White spots on a characterization map for the phase-change memory (PCM) and threshold switches

All major parameters of electronic PCM characterization happen to have some significant ¿nonuniversalities.¿ The presence of electrical contacts and interfaces allows only limited application of programming mechanisms typical for optical memory to electronic PCM. The fine structure of current voltage (IV) in a prethreshold (prethreshold conduction mechanisms can be affected by device size), and post-threshold range of currents and resistance current (RI) characteristics, will be discussed together with the dimensionality effects and the specifics of set and reset resistance programming in devices with different contact geometry. Some of discussed phenomena, and general functional possibilities of the effects of negative differential conductivity and switching in noncrystallizing and memory alloys, are presented.