Sc-doped GeTe thin films prepared by radio-frequency magnetron sputtering

Radio frequency magnetron co-sputtering method employing GeTe and Sc targets was exploited for the deposition of Sc doped GeTe thin films. Different characterization techniques (scanning electron microscopy with energy-dispersive X-ray analysis, X-ray diffraction, atomic force microscopy, sheet resistance temperature-dependent measurements, variable angle spectroscopic ellipsometry, and laser ablation time-of-flight mass spectrometry) were used to evaluate the properties of as-deposited (amorphous) and annealed (crystalline) Ge-Te-Sc thin films. Prepared amorphous thin films have Ge₄₈Te₅₂, Ge₄₆Te₅₀Sc₄, Ge₄₄Te₄₈Sc₈, Ge₄₃Te₄₇Sc₁₀ and Ge₄₁Te₄₅Sc₁₄ chemical composition. The crystallization temperatures were found in the region of ~ 153-272 °C and they increase with scandium content. Upon amorphous-crystalline material phase change, large changes in sheet resistance were measured, with electrical contrast in terms of sheet resistance ratio R_annealed/R_as-deposited in the range of 1.37.10^-4 - 9.1.10^-7. Simultaneously, huge variations of optical functions were found as demonstrated by absolute values of optical contrast values (at 405 nm) in the range of |Δn|+|Δk| = 1.88-3.75 reaching maximum for layer containing 8 at% of Sc.