier]

Abstract: In this work, Y2O3 was evaluated as a gate insulator for thin film transistors fabricated using an amorphous InGaZnO4 (a-IGZO) active layer. The properties of Y2O3 were examined as a function of various processing parameters including plasma power, chamber gas conditions, and working pressure. The leakage current density for the Y2O3 film prepared under the optimum conditions was observed to be ~3.5×10−9 A/cm2 at an electric field of 1 MV/cm. The RMS roughness of the Y2O3 film was improved from 1.6 nm to 0.8 nm by employing an ALD (Atomic Layer Deposition) HfO2 underlayer. Using the optimized Y2O3 deposition conditions, thin film transistors (TFTs) were fabricated on a glass substrate. The important TFT device parameters of the on/off current ratio, sub-threshold swing, threshold voltage, and electric field mobility were measured to be 7.0×107, 0.18 V/dec, 1.1 V, and 3.3 cm2/Vs, respectively. The stacked insulator consisting of Y2O3/HfO2 was highly effective in enhancing the device properties. [Copyright &y& Elsevier]

Abstract: Characteristics of tantalum silicon nitride (TaSiN) thin films have been investigated as an electrode material for Ge2Sb2Te5 chalcogenide phase change material. The films were deposited by co-sputtering system in which the ratio of tantalum nitride to silicon was controlled by the plasma power on each target. The TaSiN films showed tunable resistivity from 260 to 560 μΩ cm with increasing Si content. From the evaluation of PRAM cell structures consisting of the TaSiN and the Ge2Sb2Te5, we found that the SET voltages are nicely correlated with the resistivity of the TaSiN. Moreover, the sensing margin (resistance ratio: R SET/R RESET) turned out to be good for practical application. [Copyright &y& Elsevier]

Abstract: Ni doped titanate nanotubes were synthesized by hydrothermal method using Ni doped rutile TiO2 nanopowders as a starting material. The electrochemical properties were investigated by cyclic voltammmetric methods. The microstructure and morphology of the synthesized powders were characterized by XRD (X-ray diffraction), and HRTEM (high resolution transmission electron microscopy). Ni doped nanotubes were composed of H2Ti2O5·H2O with outer and inner diameter of ∼10nm and 6nm and showed a initial discharge capacity of 305mAh/g with poor cycling performance. However, after firing, the Ni doped nanotubes revealed better cycling performance due to lower reaction with hydrate and smaller diameter of the tubes. [Copyright &y& Elsevier]

Abstract: When hafnium oxide (HfO2) is directly deposited on Si by the RF sputtering method, Hf silicide is formed and post-deposition anneal (PDA) at 400°C transforms Hf silicide to Si suboxide plus Hf suboxide. The leakage current density for the 〈aluminum (Al)/HfO2/Si(100)〉 diodes without PDA is high due to the high density interface states near the Fermi level (0.86eV above the Si valence band maximum, VBM) and minute conduction channels. PDA at 400°C eliminates the interface states and the conduction channels, and improves the characteristics of the HfO2 layer, but interface states are newly formed at 0.53eV above the VBM, resulting in still high leakage current density. Silicon nitride (SiN) layers formed by Si nitridation using N2-plasma generated by the low energy electron impact method possess a high nitrogen atomic concentration ratio, N/(N+O) of 0.65. When a 1.0nm SiN layer is inserted between HfO2 and Si, interfacial reaction is completely prevented, resulting in a smaller effective oxide thickness, EOT of 1.4nm. In spite of the smaller EOT, the leakage current density is nearly the same as that with no SiN layer, possibly due to the prevention of the formation of the conduction channels. PDA at 400°C improves HfO2 characteristics without causing the interfacial reaction, leading to a decrease in the leakage current density. [Copyright &y& Elsevier]

Abstract: As a crystallization process, the field-aided lateral crystallization (FALC) technique has some outstanding advantages, such as high crystallization rate and low temperature. In this study, the electrical field was directly applied between source and drain areas of H shape patterns using the Mo–W interconnecting layer. The effects of the current density and electrical field strength on the crystallization behavior were investigated. Results show that the crystallization behaviors at different bias areas are different. The difference is attributed to the coexisting effects of electromigration and potential gradient. In addition, the dependence of the degree of crystallization on the current density was studied by Raman spectra and the microstructure crystallized by FALC was observed by a scanning electron microscope. [Copyright &y& Elsevier]

