bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dielectric and Electromechanical Behaviour of Relaxor [(1−x)Pb(Mg1/3Nb2/3)O3 -xPbTiO3] Thin Films
Authors: Donnelly N.J. , Catalan G. , Morros C. , Bowman R.M. , Gregg J.M. 
Published: April 2011

AbstractThin film capacitor structures of Au / (1−x)Pb(Mg1/3Nb2/3)O3 - xPbTiO3 /(La1/2Sr1/2)CoO3 were fabricated by pulsed laser deposition on single crystal {001} MgO substrates. Films were found to be perovskite dominated and highly {001} oriented. Dielectrically, films displayed relaxorlike features, though maximum permittivity was low compared to single crystal or bulk ceramic (∼1400 at peak @1kHz, for x=0.07, 0.1 & 0.2). A field induced piezoelectric coefficient d33 was measured by piezoresponse atomic force microscopy for specific compositions x =0, × =0.07, and x =0.1 and found to be disappointingly low - indicating poor electric field induced strain. Despite this macroscopic electrostrictive coefficients Q33 were found to be (3.6 ± 0.6) ×10−2C−2m4, (2.6 ± 0.2) ×10−2C−2m4, and (0.9 ± 0.3) ×10−2C−2m4 respectively. Crystallographic electrostrictive coefficients were determined by in-situ x-ray diffraction and found to be (4.9 ± 0.2) ×10−2C−2m4 for PMN-(0.07)PT and (1.9 ± 0.1) ×10−2C−2m4 for PMN-(0.1)PT. Considering that all these Q33 values are of the same order of magnitude as found in single crystal experiments (2.5 – 3.8 ×10−2C−2m4), it is suggested that low out-of-plane strain is entirely a result of reduced polarisability rather than reduced electrostrictive coefficients in thin films relative to bulk ceramic or single crystal. An estimate was also made of the Q13 electrostrictive coefficient for PMN and PMN-(0.07)PT by measuring permittivity as a function of applied in-plane strain. The values obtained were -1.31 ×10−2C−2m4 and -0.46 ×10−2C−2m4 respectively.
Ferroelectric and Displacement Properties of Lead Zirconate Titanate Thick Films Prepared by Chemical Solution Deposition Process
Authors: Iijima Takashi , Hayashi Yoshinori , Onagawa Jun 
Published: April 2011

AbstractCrack free 10-μm-thick Pb1.1(Zr0.53Ti0.47)O3 (PZT) films were successfully fabricated using a chemical solution deposition process, and the ferroelectric and displacement properties were evaluated. A 0.5 M PZT precursor solution was prepared from trihydrated lead acetate, titanium iso-propoxide, zirconium n-propoxide, and 2-methoxyethanol as the solvent. The process of spin coating and pyrolysis at 500 °C was repeated five times, and then the precursor films were fired at 700 °C for 5 min. This sequence was repeated 30 times. Finally, the films were fired at 700 °C for 10 min. The fabricated crack-free PZT thick films showed (100) preferred orientation. A flat surface and dense microstructure was observed. The electrical properties were comparable with the bulk PZT ceramics. The dielectric constant and dissipation factor were εr = 1453 and tan δ = 0.039, and the remnant polarization and coercive field were Pr = 25 μC/cm2 and Ec = 30 kV/cm, respectively. Field-induced displacement of the films was measured using an atomic force microscope (AFM) with and without a top electrode using a contact mode.
Compositional Effects on the Piezoelectric and Ferroelectric Properties of Chemical Solution Deposited PZT Thin Films
Authors: Kim Dong-Joo , Maria Jon-Paul , Kingon Angus I. 
Published: April 2011

