K. Z. Baba-Kishi

Topographic and phase-contrast imaging in atomic force microscopy

Phase-contrast imaging in the tapping mode atomic force microscopy (AFM) is a powerful method in surface characterization. This method can provide fine details about rough surfaces, which are normally obscured in topographic imaging. To illustrate some of the capabilities of phase-contrast imaging, AFM studies of Pt/Ti/SiO2/Si and Pb(Zr0.52Ti0.48)O3 (PZT) films were carried out. Phase-contrast imaging revealed fine details of their microstructures, including grain boundaries, triple junctions and twinning, which could not be detected by topographic imaging. The studies showed that phase-contrast imaging is capable of providing superior information about surface characteristics when compared to the standard topographic imaging.

Crystal structure refinements of disordered pb(sc0.5nb0.5)o3 in the paraelectric and ferroelectric states

Abstract The crystal structure of the relaxor ferroelectric Pb(Sc0.5Nb0.5)O3 has been refined from high-resolution neutron time-of-flight powder diffraction data in the paraelectric and ferroelectric states. In the ceramic used in this study, no evidence was found for unit cell doubling, associated with B-site cation ordering, consistent with the (NH4)3FeF6 structure in the paraelectric state. At 400 K, in the paraelectric state, Pb(Sc0.5Nb0.5)O3 is cubic, space group Pm3m, with lattice parameter 4.08153(1) A, and at 200 K, in the ferroelectric state, it is rhombohedral, space group Ram, with lattice parameters a = 4.08207(1) A and a = 89.872(1)°. Calculated absolute displacements in the ferroelectric state along the [111] ferroelectric axis are for Pb 0.094 &, Sc/Nb -0.148 A. and O -0.195 A. The 3.0 A coordination shell around the Pb cation shows evidence for a stereochemically active lone pair, whilst by contrast, the distortion in the SclNb octahedral site is small.

Characterization of butterfly single crystals of by atomic force, optical and scanning electron microscopy techniques

A comparative study of ferroelectric domain configurations and surface morphology of butterfly single crystals of by the techniques of atomic force microscopy, optical microscopy and scanning electron microscopy is described. An unusual array of defects on the surface of a highly stressed region of the crystal was investigated in detail. Surface microstructural features displaying complex and distinct morphology associated with barium-rich phases were also studied.

Nanoscale global mixed ordering of B-site cations in Pb2M′M′′O6 complex perovskite relaxors

We have observed compositionally heterogeneous, uniformly distributed and closely interconnected nanoscale and sub-nanoscale domains in complex perovskite-structured relaxors. These domains are interpreted as originating from global mixed ordering, formed by numerous non-stoichiometric combinations of B-site cations across the entire bulk of the relaxor crystals and ceramics. The association between global mixed ordering and the origin of the forbidden reflections has been explained theoretically and experimentally. Various models of global mixed order–disorder are proposed, simulated and subsequently compared with dark-field and high-resolution TEM images, showing unambiguous agreement between the models and the observed TEM images and the diffraction patterns. Careful and extensive case studies of Pb2(ScTa)O6 crystals and (0.4)Pb2(InNb)O6:(0.6)Pb(Mg1/3Nb2/3)O3 ceramics show that mixed order–disorder originates from a global B-site chemical heterogeneity. The findings are analyzed using a normal statistical distribution approach, which is supported by the length-scale of the experimentally observed domains.

Effects of the insertion of a thick sp2 buffer layer on the adhesion of cBN-rich film

A method was proposed and examined to deposit thick cubic boron nitride (cBN)-rich layer of good adhesion to silicon substrate. The method combined (i) the insertion of a thick sp2 buffer layer, and (ii) the use of an appropriate assist ion beam energy for the growth of the cBN-rich top layer. The sp2-bonded boron nitride buffer layer was deposited under irradiation of ions with energies in the range of 200–360 eV. The buffer layer was found to contain curled graphitic basal planes, and so was supposed to be relatively deformable, and facilitate the relaxation of stresses in the cBN-rich top layer. The ion assist introduced during the growth of the cBN-rich layer was supposed to both create and annihilate defects, and so resulted in the generation and relaxation of internal stresses. Results showed that the insertion of a 492 nm sp2 buffer layer, and the use of a beam energy of 450 eV for assisting the growth of the top layer can produce a 643-nm-thick cBN-rich top layer with satisfactory adhesion, a high cBN content of 87 vol %, a hardness of 57 GPa, and an elastic modulus of 612 GPa.A method was proposed and examined to deposit thick cubic boron nitride (cBN)-rich layer of good adhesion to silicon substrate. The method combined (i) the insertion of a thick sp2 buffer layer, and (ii) the use of an appropriate assist ion beam energy for the growth of the cBN-rich top layer. The sp2-bonded boron nitride buffer layer was deposited under irradiation of ions with energies in the range of 200–360 eV. The buffer layer was found to contain curled graphitic basal planes, and so was supposed to be relatively deformable, and facilitate the relaxation of stresses in the cBN-rich top layer. The ion assist introduced during the growth of the cBN-rich layer was supposed to both create and annihilate defects, and so resulted in the generation and relaxation of internal stresses. Results showed that the insertion of a 492 nm sp2 buffer layer, and the use of a beam energy of 450 eV for assisting the growth of the top layer can produce a 643-nm-thick cBN-rich top layer with satisfactory adhesion, a high...

