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Notes: A pneumatic pressure rig was designed to measure the effective d33 coefficient of thin film piezoelectrics by applying a known stress and monitoring the induced charge. It was found that the stress state imposed included components both perpendicular and parallel to the film plane. The later were due to friction and could largely be relieved through sliding of the O-rings to their equilibrium positions for a given pressure. The induced charge stabilized as equilibrium was reached and most of it was produced by the normal component of the stress. By minimizing the surface friction and compensating for the remnant in-plane stress, very good agreement was obtained among the d33 values measured by the Berlincourt method, double-beam interferometry and this method for a bulk lead zirconate titanate (PZT) sample. The d33 value of PZT thin films made by sol-gel processing was also measured. The as deposited films usually showed very weak piezoelectricity with d33 values ranging from 0 to 10 pC/N, indicating little pre-existing alignment of the domains. With increasing poling field, the d33 value also increased and saturated at poling fields exceeding three times the coercive field. Typically, films with thicknesses around 1 μm had d33 values of 100 pC/N. Good agreement between double-beam interferometry and this technique was also obtained for thin films. The small difference between the two measurements is attributed to the effect of mechanical boundary conditions on the effective d33 coefficient. © 1999 American Institute of Physics.

Notes: In this article, domain wall motion and the extrinsic contributions to the dielectric and piezoelectric responses in sol–gel derived lead zirconate titanate (PZT) films with compositions near the morphotropic phase boundary were investigated. It was found that although the films had different thicknesses, grain sizes, and preferred orientations, similar intrinsic dielectric constants were obtained for all films between 0.5 and 3.4 μm thick. It was estimated that about 25%–50% of the dielectric response at room temperature was from extrinsic sources. The extrinsic contribution to the dielectric constant of PZT films was mainly attributed to 180° domain wall motion, which increased with both film thickness and grain size. In studies on the direct and converse longitudinal piezoelectric coefficients of PZT films as a function of either stress or electric driving field, it was found that the ferroelastic non-180° domain wall motion was limited. Thus extrinsic contributions to the piezoelectric response were small in fine grain PZT films (especially those under 1.5 μm in thickness). However, as the films became thicker (〉5μm), nonlinear behavior between the converse piezoelectric coefficient and the electric driving field was observed. This indicated that there was significant ferroelectric non-180° domain wall motion under high external excitation in thicker films. The activity of the non-180° domain walls was studied through non-180° domain switching. For fine grain films with film thicknesses less than 2 μm, non-180° switching was negligible. Transmission electron microscopy plan-view micrographs evidenced non-180° domain fringes in these films, where the vast majority of grains were 50–100 nm in diameter and showed a single set of domain fringes. Taken together, these measurements suggest that the pinning of non-180° domain walls is very strong in films with thickness less than 2 μm. In thicker films, non-180° domain switching was evidenced when the poling field exceeded a threshold field. The threshold field decreased with an increase in film thickness, suggesting more non-180° domain wall mobility in thicker films. Non-180° domain switching in large grained PZT films was found to be much easier and more significant than in the fine grained PZT films. © 2001 American Institute of Physics.

Notes: A cubic Si3N4 phase/nanostructure has been characterized by means of high-resolution analytical electron microscopy. The specimen prepared from β-Si3N4 powders at a high pressure and temperature by shock wave compression contained nanometer-sized Si3N4 crystallites. The results of nano-beam electron diffraction analysis and high-resolution lattice images as well as computer simulations revealed that the Si3N4 crystallites had a cubic symmetry with spinel structure. The electron energy loss spectrum suggested that the chemical compositions of these nanostructures were close to Si3N4. © 2000 American Institute of Physics.

Notes: Schottky barrier formation for Al/ZnSe (100) and Au/ZnSe (100) was studied using photoelectron spectroscopy. The initial Fermi level position for sputter-annealed ZnSe (100) surfaces was 2.05 eV above the valence-band maximum (VBM). The final Fermi level position, established after the deposition of several monolayers of metal adatoms, was very different for Al (2.17 eV) and Au (1.25 eV, relative to the VBM). The deposition of Au interlayers for Al/Au/ZnSe and Al interlayers for Au/Al/ZnSe showed that it is possible to "tune'' the Schottky barrier height between these extremes by choosing interlayers of definite thickness.

