Ultra-Low Thermal Conductivity in a GeTeC Nanocomposite Thin Film: Implications for Memory and Thermoelectric Applications.

Achieving ultra-low thermal conductivity in phase-change materials is a key challenge for reducing power consumption in memory devices while preserving functional performance. Here, we report a crystalline GeTe-amorphous carbon nanocomposite thin film exhibiting an exceptionally low thermal conductivity, reduced by up to 80% at room temperature compared to pure GeTe. The thermal conductivity remains remarkably low and is weakly temperature-dependent, increasing only from 0.62(5) to 0.82(4) W m-1 K-1 between 300 and 660 K. This drastic suppression originates from the combined reduction of both phononic and electronic heat transport. Enhanced phonon scattering at GeTe/C interfaces, driven by strong elastic contrast, is complemented by reduced hole mobility due to scattering from Ge vacancies and amorphous carbon regions. Despite a degradation in the power factor, the ultra-low thermal conductivity compensates for this effect, resulting in a thermoelectric figure of merit only slightly lower than that of pure GeTe. The unique combination of suppressed thermal transport, high crystallization temperature, and preserved thermoelectric performance makes this nanocomposite a promising candidate for low-power phase-change memory (PCM) applications with reduced programming currents.