Structural properties of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 relaxor ferroelectric thin films on SrRuO3 conducting oxides

Coating of 0.65Pb(Mg_1/3Nb_2/3)O₃–0.35PbTiO₃ (PMN–PT) relaxor ferroelectrics by a sol–gel method is followed by growth of epitaxial SrRuO₃ (SRO) metallic oxide electrodes on SrTiO₃ (STO) single-crystal substrate by pulsed laser deposition. High-quality PMN–PT films on SRO with preferred growth orientation were successfully fabricated by controlling the operation parameters. Structural properties of relaxor ferroelectric PMN–PT thin films on SRO/STO substrates have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). In-plane and out-of-plane alignments of the heterostructure are confirmed and the structural twinning of the materials are also revealed.     

Piezoelectric and electromechanical properties of relaxor ferroelectric Pb(Mg1/3Nb2/3)O3(65%)-PbTiO3(35%) thin films observed by scanning force microscopy

Relaxor ferroelectric PbMg(1/3)Nb(2/3)O(3)(65%)-PbTiO(3)(35%) (PMN-35PT) thin films were grown by a sol-gel method on Pt(111)/TiO(2)/SiO(2)/Si(100) substrates. Piezoresponse and poling behavior appear to have a relation with the relaxor behavior of the materials. Piezoelectric images were studied in a number of regions on the films with subsequent statistical analysis of the obtained data using the contact mode of scanning force microscopy. Hysteresis loops were observed with external field applied over a wide range of the vibration frequency. The piezoelectric coefficient, d(33), and the crystallographic electrostrictive constant, Q(33), were also determined as 100pm/V and 2.8x10(-3)C(-2)m(4), respectively.     

A study of the initial growth of PtxCo(1−x) thin films on Si3N4

Pt _x Co_{(1− x )} thin films where x  =0.24 have been deposited onto Si₃N₄ windows and studied using transmission electron microscopy. The films are used in ultrahigh-density recording studies and it was found that the surface of the substrate had a strong influence on the microstructure, crystallography and magnetic properties of the film. An investigation of the early growth of the film was made by studying films of different thickness between 100 and 300 Å. It was found that the grains were hexagonal in structure with a strong c -axis orientation perpendicular to the surface.     

Characteristics of Sputter-deposited Gadolinia-doped Ceria Thin Films on Al2O3/SiO2/Si Systems

Metal oxide films prepared by thin film technology have been reported for the potential applications on thin solid electrolyte layers for solid oxide fuel cells(SOFCs). Gadolinia-doped ceria(GDC) thin films and Al2O3 layers on SiO2/Si substrates are successively deposited by RF reactive magnetron sputtering from a cerium-gadolinium (90:10 at.%) alloy target and Al target in O2/Ar gas mixture and then perform post-thermal treatments at 300-700 ℃ and 900 ℃ for 2 h, respectively. Materials characteristics and chemical compositions of GDC films and Al2O3 layers are investigated by X-ray photoelectron spectroscopy(XPS), cross-sectional scanning electron microscopy(SEM), X-ray diffraction(XRD), and atomic force microscopy(AFM). Stoichiometric Al2O3 layers with polycrystalline structures are firstly prepared onto SiO2/Si substrates. A cubic fluorite structure with columnar crystallites of GDC films is successfully deposited on Al2O3/SiO2/Si systems. The chemical composition of 700 ℃-annealed GDC films is (Ce0.91Gd0.09)O1.94 and possesses a higher film density of 7.257 g/cm3. As a result, GDC thin films prepared by RF reactive magnetron sputtering and post-thermal treatments can be used as thin solid electrolyte layers for intermediate temperature SOFCs system as compared to the well-known yttria-stabilized zirconia(YSZ).     