Characterization of (0.4)Pb2(In, Nb)O6: (0.6)Pb(Mg1/3Nb2/3)O3 relaxor ceramics

The results of the development and characterization of a new relaxor ceramic with nominal composition (x)Pb 2 (In,Nb)O 6 (1 - x)Pb(Mg 1 / 3 Nb 2 / 3 )O 3 solid solution with x = 0.4 are reported. The structural characteristics, including the long-range and short-range order, forbidden reflections, and the existence of mixed ordering, were studied by transmission electron microscopy. The most prominent microstructural feature of this compound, which has composition variations in the micro- and nano-regions, was investigated. The presence of the pyrochlore phase and the complex arrangement of inclusions that originate from processing are illustrated. The electrical characteristics of the compound including pyroelectric, piezoelectric, electrostrictive and hysteresis properties are reported. Notable properties of the compound include a reduced hysteresis loop and nonlinear behavior at high field.

Relationship between the microstructure and nanoindentation hardness of thermally evaporated and magnetron-sputtered electrochromic tungsten oxide films

Tungsten oxide (WOx) films were fabricated by (i) reactive thermal evaporation (RTE) at room temperature with oxygen ambient pressure PO2 as a parameter, and (ii) reactive magnetron sputtering (RMS) with substrate temperature Ts as a parameter. The film structure revealed by x-ray photoelectron spectroscopy, x-ray diffraction, density measurements, infrared absorption, and atomic force microscopy was correlated with the nanoindentation hardness H. The RTE WOx films deposited at high PO2 were amorphous and porous, while H depended appreciably on normalized penetration depth hD (indentation depth/film thickness) due to the closing of the pores at the point of indentation. Decrease in PO2 from 10 to 2 × 10 −3 mtorr led to smaller porosity, weaker hD dependence of H, and higher average H (measured at hD ≈ 0.2 to 0.3, for example). The RMS WOx film deposited at room temperature was amorphous and denser than all RTE films. The rise in substrate temperature Ts first densified the film structure (up to 110 °C) and then induced crystallization with larger grain size for Ts u 300 °C. Correspondingly, the hD dependence of H became weaker. In particular, H of the RMS sample deposited at 110 °C showed a peak at hD slightly above 1 owing to pileup at the contact point of indentation. For higher Ts, pileup occurred at shallower hD and the average H (measured at hD ≈ 0.2 to 0.3, for example) rose, accompanied by the increase of grain size.

Morphology of domain patterns in relaxor 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 crystals studied by transmission electron microscopy

Abstract Transmission electron microscopy studies of domain morphology in 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals reveal complex arrangements of a variety of domains. In addition to mesoscopic domains, there are those that consist of two mutually perpendicular parallel tweeds whose widths are less than 10 nm. The parallel tweeds are separated by shear strain. The superposition of two perpendicular displacements produces the various domain configurations that include sharp tips, right-angle corners and S-shaped domain walls. It appears that the competing rhombohedral and cubic phases result in asymmetrical domains. The transformation from cubic to rhombohedral phase creates a morphotropic phase-boundary material with specific ferroelectric properties. An improper martensitic phase transformation model may be used to explain the observed domain configurations.

Dielectric and Electromechanical Properties of Pb(In 1/2 , Nb 1/2 )O 3 :Pb(Mg 1/3 Nb 1/3 )O 3 Ceramics

The dielectric permittivity l r and loss of Pb(In 1/2 Nb 1/2 )O 3 -Pb(Mg 1/3 Nb 1/3 )O 3 ceramics (PIN-PMN) with compositions 40/60 and 70/30 was found to exhibit a typical relaxor behaviour. At 1 kHz, a peak in l r is observed at about 20°C for 40/60 and 30°C for 70/30, at which l r has values of 10000 and 5000, respectively. At 1 kHz, the loss tangent at the peak is about 0.1 and increases slightly with increasing frequency. Hysteresis measurements performed at room temperature at a frequency 50 Hz and under a maximum electrical field of 2 MV/m show a very slim loop for 40/60 and almost no loop for 70/30. The maximum polarization attained was 20 w C/cm 2 while the remanent polarization was less than 2 w C/cm 2 . The field-related electrostrictive coefficient M 11 for 40/60 was found to be 1.2 2 10 m 16 m 2 /V 2 , which is of the same order of magnitude as those of the best PMN-relaxor solid solutions. The polarization-related electrostrictive coefficient Q 11 , calculated according to the relation Q 11 = M 11 / l 2 , was 1.5 2 10 m 2 m 4 /C 2 .

Influence of long-range structural order on electrostriction in the as-sintered and annealed (0.4)Pb(In1/2Nb1/2)O3?:?(0.6) Pb(Mg1/3Nb2/3)O3 relaxor ceramics

Longitudinal electrostrictive strains in an as-sintered and two annealed (0.4)Pb(In1/2Nb1/2)O3 : (0.6)Pb(Mg1/3Nb2/3)O3 relaxor ceramics were measured by laser-interferometry. The field-related electrostriction coefficients (M33) of the ceramics were then determined. The electrostrictive coefficients progressively decreased with annealing and the strain responses became nonlinear. The ferroelectric hysteresis loops of the as-sintered and annealed ceramics showed progressive decrease in coercive fields and maximum polarizations with increasing annealing time. Transmission electron microscopy studies revealed enlargement of 1 : 1 B-site ordered domains with annealing. The changes in the high-field responses of the annealed ceramics are interpreted as arising from a higher degree of long-range order caused by annealing. A field-induced mechanism is proposed to explain the correlation between the B-site cation long-range order and the electrostrictive behaviour in this relaxor.