Showing papers on "Variable-range hopping published in 1974"
TL;DR: In this article, the authors presented a model which allows the conductivity due to hopping between randomly distributed localized states to be calculated for any form of density of states and applied it analytically to the case of a flatdensity of states, and produced the Mott 1/T 1/4 relation at low temperatures, if the applied electric field is sufficiently low.
Abstract: A model is presented which allows the conductivity due to hopping between randomly distributed localized states to be calculated for any form of density of states This model has been applied analytically to the case of a flat density of states, and produces the Mott 1/T 1/4 relation at low temperatures, if the applied electric field is sufficiently low. The field-dependence of the conductivity is found to be log [sgrave] ∼ F 2 at low fields, and log [sgrave] ∼ 1/F 1/4 at very high fields.
181 citations
TL;DR: In this article, Montgomery et al. measured the conductivities parallel and perpendicular to the c-axis in single crystals of K2[Pt(CN)4]Br 0·30.3(H2O) and found that the anisotropy σ|σ⊥ is of the order of 105 at room temperature but decreases to 3.103 at 35°K.
100 citations
TL;DR: In this article, it was suggested that conduction in localized states at the band edge of an amorphous semiconductor occurs by variable-range hopping, and that the hopping length is typically ten times larger than the average interatomic separation and increases with decreasing temperature.
67 citations
TL;DR: In this paper, the conductivity in n-and p-type inversion layers in Si was measured as a function of the surface carrier density (ns) and temperature, (4.2 to 0.4°K).
Abstract: Experimental evidence for a transition from localized to extended states in a two-dimensional (2D) band tail is obtained by measuring the conductivity in n- and p-type inversion layers in Si as a function of the surface carrier density (ns) and temperature, (4.2 to 0.4°K). A transition from metallic to thermally activated conductivity is observed as a function of ns while the temperature dependence at ns below the transition shows both thermally activated nearest neighbor hopping and variable range hopping as proposed by Mott [1]. Oscillatory magnetoconductivity and far-infrared cyclotron resonance measurements indicate no substantial perturbation of the 2D density-of-states at energies near the transition to metallic conductivity.
55 citations
TL;DR: The low temperature conductance in the inversion layer of an MNOSFET shows a transition from activated to metallic conduction as the Fermi level is raised as discussed by the authors.
52 citations
TL;DR: In this article, a two dimensional adaptation of Motts formula using a localisation criterion close to theoretical estimates was used to estimate the minimum metallic conductance of a P channel MNOSFET.
29 citations
TL;DR: In this paper, the authors derived a simple derivation of the formula 1/2fd2 for the DC diffusivity, which is independent of the weighting factors associated with the sites.
Abstract: For Pt. II abstr. A70018 of 1974. DC hopping conductivity is independent of the weighting factors associated with the sites. It is shown that the weighting factors may be chosen so that the probability of N hops in time t is given by the Poisson distribution. This choice allows a simple derivation of the formula 1/2fd2 for the DC diffusivity. Application of this formula to the hopping analogue of percolative conductance networks shows that their effective DC conductivity is proportional to the product of the fraction of bonds in the infinite cluster and d2 for the infinite cluster. Application of the formula to the hopping analogue of percolative spin systems shows that the spin stiffness is proportional to the product of d2 for the infinite cluster and the mean of the total exchange coupling constant associated with each site in the infinite cluster.
7 citations
TL;DR: In this paper, the effect of the stochastic dependence between the potentials of hopping sites, specifically the case when the correlation length of the potential is considerably longer than the hopping distance, was considered.
Abstract: Spatial fluctuations of the potential are inherent in hopping transport. The effect is considered of the stochastic dependence between the potentials of hopping sites, specifically the case when the correlation length of the potential is considerably longer than the hopping distance. The percolation approach is used. The behavior is found to depend on certain characteristics of the equipotential surface at the Fermi energy. If this surface is non-connected, an activated conductivity is expected. If the surface consists of parts connected through narrow channels, a T−l/2 dependence is predicted. For stronger connectivity, a T−1/3 dependence is deduced. The T−1/4 dependence, characteristic of hopping in the absence of spatial correlation, is not expected to occur.
4 citations
01 May 1974
TL;DR: In this article, the authors studied the temperature dependence of electrical conductivity of amorphous Ge films condensed at 8K but subsequently thermally heated to 30K and 80K by Mott's hopping conduction within localized states centered at the Fermi level.
Abstract: We have studied the temperature dependence (in the temperature range of 6–80 K) of electrical conductivity of amorphous Ge films condensed at 8K but subsequently thermally heated to 30K and 80K. The results are described by Mott's type of hopping conduction within the localized states centered at the Fermi level. Below 18K the conduction is due to phonon assisted tunneling between distant hopping sites (ie log σ ∝ 1/T1/4). At higher temperatures the data is consistent with conduction due to phonon assisted hopping between nearest hopping site. Quantitive comparison with the theory leads to very reasonable values of the density of states (∼ 1020 eV−1 cm−3) and other parameters for these two processes.
1 citations