Modulation of structural, optical, and dielectric properties of GeTe1-Se amorphous films with the Se content x (0 ≤ x ≤1)

The amorphous compositions within the Ge–Te–Se ternary system hold significant potential for various technological applications including optical / electrical data storage. Semiconducting GeTe 1- x Se ₓ (0 ≤ x ≤ 1) films, with a thickness of 3 µm, were synthesized in their amorphous phase via the co-evaporation deposition method onto glass substrates. A systematic investigation of the evolution of the short-range structural order with varying Se content was carried out using fluorescence-like X-ray Absorption Near Edge Structure (XANES) spectroscopy at the Ge and Se K-edges, providing new insight into the local bonding environment across the entire compositional range. To study the optical characteristics of these films, transmittance measurements were performed in the visible to near-infrared (Vis-NIR) spectral range. The indirect E g opt optical bandgap energies were determined through Tauc plot analysis, revealing a progressive augmentation of the indirect bandgap value with increasing selenium concentration. The optical refractive indexes obtained as a function of wavelengths, which also showed a decrease with x , allowed us to determine the relative permittivity ε r ∞ . Most notably, the local static relative permittivity ε r 0 was quantified for the first time in this system using electrostatic force microscopy (EFM) coupled with finite element simulations. The results reveal a strong compositional dependence of ε r 0 , correlating with the evolution of both structural and optical properties. Altogether, this study offers a comprehensive and original multi-scale analysis of GeTe₁₋ₓSeₓ thin films, combining local structural, optical, and dielectric characterizations to better understand the role of composition in tuning their functional properties. ● Ge and Se local structural evolution with x in the GeTe 1- x Se x amorphous films. ● The refractive indexes n , obtained as a function of wavelengths, decrease with x . ● Augmentation of the E g opt optical bandgap value with increasing Se concentration. ● Compositional dependence of the static relative permittivity ε r . 0