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The importance of interface and bulk transport mechanism on the leakage current of high dielectric constant thin films capacitors is examined by deriving an equation for the J-V(sub A) characteristic of a capacitor that includes the transport mechanisms of thermionic emission (TE), thermionic field emission, (TFE), and carrier drift-diffusion (DD). Implications of these results on existing transport calculations for high dielectric constant thin films capacitors are discussed.

The interaction of water and carbon dioxide with nanostructured epitaxial (Ba,Sr)TiO3(001) thin film and bulk single crystal SrTiO3(001) surfaces was studied using x-ray photoemission spectroscopy (XPS), thermal desorption spectroscopy (TDS), and density functional theory (DFT). On both surfaces, XPS and TDS indicate D2O and CO2 chemisorb at room temperature with broad thermal desorption peaks (423–723 K) and a peak desorption temperature near 573 K. A comparison of thermal desorption Redhead activation energies to adsorption energies calculated using DFT indicates that defect surface sites are important for the observed strong adsorbate-surface reactivity. Numerical calculations of the competetive adsorption/desorption equilibria for H2O and CO2 on SrTiO3(001) surfaces show that for typical atmospheric concentrations of 0.038% carbon dioxide and 0.247% water vapor the surfaces are covered to a large extent with both adsorbates. The high desorption temperature indicates that these adsorbates have the potential to impact measurements of the electronic structure of BaTiO3–SrTiO3(001) surfaces exposed to air, or prepared in high vacuum deposition systems, as well as the electrical properties of thin film ATiO3-based devices. [ABSTRACT FROM AUTHOR]

J–V–T characteristics, measured over a very wide temperature (50–441 K) range, are analyzed simultaneously with C–V measurements to investigate conduction mechanisms and the state of charge of Pt/BaxSr1-xTi1+yO3+z(BST)/Pt thin-film capacitors during an applied voltage or current stress. A time- and voltage-dependent state of charge of the Pt/BST/Pt capacitors is inferred from stress-induced voltage shifts in the C–V curves. The voltage and temperature dependence of the C–V curve shifts is shown to be consistent with a voltage-dependent charge in interface states resulting from a change in potential across interfacial dipole layers. An intimate contact Schottky barrier model incorporating a voltage-dependent charge in interface states at both cathode and anode contacts is used to investigate conduction mechanisms in Pt/BST/Pt thin-film capacitors. The basic transport mechanisms of drift-diffusion, thermionic field emission, and Fowler–Nordeim tunneling are shown to dominate leakage in limiting voltage and temperature regimes. Thermionic emission is not predicted to control current flow at any investigated voltage and temperature. [ABSTRACT FROM AUTHOR]

The leakage current density-applied field (J-E[sub A]) characteristics of (Ba[sub x]Sr[sub 1-x])Ti[sub 1+y]O[sub 3+z] (BSTO) thin film capacitors with Pt electrodes that have been annealed in forming gas (95% Ar 5% H[sub 2] or D[sub 2]) were investigated over the temperature range from -60 to +60 °C. Forming gas annealing significantly increased the leakage current density. The J-E[sub A] characteristics exhibited features that could not be fully explained by either a simple thermionic emission or tunneling (Fowler-Nordeim) formalism. Using the general charge transport theory of Murphy and Good, we show that the J-E[sub A] characteristics can be successfully interpreted in terms of tunneling of electrons through the interfacial Schottky barrier with the peak in energy distribution of the incident carriers strongly dependent on applied field. At high applied fields the energy distribution of incident carriers is peaked near the Fermi level in the electron injecting metal electrode at all temperatures considered in this study, leading to almost temperature independent J-E[sub A] characteristics. At lower applied fields the peak in energy distribution shifts towards the conduction band edge where thermally assisted tunneling occurs and a more pronounced temperature dependence of the current density is observed. Good agreement between experiment and theory is demonstrated for a reasonable parameter set for BSTO thin films strongly suggesting that the high leakage current density often observed after forming gas annealing results from tunneling of electrons through the interfacial Schottky barrier. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The interface formation between the perovskite oxides SrTiO3 and BiFeO3 was studied using in situ photoelectron spectroscopy by depositing BiFeO3 on SrTiO3 and vice versa via pulsed laser deposition. For the interfaces characterized, a type II band alignment with a valence band offset of 0.9-1.0 eV and a conduction band offset of 0.5-0.6 eV was observed. Within the margin of error the commutativity was fulfilled for the SrTiO3/BiFeO3 interface, meaning that the band alignment does not depend on the deposition sequence. [ABSTRACT FROM AUTHOR]