Label-free, all-electrical, in situ human epidermal growth receptor 2 detection

Using 3-mercaptopropyltrimethoxysilane (MPS)-coated (PbMg 1/3 Nb 2/3 O3)0.63-(PbTiO3)0.37 (PMN-PT)/tin and lead zirconate titanate/glass piezoelectric microcantilever sensors (PEMSs) with single-chain variable fragment (scFv) immobilized on the MPS surface, we have demonstrated real-time, label-free detection of human epidermal growth factor receptor 2 (Her2) in a background of 1 mg/ml bovine serum albumin. Coupled with a scFv with a KD of 3.4 x 10(-8)M, the MPS-insulated PMN-PT/tin PEMS 560 microm long and 720 microm wide exhibited a Her2 concentration sensitivity of 5 ng/ml in a background of 1 mg/ml BSA.     

Electrostatic force microscopy study on the domain switching properties of the Pb(Zr0.2Ti0.8)O3 thin films with different crystallographic orientations for the probe-based data storage

The domain switching properties of the ferroelectric Pb(Zr(0.2)Ti(0.8))O(3) (PZT) thin films with two types of crystallographic orientations were investigated by electrostatic force microscopy (EFM). The crystallographic orientations of the PZT thin films were random on the (111)Pt/MgO(100) and c-axis preferred on the (100)Pt/MgO(100), respectively. When dc bias was applied to the films for writing in micro-scale area, electrostatic force images showed that the domain switching was hard in the PZT thin films with random orientation, while the pattern could clearly be written in the PZT films with c-axis orientation. The differences in the domain switching properties of each PZT thin film were investigated in the crystallographic orientations point of view, and the domain switching dynamics were also measured by investigating the nano-sized dot switching behavior with respect to the width of the applied voltage pulse.     

MFM studies of interlayer exchange coupling in Co/Ru/Co films: Effect of Ru layer thickness

Antiferromagnetically coupled magnetic thin films are promising candidates for the design of new magnetic storage and logic devices. The ability to control the interlayer thickness, therefore the magnetic reversal response, of exchange-coupled magnetic layers is of paramount importance in nanotechnology, especially in magnetic sensing element design and applications. In this work, magnetic force microscopy (MFM) with improved sensitivity and high spatial resolution probes was used to obtain a more detailed view of magnetization reversal behavior and domain evolution in the indirect exchange-coupled trilayer system: Co/Ru/Co. The effect of the variable Ru interlayer thickness on the exchange coupling and thus the magnetic domain structure during the ferromagnetic (FM)/antiferromagnetic (AF) coupling transition in Co/Ru/Co films is well demonstrated. The MFM images display a distinct signature of AF coupling for the films with Ru thickness of 0.4 nm. MFM has proven to be an effective tool for detecting FM/AF interlayer coupling and exploring magnetic domain structures in exchange-coupled layered thin films.     

PZN-PT based smart probe for high temperature fluid viscosity measurements

A smart sensing system is proposed for high-temperature (up to 90 °C) viscosity measurement of viscous fluids. The proposed sensing system is based on a smart cantilever probe on which a new generation of piezoelectric materials, relaxor ferroelectric Pb(Zn(1/3)Nb(2/3))O(3−x)PbTiO(3) (PZN-PT), is bonded. The proposed system utilizes a PZN-PT single crystal for actuation and a laser displacement sensor for vibration detection. By analyzing the vibrational properties of the cantilever probe, the viscosity of measured fluids at different temperatures (up to 90 °C) were extracted. Lab tests were carried out to verify and evaluate the effect of this system on high-temperature measurements. Results show a consistent agreement with theoretical analysis. In comparison to the existing high-performance piezoelectric material, lead magnesium niobate-lead titanate solid solution (1−x)[Pb(Mg1/3Nb2/3)O3]−x[PbTiO3] (PMN-PT), PZN-PT has a steady performance at high temperatures and shows more reliability. The proposed sensing system can be applied to real-time monitoring of viscous fluids in high-temperature environments, such as vehicle cooling systems, power plant cooling tower fluid monitoring, and other heat transfer systems.     