AbstractThe piezoelectric, dielectric, and ferroelectric properties of highly (111)-textured polycrystalline lead zirconate titanate (PZT) films as a function of Zr/Ti composition have been investigated. The peak in piezoelectric coefficient at the morphotropic phase boundary (MPB) observed in bulk PZT ceramics has not been found in thin film PZTs. Measurement of the piezoelectric response as a function of AC amplitude suggests that non-180° domain wall motion in these films is negligible, indicating that the extrinsic contribution to the room temperature dielectric constant is dominated by only 180° domain wall motion. The semi-empirical phenomenological equation relating the piezoelectric coefficient to measured polarization and permittivity values is demonstrated to give an excellent description of the piezoelectric behavior in these films, assuming bulk electrostrictive coefficients. The small deviation between calculated and measured piezoelectric coefficients as well as the dependence of piezoelectric and polarization behavior on the external dc field, i.e., hysteresis loop, are suggested to be primarily due to backswitching of 180° domains.
Hetero-epitaxial Growth of (1, 0, m+1) One Axis-oriented Bismuth Layered Structured Ferroelectrics Thin Films Directly Crystallized by MOCVD
Authors: Nukaga Norimasa , Watanabe Takayuki , Sakai Tomohiro , Suzuki Toshimasa , Nishi Yuji 
Published: April 2011

AbstractBismuth layered structured ferroelectrics (BLSF) thin films with different number of octahedron number (m-number) were prepared by MOCVD and directly crystallized on the substrates. Directly-crystallized SrBi2Ta2O9 (SBT) (m=2) films on a (111) Pt/Ti/SiO2/Si substrate were ascertained to have a strong (103) one-axis orientation by the X-ray reciprocal space mapping and to be hetero-epitaxially grown on the (111) Pt grains by the TEM observation. Moreover, directly crystallized Bi2VO5.5 (m=1) and Bi4Ti3O12 (m=3) films deposited on the same substrate showed (102) and (104) one-axis preferred orientations, respectively. These orientations are basically the equal ones with SBT (103) orientation because the tilting angle of c-axis from the substrate surface is also about 55°. Therefore, the direct crystallization is one of the important key techniques for orientation control of BLSF films. Moreover, the directly crystallized SBT film deposited on a (111) Ir/TiOx/SiO2/Si substrate at 570 °C by ECR-MOCVD exhibited (103) one-axis orientation, which also originated from the local epitaxial growth on (111)-oriented Ir grains. The remanent polarization (2Pr), and the coercive field (Ec) of this film were 16.1 μC/cm2 and 83 kV/cm at an applied electric field of 360kV/cm, respectively. This Pr value is about 88% of the expected value of (103)-oriented SBT film from both the Pr values of the (116) and (001)-oriented epitaxial films and detailed crystal analysis.
Iridium Based Electrodes for Ferroelectric Capacitor Fabrication
Authors: Johnson J. A. , Lisoni J. G. , Wouters D. J. 
Published: April 2011

AbstractIr and its conductive oxide, IrO2, are candidates to replace Pt as the electrodes in ferroelectric capacitors (FECAPs) because of improved endurance (since e.g. Pt/PZT/Pt shows strong fatigue) and also because of the oxygen barrier properties of Ir/IrO2 stacks that enable the fabrication of stacked FECAPs on top of contact plugs. Two important issues related to these electrodes are the control of the ferroelectric layer orientation on top of these materials, as well as material stability (e.g. oxidation and possible growth of large IrO2 crystallites).In this work, we show that IrO2 bottom electrodes affect the crystallization of sol-gel deposited Pb(Zr,Ti)O3 (PZT). While PZT films deposited on (111) Pt show a (111) preferential orientation, IrO2 electrodes nucleate strongly different oriented PZT. Controlling and changing the microstructure of the bottom electrode allows tuning of these PZT orientations and the resulting grain morphology, and, consequently, their FECAP polarization hysteresis properties.
Effect of Capacitor Configuration on Oxygen-dependent Electrical Properties of Ferroelectric Pb(Zr,Ti)O3 Thin Films
Authors: McCormick M. A. , Slamovich E. B. , Metcalf P. , McElfresh M. 
Published: April 2011

