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The electrical properties of sol–gel deposited BaTiO3 thin films on Si(100) and SiO2-buffered Si(100) substrates were investigated. The dielectric constant measured as a function of frequency was fitted using the space charge relaxation model. The effective dielectric constant (ε') and dissipation factor (tan δ) were determined in the accumulation region from the results of capacitance–voltage ( C–V ) measurements at room temperature, at 1 MHz. Values of 23–185 and 0.02–0.08 were determined, respectively. The density of the interfacial surface states (N ss), calculated from the width of the memory window of the C–V curve, was of the order of 1011–1012 eV-1 cm-2. The leakage current densities for BaTiO3 films deposited on Si and SiO2-buffered Si substrates were 22–57 nA/ cm2 and 0.85–4 nA/ cm2, respectively, at an applied field of 100 kV/cm. The dielectric breakdown strength exceeded 1 MV/cm for all films.

Infrared reflection and transmission measurements of Be‐implanted GaAs have been made as functions of Be‐ion fluence and annealing temperatures from 500 to 800 °C. Semi‐insulating material was implanted with 280‐keV ions with fluences of 1×1015, 3×1015, 6×1015, and 10×1015 ions/cm2. Hole carrier concentrations calculated from the optical measurements as functions of fluence and annealing temperature compare favorably with those determined from sheet Hall‐effect data. The absorption cross section used was obtained from measurements of acceptor‐doped GaAs with concentrations similar to those of the implanted and annealed samples. After annealing at 500 °C a free‐hole plasma layer contribution to the electric susceptibility was observed by measurements of reflection interference effects. Except for the highest‐fluence case the disorder effect on the dielectric constant was largely removed by this anneal. For the highest‐fluence case the annealing results were more complicated. There are regions which still have significantly different optical properties due to residual disorder. The present results are consistent with redistribution effects produced by thermal aging at the higher temperatures.

The infrared reflectances of virgin and γ‐ray irradiated NaNO2 have been determined from the reflection spectra which have been investigated as functions of temperature (ranging from RT to 180 °C) and crystallographic orientation, and γ‐ray irradiation dose (4×107 and 3×108 rontgen.) over a frequency region between 700 and 2000 cm−1. Using the Kramers‐Kronig dispersion relation, we have obtained the dielectric function and oscillator parameters from the reflection spectra. These constants are used to explain the ferroelectric properties of NaNO2. In addition the observed differences between the reflection spectra of virgin and those of γ‐ray irradiated NaNO2 are explained using a broken‐bond model.

Free‐charge carriers in both room‐ and low‐temperature Be‐implanted GaAs were generated by annealing at 400, 450, and 475 °C and were observed by using both infrared reflection and electrical measurements. Annealing at 400 °C for 2 h removes homogeneously most of the damage‐related changes in the refractive index. Longer annealing (∼50 h) or shorter term annealing at higher temperature produces free carriers. A computer model including plasma effects was used to fit the reflection curves. In general the infrared analysis results and the electric data were in reasonable agreement. Results for the room‐temperature‐implanted samples show the free‐carrier density profile, approximated by joined half‐Gaussians, to be (i) a standard deviation for the deeper half‐Gaussian (σh≤0.1 μm), which is about the same or smaller than that observed by secondary ion mass spectrometry measurements (∼0.13 μm) for the Be profile, and (ii) a peak position 1.2 μm, which is deeper than the Be ion peak at 0.95 μm. Both peak positi...

Single crystals of SbSI: Co and SbSeI: Co were prepared by the Bridgman technique. The optical absorption spectra of these single crystals were investigated in the wavelength range 500–2500 nm. We determined the optical energy gaps of these compounds, and identified the electric states of cobalt impurity in these single crystals. We observed the impurity absorption peaks at energies of 14000-4000 cm−1 range due to cobalt impurity. It can be explained that the impurity absorption peaks are attributed to the electronic transitions between the energy levels of cobalt ions, which are sited in tetrahedral (Td) symmetry of crystal lattice as Co3+ and Co2+ ions. The crystal field parameters Dq are given by 697 cm−1 for Co3+ and 454 cm−1 for Co2+ ions in SbSI: Co single crystals, and also 847 cm−1 for Co3+ and 452 cm−1 Co2+ ions in SbSeI: Co single crystals.

Infrared reflection and transmission measurements were used to study the thermally induced regrowth of (100) oriented, Be‐implanted GaAs samples. The samples used in this study were implanted at low temperature (−100 °C) with 250‐keV Be ions to a fluence of 6×1015 cm−2. The samples were postannealed at temperatures ranging from 100 to 550 °C. Isochronal and isothermal annealing at a series of temperatures between 180 and 240 °C were performed. Infrared reflection spectra were analyzed by using a three or four layer dielectric model. Analysis of the annealing data suggests that an amorphous layer first anneals to a second metastable amorphous state and then becomes a damaged crystalline layer after annealing at 220 °C for 12 h. The observed regrowth is not by a simple epitaxial process. After annealing at 400 °C for 1 h, the damage in the layer is reduced sufficiently for the refractive index to recover almost to the preimplantation value. On annealing at 450 °C free carriers are observed. From the measure...