Abstract: The effect of the alternating field (AC voltage) instead of the static field (DC voltage) was investigated in the field-aided lateral crystallization process, which is one of the low temperature crystallization processes for the amorphous silicon films. Using a photolithography process, a 5-mm-wide bar-shaped photoresist (PR) pattern was formed on the a-Si. On the PR-patterned a-Si, a 2–3-nm-thick Cu catalyst layer was deposited by a DC sputtering, and then, the Cu layer on the PR pattern was lifted off. The silver electrodes were pasted at the opposite sides of the Cu-free bar pattern. Then, the patterned specimen was annealed at 500 °C in N2 ambient for 5 h with the application of various AC fields (ranging from 1 to 5 V/cm) along with a DC field of 30 V/cm. As compared with the case of a DC field of 35 V/cm only, the specimen from a mixed field of 30 V/cm DC and 5 V/cm AC resulted in 1.5 times faster crystallization rate, regardless of experimental frequency values ranging from 10 Hz to 50 MHz. Presumably, the enhancement of the crystallization rate under the combined field is associated with an increase in the flux of the crucial diffusion species, Cu atoms, which govern the overall crystallization rate due to the effect by the AC field. [Copyright &y& Elsevier]

Abstract: Effects of BaO–B2O3–SiO2 glass additive on densification and dielectric properties of BaTiO3 ceramics started from hydrothermally synthesized nano-sized BaTiO3 powders (∼60nm) were investigated. Addition of an optimal amount of the BaO–B2O3–SiO2 glass to BaTiO3 compacts accelerated densification with a limited grain growth. The sintering temperature of the BaTiO3 ceramics was lowered to 900°C with high density above 93%. Furthermore, there was no formation of secondary phases in the sintered bodies at the optimal amount of the glass. Higher dielectric constant was obtained from the BaTiO3 ceramics with 1wt% BaO–B2O3–SiO2 glass, sintered at 900°C, than those observed for the pure BaTiO3 sintered at 1350°C. [Copyright &y& Elsevier]

Abstract: The semiconductor–passivating layer interface, as well as the dielectric properties of the passivants, plays an important role in HgCdTe based photodiodes. ZnS is a commonly used surface passivant for HgCdTe. This study examined the effects of sulfidation on the HgCdTe surface and interfacial characteristics of metal/ZnS/HgCdTe structures. The ZnS layer was deposited by thermal evaporation after sulfidation. The interfacial properties of the metal insulator semiconductor (MIS) structures were determined. A comparison of an untreated capacitor and a sulfide treated MIS capacitor showed that the fixed charge density (untreated 6.37×1011, treated 3.2×1011 cm−2) and slow state density (untreated 5.5×1011, treated 7.5×1010 cm−2) were 2 and 7 times lower in the treated than in the untreated specimens. Sulfidation results in a decrease in the concentration of contaminants originating from the native oxide-covered HgCdTe substrates. This reduction may be due to the formation of S–S or II–S bonds at the surface layer. These bonds might act as barriers against native oxide formation when (NH4)2Sx-treated HgCdTe substrates are exposed to air. [Copyright &y& Elsevier]

(Ba, Sr)RuO3 oxide electrodes have been studied for high dielectric (Ba, Sr)TiO3 film in DRAM capacitors. Metal organic chemical vapor deposition (MOCVD) is used for large-scale deposition and provides better step coverage properties. In this work, methoxyethoxytetramethylheptanedionate (METHD) precursor and solvent [n-butylacetate(C6H12O2)] were mixed together into a single solution source. Post deposition annealing is carried out in oxygen atmosphere using rapid thermal annealing (RTA) to investigate the effect of organic impurities such as carbon during deposition. After annealing, resistivity of the BSR film decreased drastically compared to the as-deposited film. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis were used to describe this phenomenon accurately. The decrease in carbonate with increasing annealing time was confirmed by XRD analysis. [Copyright &y& Elsevier]

Abstract: In this investigation, an operating voltage as low as 5V has been achieved for Oxide TFT with Y2O3 as a gate oxide and a-IGZO as an active layer. The OTFT has been fabricated at room temperature using RF sputter. The mobility and threshold voltages are 11.3cm2/Vs and 3.4V for the device with W/L =0.8, respectively. The annealing at 400°C in N2 containing 5% H2 ambient has been utilized to improve the electrical performance of TFT. The on–off current which is determined by gate dielectric has been observed to be 104. It has also been observed that the dielectric properties of gate oxide deteriorate on annealing. The dielectric constant of Y2O3 is observed in the range between 5.1 and 5.4 measured on various devices. [Copyright &y& Elsevier]

