Tailoring Crystallization Kinetics of Chalcogenides for Photonic Applications

Abstract

Chalcogenides possess interesting optical properties, which are attractive for a variety of applications such as data storage, neuromorphic computing, and photonic switches. Lately a group of covalently bonded chalcogenides including Sb2Se3 and Sb2S3 has moved into the focus of interest for such photonic applications, where high optical contrast as well as reliable and fast switching is of crucial importance. Here, these properties of Sb2Se3 are examined and compared with typical phase change materials such as GeSb2Te4 and Ge2Sb2Te5. Sb2Se3 is favorable for many photonic applications due to its larger band gap, yet, the maximum optical contrast achievable is smaller than for GeTe and Ge2Sb2Te5. Furthermore, crystallization needs significantly longer and exhibits a distinctively wider stochastic distribution of reflectances after crystallization, which provides challenges for the usage in photonic applications. At the same time, the glassy/amorphous state of Sb2Se3 is more stable. These differences can be attributed to differences in bonding of the crystalline state, which is more covalent for Sb2Se3. A quantum‐chemical map can help to understand and explain these trends and facilitates the design of tailored materials for photonic applications.

Interlaboratory study on Sb2S3 interplay between structure, dielectric function, and amorphous-to-crystalline phase change for photonics

“…Thus, in the last decade, numerous attempts have focused on identifying PCMs with large band gap and a pronounced optical contrast at photon energies higher than 1 eV to enable optical amplitude and phase modulations schemes in the visible range ( Müller et al., 2021 ).…”

Photonic time crystals: A materials perspective

“…One such material class is phase change materials that can undergo large refractive index changes as they transition from an amorphous to a crystalline state, and vice versa [12,13].…”

“…This change can occur in a short time spanning a few hundred femtoseconds [20,37,38]. The use of TCOs has been demonstrated in reflectance and transmittance modulation, as well as in optical polarization switches [13,20,21], making them a promising platform for PTC realization. Furthermore, the large optical nonlinearities near their epsilon-near-zero regimes result in lower power requirements for the same refractive index changes, relaxing the power constraints [20,37].…”

Time-Resolved Temperature Mapping Leveraging the Strong Thermo-Optic Effect in Phase-Change Materials

“…A 637 nm CW diode laser (OBIS 637LX) was used as the optical probe and operated at an average power of 520 μW and fwhm of about 10 μm to avoid phase changes in the GST. This is equivalent to an optical intensity of ∼240 W/cm 2 , which is 3 orders of magnitude lower than that required to crystallize GST at similar wavelengths . For steady-state measurements shown in Figure d, the probe beam was modulated, and its reflected signal was detected using a lock-in amplifier (SRS860) to increase the signal-to-noise ratio.…”