Showing papers on "Variable-range hopping published in 1978"
63 citations
TL;DR: In this article, a technique for the calculation of the thermoelectric power in many-particle systems exhibiting hopping conduction is presented, which provides very useful information about the microscopic nature of the ion hopping process in solid electrolytes.
57 citations
TL;DR: In this article, the absence or presence of unpaired spin and variable range hopping due to the localized gap states (dangling bond states) in various amorphous semiconductors is explained based on the chemical nature of constituent atoms and randomness of the glass structure.
35 citations
IBM1
TL;DR: In this paper, three modes of conduction were observed: activation to the mobility edge, nearest neighbor hopping, and variable range hopping, by varying the density of ions information about binding energy, impurity band width, and the extent of the bound wave functions as a function of the electron density, ion concentration and substrate bias may be inferred.
25 citations
TL;DR: In this paper, Percolation arguments are used to develop formulae for hopping conductivity involving localized states distributed over a bandwidth of energies, where all possible locations of the Fermi level are treated.
Abstract: Percolation arguments are used to develop formulae for hopping conductivity involving localized states distributed over a bandwidth of energies. All possible locations of the Fermi level are treated. When the Fermi level lies in the centre of the band the formulae are used to analyse activated hopping conductivity in an impurity band formed by drifting Na + ions near the Si-SiO2 interface in a MOSFET. All the system parameters may be deduced from the activated conductivity data. The transition to variable-range hopping at lower temperatures may then be predicted. It is found to be in good agreement with the experimental data.
17 citations
TL;DR: In this paper, the apparent hopping conductivity parameters derived from a standard T−0.25 plot undergo changes by several orders of magnitude when plotted with the exact scaling of the abscissa.
Abstract: Hill's analysis of hopping conductivity data has been applied to ion-bombarded amorphous-silicon samples. The apparent hopping conductivity parameters derived from a standardT−0.25 plot undergo changes by several orders of magnitude when plotted with the exact scaling of the abscissa. A typical example is characterized by a temperature dependence ofdc conductivity according toσ=σ0 exp (—(T0/T)m), withm=0.45,T0 =6.4⋅104K andσ0=6.6⋅101 Ω−1 cm−1. Fromσ0 a phonon frequency of about 3−15⋅1012 s−1 is derived.
12 citations
TL;DR: In this paper, a series of polyacene quinone radical (PAQR) polymers as a function of temperature was measured and the Hall coefficient, measured on one sample, is negative and decreases with temperature; the Hall mobility is less activated than the conductivity and is of the order of 3 × 10−2 cm2 V−1 s−1 at room temperature.
Abstract: Electrical conductivity, thermopower and Hall effect measurements have been made on a series of polyacene quinone radical (PAQR) polymers as a function of temperature. The PAQR polymers, prepared by condensing pyrene with three different acidic compounds, are highty conjugated and show fairly high conductivities (in the range 10−4-10−3 Ω−1 cm−1 at room temperature). The thermopower is positive and increases slightly with increasing temperature. The Hall coefficient, measured on one sample, is negative and decreases with temperature; the Hall mobility is less activated than the conductivity and is of the order of 3 × 10−2 cm2 V−1 s−1 at room temperature. In order to alter the electrical properties by doping, the PAQR polymers were treated with iodine. This results in an increase of the conductivity, a sign reversal of the thermopower and a lowering of the Hall mobility. The conductivity and thermopower data seem to be explained in their general features by the two-dimensional variable-range hoppin...
6 citations
TL;DR: In this paper, amorphous Si and Ge are doped with Mn by co-sputtering, and the electrical conductivity is incresed by as much as a factor of 10 6 ∼10 7 in some cases by the addition of several at.% Mn.
6 citations
TL;DR: In this article, a frequency dependent conductivity typical of many disordered systems has been observed in the superionic conductor β-AgI at low temperatures with no evidence for a contribution from ionic hopping.
4 citations
TL;DR: In this paper, a detailed discussion of the static hopping transport is given for the case that the electron transitions between localized gap states are caused by intense illumination of the specimen, and statistical correlations of the excited hopping system taking into account by means of the percolation theory, the resulting conductivities in the low-frequency and highfrequency limits are analyzed with respect to their spectral dependences and their orders of magnitude in relation to Mott's phonon induced variable range hopping.
