Materials Literature
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New series of ferroelectric liquid crystals with two chiral carbons or bulky molecular components at the chiral carbon are synthesized and are found to possess extremely large spontaneous polarization exceeding 2×10−7 C/cm2 and a dielectric constant larger than 7000. These compounds are stable and exhibit a novel diel…
We have found that decagonal quasicrystal and 10-fold twins of monoclinic ${\mathrm{Al}}_{13}$${\mathrm{Fe}}_{4}$ coexist in rapidly cooled Al-Fe alloy. The tenfold axis of the decagonal phase is parallel to the pseudotenfold [010] axis of the twins. There is good coincidence between the strong spots of the decagonal…
We have obtained Raman spectra of phase-I, -II, and -III ${\mathrm{KNO}}_{3}$ films 0.26 \ensuremath{\mu}m thick. The primary aim was to establish the physical mechanism for stabilization of the ferroelectric phase III in thin films. In bulk, phase III exists only as a reentrant phase stable from \ensuremath{\sim}113…
Epitaxial growth of SrO thin films onto Si(111) and (100) substrates by means of molecular-beam epitaxy has been demonstrated. The orientation relationships between epitaxial SrO and Si were found to be (111)SrO//(111)Si and [112̄]SrO//[112̄]Si, (100)SrO//(100)Si and [011]SrO//[001]Si. The composition of the grown fil…
The size dependence of the lowest electron-hole state in semiconductor microcrystals is calculated using the variational principle with a three-parameter Hylleraas-type wave function. For very small particles the Coulomb interaction may be treated as a perturbation. For larger particles the size dependence of the ener…
A new investigation of the optical properties of scandium is presented. Near-normal-incidence reflectivity measurements were performed from 0.22 to 5.5 eV on polycrystalline thin films evaporated in situ in ultrahigh vacuum. The reflectivity, from 0.22 to 35 eV, of the same samples after they had been exposed to air w…
Resonance Raman scattering (RRS) in CdSe is investigated in the region of the A excitonic transition. Three new Raman lines at 182, 195, and 208 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ are observed which become stronger than even the line due to the longitudinal optic (LO) phonon under appropriately resonant condit…
Transmission measurements on single-crystal ${\mathrm{SrTiO}}_{3}$ between room temperature and 1200?deC are reported. Urbach broadening of the absorption edge is observed at all temperatures. Below 200?deC the broadening is typical of the lowest indirect band gap. Above 400?deC the dominating broadening is due to the…
The optical properties of the transition-metal ions, ${\mathrm{Ni}}^{2+}$, ${\mathrm{Co}}^{2+}$, and ${\mathrm{Mn}}^{2+}$, in zirconium-barium-lanthanum-aluminum (ZBLA) fluoride glass are reported. Comparisons of the absorption spectra, luminescence spectra, and luminescence lifetimes for these ions in ZBLA and in ${\…
The hyperfine field, H hf , and the nuclear spin-lattice relaxation rate, 1/ T 1 , of 59 Co and 27 Al nuclei have been measured in the weak itinerant ferromagnets Y(Co 1- x Al x ) 2 . The temperature and magnetic field dependence of 1/ T 1 T has been found to be well described by the self-consistent renormalization (S…
The Cu+ ion impurity in a NaF host has been modeled using a finite cluster of ions to represent the crystal lattice. Several approximations to the lattice potential in the region of the cluster were compared to the exact Madelung potential. The error in the calculated nearest-neighbor distance for the pure host was fo…
The c-axis resistivity of highly oriented pyrolytic graphite has been measured from 2 to 300 K under hydrostatic pressures of up to 40 kbar. A resistivity peak near 40 K, typical for this type of graphite at ambient pressure, rapidly diminishes with increasing pressure but does not shift its position with respect to t…
Optical reflection and absorption spectra of SrTe and BaTe have been measured in the pressure range of 0 to 400 kbar at 300 K. Excitonic transitions related to the lowest direct gap in the rocksalt (B1) structure shift to lower energy with increasing pressure and are attributed to a Te 5p to Ba 5d (Sr 4d) transition a…
The effects of the local dielectric environment on the surface-plasmon resonances of annealed metal-island films are studied experimentally and modeled theoretically. Silver-island films were annealed to produce spheroidal shaped particles which exhibit well-resolved resonances in polarized, angle-resolved, absorption…
An interpretation model for low reflectivity in ultrahigh spatial-frequency holographic relief gratings is proposed. The model is based on the concept that the grating effective index, caused by grating ultrahigh spatial frequency, is graded in the depth direction and forms an antireflective constitution similar to th…
The proton spin lattice relaxation rate (1 / T 1 ) in the superconducting state of(TMTSF) 2 ClO 4 has been measured at zero magnetic field using the field cycling technique. It was found that the enhancement of 1 / T 1 just below T c , commonly observed in typical BCS superconductors, was absent and 1 / T 1 varied as…
Near-edge x-ray-absorption fine-structure studies of ${\mathrm{O}}_{2}$ chemisorbed on Ag(110) and Pt(111) surfaces near 100 K reveal different predissociation stages of molecular oxygen. ${\mathrm{O}}_{2}$ on Ag(110) exhibits only a ${\ensuremath{\sigma}}^{\mathrm{*}}$ resonance and resembles a single-bonded peroxo s…
We have measured the thermal conductivity of polymethylmethacrylate (PMMA), amorphous ${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$, Ca-K nitrate glass, three ${\mathrm{SiO}}_{2}$-based glasses, and glycerol in the temperature range 30--300 K, using an ac technique that eliminates errors from blackbody radiation. This techniq…
It is shown how the results of low-temperature electrical and thermal conductivity measurements may be used to characterise and determine the defect structure of pristine and intercalated carbon fibres of various origins.
The aromatic (A) and quinoid (Q) forms of polythiophene (PT) have entirely different energy gaps: ∼0.5 eV for the quinoid form and ∼2 eV for the aromatic form, respectively. The energy gaps and stability of derivatives of PT are studied by total MNDO geometry optimization using energy band theory for the total energy…