Negative thermally stimulated currents in ice

Using precision equipment of our own design, we measured thermally stimulated currents (TSCs) in pure crystalline ice and crystalline ice doped with HCl or NH₄OH. The conditions for heterocharge and homocharge decay under thermally stimulated depolarization (TSD) were studied. The role of proton relaxation during the formation of an electret state of the ice was determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 3–10, December, 1993.     

Dielectric relaxation in Ih ice

Relaxation processes in Ih ice are studied in the temperature interval 77–27G°K and frequency band 5 Hz–500 kHz. A new maximum in thermally stimulated currents was found at 97°K, clarifying the nature of the relaxing defects. The parameters of the peaks of the thermally stimulated currents at 97, 127, 139, and 158°K are determined, and the concentrations of L defects and oriented H₂O dipoles are evaluated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 72–76, October, 1986.     

Evolution with time of the dielectric properties of dispersed ice microcrystals

Summary The evolution with time of the characteristics of the dielectric relaxation of water molecules in dispersions of ice microcrystals has been studied by means of the thermally stimulated depolarization current (TSDC) method. With advancing stage of evolution,i.e. with increasing preservation time at constant preservation temperature and with increasing preservation temperature at constant preservation time, the mean values of relaxation time and activation energy have been found to decrease. The extent and the rate of the evolution have been compared to those in other forms of ice: ice samples with high content of disturbance, polycrystalline ice samples and single ice crystals. The observed similarities and differences in the behaviour of the different ice forms have been discussed in terms of the influence of extrinsic physical and chemical defects on the generation and motion of orientational Bjerrum defects.     

Proton ordering in ice at an ice-metal interface

The structure of the proton sublattice of ice at an ice-metal interface is analyzed by solving the Ginzburg-Landau equation for an order parameter describing the proton ordering under an appropriate boundary condition [1, 2]. When the interaction between protons and the substrate is weak, the ice rules that govern proton order are weaker at the interface as compared to bulk ice, but to a lesser extent than at the free ice surface. In the case of strong proton-substrate interaction (clean interface and/or high conductivity of the substrate), the ice rules are stronger at the interface as compared to bulk ice, which corresponds to a more ordered proton sublattice. The latter case corresponds to a lower concentration of defects in the proton sublattice, which determine important properties of ice, such as adhesion, electrical conductivity, plasticity, and electric field distribution near the interface. A qualitative correlation is described between electrical properties of the substrate and mechanical properties of the interface, including adhesion and friction.     

Thermally stimulated relaxation currents due to forces of nonelectrostatic origin

It is shown that unusual thermally stimulated relaxation currents can arise in the external circuit on homogeneous heating of an insulator with a polar direction that is in a thermodynamically nonequilibrium state. These currents differ from thermally stimulated depolarization currents in being observed in a specimen that is unpolarized or has been depolarized. The temperature dependence of these relaxation currents is obtained for a particular model.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 32–35, July, 1982.     

The conductivity properties of protons in ice and mechanism of magnetization of liquid water

From a study of electrical conductivity of protons in the hydrogen-bonded chains in ice we confirm that the magnetization of liquid water is caused by proton transfer in closed hydrogen-bonded chains occurring as a first order phase transition, through which the ice becomes liquid water. We first study the conductive properties of proton transfer along molecular chains in ice crystals in our model. Ice is a typical hydrogen-bonded molecular system, in which the interaction of localized fluctuation of hydrogen ions (H⁺) with deformation of a structure of hydroxyl group (OH) results in soliton motion of the protons along the molecular chains via ionic and bonded defects. We explain further the quantum conductive properties of proton transfer and determine its mobility and conductivity under constant electric-field using a new theory of proton transfer, which agree with experimental values. From features of first order phase-transition for ice, and some experimental data of pure and magnetized water we confirm further that there are not only free water molecules, but also many linear and closed hydrogen-bonded chains consisting of many polarized water-molecules in the liquid water. Thus a ring proton-current, which resembles to a “molecular current” or a “small magnet” in solids, can occur in the closed hydrogen-bond chains under action of an externally applied magnetic field. Then the water molecules in the closed chains can be orderly arrayed due to the magnetic interaction among these ring proton currents and the externally applied magnetic field. This is just the magnetized effect of the water. In such a case the optical and electronic properties of the water, including the dielectric constant, magnetoconductivity, refraction index, Raman and Infrared absorption spectra, are changed. We determine experimentally the properties of the magnetized water which agree with the theoretical results of our model. However, the magnetized effect of water is, in general, very small, and vanishes at temperatures above 100 ^○C.     

