Switchable Piezoresistive SmS Thin Films on Large Area

Area of Science:

• Materials Science
• Condensed Matter Physics
• Thin Film Deposition

Background:

• Samarium monosulfide (SmS) is a unique material known for its pressure-induced semiconductor-to-metal transition.
• This property makes SmS suitable for applications in piezoresistive sensors and memory devices.

Purpose of the Study:

• To develop a method for depositing semiconducting SmS thin films on silicon wafers using e-beam sublimation.
• To investigate the influence of deposition parameters on SmS film properties.
• To characterize the material's behavior during and after the semiconductor-to-metal transition.

Main Methods:

• Electron-beam (e-beam) sublimation of samarium metal in a reactive H2S atmosphere.
• Deposition of SmS thin films on 150 mm silicon wafers.
• In-situ X-ray diffraction (XRD) for studying back-switching and stability.
• X-ray photoelectron spectroscopy (XPS) for determining samarium valence states.

Main Results:

• Successful deposition of semiconducting SmS thin films with controlled properties by optimizing deposition rate, substrate temperature, and H2S partial pressure.
• Observation of changes in optical, structural, and electrical properties upon pressure-induced transition to the metallic state.
• Thermally induced back-switching observed starting at 250 °C, with Sm2O2S formation above 500 °C.
• Valence state of samarium ions characterized using XPS.

Conclusions:

• E-beam sublimation is a viable technique for producing SmS thin films for electronic applications.
• The study provides insights into the switching behavior, stability, and characterization of SmS thin films.
• Further research can leverage these findings for developing novel SmS-based devices.