共查询到20条相似文献,搜索用时 0 毫秒
1.
T. Kishore kumar M. Victor Antony Raj P. Sagayaraj 《Journal of Physics and Chemistry of Solids》2008,69(11):2634-2638
Physical properties such as photoconductivity, dielectric and thermal stability have been investigated for pure benzoyl glycine (BG) crystals. In addition to this, the influence of dopants (benzophenone and iodine) of these properties on BG crystals has been studied. Photoconductivity studies on pure BG, benzophenone-and iodine-doped BG revealed the positive photoconducting nature. The dielectric responses of the samples have been studied in the frequency range 100 Hz-500 KHz at room temperature and the results are discussed in detail. The thermogravimetric studies of pure and doped BG crystals indicate that the presence of dopants has slightly increased the decomposition temperature of pure BG samples, thereby enhancing thermal stability to the doped ones. 相似文献
2.
Yutaka Nagai Nakahara Kouji Yoneyama Yoshifumi Kawano Katsuyasu Tanaka Katsumi Nakata Ryouhei 《Journal of Physics and Chemistry of Solids》2004,65(11):1861-1870
The characteristics of high-temperature ionic thermocurrent (HT ITC) in CaF2 doped with different sodium concentrations were studied by the Teflon-insulated electrode ITC method. It was shown that, with increasing sodium concentration, the HT ITC band moved toward a Na+-FV dipole band with a peak at 162 K. The results of analyses of the HT ITC spectra using an equivalent electric circuit proved that the activation energy of space charge migration related to HT ITC was also strongly dependent on the doped sodium concentrations if varied from 0.94 to 0.46 eV with increasing sodium concentration in our ITC study. In addition, the broadening of the Na+-FV dipole band was observed in 3 nominal mole% NaF-doped CaF2, which was accompanied by a considerable decrease of the activation energy from 0.46 to 0.29 eV without showing marked temperature shifts of the peak ITC bands. 相似文献
3.
In this study, we prepared a Metal(Al)/Organic Interlayer(Congo Red=CR)/Inorganic Semiconductor (p-Si) (MIS) Schottky device formed by coating of an organic film on p-Si semiconductor wafer. The Al/CR/p-Si MIS device had a good rectifying behavior. By using the forward bias I-V characteristics, the values of ideality factor (n) and barrier height (Φb) for the Al/CR/p-Si MIS device were obtained as 1.68 and 0.77 eV, respectively. It was seen that the Φb value of 0.77 eV calculated for the Al/CR/p-Si MIS device was significantly higher than value of 0.50 eV of the conventional Al/p-Si Schottky diodes. Modification of the interfacial potential barrier of the Al/p-Si diode was achieved by using a thin interlayer of the CR organic material. This was attributed to the fact that the CR organic interlayer increased the effective barrier height by influencing the space charge region of Si. The interface-state density of the MIS diode was found to vary from 1.24×1013 to 2.44×1012 eV−1 cm−2. 相似文献
4.
Recent experiments have demonstrated that the performances of organic FETs strongly depend on the dielectric properties of the gate insulator. In particular, it has been shown that the temperature dependence of the mobility evolves from a metallic-like to an insulating behavior upon increasing the dielectric constant of the gate material. This phenomenon can be explained in terms of the formation of small polarons, due to the polar interaction of the charge carriers with the phonons at the organic/dielectric interface. Building on this model, the possible consequences of the Coulomb repulsion between the carriers at high concentrations are analyzed. 相似文献
5.
The enthalpies of solution of pure silver halides AgCl and AgI and a composite material with molar composition 0.5 AgCl-0.5 AgI were measured at 298 K in a mixture of Na2S2O3 (1 M) and NH4OH (1 M). X-ray diffraction patterns showed that the composite material contained the metastable γ-AgI phase; different mechanisms for its stabilization were discussed. The phase transition enthalpies of AgI modifications and the enthalpy of formation of the composite material were deduced from the measurements. The latter could be related to a change of interfacial enthalpies. 相似文献
6.
