Nanocomposites and nanomaterials

Analysis of stress dependence of giant piezo-dielectric 
effect in high-resistivity GaSe crystals
Fliunt O. Ye.
Faculty of Electronics and Computer Technologies, Ivan Franko National University of Lviv, Dragomanov Str., 50, Lviv-79005, Ukraine 
E-mail: ofliunt@gmail.com

Fractional power dispersive systems show interesting unexpected behavior on frequency and temperature. For example, so called materials with colossal dielectric constant, show unexpectedly high-values of dielectric constant. Revealed in [1, 2] high-stress dependence of dispersive dielectric constant in layered GaSe single crystals also could be explained by high stress sensitivity of low-frequency dispersive subsystem of the crystal in the result of serial character of elementary processes taking place. Different types of disordering due to layered structure of GaSe crystals may causes one and two dimensional charge carrier’s localization. It allows to call the high stress dependence of impedance parameters of GaSe crystals as giant piezo-impedance or piezo-dispersive effect. 
Obtained coefficient of relative change on uniaxial stress along to a normal to the layers of GaSe crystals riches the value up to 8·10-7 Pa-1 that gives about 27000 gauge factor, that is a few orders of magnitude higher than for usual stress dependencies of some parameters of crystals. In this work a model of stress dependence of fractional dispersive system proportional to 1/ω1-n, where ω – circular frequency, with exponent 1-n ≈ 0.2 in high-resistivity GaSe layered crystals characterizing for hopping charge carrier’s systems has been described. 
The proposed model is based on the assumption of availability of hopping charge carriers distribution concentration of which obeys fractional power law, that reflects the complex behavior of serial in their nature elementary processes with interaction. Model explains correlation between stress dependence of dispersive dielectric constant on certain frequency and increasing of exponent 1-n with increasing stress. 

1. Fliunt O., Fiyala Ya. M. Dispersive capacity of high-resisitvity GaSe crystalls under different uniaxial stress // X international seminar on physics and chemistry of solid state (ISPCS’04). Book of Abstr. - 2004. - P. 68.
2. Stakhira J. M., Fl'unt O. Ye., Fiyala Ya. M. Effect of uniaxial stress on low-frequency dispersion of dielectric constant in high-resistivity GaSe crystals // Ukrainian Journal of Physics. - 2011. - 56, N 3. - P. 267-271.