bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physical and Electrical Characterization of Hafnium Silicate Thin Films
Authors: Lysaght Patrick S. , Foran Brendan , Bersuker Gennadi , Larson Larry , Murto Robert W. , Huff Howard R. 
Published: April 2011

ABSTRACTEvaluation of physically thicker gate insulator materials with significantly higher dielectric constants (k = 10 – 25) as potential replacements for silicon dioxide, SiO2 (k = 3.9), and silicon oxynitride continues to be a focus of the semiconductor industry. The challenge is to provide a film with lower leakage current and with capacitance equivalent to < 1.0 nm SiO2 [1–4]. One such candidate material; metal-organic chemical vapor deposited (MOCVD) hafnium silicate, has been physically characterized by high resolution transmission electron microscopy (HRTEM) in plan view, as a blanket, uncapped film and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) in cross section following integration into capacitors and complementary metal oxide semiconductor (CMOS) transistors. Changes in the material microstructure associated with phase segregation and crystallization as a function of Hf silicate composition and rapid thermal anneal (RTA) temperature have been observed and a discussion of the segregation mechanisms is presented [5–8]. Also, various methods of incorporating nitrogen into bulk hafnium silicate films have been investigated and resultant transistor electrical performance data has been correlated with physical characterization for NH3 post deposition anneal (PDA) treatments at various temperatures.
Hrtem Investigation of Effect of Various Rare Earth Oxide Dopants on Epitaxial Zirconia High-K Gate Dielectrics
Authors: Kiguchi Takanori , Wakiya Naoki , Shinozaki Kazuo , Mzutani Nobuyasu 
Published: April 2011

ABSTRACTThe effects of several rare earth oxide on the capacitance-voltage (C-V) characteristics and the SiO2 interlayer growth of ZrO2 based gate dielectrics were examined. The width of the hysteresis window of La2O3 stabilized ZrO2 (LaSZ) gate dielectric was only 0.2V, on the other hands, that of Sc2O3 stabilized ZrO2 (ScSZ) gate dielectric was 1.4V HRTEM analysis indicated that the growth of SiO2 interlayer of RSZ (R=Sm,Nd,La) gate dielectric was about 1nm, which was less than half of the ScSZ one. These results indicate the advantage of the ZrO2 gate dielectric doped with rare earth oxide composed of larger ionic radius cation.
Study of poly-Si/TaSiN/Pt structure for stacked capacitors
Authors: Letendu F. , Hugon M. C. , Voldoire O. , Agius B. , Vickridge I. , Berthier C. , Lameille J. M. 
Published: April 2011

ABSTRACTDue to its high oxidation resistance, TaSiN is a promising candidate as an electrically conductive barrier layer for integration of high permittivity oxides in advanced memory devices. In this work, we report on the properties of TaSiN thin films deposited by reactive magnetron sputtering of a TaSi2 target. We have mainly studied the influence of deposition pressure and power density on film properties (composition, density, resistivity). The oxidation resistance of TaSiN films has been investigated at typical conditions for crystallization of perovskite dielectrics. The as-deposited and annealed samples were characterized using Rutherford backscattering spectroscopy and nuclear reaction analysis for atomic composition and XPS for chemical bonding. To study oxidation resistance, films have been processed in 18O2. The concentration depth profiles of 18O was measured after thermal treatments via the narrow resonances of 18O(p,α)15N at 151 keV (fwhm=100eV). The different results suggest that a pressure of 0.5 Pa, a power density of 2.63W/cm2 and a gas flow ratio N2/Ar of 5% allow to perform TaSiN films with high density, low resistivity and good oxidation resistance.
Ferroelectric Oxide Single-Crystalline Layers by Wafer Bonding and Hydrogen/Helium Implantation
Authors: Radu Ionut , Szafraniak Izabela , Scholz Roland , Alexe Marin , Gösele Ulrich 
Published: April 2011

ABSTRACTLayer splitting by helium and/or hydrogen and wafer bonding was applied for the transfer of thin single-crystalline ferroelectric oxide layers onto different substrates. The optimum conditions for achieving blistering/splitting after post-implantation annealing were experimentally obtained for LiNbO3, LaAlO3, SrTiO3 single crystals and transparent PLZT ceramic. Under certain implantation conditions large area exfoliation instead of blistering occurs after annealing of as-implanted oxides. Small area single-crystal oxide layer transfer was successfully achieved.
Dielectric Studies of laser ablated Ca doped BaTiO3 thin films.
Authors: Victor P. , Ranjith, Asis Sarkar R. , Vinayak R. , Saha S. , Krupanidhi S. B. 
Published: April 2011

