Narrow Results

We characterize granular NbN_x thin cermet films deposited on either sapphire substrate or on SiO₂ and compare the 1/f noise at 300 K and 80 K. The films were characterized with an impedance analyzer from 20 Hz to 1 MHz and analyzed as a resistor R in parallel with a capacitor C. The calculated noise voltage spectral density S_vTh of the sample is in agreement with the experimentally observed noise for unbiased samples.

The noise measurements on biased samples show 1/f noise. We checked that contact noise does not contribute to our measurements. The 1/f noise was compared for the films deposited on the silicon substrate and on the sapphire.

Finally a model is proposed to explain the observed trends in the temperature resistance coefficient (TRC < 0 for all samples) and the relative 1/f noise at 300 K and 80 K with the composition x = N/Nb of the layers.

Equilibrium state disturbance and restoration processes of an electron gas interacting with phonon system in an equilibrium semiconductor have been investigated. Damping peculiarities of small deviations (fluctuations) of electron system from equilibrium state due to electron-acoustic phonon random scattering have been analyzed. A second-order linear partial differential equation for symmetric component of fluctuation of electron distribution function was obtained via linearization of the Boltzmann equation. This equation describes the chaotic movement of electrons along the energy axis, which can be interpreted as diffusion in momentum space. Another equation which describes the time dependence of electron lattice mobility fluctuations was obtained. It was shown that in the Boltzmann equation linearization approximation, lattice mobility fluctuations do not decay over time. The time dependence of the mobility fluctuations is described by stochastic harmonic function with random amplitude and random initial phase.