Notes: High-resolution synchrotron radiation photoelectron spectroscopy has been used to study Au/Si and Au/CoSi2/Si interface formation at room temperature. Our results show Au-Si intermixing, the absence of a well defined Au-Si compound, and surface segregation of small amounts of Si to the Au surface. An interlayer formed by the deposition of ≤3 A(ring) of Co has relatively small effect on this Au-Si atomic profile. Intermixing is abruptly quenched, however, when the Co deposition exceeds 3.5 A(ring), and a Au film free of Si can grow on the CoSi2 layer. These results demonstrate the effectiveness of CoSi2 layer as a barrier against Au-Si intermixing and identify the critical coverage of Co needed to passivate the Si surface.

Notes: We present studies of Au film formation on the III-V compound semiconductors GaAs and InSb based on polar-angle-dependent x-ray photoelectron spectroscopy. The results highlight the power of this technique as a nondestructive tool for atom profiling. The Au overlayer is highly heterogeneous due to disruption of the original surface and significant anion segregation in Au. Although GaAs and InSb show common behavior, significant differences are observed because the anion–cation bond strength determines the extent of the surface disruption and semiconductor atom solid solubilities in Au dominate the segregation patterns in each system. We present a model of the overlayer structure, based on thermodynamic considerations, which shows very good quantitative agreement with the observed profiles.

Notes: For a long time cerium ions, both Ce3+ and Ce4+, have not been considered to be able to enter the interstitial sites in an α-sialon structure until recent successes in the preparation of cerium-doped α-sialon materials using CeO2 as the starting powder. It is then of great importance and necessity to know the chemical valence of these incorporated cerium ions. Meanwhile, the specific structure of the interstices in α-sialon provides quite a different chemical environment upon which the electronic structures of cerium ions could be different from those ever reported in, for instance, metallic compounds and oxides. Electron energy loss spectra (EELS) in the M-edge region of rare-earth elements carries information on the initial state 4f occupancy. We have acquired and examined the M4,5-edge spectra of cerium at different locations in the microstructure. It has been found that all the Ce(IV) ions in the intergranular glass and the majority inside the α-sialon crystals have been reduced to Ce(III) while there exist inside the crystal cerium ions showing 4f0 initial-state peaks on the EELS spectrum. The 4f0 peak locates at about 0.6 eV higher in energy than that for CeO2. An increased and possibly by far the highest weight of f0 state is derived for Ce(IV) ions in α-sialon. The spectral evidences confirm the general suggestion of the unstability of Ce(IV) ions with silicon nitride. © 2001 American Institute of Physics.

Notes: We present a novel method, by using an ion implantation and subsequent heat treatment, to prepare Fe nanocrystalline in SiO2. The formation process of Fe granules was monitored by means of conversion electron Mössbauer spectroscopy and the size of which was determined by transmission electron microscopy. The magnetic coercivity of 100 and 70 Oe have been observed at room temperature and 80 K, respectively. A decrease of the coercivity at 80 K is probably caused by the appearance of a multidomain structure in the granules due to reducing the critical radius of single domain.

Notes: A sulfur passivation method for GaAs, CH3CSNH2 treatment has been developed. It is quite effective for removing the surface oxide layer and forming the sulfide passivation layer on GaAs surface. The enhancements of the PL intensity reveal the reduction of the surface recombination velocity and the reduction of density of defect states by this treatment. The synchrotron radiation photoemission spectroscopy measurements show that sulfur atoms bond both Ga and As atoms. After being annealed, a stable sulfur passivation layer is terminated on the surface due to the As2S3 component react with GaAs into the GaS component. © 1996 American Institute of Physics.

Notes: Soil boron (B) deficiency, a world-wide problem in agriculture, exists for more than 33 million hectares of cultivated land in China. Genetic variation exists for B-efficiency among different Brassica napus germplasms. To identify genes controlling B efficiency, an F2 population of B. napus was constructed from a cross between a high B-efficiency cultivar, ‘Qingyou 10’, and a low B-efficiency cultivar, ‘Bakow’, and then evaluated for seed yield, bolting date and maturity date under B-deficient conditions. The ratio of high B-efficiency to low B-efficiency individuals fitted the expected ratio of 3:1, indicating a major gene controlling the B-efficiency trait. The major gene was mapped in the ninth linkage group of B. napus. Genome-wide quantitative trait loci (QTL) analyses detected one major locus near the major gene, which explained 64.0% of the phenotypic variance. At the same time, three minor loci in three linkage groups were also detected, and these minor loci individually explained 39.2%, 32.5% and 36.9%, respectively, of the phenotypic variance. A total of 11 QTLs were detected for bolting date and maturity date, some of which were associated with B-efficiency.