ABSTRACTRecently, there has been growing interest in Ca modified BaTiO3 structures due to their larger electro-optic coefficients for their use in optical storage of information over conventional BaTiO3 crystals. Barium Calcium Titanate (BCT) shows promising applications in advanced laser systems, optical interconnects and optical storage devices. BaTiO3 thin films of varied Ca (3 at. % - 15 at. %) doping were deposited using pulsed laser ablation (KrF excimer laser) technique over Pt/Si substrates. The stoichiometric and the compositional analysis were carried out using EDAX and SIMS. The dielectric studies were done at the frequency regime of 40 Hz to 100 kHz at different ambient temperatures from 200 K to 600 K. The BCT thin films exhibited diffuse phase transition, which was of a typical non lead relaxor behavior and had high dielectric constant and low dielectric loss. The phase transition for the different compositions of BCT thin films was near the room temperature, showing a marked departure from the bulk phase transition. The C - V and the hysteresis behavior confirmed the ferroelectric nature below the phase transition and paraelectric at the room temperature.
Hysteresis Offset in Stress Induced Polarization-Graded Ferroelectrics
Authors: Mantese J. V. , Schubring N. W. , Micheli A. L. , Thompson M. P. , Naik R. , Auner G. W. , Misirlioglu I. B. , Ban Z.-G. , Alpay S. P. 
Published: April 2011

ABSTRACTPolarization-graded ferroelectrics and their electrically active counterparts, graded ferroelectric devices (GFDs) and transpacitors has been achieved in a number ways, including a variation in the composition of the material, or impressing a temperature gradients across the structure. In this article, we report how these same devices can be formed from homogeneous ferroelectric films of lead strontium titanate by imposing stress gradients on the materials normal to their electrode surfaces. A qualitative description of asymmetric hysteresis behavior based on a modified Landau potential is provided.
Piezoelectric property investigation for sol-gel derived Bi4Ti3O12 thick films
Authors: Matsuda Hirofumi , Ito Sachiko , Iijima Takashi 
Published: April 2011

ABSTRACTStrongly (117)-oriented Bi4Ti3O12 (BIT) thin (300 nm in thickness) and thick (900 nm in thickness) films were successfully synthesized from chemical solution and the piezoelectric and ferrelectric properties were studied. The chemical solution of Bi-acetate and Ti-iso-propoxide dissolved in 2-methoxyethanol was spin-coated on Pt(111)/Ti/SiO2/Si(001) substrate, pyrolysed at 450–600 °C and annealed at 600 °C. On 300-nm-thick BIT thin film, Pt top electrodes were deposited through a metal mask by RF-sputtering. For longitudinal piezoelectric displacement measurement in partially unconstraint, 900-nm-thick BIT thick film, an array of disk-shape BIT capacitor cells with Pt top electrode layers standing on the Pt bottom electrode were fabricated by photolithography with the diameter of 80, 50, 30, 20 μm. To recover from plasma damage, post deposition annealing of 300-nm-thick BIT film and post lithograph annealing of 900-nm-thick BIT film were performed, respectively. Longitudinal piezoelectric displacement was measured directly from the Z-feedback and Z-error signals of an AFM piezoscanner head with application of ac electric field at 5 Hz and 1 kHz, respectively between the conductive cantilever tip contacted to the top Pt electrode and the bottom Pt electrode. By the removal of sidewalls of BIT, positive piezoelectric displacement response was measured. The maximum strain was about 0.1 % under bipolar drive (amplitude of 400 kV/cm or 4Ec). From the unipolar driven piezoelectric displacement, piezoelectric coefficient AFM-d33 was measured. The value of AFM-d33 increased to decreasing cell diameter and approached to a somewhat constant value of 12–13 pC/N. Considering the crystalline orientation, this value well corresponds to that of 20 pC/N which were reported previously in single crystal. The result of ferroelectric property measurement was rather contradictory. The values of remanent and saturated polarization Pr=20 and Psat=28 μC/cm2, respectively measured in 300-nm-thick BIT thin film were in good agreement with reported spontaneous polarization Ps=50 μC/cm2 along a-axis with the consideration of measured inclination angle of Ψ=58° between (200) and (117). In 900-nm-thick BIT thick film, on the other hand, measured values of Pr=6–7 μC/cm2 were much poorer than those of the thin film even with the consideration that measurement frequencies were 1 kHz in the thick film and 50 Hz in the thin film, although the films showed (117)-orientation. Measured piezoelectric response may reflect a specific single grain with favorable orientation in a cell, on the other hand, average value of ferroelectric property throughout a cell in the 900-nm-thick BIT thick film having mixed orientation of (117) and (020).
Novel Candidate of c-axis-oriented BLSF Thin Films for High-Capacitance Condenser
Authors: Kojima Takashi , Sakashita Yukio , Watanabe Takayuki , Kato Kazumi , Funakubo Hiroshi 
Published: April 2011