AbstractPolarization versus applied field (P-E) hysteresis loop measurements on Pb(Zr,Ti)O3 (PZT) thin films were performed using a controlled-atmosphere probe station. Measurements were made using two different capacitor configurations, each producing differing results. The capacitor configurations included using either the typical arrangement of two top electrodes (planar) or an arrangement using contacts to the top and the bottom electrodes (sandwich). The films included PZT films deposited using pulsed laser deposition (PLD) and commercially-available rfsputtered PZT thin films. Qualitatively similar results were obtained for both types of films. For both PLD and Ramtron PZT films, translation of ferroelectric hysteresis loops along the polarization axis was observed for sandwich capacitors. The magnitude of this voltage was strongly dependent on the partial pressure of oxygen at room temperature. Translations were not observed for the same films using the planar capacitor configuration. However, for both sandwich and planar configurations, the thin film capacitance was sensitive to changes in pO2.
Characteristics of Memory Window and Retention Properties of One Transistor Memory Devices
Authors: Li Tingkai , Hsu Sheng Teng , Ulrich Bruce , Evans Dave 
Published: April 2011

AbstractPb3Ge5O11(PGO) metal-ferroelectric-metal-oxide-semiconductor (MFMOS) and metalferroelectric-oxide-semiconductor (MFOS) one-transistor ferroelectric memory devices have been fabricated. The memory windows of the memory transistors can be characterized in terms of MFMOS or MFOS capacitor and the threshold voltages of the transistor. The retention properties of one-transistor memory devices can be measured from the changes of the capacitance of MFMOS or MFOS capacitors. Alternatively the retention properties can be evaluated from the threshold voltages or drain currents of the transistor with retention time. There are inconsistencies between the capacitor data and the transistor data. In this paper, we present the memory windows and retention properties of MFOS and MFMOS one-transistor memory devices measured with various methods. The different results obtained from various methods and device structures will be discussed.
Structural Inhomogeneity of SrBi2Ta2O9Thin Films Prepared by Layer-by-Layer Technique
Authors: Xu J. B. , Hu G. D. , Wong S. P. 
Published: April 2011

AbstractGrazing incidence x-ray diffraction has been employed to perform the depth-profile analysis on SrBi2Ta2O9 (SBT) thin films with different preferential orientations. For the polycrystalline SBT thin film, the change in structural orientation occurs only within the 15-nm-thick top layer, which is associated with the formation of the (200)-predominant SBT thin film prepared by the layer-by-layer annealing process. The inhomogeneity of structural orientation is more significant in the full film thickness for the (200)- predominant SBT thin film. (0010) peak can only be observed for the grazing angle larger than 0.6°. A layer with the highest ratio of I(200)/I(115) is found in the top surface layer (i.e., the latest layer during deposition) of the (200)-predominant SBT thin film.
Thermal Stability and Electrical Properties of RhO2 Thin Films
Authors: Abe Yoshio , Kato Kiyohiko , Kawamura Midori , Sasaki Katsutaka 
Published: April 2011

AbstractRhO2 belongs to the family of conducting oxides with a rutile structure, which have attracted attention as capacitor electrode materials for memory devices. In this study, effects of thermal treatment under various oxygen pressures on structural and electrical properties of RhO2 thin films prepared by reactive sputtering were investigated. The RhO2 films were found to be stable up to 700°C under oxygen pressure of 1 atm and a metallic conduction property with a resistivity of about 80 μΩcm was obtained. However, the RhO2 films decomposed to semiconducting Rh2O3 at 750°C. The decomposition temperature decreased to 500°C under oxygen pressures of 0.5-5 mTorr.
Microwave Properties of Strontium Barium Niobate Thin Films Grown by Pulsed Laser Deposition
Authors: Rodríguez-Santiago Víctor , González Yelitza , Fernández Félix E. , Mueller Carl H. , Keuls Fred W. Van , Miranda Félix A. 
Published: April 2011