Urea-succinic acid crystals have been grown at room temperature from aqueous solution in the presence of maleic acid by a slow evaporation technique. The structural parameters were determined using powder X-ray diffraction (XRD) and found to have monoclinic symmetry (space group P21/m) with a=9.902, b=17.510, c=5.555 Å and α=γ=90°, β=96.46°. The transparency and optical analysis were carried out using UV-vis analysis. The optical band gap is found to be 4.71 eV. The presence of various functional groups was confirmed by FTIR analysis. The samples have shown piezoelectric behavior with a fairly good piezoelectric charge coefficient (d33) of 5 pC/N, when it is poled at 7 kV/cm. The hysteresis loop was plotted and the remnant polarization and coercive field were found to be 2.8 μC/cm2 and 4 kV/cm, respectively. The dielectric analysis was carried out as a function of temperature at various frequencies and the results were also discussed. 相似文献
7.
M.E. Aydin 《Journal of Physics and Chemistry of Solids》2007,68(9):1770-1773
Electrical transport properties of Ag metal-fluorescein sodium salt (FSS) organic layer-silicon junction have been investigated. The current-voltage (I-V) characteristics of the diode show rectifying behavior consistent with a potential barrier formed at the interface. The diode indicates a non-ideal I-V behavior with an ideality factor higher than unity. The ideality factor of the Ag/FSS/p-Si diode decreases with increasing temperature and the barrier height increases with increasing temperature. The barrier height (φb=0.98 eV) obtained from the capacitance-voltage (C-V) curve is higher than barrier height (φb=0.72 eV) derived from the I-V measurements. The barrier height of the Ag/FSS/p-Si Schottky diode at the room temperature is significantly larger than that of the Ag/p-Si Schottky diode. It is evaluated that the FSS organic layer controls electrical charge transport properties of Ag/p-Si diode by excluding effects of the SiO2 residual oxides on the hybrid diode. 相似文献
8.
A.N Papathanassiou J GrammatikakisS Sakkopoulos E VitoratosE Dalas 《Journal of Physics and Chemistry of Solids》2002,63(9):1771-1778
The charge trapping centers in fresh and thermally aged conductive polyaniline-polypyrrole copolymers (starting from pure polyaniline and ending in pure polypyrrole by steps of 10 wt%) were studied by thermally stimulated depolarization current (TSDC) spectroscopy and dc conductivity measurements. One low temperature (115-135 K) relaxation mechanism appears in polyaniline-rich copolymers and disappears after thermal anneal. It is attributed to polaron trapping in the vicinity of chlorine anion dopants. Another relaxation mechanism operates close to room temperature and is related to conformational relaxation, which corresponds to the influence of the annihilation of the conformons on the conduction mechanism. The relaxation is sensitive to thermal aging as a result of the thermal annealing on the conductivity. The temperature derivative of the dc conductivity supports the latter assertion. The activation energy values were obtained as a function of composition for both fresh and heated samples. The TSDC spectroscopy is a sensitive tool which is an alternative to the standard conductivity studies for the characterization of polypyrrole-polyaniline conductive copolymers and the study of the thermal degradation. 相似文献
9.
The nanotwinned structures in metals exhibit the unique combination of physical properties. The unifying approach is developed that can be applied to nanocrystalline (nc) materials with different crystal structures. It is used to make a bridge between microscopical mechanisms of twin nucleation and macroscopic characteristics of the twinning and calculate them. The grain size range of the nanotwinning propensity, the grain size of its peak, and the requisite external twinning stress are calculated for the nc face-centered cubic metals Al, Cu, Ni, Pd, Au, Ag, for nc body-centered cubic metals Ta, Fe, Nb, Mo, and for hexagonal close-packed nc metals Co, Zr, Mg, Ti. 相似文献
10.
Dielectric properties of thin films (TF) of molecular crystals, including the effect of size and the boundary surfaces were analysed using Green's function method. Polarisability of molecules in various film layers and dielectric susceptibility of TF were calculated. A comparison with crystal bulk has shown that dielectric properties of TF are strongly influenced both by the sample dimensions and by the boundary conditions.The frequency dependence of the dielectric susceptibility has also been derived. One obtains the monotonous variation for the frequencies above and below exciton band. However, for the frequencies within the exciton band there appears to be complicated, non-monotonous dependence. The relationship between the dielectric susceptibility and the film width for the same frequency shows a complex, oscillatory behaviour. Furthermore, the amplitude of these oscillations increases with increasing film width, demanding the introduction of a damping factor. Finally, the thickness dependence of dielectric susceptibility was analysed in the Cole-Cole plot. 相似文献
11.