ABSTRACTc-axis-oriented SrBi2Ta2O9 thin films with various thickness ranging from 20–170 nm were epitaxially grown on (100)SrRuO3 (SrRuO3 is give for the pseudo-cubic unit cell)//(100)SrTiO3 substrates by metalorganic chemical vapor deposition (MOCVD). The relative dielectric constants of these films kept a constant value of about 55 with decreasing film thickness down to 20 nm. The capacitances of these films were almost independent of the applied electric field; change of capacitance for these films on applied electric field from 0 kV/cm to 100 kV/cm was within 0.017 % and tano value was within 1.3 %. The leakage current densities were constant against the film thickness on the order of 10-8 A/cm2 at 150 kV/cm. Surface flatness of these films were also almost the same irrespective of the film thickness. These characteristics are very attractive for high-capacitance condenser application. Therefore, c-axis-oriented BLSF thin films are novel candidates for high-capacitance condenser application having both bias-free and thickness independent characteristics together with the good surface smoothness.
Tuning the Tunability in Epitaxial Barium Strontium Titanate Film via Internal Stresses
Authors: Ban Z.-G. , Alpay S. P. 
Published: April 2011

ABSTRACTThe tunability of epitaxial barium strontium titanate films is analyzed theoretically for the first time using a modified phenomenological Landau-Devonshire approach taking into account the formation of unusual ferroelectric phases that cannot form in bulk and single-crystal ceramics. It is shown that enhanced tunability can be achieved by adjusting the misfit strain especially in the vicinity of a structural phase transformation. The internal stresses in epitaxial films as characterized by the misfit strain can be controlled by changing the substrate material and/or varying the film thickness. The latter is due to the possibility of stress relaxation by formation of misfit dislocations that relieve epitaxial stresses at film growth temperature. Based on the thermodynamic model, we provide quantitative estimations of tunability of (001) Ba0.5Sr0.5TiO3 films on (001) LaAlO3 (LAO) and SrTiO3 (STO) as a function of film thickness. The analysis indicates that films on STO substrates should be as thick as possible in order to achieve optimum tunability. To obtain maximum tunability on LAO substrates, the thickness of films should be as close as possible to a critical film thickness (∼120 nm).
Long-Range Lattice Matching between (100)/(010) Bismuth-Layered Perovskite Structure and (101) Rutile Structure
Authors: Watanabe Takayuki , Saito Keisuke , Osada Minoru , Suzuki Toshimasa , Fujimoto Masayuki , Yoshimoto Mamoru , Sasaki Atsushi , Liu Jin , Kakihana Masato , Funakubo Hiroshi 
Published: April 2011

ABSTRACTa-/b-axis-oriented epitaxial bismuth layer-structured ferroelectric thin films were epitaxially grown on (101)-oriented oxide with rutile structure. The long-range lattice matching between the ferroelectric layer and the bottom rutile layer, particularly the number of rutile units facing one ferroelectric unit and the surface orientation, were discussed for (100)(010)Bi4Ti3O12//(101)TiO2 structure. Cross sectional transmission electron microscope analysis suggests that seven rutile units lie under one a-/b-axis-oriented Bi4Ti3O12 unit with lower misfit dislocation density comparing to eight rutile units by one Bi4Ti3O12 model. Based on this result, the surface orientation at the interface was simulated to give us an appropriate ion alignment model. The titanium layer in the (101)TiO2 structure is most likely to match with the oxygen layer in the a-/b-axis-oriented Bi4Ti3O12 film.
Seed Layers of the titania - lead oxide system
Authors: Muralt Paul , Hiboux Stephane , Cantoni Marco 
Published: April 2011