AbstractStrontium barium niobate (SrxBa1−xNb2O6 - SBN) with 0.25≤x≤0.75 is a ferroelectric material of interest for diverse optoelectronic applications. Dielectric properties of bulk SBN crystals were comprehensively studied over 30 years ago for a range of compositions and at frequencies up to 30 MHz, but there is little information on properties at higher frequencies. In particular, and up to the best of our knowledge, there are no published results about SBN thin film dielectric properties at high frequencies. For the study reported here, SBN thin films with x = 0.61 were grown on MgO and LaAlO3 substrates by Pulsed Laser Deposition (PLD). Films with good crystallinity and oriented with c-axis normal to the substrate surface were obtained on both types of substrates, while films on MgO had much better texture due to better lattice matching. Interdigital electrode (IDE) capacitors and coupled microstrip phase shifters (CMPS) were fabricated with both types of samples in order to study dielectric response. Capacitance of the IDE capacitors was measured at 1 MHz as a function of temperature and bias voltage, revealing very low losses but poor capacitance tunability, particularly for samples on MgO. Response of the CMPS structures was measured at room temperature and at high frequencies, up to 21 GHz. Insertion losses were measured up to 28 GHz.
Reactive Coevaporation of SrTiO3 Thin Films for Tunable Microwave Devices
Authors: Peng Luke S.-J. , Heinig Nina F. , Moeckly Brian H. 
Published: April 2011

AbstractWe have successfully grown SrTiO3 films on LaAlO3 and MgO substrates up to 2” in diameter using the deposition technique of reactive coevaporation. We have explored a wide range of deposition temperatures, oxygen pocket pressures, and compositions in order to determine the optimal growth process window. X-ray diffraction analyses indicate that the process window for growth on MgO substrates is narrower than for LaAlO3 substrates. Dielectric property measurements show that samples near stoichiometry have higher tunability, but their peak loss tangents are also high (∼0.02). The slightly Sr-poor samples (46-48 at.%) show a reduced loss tangent (<0.01) while maintaining an acceptable tunability (∼50%) at an average electric field of 1.7 V/μm.
Thickness Dependence of Transport Properties of Epitaxial SrRuO3 Thin Films Grown on SrTiO3 Substrates
Authors: Herranz G. , Sánchez F. , García-Cuenca M.V. , Ferrater C. , Varela M. , Martínez B. , Fontcuberta J. 
Published: April 2011

ABSTRACTTo study the effect of the film/substrate interface in thin films we have analyzed the thickness dependence of the transport properties of SrRuO3 films grown on SrTiO3 substrates. Our data makes evident the failure of the so-called deadlayer model to describe the observed thickness dependence of the conductivity. This is interpreted as due to a non-monotonous change of microstructure as thickness increases. Indeed, Atomic Force Microscopy studies indicate substantial modifications of the growth mechanism with thickness.
Photoinduced Heating and Phase Transition in CMR Materials
Authors: Noginova N. , Arthur E. , Ulysse R. , Gillman E. S. , Bonner C. E. 
Published: April 2011

ABSTRACTFast switching from conductor to insulator induced by laser light illumination has been studied in single crystals and thin films of La1−xSrxMnO3 in the range of the ferromagnetic phase transition. Based on our experimental data on the photoresponse as a function of temperature, electric current, and intensity, we have demonstrated that the switching and relaxation processes are determined by heating and heat conduction processes. The relaxation time, specific heat and the latent heat constants have been estimated.
Synthesis and Studies of Ti1-xCoxO2 for Device Applications
Authors: Hidalgo A. , Tomar M.S , Melgarejo R.E. , Katiyar R.S. 
Published: April 2011