Effects of 10 MeV electron irradiation at high temperature of a Ni-Mo-based Hastelloy

A Hastelloy alloy was irradiated with 10 MeV electrons at 650 degrees C for 700 h to a total dose of 2 x 10(-3) displacements per atom (dpa). The microstructure of irradiated and non-irradiated specimens of this alloy were investigated by transmission electron microscopy (TEM). The non-irradiated specimens were analyzed by 3-D atom probe tomography (APT) in a local-electrode atom-probe (LEAP). TEM analysis before the irradiation detects small precipitates with a mean diameter of 22 nm, which are coherent with the FCC matrix. The number density of these precipitates is approximately 7 x 10(18) m(-3). Electron diffraction patterns from these precipitates exhibit superlattice reflections corresponding to the L1(2) ordered structure. The chemical composition of the precipitates, as measured by APT, is around 75 at% Ni with additions of Al, Ti and Mo. After electron irradiation, small precipitates with an irregular morphology are observed. The number density of these new precipitates about 10(20) m(-3) is greater than that of the L1(2) ordered precipitates before irradiation. The L1(2) superlattice reflections disappear completely, instead diffuse diffraction spots are observed at 1(1/2)0(FCC), which is attributed to compositional short-range order (SRO). The results are discussed with respect to the influence of the electron irradiation on the morphology and structure of the ordered precipitates.     

3-mercaptopropyltrimethoxysilane as insulating coating and surface for protein immobilization for piezoelectric microcantilever sensors

We have examined coating (PbMg(13)Nb(23)O(3))(0.63)-(PbTiO(3))(0.37) (PMN-PT)/tin and lead zirconate titanate (PZT)/glass piezoelectric microcantilever sensor (PEMS) with 3-mercaptopropyl-trimethoxysilane (MPS) by a simple solution method to electrically insulate the PEMS for in-water applications. In contrast to earlier methytrimethoxysilane insulation coating, the MPS coating also facilitated receptor immobilization on the sensor surface via bonding of its sulhydryl group to a bifunctional linker, sulfosuccinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate. We showed that a MPS coating of 21 nm in thickness is sufficient to electrically insulate and provide immobilization surface to the PEMS for in-liquid electrical self-excitation and self-sensing. The in-phosphate buffered saline solution resonance spectra were stable with Q values ranging from 41 to 55. The mass detection sensitivities were determined to be 5x10(-11) and 8x10(-12) gHz for the MPS-insulated PZT-glass and PMN-PT/tin PEMSs, respectively.     

Electron and light microscopy studies on the domain structures of Zn3B7O13Cl, Zn3B7O13Br and Zn3B7O13I ferroic boracites

The domain structures of Zn₃B₇O₁₃Cl, Zn₃B₇O₁₃Br and Zn₃B₇O₁₃I boracite single crystals were studied by means of polarized light in conjunction with electron microscopy. Single crystals of the three compositions were grown by chemical transport reactions in closed quartz ampoules, at a temperature of 900 °C and were examined by polarizing optical microscopy (PLM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For both PLM and SEM, the same as‐grown samples were used without having to resort to metallization of the crystal faces. For TEM the single crystals were crushed and mounted on holey carbon films. Comparative electron microscope images were useful for revealing the domain structure of these ferroelectric/ferroelastic materials previously observed between the crossed polars of an optical microscope. X‐ray diffraction analysis of the pulverized crystals was performed for this triad of halogen boracites containing zinc as a common metal.     

HAADF-STEM analysis of layered double perovskite La2CuSnO6 grown epitaxially

Structural observation of layered double perovskite oxide La₂CuSnO₆ thin films grown epitaxially on SrTiO₃ is reported by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Particularly the transition layer at the interface was observed, and the first B site layer at the interface was found to be almost formed by the Cu atomic layer as the random structure, followed by formation of the layered structure.
In addition, HAADF-STEM images indicate that the thin film is not single crystalline, but some irregular structures were observed to grow around the interface near atomic steps of the substrate of SrTiO₃. Therefore, the steps largely affect the growth process of the thin film.     

