New universality class in percolation on multifractal scale-free planar stochastic lattice

We investigate site percolation on a weighted planar stochastic lattice (WPSL) which is a multifractal and whose dual is a scale-free network. Percolation is typically characterized by percolation threshold $p_c$ and by a set of critical exponents $\beta$, $\gamma$, $\nu$ which describe the critical behavior of percolation probability $P(p)\sim (p_c-p)^\beta$, mean cluster size $S\sim (p_c-p)^{-\gamma}$ and the correlation length $\xi\sim (p_c-p)^{-\nu}$. Besides, the exponent $\tau$ characterizes the cluster size distribution function $n_s(p_c)\sim s^{-\tau}$ and the fractal dimension $d_f$ the spanning cluster. We obtain an exact value for $p_c$ and for all these exponents. Our results suggest that the percolation on WPSL belong to a new universality class as its exponents do not share the same value as for all the existing planar lattices.Comment: 5 pages, 5 figure

Dielectric relaxation and Charge trapping characteristics study in Germanium based MOS devices with HfO2 /Dy2O3 gate stacks

In the present work we investigate the dielectric relaxation effects and charge trapping characteristics of HfO2 /Dy2O3 gate stacks grown on Ge substrates. The MOS devices have been subjected to constant voltage stress (CVS) conditions at accumulation and show relaxation effects in the whole range of applied stress voltages. Applied voltage polarities as well as thickness dependence of the relaxation effects have been investigated. Charge trapping is negligible at low stress fields while at higher fields (>4MV/cm) it becomes significant. In addition, we give experimental evidence that in tandem with the dielectric relaxation effect another mechanism- the so-called Maxwell-Wagner instability- is present and affects the transient current during the application of a CVS pulse. This instability is also found to be field dependent thus resulting in a trapped charge which is negative at low stress fields but changes to positive at higher fields.Comment: 27pages, 10 figures, 3 tables, regular journal contribution (accepted in IEEE TED, Vol.50, issue 10