Thermal defect formation in undoped and Cr-and Mn-doped Bi12SiO20 crystals

The thermally stimulated depolarization currents and the temperature dependences of optical absorption are investigated. Interaction processes between defects are observed. A model consisting of association-dissociation of quasidipoles in the form of donor-acceptor pairs with a distribution of activation energies and relaxation times is proposed. Fiz. Tverd. Tela (St. Petersburg) 41, 1593–1596 (September 1999)     

TSC measurements and their correlation with photocurrent techniques

Deep level energy spectroscopy using the thermal release of trapped charge in pn junctions or Schottky barriers has recently been suggested as a useful method for evaluating deep level parameters in semiconductors [1, 2]. Although the measurements of thermally stimulated currents (TSC) may be a rapid method the use of which simplifies the investigation of known deep centers, considerable difficulties arise when TSC measurements are used for the characterization of unknown deep levels.     

Effects of exposure temperature on thermally stimulated currents in InSe single crystals

The thermally stimulated currents (TSC) in InSe single crystals are investigated as a function of initial temperature T₀ at which the samples examined are excited. In particular, experiments show that the peak at low temperature increases considerably in height and shifts markedly to lower temperatures as T₀ is reduced. A kinetic model is proposed for the interpretation of the results.     

Quantum polarization and dielectric losses at low temperatures

We propose a mechanism for the quantum polarization of solid dielectrics, and use it to create and study the kinetic equation taking into account the tunneling of relaxation oscillators. The frequency dependences of both and tan are determined theoretically and compared with experiment. The density of thermally stimulated currents in the dielectrics are calculated. We find that one must take into account tunneling transitions of relaxation oscillators in order to explain the low-temperature features in the dielectric spectra.Translated from Izvestiya Vysshikh Uchebnykh Zavenenii, Fizika, No. 2, pp. 6–9, February, 1984.     

Electret processes in disordered systems based on liquid dispersion media

Electret-thermal analysis (ETA) of disordered systems based on dispersed media is carried out. It is shown that the method of thermally stimulated currents makes it possible to estimate the structural changes occurring in a liquid dispersion medium. It is found that liquid water in a free state exhibits the electret properties. The observed multiple peaks on the thermally stimulated current curve are the evidence of the multicomponent nature of the ??free water?? system. The mechanisms of processes leading to the formation of the electret state in such systems are considered.     

Positronium formation from silver

Characterization of a positronium (Ps) gas target to be used for the charge conjugate reaction for antihydrogen formation [1], namely proton + Ps-atom → hydrogen + positron, has been performed [2–4]. In the above collision the Ps target utilised is produced efficiently on the transmission side of a hot thin (1900 Å) Ag(100) foil with 12% efficiency at 800 K foil temperature, with a mean velocity of thermally activated Ps of 1.2×10⁵ m/s and with a maximum kinetic energy of prompt emitted Ps of 1.5±0.2 eV.     

Study of defect annealing by supercurrent proton beam irradiation and of radiation defect profiles in GaAs by the positron annihilation method

The annealing of radiation defects in GaAs by a supercurrent proton beam with currents up to 200 A cm^?2 and 4.8 MeV energy was studied. The positron annihilation method (measurement of angular distribution of annihilation photons) has been used to study the depth profiles of radiation defects in solids. Profiles of vacancy-type defects in GaAs irradiated by a supercurrent proton beam have been measured.     

Nonisothermal relaxation and electromigration in single crystals of Ca3Ga2Ge4O14

The photoconductivity and electrical conductivity, the thermally stimulated polarization and depolarization currents, the permittivity, and the dielectric losses of noncentrosymmetric Ca₃Ga₂Ge₄O₁₄ crystals of a structural type of trigonal calcium gallogermanate (CGG) have been studied for the first time in the temperature interval 100–700 K in air and in vacuum. The features of the temperature behavior of CGG are associated, in particular, with the effect of electrically active defects and partial disordering of the cation sublattice of the crystal structure, which generates polar formations (dipoles) of several kinds. Certain parameters of the electromigration and of the electrically active defects that cause charge-relaxation and polarization effects are determined. It is concluded that dipole relaxation in CGG makes it a new representative of a class of materials in which reorientation of the dipoles as a system of mobile local distortions of the structure has a substantial effect on the physical properties. Fiz. Tverd. Tela (St. Petersburg) 39, 871–876 (May 1997)     

New Methods of Computer Modeling and Analysis of Thermally Stimulated Depolarization Currents

New methods of computer modeling and analysis of thermally stimulated depolarization currents in dielectrics are theoretically substantiated and their practical application is described. Particular examples of data processing are given and their advantages over the existing data processing techniques are demonstrated. The procedure of computer modeling and analysis of thermally stimulated depolarization currents is recommended to experimenters for wide application.     