Atomic force microscopy imaging of polycrystalline CuInSe2 thin films

In this study, atomic force microscopy (AFM) imaging has been used to study the structural properties of polycrystalline CuInSe₂ films, which are widely used as absorber materials in thin film solar cell devices. This technique demonstrated an excellent capability for the reproducible imaging of these rough polycrystalline materials. AFM imaging in combination with statistical analysis revealed distinct differences in the structural properties (i.e. grain width and height distributions, root‐mean‐square (RMS) and peak to valley (R_(p–v)) roughness values) as a function of the specific growth technique used and the bulk composition of the films. In the case of Cu‐rich films, prepared by the H₂Se/Ar treatment of Cu/In/Cu alloys, rough surface structures were in general observed. Statistical analysis revealed two distinct distribution of grains in these samples (1.0–2.5 μm and 3–5.5 μm) with large RMS and R_(p–v) roughness values of 380 nm and 2.6 μm, respectively. In‐rich films were characterized by the presence of much smaller, roughly circular clusters with a significant reduction in both the width and height distributions as well as RMS and R_(p–v) roughness values. The most successful growth techniques, in terms of producing homogeneous and dense films, were in the cases of H₂Se/Ar treated metallic InSe/Cu/InSe alloys and the coevaporation of all materials to form CuInSe₂. Both these techniques produced absorber films with very narrow grain width and height distributions as well as small roughness values. It was possible to establish that high efficiency devices are associated with the use of absorber films with narrow width distributions between 0.5 and 2 μm and small RMS (> 300 nm) roughness values. These values are used as a figure of merit in our laboratories to evaluate the structural properties of our CuInSe₂ thin films.     

Formation of pentacene wetting layer on the SiO2 surface and charge trap in the wetting layer

We studied the early-stage growth of vacuum-evaporated pentacene film on a native SiO(2) surface using atomic force microscopy and in-situ spectroscopic ellipsometry. Pentacene deposition prompted an immediate change in the ellipsometry spectra, but atomic force microscopy images of the early stage films did not show a pentacene-related morphology other than the decrease in the surface roughness. This suggested that a thin pentacene wetting layer was formed by pentacene molecules lying on the surface before the crystalline islands nucleated. Growth simulation based on the in situ spectroscopic ellipsometry spectra supported this conclusion. Scanning capacitance microscopy measurement indicated the existence of trapped charges in the SiO(2) and pentacene wetting layer.     

Electrostatic force microscopy study on the domain switching properties of the Pb(Zr0.2Ti0.8)O3 thin films with different crystallographic orientations for the probe-based data storage

The domain switching properties of the ferroelectric Pb(Zr_0.2Ti_0.8)O₃ (PZT) thin films with two types of crystallographic orientations were investigated by electrostatic force microscopy (EFM). The crystallographic orientations of the PZT thin films were random on the (1 1 1)Pt/MgO(1 0 0) and c-axis preferred on the (1 0 0)Pt/MgO(1 0 0), respectively. When dc bias was applied to the films for writing in micro-scale area, electrostatic force images showed that the domain switching was hard in the PZT thin films with random orientation, while the pattern could clearly be written in the PZT films with c-axis orientation. The differences in the domain switching properties of each PZT thin film were investigated in the crystallographic orientations point of view, and the domain switching dynamics were also measured by investigating the nano-sized dot switching behavior with respect to the width of the applied voltage pulse.     

Probing the local temperature by in situ electron microscopy on a heated Si3N4 membrane

We present a method allowing us to obtain localized heating that is compatible with high-temperature operation and real time scanning and transmission electron microscopy. Localized heating is induced by flowing current through tungsten nanowires deposited by focused ion-beam-induced deposition on a 50-nm-thick Si₃N₄ membrane. Based on the heat transport between the nanowire and the substrate, we applied an analytical model to obtain the temperature profile as a function of electrical power. In this model, the key parameter is the thermal resistance between the nanowire and the substrate that we determined experimentally by measuring electrical power and local temperature. The local temperature is measured by observing the evaporation of gold nanoparticle by electron microscopy. These in situ heating and temperature-probing capabilities are used to study the crystallization of the Si₃N₄ membrane and the growth of silicon nanowires.     