(1−x)NaNbO3-(x)ABO3 perovskite solid solutions belonging to group II according to the Krainik classification [Izv. Akad. Nauk SSSR, Ser. Phys. 28 (1964) 643] exhibit a dramatic diffusion of the dielectric permittivity ε′ maximum and relaxor-type behavior when the second component concentration exceeds a threshold value x0. The concentration phase transition to this relaxor-like phase is abrupt (of the first order kind) that is seen from the step in the dependence of the ε′(T) maximum temperature, Tm, on x. Some relaxor-like properties appear even at x<x0 in the course of cooling while disappear during the course of heating. Due to this fact and because of coupling of the antiferroelectric (AFE) and ferroelectric (FE) order parameters a giant (up to 100 K) temperature hysteresis of ε′(T) arises at AFE-AFE first order phase transition. The Tm values of all the known NaNbO3-ABO3 relaxor-type compositions are well below the room temperature and the dielectric permittivity maximal values, ε′m, are much lower than in the case of Pb-containing relaxors. However both Tm and ε′m values can be increased substantially by Li or K-doping leading to the formation of NaNbO3-ABO3-LiNbO3 (KNbO3) solid solutions. 相似文献
12.
P. Szklarz 《Journal of Physics and Chemistry of Solids》2005,66(1):121-125
The pyroelectric effect is measured in tricycloheylmethanolmethanol (TCHM) crystal around the second-order phase transition at 104 K. The presented results confirm that the spontaneous polarization exists in the low temperature phase of TCHM and is reversible in external electric field. It is suggested that TCHM is an improper ferroelectric below 104 K. 相似文献
13.
Chemical reactions in cracks of aluminum crystals: Generation of hydrogen from water 总被引:1,自引:0,他引:1
Masao Watanabe 《Journal of Physics and Chemistry of Solids》2010,71(9):1251-1258
Pure hydrogen is generated from water molecules which are dissociated by specific aluminum particles called activated Al powder. Reaction mechanism of Al atoms with H2O molecules is investigated in micro-cracks of Al crystals. It becomes obvious that hydrogen atoms exist in Al crystal mainly in states of AlH3 hydrides. It is concluded that virgin walls of micro-cracks right after the creation provide virtually Al radical atoms of (Al−) or (Al=) with one or two free bonds, which react with H2O molecules via surface diffusion resulting in producing AlH3 and eventually in producing H2. The production of H2 seems to be a result of micro-tribochemical reactions in cracks, which are produced by mechanical crushing of Al crystals in water; tips of cracks as stress-focused points play a major role to create AlH3. Peculiar environments of nano-spaces in micro-cracks surrounded by reactive atoms enable us to realize unusual chemical reactions at low temperatures as exemplified in the present paper. 相似文献
14.
The dependence of photovoltaic performance of the bulk heterojunction photovoltaic device based on the blend of sulphonated nickel phthalocyanine (NiPcS) and rose Bengal (RB) on their composition, thermal annealing and oxygen exposure has been investigated. It is found that both electron and hole mobility in RB phase and NiPcS phase, respectively has been increased on thermal annealing. The power conversion efficiency of the device increases upon thermal annealing, attributed the balance charge transport. The power conversion efficiency of the device experiences a drastic increase upon oxygen exposure, which attributed to the photo-induced doping, increase in exciton diffusion length in NiPcS phase and increased volume of exciton dissociation interfacial sites. From the impedance spectroscopy, we conclude that the change in bulk resistance and dielectric constant of the active material due to the illumination has a direct relevance to the photocurrent generated by the device. 相似文献
15.
Hiroshi Matsui Mai Nagatori Kenji Mizoguchi 《Journal of Physics and Chemistry of Solids》2010,71(4):440-443
Temperature dependence of the complex dielectric constant at 16.3 GHz has been measured on dry poly(dA)-poly(dT) DNA with Na+ counterions under different relative humidity (RH). The rotational motion of sole water dipoles hydrated in PO2− is detected at low RH, and the collective motion due to water network in major groove is successfully observed at high RH. From the infrared (IR) spectroscopy in dry DNA introducing metallic ions (M-DNA), the symmetric and antisymmetric stretching bands of PO2− distinctly depend on RH and type of metallic ions. The IR spectral change indicates that the monovalent ions (Li and Na) are arranged in PO2− though the divalent and trivalent ions connect to the base molecules. 相似文献
16.
