Near-infrared photonic phase-change properties of transition metal ditellurides.
Albert Davydov, Sergiy Krylyuk, Yifei Li, Akshay Singh, Rafael Jaramillo
We use the (Mo,W)Te2 system to explore the potential of transition metal dichalcogenides (TMDs) as phasechange materials for integrated photonics. We measure the complex optical constant of MoTe2 in both the 2H and 1T phases by spectroscopic ellipsometry. We find that both phases have large refractive index, which is good for confined light-matter interaction volume. The change Δ𝑛 between phases is of ℴ(1) , which is large and comparable to established phase-change materials. However, both phases have large optical loss, which limits to figure of merit throughout the measured range. We further measure the NIR reflectivity of MoTe2 and Mo0.91W0.09Te2, in both the 2H and 1T phases. The data show that the strong optical contrast between the 2H and 1T structures persists even as the thermodynamic barrier between them is reduced by alloying. This bodes well for alloy design of phase-change materials.