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1

Electrical properties and Mott parameters of polycrystalline diamond films synthesized by HF CVD method from hydrogen/methanol gas mixture

Banaszak-Piechowska A., Fabisiak K., Staryga E., Paprocki K.

Materials Science Poland

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2017

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Vol. 35, No. 4

830--837

EN

The influence of diamond crystallinity and preferred orientation on electronic conductivity of synthetic diamond films grown by hot filament chemical vapour deposition (HFCVD) was investigated. The CVD diamond films of different morphologies and crystallite sizes varying from 36 nm to 67 nm, measured in ‹2 2 0› direction were considered. The charge transport mechanism in the diamond samples was studied using temperature dependent DC conductivity measurements. The obtained results showed that in the temperature range of 90 K to 300 K charge transport is realized via Variable Range Hopping (VRH, m = 1/4) mechanism. Using VRH model, the Mott parameters were evaluated i.e. density of states at Fermi level N(EF) (0.22 × 1015 eV-1·cm-3 to 1.7 × 1015 eV-1·cm-3), hopping energy W (43.5 meV to 142.3 meV) and average hopping distance R (1.49 × 10-5cm to 2.56 × 10-5cm). It was shown that above mentioned parameters strongly depend on diamond film preferential orientation.

2

Studies of the dc and ac hopping electrical conductivity in ferroelectric Pb[(Fe[1/3]Sb[2/3])[x]Ti[y]Zr[z]]O[3]

Osak A., Piwowarczyk J.

Czasopismo Techniczne. Nauki Podstawowe

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2011

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R. 108, z. 1-NP

59-75

EN

In the paper results of the dc and ac conductivity measurements in ferroelectric ceramics Pb[(Fe[1/3]Sb[2/3])[x]Ti[y]Zr[z]]O[3] with x + y + z = 1, x = 0.1 and y = 0.43 - 0.47 are presented. The measurements have been carried out in the temperature range 77-750 K. DC conductivity in the range low temperature obeys Mott's law [sigma](0) [tilde] exp[-(T[0]/T)[^1/4]]. The values of T[0] are the order 10[^6] K. In the high temperature range dc conductivity shows an activated temperature dependence. Ac conductivity has been measured in the range of frequency 50 Hz-100 kHz. It is shown that ac conductivity fulfills the relations [sigma]([omega]) [tilde] [omega][^S], where the power exponent depends on temperature and frequency. The values of the density of states at the Fermi level N(E[F]), the most probable Mott's hopping distance R and hopping energy W were also determined.

PL

W artykule przedstawiono wyniki pomiarów przewodnictwa zmienno- i stałoprądowego ferroelektrycznej ceramiki [Pb(Fe[1/3]Sb[2/3])[x]Ti[y]Zr[z]]O[3] gdzie x + y + z = 1, x = 0,1 i y = 0,43 -0,47. Pomiary zostały wykonane w zakresie temperatur 77-750 K. Przewodnictwo stałoprądowe w niskich temperaturach jest opisane prawem Motta [sigma](0) [tylda] exp[-(T[0]/T)[^1/4]]. Wartość T[0] jest rzędu 10[^6] K. W zakresie wysokich temperatur przewodnictwo stałoprądowe ma charakter aktywacyjny. Przewodnictwo zmiennoprądowe zostało zmierzone w zakresie od 50 Hz do 100 kHz. Przewodnictwo zmiennoprądowe jest opisane zależnością [sigma]([omega]) [tylda][omega][^S], gdzie wykładnik potęgowy jest zależny zarówno od temperatury, jak i częstotliwości. W pracy wyznaczono również wartości gęstości stanów na poziomie Fermiego N(E[F]), najbardziej prawdopodobną odległość hoppingu Motta R i energię hoppingu W.

3

The transport properties of sputter-deposited Ge-Sb-V thin films

Beensh-Marchwicka G., Prociów E., Berlicki T.

Elektronika : konstrukcje, technologie, zastosowania

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2007

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Vol. 48, nr 12

49-50

EN

Temperature-dependent transport properties of p-type Ge-Sb-V films prepared by the pulse magnetron sputtering technique have been studied. Doping of Ge by Sb and V and post-deposition annealing in air atmosphere at 823 or 923 K were the necessary preconditions of obtaining enhanced p-type conduction and considerable high values of Seebeck coefficient ranging from 400 to 160 µV/K. The temperature of post-deposition annealing and V content were taken as varying parameters to observe any variations in temperature dependent resistivity and thermoelectric power in the film and tried to explain the electrical transport mechanism therefrom. The structural analysis showed that films 3 µm thick remained microcrystalline and the variable range hopping (VRH) in three dimension system was dominant mechanism for d.c. charge transport.

PL

Analizowano temperaturowo zależne własności transportu warstw Ge-Sb-V, otrzymywanych techniką impulsowego rozpylania magnetronowego, wykazujących przewodnictwo typu p. Domieszkowanie Sb i V germanu i starzenie po wytworzeniu w atmosferze powietrza przy 823 lub 923 K było warunkiem koniecznym otrzymania przewodnictwa typu p i bardzo dużej wartości współczynnika Seebecka od 400 do 160 µV/K. Temperaturę wygrzewania warstw po nanoszeniu i zawartość wanadu w warstwie przyjęto jako zmienne parametry do badania wpływu na zachowanie się rezystywności i siły termoelektrycznej w funkcji temperatury i na tej podstawie próbowano określić mechanizm transportu nośników w warstwach. Analiza struktury wykazała, że warstwy o grubości około 3 µm pozostają mikrokrystaliczne oraz, że dominującym mechanizmem transportu nośników dla prądu stałego był trójwymiarowy hopping zmienno-zasięgowy (VHR).

4

Discontinuous metal films on dielectric substrates, their optical and electrical properties, structures and statistical descriptions

Dobierzewska-Mozrzymas E., Biegański P., Pieciul E.

Optica Applicata

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2001

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Vol. 31, nr 1

53-81

EN

A brief survey of some results concerning optical and electrical properties of discontinuous metal films on dielectric substrates and their statistical description is given. Optical properties (transmittance and imaginary part of dielectric permittivity spectra) of Al, Cu and Mn discontinuous films are presented and interpreted in terms of effective medium theories; modified Maxwell-Garnett and Bruggeman. The ranges of dielectric properties, the percolation threshold, and the range of metallic properties are determined for optical and electrical properties of the film examined. The considerations concerning electrical properties include such conduction mechanisms as metal conduction, substrate conduction, quantum tunneling, thermally activated tunneling and hopping. Real structures of the films are examined making use of electron microscope. Also the computer model for determining the contribution of the fundamental conduction mechanisms in discontinuous films is introduced. The inverse power law is used to describe the structure and the statistical distributions of inhomogeneous films of Au, Cu and Mn on dielectric substrates. To this end, the rank of an island is connected with its area for the films with different coverage coefficients (metal content). The dependencies of the island areas on the rank orders in a double-logarithmic plot are straight lines according to the Mandelbrot law. The slope of the straight line characterises the ranges of the distributions of the islands: (i) the log-normal or the Gaussian one (with two parameters of statistical distribution-the mean value and the variance), (ii) the Poisson distribution (with one parameter-the mean value), (iii) Levy stable distribution (the parameters of distribution are infinite). The correlation between optical and electrical properties of discontinuous metal films and their structures and statistical description is found.