The tribological properties of YBa2Cu3O7 films in ambient environment

In the present study, high-T_c superconducting thin YBa₂Cu₃O₇ films and polysilicon films were prepared to investigate the initial sliding friction properties using a ball-on-flat tribometer when samples were moved against a sapphire ball or a steel ball in ambient environment. The surface topography was measured with atomic force microscope (AFM). After five times testing, the experimental results indicate that the friction coefficient of YBa₂Cu₃O₇ films is lower than that of polysilicon films when sliding against a sapphire ball and almost the same when sliding against a steel ball. In particular, the initial friction of YBa₂Cu₃O₇ films is more stable when sliding against a sapphire ball. However, the initial friction of polysilicon films fluctuates during a cycle period when sliding against a sapphire ball. They are both stable when sliding against a steel ball. Although, the surface profile of the YBa₂Cu₃O₇ film is rough and can be seen to be rougher than the polysilicon film, but the friction coefficient of the YBa₂Cu₃O₇ film is lower than that of polysilicon film. Also, although the topography of YBa₂Cu₃O₇ films changes during friction, the friction coefficients are stable. This clearly shows that the initial sliding friction of YBa₂Cu₃O₇ films under microfriction is stable. The observation signifies YBCO film is a good film to prevent stick–slip motion in ambient environment. The wear properties of YBa₂Cu₃O₇ films suggest that the superconducting outgrowths (CuO) are loose and they can be easily removed.     

Effects of morphological control on the characteristics of vertical-type OTFTs using Alq3

We have fabricated vertical-type organic thin-film transistors (OTFTs) using tris-(8-hydroxyquinoline) aluminum (Alq(3)) as an n-type active material. Vertical-type OTFT using Alq(3) has a layered structure of Al(source electrode)/Alq(3)(active layer)/Al(gate electrode)/Alq(3)(active layer)/ITO glass(drain electrode). Alq(3) thin films containing various surface morphologies could be obtained by the control of evaporation rate and substrate temperature. The effects of the morphological control of Alq(3) thin layer on the grain size and the flatness of film surface were investigated. The characteristics of vertical-type OTFT significantly influenced the growth condition of Alq(3) layer.     

High-resolution electron microscopy of disordered lithium ferrites

The disordered phase of lithium ferrite (α-LiFeO₂) shows characteristic circular short-range order (SRO) diffuse scattering around the 110 and the equivalent reciprocal lattice points in the diffraction pattern with the [001] incidence. The origin of the diffuse scattering has been explained by the SRO arrangement of lithium and iron ions inside an octahedron as the unit of the sodium chloride derivative structure (cluster model). In the present study, the local structure of the specimen is directly observed by high-resolution electron microscopy and microdiffraction to clarify the origin of the SRO diffuse scattering. The results obtained from the micrographs show that the SRO state of the specimen consists of regular arrangements of iron-rich regions with total size of 1.5 to 2.0 nm in the [001] and [0$\text{1}$1] projections. It is confirmed from the optical diffraction patterns of the micrographs and the microdiffraction patterns that the arrangements, as the results by the projections, explain the loci in the 001 and 0$\text{1}$1 sections of the characteristic SRO diffuse scattering. These results show that a part of the origin of the SRO diffuse scattering arises from ordering in the regions larger than the octahedral unit.     

Neutron scattering studies of BiFeO3 multiferroics: a review for microscopists

Application of the neutron scattering technique in the study of crystal and magnetic properties of multiferroic BiFeO₃ is presented. The crucial role of the neutron scattering technique, complementary to X-ray diffraction method and transmission electron microscopy, is shown. Especially the ultra high-resolution time-of-flight (TOF) neutron diffraction technique used by Sosnowska et al. to detect the magnetic cycloid ordering and its role in studies of physical properties of BiFeO₃ and its alloys are reviewed. The first inelastic neutron scattering patterns of magnetic excitations in BiFeO₃ are also presented. Applications of different microscopy techniques such as transmission electron microscopy (TEM), scanning electron microscopy ( SEM), field emission TEM and SEM (FESEM and FETEM), magnetic force microscope (MFM) and polarization force microscopy (PFM) bring insight on the fundamental problem of ferroelectricity and confirm the potential of BiFeO₃ multiferroic material for nanoscale devices.