Abstract: Based on the Kubo formalism a detailed discussion of the static hopping transport is given for the case that the electron transitions between localized gap states are caused by intense illumination of the specimen. The statistical correlations of the excited hopping system taking into account by means of the percolation theory, the resulting conductivities in the low-frequency and highfrequency limits are analyzed with respect to their spectral dependences and their orders of magnitude in relation to Mott's phonon-induced variable range hopping. Apart from its purely theoretical interest this new mechanism of photoconduction should also deserve experimental interest, in particular, because of the possibility of a frequency-controlled „reading” of the electronic density of states within the mobility gap.
Unter Verwendung des Kubo-Formalismus wird die statische Hopping-Leitfahigkeit fur den Fall eingehend diskutiert, das die elektronischen Ubergange zwischen den lokalisierten Gapzustanden durch eine intensive Beleuchtung der Probe hervorgerufen werden. Die statistischen Korrelationen des angeregten Hoppingsystems mittels der Perkolationstheorie berucksichtigend, werden die im nieder- und im hochfrequenten Grenzfall erhaltenen Leitfahigkeiten hinsichtlich ihrer spektralen Abhangigkeiten und ihrer Grosenordnungen im Verhaltnis zum phononindzuierten Mottschen „variable range”-Hopping analysiert. Abgesehen von seinem rein theoretischen Interesse, sollte dieser neue Mechanismus von Photoleitung auch experimentelles Interesse verdienen, insbesondere wegen der Moglichkeit eines frequenzkontrollierten „Abtastens” der elektronischen Zustandsdichte innerhalb des Beweglichkeitsgaps.
4 citations
TL;DR: In this paper, Gershenzon et al. derived an expression of the magneto-resistivity of lightly doped semiconductors in the variable range hopping region, where the resistivity takes the form of ρ∝exp {const. [λ 2 a H g (µ) k 0 T ] -1/3 } in strong magnetic field, where a H denotes the field-dependent Bohr radius, λ the magnetic length defined by
Abstract: Shklovskii derived an expression of the magneto-resistivity of lightly doped semiconductors in the variable range hopping region. According to his result the resistivity takes the form of ρ∝exp {const. [λ 2 a H g (µ) k 0 T ] -1/3 } in strong magnetic field, where a H denotes the field-dependent Bohr radius, λ the magnetic length defined by \(\lambda{=}\sqrt{\hbar c/eH}\) and g (µ) is the density of states at the Fermi level µ. However, the experiments carried out by Gershenzon et al. revealed that ρ of highly compensated n -InSb behaves quite differently from the Shklovskii's prediction. Such discrepancy can be attributed to an assumption of constant density of states on which Shklovskii's result is based. This assumption leads to an erroneous conclusion because in the case of highly compensated samples the density of states is strongly energy-dependent. By extending the percolation theory to the strong magnetic field region and considering the energy-dependent density of states, a qualitative agreement w...
TL;DR: In this article, the experimental data on the d.c. conductivity, a.k.a. thermoelectric power of evaporated or sputtered films of amorphous germanium and silicon are critically examined.
TL;DR: In this paper, the peculiarities of the low-temperature transport of carriers (a sort of "magnetic polarons") are revealed in translationally perfect paramagnetic 3-and 2-dimensional systems of the Mott-Hubbard type, in particular, of the vacancy on diffusion in paramagnetic3He crystal.
Abstract: The peculiarities of the low-temperature transport of carriers (a sort of 'magnetic polarons') are revealed in translationally perfect paramagnetic 3- and 2-dimensional systems of the Mott-Hubbard type, in particular, of the vacancy on diffusion in paramagnetic 3He crystal. Mott hopping diffusion is considered for a disordered system with both essential multiphonon hops and strong changes of the 'single-particle' spectral density; the situation for defectons in the Mott region is analysed.
TL;DR: In this article, the main mechanisms of dc electrical conductivity in disordered systems and how the conductivity depends on temperature are discussed and conditions necessary to observe these effects in thin metallic wires are discussed.
Abstract: A survey is given of the main mechanisms of dc electrical conductivity in disordered systems and of how the conductivity depends on temperature. If the localization length is large, metallic behaviour will be observed at high temperatures, at lower temperature the resistance will increase with a power of T-1, and at very low temperatures, when variable range hopping occurs, the resistance will increase exponentially. The conditions necessary to observe these effects in thin metallic wires are discussed.
TL;DR: Amorphous Ge-Se-Fe films prepared by r.f. sputtering have shown paramagnetic, and ferromagnetic properties for the films with low and high Fe content, respectively.