Abstract
Chalcogenide materials such as Ge2Sb2Te5 (GST) which undergo structural transition between amorphous and crystalline phases with applied thermal load, have emerged as potential material candidates for new memory technologies due to prospective gain in speed, device lifetime, and capacity. In these devices, each memory cell is composed of various components with different material compositions and functionalities. Therefore, a solid understanding of how heat transfers between each component is pivotal in the enhancement of performance and minimization of power consumption. In this study using time-domain thermoreflectance, we measure thermal properties relevant to device operation, at material length scales (< 40 nm) similar to those used in actual devices, such as sound speed, thermal conductivity and thermal boundary conductance (TBC) for a temperature range from 25 °C to 400 °C. According to acoustic echoes obtained from picosecond acoustic measurements, the speed of sound in GST is calculated to be around 2,900 m/s. Moreover, we report the thermal boundary resistance (TBR) when different spacer compositions (W, SiO2, SiNx) are introduced to separate GST from the other components where SiNx/GST interface showed the highest TBR compared to both W and SiO2 interlayers. Additionally, the temperature dependent results indicate that the GST change phase from amorphous to cubic structure at 150 C and again from cubic to hexagonal at approximately 340 C. The thermal conductivity of GST experiences a significant jump at the transition temperature of 150 from 0.15 W/m/K to 0.30 W/m/K and continue to linearly increase by raising the temperature until its crystal structure completely transforms into the hexagonal where the thermal conductivity flattens out to the value of 1.4 W/m/K.
Published Version
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