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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]

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 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]

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: 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: 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: 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]