The interface formation between SrTiO3 and SrZrO3 has been studied using in situ photoelectron spectroscopy. Epitaxial SrZrO3 thin films were grown on (0 0 1)-oriented SrTiO3 : Nb single crystals via pulsed-laser deposition. The epitaxial SrZrO3 growth was verified via x-ray diffraction and Cs-corrected high angle annular dark field scanning transmission electron microscopy. A type I straddling configuration has been found for the interface analysed with a valence band and conduction band offset of 0.5 eV and 1.9 eV, respectively. [ABSTRACT FROM AUTHOR]

Above room temperature electronic transport properties of SrxTiyO3-δ films with cation A/B = (La + Sr/Nb + Ti) ratios of 0.9 to 1.2 are compared to STO single crystals with combined Hall carrier densities of 3 × 1016 cm-3 ≤ nH ≤ 1022 cm-3. In contrast to Hall mobility which is single crystal-like (μH ≈ 6 cm2/Vs) only near A/B = 1, the Seebeck coefficient (S) is single crystal-like over a range of nonstoichiometry. For nH < 1020 cm-3, S is well described by nondegenerate band-like transport with a constant effective mass m*/mo ≈ 5-8. For nH > 1021 cm-3, S is metallic-like with m*/mo ∼ 8. No marked increase in m* with decreasing nH owing to a carrier filling dependence is observed. [ABSTRACT FROM AUTHOR]

The frequency dispersion of the dielectric constant of yttrium (Y)-doped (Ba,Sr)TiO3 thin films (Y-BST) in the high-frequency domain (10 kHz–67 GHz) was investigated. In order to remove the substantial parasitic capacitances, inductances, and resistances from the measured impedance data, test samples, short-circuit standard, and open-circuit standard structures were fabricated and their frequency response was measured. Before removing parasitic components, the measured dielectric response showed a rolloff at approximately 4 GHz. However, after circuit calibration, the dielectric constant was almost constant up to 40 GHz where another rolloff was observed. However, this rolloff was due to the uncompensated small parasitic components. Therefore, the dielectric constant of the Y-BST films (170 with a film thickness of 30 nm) showed small frequency dispersion corresponding to the Curie–von Schweidler dispersion, of which the exponent is -0.0131, up to 40 GHz. Furthermore, the decrease of the capacitance was 17% in the frequency range from 10 kHz to 40 GHz. [ABSTRACT FROM AUTHOR]

We have investigated the influence of H[SUB2]O vapor on the leakage characteristics of Pb(Zr, Ti)O[SUB3] (PZT) thin-film capacitors with Pt and IrO[SUB2] top electrodes by conducting electrical measurements ex situ in air and in situ in an 80% N2/20% O[SUB2] atmosphere with controlled humidity ranging from <0.1% to 95.5% relative humidity at 20°C. The results show that the leakage characteristics of PZT thin-film capacitors are strongly sensitive to H[SUB2]O vapor in the atmosphere. The onset to H[SUB2]O-induced leakage degradation depended on the relative humidity and on the quantity of charge passed through the capacitor. A degradation mechanism based on the electrolysis of H[SUB2]O that has adsorbed on the capacitor from the atmosphere and the role of the electrode material in the degradation process are discussed. [ABSTRACT FROM AUTHOR]

A correction to the article "A study of current transport in (BaxSr1-x)Ti1+yO3+z thin-film capacitors containing a voltage-dependent interface state charge distribution," published in the 2005 issue of the "Journal of Applied Physics".

Presents corrections to the typographical errors in the article "Hydrogen induced tunnel emission in Pt/ (Ba[sub x]Sr[sub 1-x]) Ti [sub 1+y] O[sub 3+z]/Pt thin film capacitors" published in the December 2003 issue in the "Journal of Applied Physics."

The dielectric relaxation of Ba[sub 0.7]Sr[sub 0.3]TiO[sub 3] thin films was investigated up to K band (20 GHz) using time domain and frequency domain measurements. Our results show that from 1 mHz to 20 GHz, the dielectric relaxation of the complex capacitance of Ba[sub 0.7]Sr[sub 0.3]TiO[sub 3] thin films can be understood in terms of a power law dependence known as the Curie–von Schweidler law. The small dispersion (less than 7% decrease in capacitance from 1 mHz to 20 GHz) and low loss (loss angle less than 0.006 at 20 GHz) measured in Ba[sub 0.7]Sr[sub 0.3]TiO[sub 3] thin films indicate that these films are applicable to device application up to at least K band. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have investigated the effects of Mn impurities on Ba[sub 0.7]Sr[sub 0.3]TiO[sub 3] thin films using x-ray photoemission spectroscopy. Mn acts as an electron acceptor, compensating for the charge density found in nominally undoped films. This causes a greatly increased depletion width in acceptor-doped films. We also present evidence that acceptor-doped films have an increased barrier to thermionic emission of electrons from Pt contacts into the dielectric. This may explain the decrease in leakage current observed in some acceptor-doped titanates. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]