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Large area (up to 4 squared inches) epitaxial VO 2 films, with a uniform thickness and exhibiting an abrupt metal-insulator transition with a resistivity ratio as high as 2.85 × 10 4 have been grown on (001)-oriented sapphire substrates by electron beam evaporation. The lattice distortions (mosaicity) and the level of strain in the films have been assessed by X-ray diffraction. It is demonstrated that the films grow in a domain-matching mode where distortions are confined close to the interface which allows to grow high-quality materials despite the high film-substrate lattice mismatch. It is further shown that a post-deposition high-temperature oxygen annealing step is crucial to ensure the correct film stoichiometry and provide the best structural and electrical properties. Alternatively, it is possible to obtain high quality films with an RF discharge during deposition, which hence do not require the additional annealing step. Such films exhibit similar electrical properties and only slightly degraded structural properties.

This paper presents the design, fabrication and characterization of Ge2Te2Sb5-based phase change material RF switches. The material exhibits non-volatile reversible amorphous to crystalline phase change with resistivity changes up to 105 orders of magnitude. Being non-volatile, these RF switches do not require permanent bias to be maintained in a given state. We present the design of a 4-terminal RF switch integrating an indirect heating system to induce amorphous to crystalline phase change of the material. The measured figure of merit FOM (Ron× Coff) is about 450 fs, which is comparable to FOM obtained for SOI and SOS technologies, without permanent bias.

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