《Journal of Physics and Chemistry of Solids》2014,75(4):570-582
We consider theoretically valence transformations of doping metal ions in oxide crystals induced by oxidation and reduction obtained by changes in the ambient oxygen partial pressure. Three types of oxygen vacancies are assumed to mediate transformations: neutral, singly ionized, and doubly ionized. In the companion part I paper we provide thermodynamic analyses yielding concentration relations among the oxygen vacancy, metal ions, holes and electrons, as functions of the ambient oxygen pressure. In the present companion part II paper we provide time dependent concentration profiles of the various species and reaction rate profiles. The diffusion exhibits a complex behavior; under some conditions, it may be described by a constant diffusivity, and is symmetric with respect to oxidation and reduction. However, under a wide range of conditions, the ionic state changes are highly asymmetric with respect to oxidation and reduction. For example, in the case of a neutral vacancy, a very narrow reaction front may establish during reduction. In the inverse (oxidation) process, however, the different species' profiles are quite smooth. 相似文献
17.
《Journal of Physics and Chemistry of Solids》2014,75(4):512-517
We consider theoretically valence transformations of doping metal ions in oxide crystals induced by oxidation and reduction obtained by changes in the ambient oxygen partial pressure. Three types of oxygen vacancies are assumed to mediate transformations: neutral, singly ionized, and doubly ionized. We provide thermodynamic equilibrium analyses, yielding concentration relations among the oxygen vacancy, metal ions, holes and electrons as functions of the ambient oxygen pressure. The results suggest that experimental study of different species concentrations at thermodynamic equilibrium as functions of pressure and temperature should allow assessment of various reversible reaction constants controlling the process. In the Part II companion paper, the kinetic (diffusion) characteristics are considered in detail. 相似文献
18.
Effect of lateral fluorination in the rigid core on several macroscopic and microscopic properties of a terphenyl based mesogenic chiral ester has been studied by synchrotron X-ray, dielectric and electro-optic techniques. Correlation lengths across the smectic planes, in para-, ferro- and antiferroelectric phases, are found to be significantly less in the fluorinated compound. Para to ferroelectric transition is found to be tricritical in nature in both the compounds. Fluorination resulted in slower response under a square pulse. Collective mode relaxation behaviour, with and without bias field, in all the phases are also found to be different in the fluorinated compound. 相似文献
19.
The trap levels in nominally undoped Ga3InSe4 crystals were investigated in the temperature range of 10-300 K using the thermally stimulated currents technique. The study of trap levels was accomplished by the measurements of current flowing along the c-axis of the crystal. During the experiments we utilized a constant heating rate of 0.8 K/s. Experimental evidence is found for one hole trapping center in the crystal with activation energy of 62 meV. The analysis of the experimental TSC curve gave reasonable results under the model that assumes slow retrapping. The capture cross-section of the trap was determined as 1.0×10−25 cm2 with concentration of 1.4×1017 cm−3. 相似文献
20.
Minoru Arita 《Journal of Physics and Chemistry of Solids》2007,68(9):1730-1744
Published measurements of sulfur vapor pressure and silver electromotive force were used to determine thermodynamic properties of silver sulfide above 379 K. They were Gibbs-Duhem integrated to estimate the formation properties of stoichiometric Ag2S of fcc, bcc, and monoclinic crystal structures. Statistical thermodynamics was applied to estimate free energies and find possible atom arrangements in off-stoichiometric silver sulfide. Theoretical calculations show that silver vacancies and atoms may be in quasi-chemical equilibrium between tetrahedral and octahedral sites in the fcc structure and between two states of atoms within tetrahedral sites in the bcc structure and within octahedral sites in the monoclinic structure. A strong indication is that vacancy clusters should predominate, each containing four-atom vacancies in the fcc phase and three-atom vacancies in the bcc phase. 相似文献