ABSTRACTSeed layers of (TiO2)x(PbO)y for the growth Pb(Z,Ti)O3 (PZT) thin films have been studied as a function of thickness and composition. The seed layers have been deposited by reactive in-situ sputter deposition at 530°C from two metal targets in a dynamic sputtering mode. The compositional variation was achieved by varying the relative fluxes. The PZT process was run with a limited lead excess resulting in pyrochlore nucleation on bare Pt electrodes. When the electrode was covered with a dense seed layer, perovskite was obtained everywhere. Ti rich seed layers yielded (111)-textured PZT even for very thin seed layers. Pb rich seed layers nucleated as PbTiO3{100} and gave rise to (100)-textured PZT. In an intermediate zone, the major perovskite orientations (100), (110) and (111) have been found together with pyrochlore for a small seed layer thickness. In this zone, the seed layer nucleates in islands leaving bare Pt spots. The intermediate region is a transition region between (111) seeds and (100) seeds. The latter exhibit diverging critical sizes at a given critical flux ratio, leading to large nuclei and bare Pt. Small perovskite(111) seed grains in the 10 to 100 nm range are found at equal lead oxide and titania flux.
Ferroelectric Properties of 15–20nm-Thick PZT Ultrathin Films Prepared by MOCVD
Authors: Nonomura H. , Fujisawa H. , Shimizu M. , Niu H. , Honda K. 
Published: April 2011

ABSTRACTWe investigated ferroelectric properties of 20nm-thick epitaxial Pb(Zr,Ti)O3 (PZT) ultrathin films prepared on SrRuO3 (SRO)/SrTiO3 (STO) by metalorganic chemical vapor deposition (MOCVD). When SRO with terrace ledges was used as a bottom electrode, 20nm-thick PZT ultrathin films with ferroelectricity were successfully obtained. These PZT films exhibited saturated hysteresis loops with remanent polarizations (Pr) of 29–33 μC/cm2 and coercive electric fields (Ec) of 340–370 kV/cm. On the other hand, when PZT films were grown on SRO without terrace ledges, PZT films showed no saturated hysteresis loops because of large leakage current. The 15nm-thick PZT ultrathin film exhibiting unsaturated hysteresis loop was also obtained.
Possible Ferroelectricity in SnTiO3 by First-Principles Calculations
Authors: Konishi Yoshinori , Ohsawa Michio , Yonezawa Yoshiyuki , Tanimura Yoshiya , Chikyow Toyohiro , Wakisaka Toshiyuki , Koinuma H. , Miyamoto Akira , Kubo Momoji , Sasata Katsumi 
Published: April 2011

ABSTRACTThe prospect of lattice structure and ferroelectricity of SnTiO3 have been studied by first-principles calculations within local density approximation. The results showed that the SnTiO3 has the minimum total energy within almost tetragonal perovskite structure of a=b=3.80 Å, c=4.09 Å. The calculated electronic structure of SnTiO3 resembles that of PbTiO3 because the Ti 3d states, Sn 5s and 5p states hybridize with the O 2p orbitals. The moment of spontaneous polarization of SnTiO3 was estimated as 73 μ C/cm2, which is as large as that of PbTiO3.
Simulation of Steady State Leakage Current in Thin Films
Authors: Schroeder Herbert , Schmitz Sam , Meuffel Paul 
Published: April 2011

ABSTRACTNumerical simulation studies were performed in order to shed light on the controlling mechanism for the steady state leakage current through metal/insulator/metal capacitors with high permittivity dielectric or ferroelectric materials such as SrTiO3, (Ba,Sr)TiO3 or Pb (Zr,Ti)O3. As a model we used an extension of the combined injection-diffusion model, i.e. we have solved the Poisson and continuity equations inside the dielectric assuming thin, low permittivity (“dead”) layers at the electrode interfaces. As “new” boundary conditions we used injection / recombination terms at both electrodes, also taking into account the barrier lowering due to the coulomb mirror potential.The simulation data are presented in dependence on several extrinsic and intrinsic parameters (voltage, temperature, film thickness, barrier height, dead layer properties, etc.) for symmetrical electrodes together with first results on asymmetrical ones. The most important result is that for nearly all parameter sets the leakage current is (film) bulk-limited, mostly due to the low carrier mobilities in these insulating materials. Only for very special conditions the interface-limited current, e.g. thermionic injection at the cathode for electrons, is a good approximation. The numerical data are compared to experimental true leakage current results on STO and BST.
Investigations of Mesoscopic Ferroelectric Structures Prepared by Imprint Lithography
Authors: Harnagea C. , Alexe M. , Schilling J. , Wehrspohn R. B. , Hesse D. , Gösele U. 
Published: April 2011