Nanostructured semiconducting metal oxides and particularly nanofiber-based photoelectrodes can provide enhanced energy conversion efficiencies in dye-sensitized solar cells (DSSCs). In this study ZnO/poly(vinyl acetate) composite nanofiber mats were directly electrospun onto a glass substrate coated with F:SnO2, then hot pressed at 120 °C and calcined at 450 °C. This resulted in multiple nanofiber networks composed of a twisted structure of 200–500 nm diameter cores with ∼30 nm single grains. The DSSCs using ZnO nanofiber mats exhibited a conversion efficiency of 1.34% under 100 mW/cm2 (AM-1.5G) illumination. [ABSTRACT FROM AUTHOR]

The effects of hydrogen incorporation in the active layer of amorphous InGaZnO (a‐IGZO) thin‐film transistors (TFTs) on device characteristics and instability under positive bias stress (PBS) and positive bias temperature stress (PBTS) are studied. To control the amount of incorporated hydrogen, rapid thermal annealing (RTA) treatment is conducted on the gate insulator layer before active layer deposition. It is confirmed that the amount of residual hydrogen in the gate insulator layer decreases with increasing RTA treatment time. Device stability is examined with RTA treatment times of 1 and 3 min under PBS. The device fabricated with a shorter RTA treatment time shows relatively better stability. This result is attributed to defect passivation by hydrogen that diffuses to the active layer from the gate insulator during the post‐annealing process. Additionally, TFT shows the negative shift of Vth under a high‐temperature PBTS condition. This result is due to the additional diffusion of residual hydrogen from the gate insulator into the active layer and hydrogen‐related deep state transition in the active layer by external thermal energy and a PBS condition. [ABSTRACT FROM AUTHOR]

The dielectric relaxation of HfO2 thin films grown by atomic-layer deposition (ALD) was studied as a function of frequency from 1 kHz to 5 GHz. The dielectric relaxation of the ALD HfO2 films followed a power-law dependence known as the Curie–von Schweidler relaxation law both in the kHz and GHz ranges, and the relaxation exponents were consistent with the measured dielectric losses. The behavior of the dielectric response for the HfO2 thin films may be attributed to defect sites in the HfO2 layer and/or interface. [ABSTRACT FROM AUTHOR]

In this work, the effect of control oxide thickness on the storage characteristic of MOSCAP based on nano floating gate memory (NFGM) structure was explored in order to apply the results to a stepped NFGM. A stepped MOSCAP structure can realize multi-level storage characteristic via control of electric field strength in the tunneling oxide using a stepped control oxide. Through simulation, we have predicted that a 20 nm step height is optimal to exhibit multi-level storage behavior for a 40 nm thick HfO 2 control oxide. First, we prepared two step-free NFGM MOSCAP structures consisting of Au nanocrystals: one with 20 nm thick HfO 2 control oxide and the other with 40 nm thick HfO 2 control oxide. The C–V behavior of NFGM MOSCAP structures having different control oxide thicknesses was measured in a parallel mode in order to simulate the stepped MOSCAP structure. Finally a stepped NFGM MOSCAP stricture was fabricated. As a consequence, we successfully demonstrated multi-level storage behavior in an NFGM MOSCAP structure with 40/20 nm step-shape control oxide as simulation predicted. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the characteristics of positive bias temperature instability (PBTI) and cyclic constant voltage stress (CVS) in thin film transistors (TFTs) incorporating Ni-FALC poly-Si film were investigated under various stress conditions. In PBTI, the threshold voltage (V TH) was degraded by a vertical electric field on the gate stack, and an abrupt variation of V TH was attributed to the creation of defects in the gate oxide and the increase of the effective interface trap state. In contrast to the formation of defects, the poly-Si film was not sensitive to PBTI stress (the fluctuation in the grain boundary trap density was just 5.6%). In two-cycle CVS of devices before and after O2 plasma treatment, the direction of the V TH shift and polarity of bias showed good correlation. In particular, the O2 plasma-treated device demonstrated low Subthreshold swing (S.S) and low minimum drain current compared to the untreated one. The improvement of device performance seemed to originate from the reduction of effective interface trap sites and leakage current paths. [Copyright &y& Elsevier]