UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2012 Meeting


Section: Solid State Physics and Materials Science


Title:
Study of electrical properties of SiO2 films containing germanium nanoparticles


Authors:
C. PALADE (1,2), Ana-Maria LEPADATU (1,2), I. STAVARACHE (2), A. MARALOIU (2), V. TEODORESCU (2) and Magdalena Lidia CIUREA (2)


Affiliation:
(1) University of Bucharest, Faculty of Physics, str. Atomistilor 405, Magurele, Ilfov.

(2) National Institute of Materials Physics, str. Atomistilor 105b, Magurele


E-mail
catalin.palade@infim.ro


Keywords:
Ge nanoparticles, electrical investigations, hopping mechanism, Arrhenius dependence


Abstract:
The electrical behaviour of films containing Ge nanoparticles embedded in silicon dioxide matrix was investigated. The films were deposited by RF magnetron co-sputtering, followed by a thermal annealing in H2 at the pressure of 2 atm and the temperature of 500 deg. C. The film structure, investigated by transmission electron microscopy (TEM) and high resolution TEM, revealed a low density of big Ge nanoparticles (20-50 nm) and a network of small amorphous Ge nanoparticles (5 nm) with high density, both embedded in the amorphous SiO2 matrix. For electrical investigations, current-temperature (I-T), and current-voltage (I-V) measurements were performed. The I-T characteristics has two parts with different temperature dependencies indicating that different conduction mechanisms occur at low and high temperatures. At low temperatures has been evidenced a T^(-1/4) dependence of the logarithm of the current while at high temperatures has been observed an Arrhenius dependence. The electrical behaviour at low temperatures is explained by the hopping mechanism on localized states located in a band near the Fermi energy, while at high temperature by the charge excitation to the extended states. At both low and high temperatures, the conductivity is nearly constant, supporting the proposed mechanisms.