ABSTRACTArrays of mesoscopic ferroelectric PZT structures with lateral sizes from several micrometers down to below 300 nm were prepared applying nanoimprint lithography. The ferroelectric properties of the mesoscopic structures were investigated by scanning force microscopy in piezoresponse mode. The best chemical route to obtain ferroelectric structures was found to be the sol-gel method. Using Nb-doped SrTiO3 single crystals as bottom electrodes, the crystallization into the ferroelectric phase was uniform with grain sizes in the 35 nm range. The best ferroelectric properties of individual 300 nm structures were obtained if an intermediate, continuous ferroelectric layer was present on the bottom electrode.
Growth, Structure, and Properties of Uniformly a-Axis Oriented Ferroelectric Bi3.25La0.75Ti3O12 Thin Films on Si(100) Substrates
Authors: Hesse D. , Lee H. N. , Zakharov N. D. , Gösele U. 
Published: April 2011

ABSTRACTUniformly a-axis-oriented, epitaxially twinned Bi3.25La0.75Ti3O12 (BLT) thin films having the major spontaneous polarization entirely along the film normal were grown by pulsed laser deposition on yttria-stabilized zirconia-buffered Si(100) substrates covered with very thin SrRuO3 bottom electrodes. Using SrRuO3 bottom electrodes of a specific low thickness in combination with a relatively high growth rate and a high oxygen pressure, the volume fraction of the BLT (100) orientation, which is competing with the BLT (118) orientation, was increased up to 99%. In this way the growth of fully a-axis-oriented BLT epitaxial films was achieved, attaining a remanent polarization of 32 mC/cm2. Initial fatigue experiments indicated hardly any fatigue after 109 switching cycles.
Fabrication of Sequential Nanostripes by Controlled Electrodeposition
Authors: Mikhaylova M. , Kim D. K. , Toprak M. , Muhammed M. 
Published: April 2011

ABSTRACTAu nanowires and sequential metal nanostripes were prepared by AC pulse electrodeposition in anodic alumina membrane (AAM). Due to the high toxicity of cyanide-based electrolytes, which commonly used for electrodeposition of noble metals, new types of Au electroplating solution has been introduced. Electroplating solutions of noble metals Au, Ag and Pt were alternately used for nanostripes fabrication. The AAM was prepared by a two-step electrochemical anodization process in oxalic acid. The pore size was controlled by varying anodizing voltage and current density. The AAM was investigated by SEM and AFM. The results show hexagonally ordered channels with a pore diameter 50 nm. The morphology and composition of nanowires and nanostripes were examined by TEM and optical microscopes, which show uniformly, ordered Au nanowires with a length about 250 nm and a diameter about 50 nm. Au-Ag-Au-Pt-Au sequential nanostripes have a length about 3.5 μm and diameter 50 nm has been successfully prepared.
Fabrication of Zirconia Coatings using Electrophoretic Deposition and Reactive Sintering
Authors: Yuan Ying , Wang Xin , Xiao Ping 
Published: April 2011

ABSTRACTElectrophoretic deposition (EPD) technique has been used to fabricate green YSZ/Al composite coatings with controlled thickness and morphology. Such green coating was transformed into the YSZ/Al2O3 composite coating during following thermal treatment in air at temperatures up to 1200°C. Suspension for EPD was prepared by attrition-milling a mixture of yttria -stabilised zirconia (YSZ) and aluminium (Al) in acetyl-acetone (ACAC). The attrition milling reduced the particle size of the powder mixture. A mechanical alloying behaviour is believed to control the agglomeration and the breaking of large Al particles. Attrition milling also reduced the YSZ crystallite size, which can be attributed to the chemical reaction between YSZ/Al particles and ACAC. Thermal analyses and dilatometry measurements of the green compact indicate the temperature range for oxidation of Al and its effect on sintering of the coating. The coating obtained from EPD in the suspension after a longer milling time was found to have more uniform in microstructure.
Effects of Irradiation by Low Energy Nitrogen Ions on Carbon Nitride Thin Films
Authors: Nasu Yuka , Aono Masami , Aizawa Shinichiro , Kitazawa Nobuaki , Watanabe Yoshihisa 
Published: April 2011

ABSTRACTCarbon nitride (CNx) thin films have been prepared by hot carbon filament chemical vapor deposition, and the nitrogen content in the films is approximately 0.05. The CNx films have been irradiated by 0.1 keV nitrogen ions to increase the nitrogen content after deposition. The nitrogen content in the CNx films was obtained with X-ray photoelectron spectroscopy. Scanning electron microscopy was employed to study microstructures of the films. The experimental results show that nitrogen ions are chemically combined with the CNx films and as a result the nitrogen content increases up to approximately 0.30. Furthermore, it is found that nitrogen ions change the film microstructures and sputter the surfaces of CNx films.