A theory of field-induced crystal nucleation is developed and verified experimentally for the case of switching in nanoglasses of phase change memory. For symmetry-breaking strong electric fields, it predicts needleshaped crystallites with nucleation barriers lower than that of spherical nuclei and a strong field dependent. We have observed bias dependent switching for times and temperatures far beyond those typically reported and supportive of our predictions, in particular, switching time exponential in voltage and temperature.

The authors propose a simple physical model of threshold switching in phase change memory cells based on the field induced nucleation of conductive cylindrical crystallites. The model is solved analytically and leads to a number of predictions including correlations between the threshold voltage Vth and material parameters, such as the nucleation barrier and radius, amorphous layer thickness, as well as Vth versus temperature and switching delay time. The authors have carried out verifying experiments, and good agreement is achieved.

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We present the data on temporal (t) drift of parameters in chalcogenide phase change memory that significantly complement the earlier published results. The threshold voltage Vth and the amorphous state resistance R are shown to drift as ΔVth∝v ln t and R∝tα in broad intervals spanning up to nine decades in time; the drift coefficient v depends on glass parameters and temperature, but does not depend on device thickness. We have demonstrated that drift saturates at long enough times that can be shorten with temperature increase. All available data on drift dynamics are fully consistent with the classical double-well-potential model, which gives simple analytical expressions for the observed temporal dependencies including numerical parameters.

Electrical conduction in chalcogenide glasses of phase change memory App. Phys. Rev. 2012, 8 (2012 Understanding the multistate SET process in Ge-Sb-Te-based phase-change memory J. Appl. Phys. 112, 064901 (2012) Highly sensitive tactile sensors integrated with organic transistors Appl. Phys. Lett. 101, 103308 (2012) Highly sensitive tactile sensors integrated with organic transistors APL: Org. Electron. Photonics 5, 206 (2012) On the nature of the interfacial layer in ultra-thin TiN/LaLuO3 gate stacks Amorphous chalcogenides have been extensively studied over the last half century due to their application in rewritable optical data storage and in non-volatile phase change memory devices. Yet, the nature of the observed non-ohmic conduction in these glasses is still under debate. In this review, we consolidate and expand the current state of knowledge related to dc conduction in these materials. An overview of the pertinent experimental data is followed by a review of the physics of localized states that are peculiar to chalcogenide glasses. We then describe and evaluate twelve relevant transport mechanisms with conductivities that depend exponentially on the electric field. The discussed mechanisms include various forms of Poole-Frenkel ionization, Schottky emission, hopping conduction, field-induced delocalization of tail states, space-charge-limited current, field emission, percolation band conduction, and transport through crystalline inclusions. Most of the candidates provide more or less satisfactory fits of the observed non-linear IV data. Our analysis calls upon additional studies that would enable one to discriminate between the various alternative models. V C 2012 American Institute of Physics. [http://dx.