Infrared reflection and transmission measurements of GaAs implanted with large fluences of Be ions have been made as a function of post‐implantation annealing temperature. Annealing up to 400 °C resulted in decreases in the lattice disorder responsible for changes in the dielectric constant. This decrease appears to take place uniformly throughout the disordered layer rather than by an epitaxial process. Annealing at 400 °C for 2 h returns the dielectric constant to essentially the preimplantation value with no significant carrier activation being observed. Carrier activation is observed only after prolonged annealing at 400 °C, i.e., ≳50 h. Annealing for 1 h at 450 °C also produces measurable carrier activation. These results are in general accord with prior electrical data and transmission electron microscope measurements and suggest that the removal of the disorder‐induced changes in the dielectric constant and the activation of free carriers might involve different annealing processes.

For the present calculation of the mobile bond orders of para‐quaterphenyl and meta‐terphenyl molecules, Pople's simplified SCF—LCAO—MO theory for unsaturated hydrocarbon molecules in their ground states is utilized. The symmetry orbitals for these molecules are formulated in order to simplify the calculations by the use of group theory. The symmetry properties of these molecules and the pairing properties of the molecular orbitals are discussed. Planar configurations of both molecules are assumed as a first approximation. The unreasonable mobile bond orders calculated from the Huckel MO theory are improved in the present calculations. The results are discussed in connection with the recent experimental values of the bond lengths of biphenyl.

A review of the techniques developed for using infrared reflection spectroscopy to study properties of heavily implanted semiconductors is presented. Several structural models are considered and calculations based on them are applied to measurements of implanted Si, Ge and GaAs. These comparisons of model calculations and measured spectra show how a number of important physical parameters can be obtained as well as new information concerning implantation-induced amorphous material.© (1984) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Specific-heat measurements on virgin and \ensuremath{\gamma}-ray\char21{}irradiated single crystals of ${\mathrm{NaNO}}_{2}$ have been carried out to study the effects of defects on the incommensurate phase. Observation of a small specific-heat anomaly at a temperature just above the commensurate-incommensurate (CI) phase-transition point is reported for the first time. It is suggested that this new anomaly may be evidence for a defect-induced intermediate state between the commensurate and incommensurate phases. We discuss qualitatively the observed new anomaly and thermal hysteresis in the CI phase transition.

Single crystals of SbSeI:Ni were grown by the Bridgman technique. The impurity optical absorption spectra of these single crystals were investigated at room temperature. We observed impurity optical absorption peaks at 4334, 7763, 8857, 8952, and 11 587 cm−1 due to nickel impurity. These impurity optical absorption peaks are assigned to the electronic transitions from the ground state 3T1(3F) to the excited states 3T2(3F), 3A2(3F), 1T2(1D), 1E(1D), and 3T1(3P) of Ni2+ ions sited at Td symmetry of the SbSeI host lattice.

Single crystals of SbSI and SbSI: Ni were grown by the Bridgman technique. The optical absorption spectra of these single crystals were investigated, and also the electronic states of nickel impurity in the SbSI: Ni single crystal were identified. We observed the impurity absorption peaks at 4502, 7770, 8904, 9090, 12 180 and 14 598 cm−1 due to the electron transitions between the energy levels of Ni2+ ions sited at Td symmetry of SbSI host lattice. The crystal field parameter and the Racah parameter are given by Dq = 327 and B = 663 cm−1, respectively.

Experimental results on mixed crystals of K1-x (NH4) x H2PO4 and KH2P1-x As x O4 are reported as a function of concentration (for x\lesssim0.13) and explained by the modified proton lattice coupled model. Some physical properties of the mixed crystals obtained from measurement of the Curie constants, spontaneous polarizations, and specific heats are related to the role of impurities in the phase transition of the crystals. We found that the interaction energy beween host and impurity is negative for mixed crystal with ADP impurities. This indicates that in this mixed crystal, there is competition between ferroelectric and antiferroelectric exchange interactions.

The infrared reflectances of the single crystal (NH4)2SO4 have been measured as functions of temperature and crystallographic axis. It is observed that the asymmetric streching internal mode (ν3) of SO4 2 ions which has triple degeneracy at room temperature is split into two modes around the phase transition temperature along each axis, but only along the ferroelectric c-axis these two modes are split again into three modes far below the transition temperature. The triplet asymmetric bending mode (ν4) of NH4 + ions shows no apparent change except the splitting of the peak into two in the c-axis polarized light below transition temperature. The optical constants, the mode parameters and the oscillator strengths are calculated by using Kramers-Kronig relations and the results are interpreted physically.