Abstract
Although some methods to improve phase-change memory efficiency have been proposed, an effective experimental approach to induce a phase-change like process without external heat energy has not yet been reported. Herein we have shown that GeTe is a prototype phase-change material, which can exhibit a non-thermal phase-change-like process under uniaxial stress. Due to its structural characteristics like directional structural instability and resonance bonding under 1% uniaxial stress, we observed that bond switching in the GeTe film between short and long bonds is possible. Due to this phase change, GeTe displays the same phase-change as crystal layer rotation. Crystal layer rotation has not been observed in the conventional phase change process using intermediate states, but it is related to the structural characteristics required for maintaining local coordination. Moreover, since the resonance bonding characteristics are effectively turned off upon applying uniaxial stress, the high-frequency dielectric constant can be significantly decreased. Our results also show that the most significant process in the non-thermal phase transition of phase-change materials is the modulation of the lattice relaxation process after the initial perturbation, rather than the method inducing the perturbation itself. Finally, these consequences suggest that a new type of phase-change memory is possible through changes in the optical properties under stress.
Highlights
A group of phase-change materials in the pseudobinary GeTe-Sb2Te3 tie-line (GST) has been widely used in memory devices[1,2]
We investigated changes in electrical properties upon application of reversible bending stresses in well oriented rhombohedral crystalline GeTe (r-GeTe)
The resistivity of the strained r-GeTe does not show divergence tendency even at 2 K, a transition from negative temperature coefficient of resistance (TCR) to positive TCR is typically occurs near the Anderson localization limit[33,34]: i.e., 0.2 Ω·cm is derived from the Ioffe-Regal condition, as in previous reports[16,32]
Summary
A group of phase-change materials in the pseudobinary GeTe-Sb2Te3 tie-line (GST) has been widely used in memory devices[1,2]. In order to apply the materials in storage device development, the possibility of information storage using contrast difference in optical and electrical changes arising from the thermally-induced phase transition between a partially covalently-bonded “amorphous phase” and the resonantly-bonded “crystalline phase” with inherent distortions, has been explored[6,7,8,9]. With excellent properties such as desired scalability, endurance, and on-off ratio, phase-change memory has been commercialized and shipped as storage class memory rather than as universal memory owing to its limited switching speed and high power consumption. Without appropriate lattice relaxation process for the resonantly bonded crystal, structures with similar local coordination are preferred over intermediate structures with other local coordination
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