ABSTRACTTi1-xCoxO2 material has reported to show ferromagnetosmat room temperature. Thus, there is research interest in synthesis and structural properties of thismaterial system. The material is synthesized using a soulution chemistry route. X-ray diffraction and Raman spectroscopy is used for the structural characterization.
Stress Evolution During Fe(001) Epitaxy on GaAs(001)
Authors: Koch R. , Nötzel R. , Wassermann B. , Wedler G. 
Published: April 2011

ABSTRACTFe films on GaAs substrates have evolved as a model system for the integration of magnetic materials with semiconductors. We report on in situ stress measurements of Fe/GaAs(001), which enlighten the dynamics of the interface formation of this important magnetic metal/semiconductor system. At deposition temperatures of 300 K and 450 K, the stress evolution during growth is very similar. In Fe films thicker than 6–7 nm, the stress is compressive owing to the misfit between the lattices of Fe and GaAs. Thinner films surprisingly are dominated by a tensile stress contribution due to considerable As (and Ga) interdiffusion even at 300 K. Magnetization and in-plane anisotropy of both films are bulk-like.
Critical Magnetism of the CMR Ruddlesden-Popper Manganite La1.2Sr1.8Mn2O7
Authors: Velázquez Matias , Revcolevschi Alexandre , Renard Jean-Pierre , Dupasa Claire 
Published: April 2011

ABSTRACTWe present a thermodynamic study of the critical magnetic properties of La1.2Sr1.8Mn2O7, including the determination of the fundamental characteristics of a magnetic system: anisotropy, critical exponents and crossovers in the vicinity of the Curie temperature, TC∼108K. It appears that two-dimensional correlations above TC do not spread very fast, and that thus the critical fluctuations regime occurs in a moderately narrow temperature range, assessing the three- dimensional nature of the ferromagnetic ordering.
Pulsed Laser Deposition and Characterization of Zn1−xMnxO Films
Authors: Jin C. , Tiwari A. , Kvit A. , Kumar D. , Muth J. , Narayan J. 
Published: April 2011

AbstractHere we present our results of structural, optical, and magnetic measurements of Zn1−xMnxO thin films. These films were grown epitaxially on (0001) sapphire substrates by using pulsed laser deposition technique. The maximum Mn content (x=0.36) is found to be much higher than allowed by thermal equlibrium limit (x∼0.13) due to the non-equilibrium nature of the pulsed laser deposition. All the films investigated here were found to be single phase with <0001> orientation epitaxial relationship. A linear increase in the c-axis lattice constant was observed with increase in Mn concentration. Optical transmittance measurements showed an increase in the insulating band-gap (Eg) with increase in Mn concentration. DC magnetization measurements showed that there is no long range ferromagnetic ordering down to 10 K.
Effects of As Doping on Properties of ZnO Films
Authors: Huh K. S. , Hwang D. K. , Bang K. H. , Hong M. K. , Lee D. H. , Myoung J. M. , Oh M. S. , Choi W. K. 
Published: April 2011

AbstractA series of ZnO thin films with various deposition temperatures were prepared on (100) GaAs substrates by radio-frequency magnetron sputtering using ZnO target. The ZnO films were studied by field emission scanning electron microscope(FESEM), x-ray diffraction(XRD), photoluminescence(PL), cathodoluminescence(CL), and Hall measurements. The structural, optical, and electrical properties of the films were discussed as a function of the deposition temperature. With increasing temperature, the compressive stress in the films was released and their crystalline and optical properties were improved. From the depth profile of As measured by secondary ion mass spectrometry(SIMS), As doping was confirmed, and, in order to activate As dopant atoms, post-annealing treatment was performed. After annealing treatment, electrical and optical properties of the films were changed.
Growth of the Single-Crystalline ZnO Films on Si (111) Substrates by Plasma-Assisted Molecular-Beam Epitaxy
Authors: Koike Kazuto , Tanite Takanori , Sasa Shigehiko , Inoue Masataka , Yano Mitsuaki 
Published: April 2011

