Mixed-Phase Crystallization and Resonance Tuning in Sn-Incorporated GST Thin Films: Experimental Study with THz...

Tin (Sn) was incorporated into Ge₂Sb₂Te₅ (GST) thin films to create a tunable platform for terahertz (THz) sensing. The films were prepared by DC magnetron cosputtering and examined using energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) to analyze composition and phase evolution. Results show that Sn modifies the crystallization pathway of GST, forming mixed SnTe and SnSb phases that enable phase transformation at a lower thermal energy. THz time-domain spectroscopy (THz-TDS) revealed a pronounced dielectric contrast between amorphous and crystalline states, with Sn incorporation enhancing phase transition. The measured optical parameters were implemented in simulations of split-ring resonator (SRR) metasurfaces containing a GST underlayer. Phase switching in pure GST produced a resonance shift of about 0.16 THz; however, the Sn-incorporated GST sample could improve modulation efficiency with reduced thermal input. These findings identify Sn-incorporated GST as a promising material for reconfigurable, energy-efficient THz device platforms.