Impact of Maxwell rigidity transitions on resistance drift phenomena in GexTe1−x glasses

Abstract

Amorphous chalcogenides usually exhibit a resistivity, which increases with age following a power law ρ ∼ tα. Existing theories link this change in amorphous state resistivity to structural relaxation. Here, the impact of fundamental glass properties on resistance drift phenomena in amorphous GexTe1−x networks is studied. Employing Raman spectroscopy, the Maxwell rigidity transition from flexible to stressed rigid is determined to occur in the compositional range 0.250 < xc < 0.265. Stressed rigid glasses (x > 0.265) exhibit rather strong resistance drift, where the drift parameters increase steadily from α = 0.13 for amorphous GeTe to α = 0.29 for compositions near the stiffness threshold xc. On the other hand, the drift parameter in flexible glasses (x < 0.25) decreases with decreasing Ge content x to values as low as α = 0.05. These findings illustrate the strong impact of the stiffness threshold on resistance drift phenomena in chalcogenides.

Structural singularities in GexTe100−x films

“…%. We can, thus, conclude that the obtained correlations between resistance drift threshold compositions 16 and the threshold compositions detected from a structural analysis indicate the central role played by the presence of Ge-Ge correlations, both in real space and reciprocal space, in the ageing of PCMs. Their evolution as a function of Ge content appears to be a key-point for further understanding 54,55 and material optimization.…”

“…The drift parameter α determines the change in resistivity, the higher the value of α, the stronger the resistance drift. Recently, it has been shown 16 that the same families of Ge-Te films as the ones studied here but elaborated in a different way (co-sputtering) exhibit for x < 25 at. % (i.e., flexible glasses) a continuous decrease of the drift parameter α with decreasing Ge content.…”

“…On this basis, it can be shown that a decrease of the tetrahedral fraction will increase the location of the flexible/rigid transition, while at the opposite, an increase of the Te coordination number will lower the threshold. Based on this work, Luckas et al 16 evaluated the flexible/rigid transition at about 23 at. % Ge.…”

Phase-change materials and rigidity

“…9 Two domains of compositions corresponding to different evolutions of the  coefficient with a sudden change at the rigidity threshold are observed. All stressed rigid glasses demonstrate high values for  ranging from = 0.13 for a-GeTe up to 0.29…”

“…9 The drift of the resistivity of an amorphous phase over time is generally described by a power law of the form:…”