Multiplicity of dielectric relaxation times of dispersed ice microcrystals

Summary The multiplicity of relaxation times of the dielectric relaxation of water molecules in dispersed ice microcrystals has been studied by means of the thermally stimulated depolarization (TSD) current method. Using several experimental techniques offered by the TSD method we have shown that the relaxation mechanism is characterized by a continuous distribution of relaxation times with both the activation energy.W and the pre-exponential factorτ ₀ in the Arrhenius equation being distributed parameters. A linear relationship has been found to exist betweenW and lnτ ₀. The dielectric behaviour of ice emulsions has been found to resemble strongly in some aspects that of HF-doped ice and ice samples with high concentrations of crystal imperfections. The multiplicity of relaxation times has been explained by the interaction of intrinsic ionic defects with water molecules. Work supported in part by the Greek Ministry of Research and Technology.     

Untersuchungen zur Fehlordnung von NH4 Cl-Kristallen

Results of measurements of thedc andac-conductivity and of the thermally stimulated depolarization carried out on undoped, NiCl₂-doped and NH₃-saturated NH₄Cl crystals respectively are reported. They give some information about the kind and properties of the point defects. They further show that the formation of defects depends even in the intrinsic range on the quantity of H₂O adsorbed on the samples and that thedc andac conductivity are different at lower temperatures. These effects are to be attributed to the properties of the complex cation and to the special charge transport mechanism realized by a sequence of vacancy and proton jumps.     

Thermally stimulated currents for a mixed free-carrier recombination mechanism

Analytical expressions are obtained in this paper for thermally stimulated currents in the ordinary and photoelectret modes for a mixed mechanism of free-charge-carrier recombination and a strong duplicate attachment. It is shown that in this case the same trap parameters can be determined from experimental curves for thermally stimulated currents as for bi- and monomolecular recombination; however, the majority of computation methods should be modified. Modified formulas are proposed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 92–97, July, 1976.The authors are grateful to A. R. Regel' for interest in the research and for useful consultation, and also to B. S. Medved' for aid in computing the curves on an electronic computer.     

Mechanisms of electron-stimulated desorption of protons from water: Gas,chemisorbed and ice phases

The stimulated desorption of ions from gas phase and condensed phase H₂O on Ni(111) has been examined theoretically and experimentally for the near threshold excitation region, 15 to 40 eV. The excited state potential energy curves have been calculated using configuration interaction for H₂O and a restricted Hartree-Fock (RHF) approach for a variety of small clusters including (H₂O)₅ and NiH₂O. Both proton yield and kinetic energy distributions have been measured for chemisorbed, ice phase, and gas phase water and are discussed in terms of specific electronic excitations corresponding to possible desorption pathways. For condensed phase water, the major proton desorption threshold occurs at 20–21 eV and is due to surface predissociation. The final state potential energy curves reached in this process are, in general, described by two electron excitations from the ground state and are thus not dipole allowed. At threshold, these potential energy curves correspond to the excited states of the neutral rather than the ionized molecule. Above 28–29 eV, predissociation or shake-up involving excitations from the O 2s orbital contributes to the ion yield and can give rise to protons of high (7–8 eV) kinetic energy.     

Proton Diffusion in High Pressure Ice

We have developed a spectroscopic method for measuring proton diffusion process in ice at high pressure and temperature using a diamond anvil cell (DAC). It enables us to determine the self diffusion constant of proton (deuteron) from infrared reflection spectra collected as a function of time for a H 2 O/D 2 O ice bilayer prepared and pressurized in the DAC. A preliminary experiment for ice VII at 14 GPa and 400 K provided a diffusion constant D=1.2\times1^{-15} m 2 /s. This was the first measurement of the proton diffusion in pure ice.