GeTe₂ Phase Change Material for Terahertz Devices with Reconfigurable Functionalities Using Optical Activation

Area of Science:

• Materials Science
• Optoelectronics
• Condensed Matter Physics

Background:

• Phase change materials (PCMs) offer dynamically controllable properties for advanced optical devices.
• Germanium telluride (GeTe2) is a novel PCM with significant differences in optical characteristics between its amorphous and crystalline states.

Purpose of the Study:

• To investigate the terahertz (THz) dielectric permittivity and optical properties of GeTe2.
• To design and demonstrate a tunable THz metasurface using GeTe2 films.
• To explore methods for dynamic control of the metasurface's THz resonance.

Main Methods:

• GeTe2 films were prepared using pulsed laser deposition (PLD).
• THz spectra were analyzed using harmonic oscillator and Drude models.
• A THz metasurface was fabricated and characterized.
• Density functional theory (DFT) was employed for modeling.

Main Results:

• GeTe2 exhibited a remarkable 7-order-of-magnitude difference in conductivity between crystalline and amorphous states.
• The THz resonance of the GeTe2 metasurface could be tuned dynamically via thermal or light-induced crystallization.
• Raman spectroscopy at 155 cm-1, assigned to Te-Te stretching, was identified as a control mechanism for the metasurface state.

Conclusions:

• GeTe2 is a promising PCM for creating dynamically tunable THz metasurfaces.
• The observed contrast in conductivity and tunable resonance enable novel THz device functionalities.
• Raman peak intensity at 155 cm-1 provides a viable method for monitoring and controlling the phase state of the metasurface.