Abstract
Germanium telluride (GeTe) is both polar and metallic, an unusual combination of properties in any material system. The large concentration of free-carriers in GeTe precludes the coupling of external electric field with internal polarization, rendering it ineffective for conventional ferroelectric applications and polarization switching. Here we investigate alternate ways of coupling the polar domains in GeTe to external electrical stimuli through optical second harmonic generation polarimetry and in situ TEM electrical testing on single-crystalline GeTe nanowires. We show that anti-phase boundaries, created from current pulses (heat shocks), invert the polarization of selective domains resulting in reorganization of certain 71o domain boundaries into 109o boundaries. These boundaries subsequently interact and evolve with the partial dislocations, which migrate from domain to domain with the carrier-wind force (electrical current). This work suggests that current pulses and carrier-wind force could be external stimuli for domain engineering in ferroelectrics with significant current leakage.
Highlights
Germanium telluride (GeTe) is both polar and metallic, an unusual combination of properties in any material system
We developed a variant of the optical second harmonic generation (SHG) polarimetry[18,19,20], which is sensitive to material structure in crystals with no inversion symmetry[21,22,23,24,25,26] to quantify different domain fractions in single-crystalline GeTe
In conjunction with in situ transmission electron microscope (TEM) characterization of the GeTe devices[27,28,29,30], we studied the interaction of these domains and domain boundaries with extended defects such as anti-phase boundaries (APBs) and associated partial dislocations created by heat shocks from current pulses
Summary
Germanium telluride (GeTe) is both polar and metallic, an unusual combination of properties in any material system. We developed a variant of the optical second harmonic generation (SHG) polarimetry[18,19,20], which is sensitive to material structure in crystals with no inversion symmetry[21,22,23,24,25,26] to quantify different domain fractions in single-crystalline GeTe. In conjunction with in situ transmission electron microscope (TEM) characterization of the GeTe devices[27,28,29,30], we studied the interaction of these domains and domain boundaries with extended defects such as anti-phase boundaries (APBs) and associated partial dislocations created by heat shocks from current pulses. We show that neither static fields nor steady currents can couple to the domain polarizations, emphasizing that the only possible external electrical stimulus that can do so are the electrical pulses
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