Inverting polar domains via electrical pulsing in metallic germanium telluride

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.

Polar metals as electrodes to suppress the critical-thickness limit in ferroelectric nanocapacitors

“…Alternative approaches have also been applied to degenerately doped ferroelectrics. [43] IV. CONCLUSION In summary, we proposed a ferroelectric capacitor where the conventional metallic electrodes are replaced by noncentrosymmetric metallic electrodes.…”

Polar and phase domain walls with conducting interfacial states in a Weyl semimetal MoTe2

“…In principle, itinerant electron screening in a (semi)metal might rule out the necessity of electrostatically driven domain formation due to the fundamental incompatibility of polarity and metallicity, but the existence of polar domains, formed by local bonding preferences, is still possible since this mechanism is insensitive to the presence of charge carriers 22 . Some progress has been made in, for example, the polar interlocked ferroelastic domains in polar metal Ca 3 Ru 2 O 7 25,26 and the structural defect-mediated polar domains in metallic GeTe 27 . In this context, exploring the domain structures in polar Weyl semimetal would be particularly important because the Weyl points and Fermi-arc connectivity can be manipulated via domain reorientation or locally modified order parameters at these DWs 28–31 .…”

Ferroelectric Self-Poling in GeTe Films and Crystals

“…Therefore, a possible explanation for the striking difference in domain mapping between crystal and film is that in local contact mode the surface excitation is different compared to domain mapping: in the first case, the cantilever is fixed in position; in the latter, it is sweeping the surface. It turns out that for "leaky" ferroelectrics, i.e., those with significant electric conductivity such as our slightly p-doped GeTe, heat and pulsed currents are essential ingredients in manipulating the FE domains [52]. Therefore, it is reasonable to assume that a DC voltage applied to the cantilever in local contact mode, combined with pulsed currents induced by AC voltage, are sufficient to reorient the surface-interface FE domain structure depicted in Figure 4f such that the hysteresis is consistent with data obtained from the crystal.…”