Search

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]

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 report on the influence of Mg acceptor doping on the markedly reduced leakage current characteristics (<5×10-8 A/cm2 at 2 MV/cm) of Ba0.6Sr0.4TiO3 thin films. The suitability of room temperature deposited Mg-doped Ba0.6Sr0.4TiO3 films as gate insulators for low-voltage ZnO thin-film transistors (TFTs) (<6 V) was investigated. All room temperature processed ZnO-TFTs on plastic substrates exhibited a high field-effect mobility of 16.3 cm2/V s and a current on/off ratio of 6.4×104. The threshold voltage and subthreshold swing were 2.8 V and 400 mV/decade, respectively. [ABSTRACT FROM AUTHOR]

The authors report on the role of MgO capping layers in notably reducing leakage currents and improving mobility in ZnO thin film transistors (TFTs) utilizing compatible high-k Bi1.5Zn1.0Nb1.5O7 (BZN) gate insulators. All room temperature processed ZnO based TFTs with stacked MgO/BZN gate insulator exhibited a much enhanced field effect mobility of 5.4 cm2/V s with excellent saturation characteristics as compared to that (μFE=1.13 cm2/V s) of ZnO based TFTs with BZN gate insulator. This work demonstrates the suitability of MgO/BZN stacked gate insulators in the fabrication of low voltage ZnO based TFTs on plastic substrates. [ABSTRACT FROM AUTHOR]

Employing high-tunability PbO–ZnO–Nb2O5 thin film dielectrics, low-voltage and high-tunability interdigital capacitors (IDCs) were implemented on a silicon substrate. In order to reduce the bias voltage of the IDC and increase its tunability, its electrodes were fully embedded into the thin film dielectrics to confine fringing electric fields within them. At 4 V, the tunability of the IDCs was analyzed in terms of the electrode width and spacing by measuring reflection coefficients at 1 GHz. The fabricated IDC with width and spacing of 1.5 and 1.8 μm, respectively, achieved tunability of 26% and a Q factor of 10 at 5.5 V. [ABSTRACT FROM AUTHOR]