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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]

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.

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 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]

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]