AbstractThis report describes the growth of single-crystalline ZnO films on Si (111) substrates by plasma-assisted molecular-beam epitaxy. X-ray diffraction measurement shows that c-axis oriented ZnO films are easily grown on Si (111) substrates. However, in-plane random rotational domains are included in the ZnO films due to the inevitable oxidation of substrate surface at the initial stage of ZnO growth. By employing a thin CaF2 buffer layer between the ZnO films and Si substrates, we have succeeded in suppressing the generation of rotational domains and in obtaining an intense ultraviolet photoluminescence even at room temperature. These results indicate that the use of CaF2 buffer layer is promising for the growth of device-quality ZnO films on Si (111) substrates.
Nature and Formation of Non-Radiative Defects in GaNAs And InGaAsN
Authors: Chen W. M. , Thinh N. Q. , Buyanova I. A. , Hai P. N. , Xin H. P. , Tu C. W. , Li Wei , Pessa M. 
Published: April 2011

AbstractThe optically detected magnetic resonance (ODMR) technique has been employed to examine the nature and formation mechanism of non-radiative defects in GaNAs and InGaAsN. In both alloys, two defects were observed and were shown to be deep-level, non-radiative recombination centers. One of the defects has been identified as a complex involving an AsGa antisite. These two defects gain more importance with increasing N composition up to 3%, presumably due to an increase in their concentration. With a further higher N composition, the defects start to lose importance in carrier recombination that is attributed to an increasingly important role of other new non-radiative channels introduced with a high N composition. On the other hand, effect of In composition up to 3% seems to be only marginal. Both defects were shown to be preferably introduced in the alloys during low-temperature growth by molecular beam epitaxy (MBE), but can be rather efficiently removed by post-growth rapid thermal annealing.
Multi-Color Quantum Well Infrared Photodetectors for Mid-, Long-, and Very Long- Wavelength Infrared Applications (invited)
Authors: Li Sheng S. 
Published: April 2011

AbstractQuantum well infrared photodetectors (QWIPs) have been widely investigated for the 3–5 μm mid-wavelength infrared (MWIR) and 8–12 μm long-wavelength infrared (LWIR) atmospheric spectral windows as well as very long wavelength infrared (VLWIR: λc 14 μm) detection in the past decade. The mature III-V compound semiconductor growth technology and the design flexibility of device structures have led to the rapid development of various QWIP structures for infrared focal plane arrays (FPAs) applications. In addition to the single-color QWIP with narrow bandwidth, the multi-color QWIP required for advanced IR sensing and imaging applications have also been emerged in recent years. Using band gap engineering approach, the multi-color (2, 3, and 4- color) QWIPs using multi-stack quantum wells with different well width and depth and voltage-tunable triple- coupled quantum well (TCQW) structure for detection in the MWIR, LWIR, and VLWIR bands have been demonstrated. In this paper, the design, fabrication, and characterization of a voltage-tunable 2-stack 3-color QWIP for MW/LW/LW IR detection and a 3-stack 3-color QWIP for detection in the water, ozone, and CO2 atmospheric blocking bands are depicted.
Photoluminescence From Er− Implanted 4h And 6h-SiC
Authors: Uekusa Shin-ichiro , Goto Takayuki 
Published: April 2011

AbstractErbium (Er) ions were implanted into 4H and 6H silicon carbide (SiC). The temperature-dependent photoluminescence (PL) and PL lifetime were characterized. The optimum annealing temperature for SiC : Er were 1600 °C, PL intensity decreased at 1700 ° C, and the bandedge luminescence changed in relation to the luminescence of Er3+. Thermal quenching of the luminescence of Er3+ was suppressed by using SiC with a wide band gap as a host material. The Er3+ -PL was observed at room temperature (RT). We monitored the auger effect that is believed to be the main cause of the thermal quenching process and concluded that, in the temperature range 15 K to 70 K, the thermal quenching process has a close relation to nonradiative recombination from the first excited state (4I13/2) to the ground state (4I15/2) of Er3+.