Sandia Labs FY22 Laboratory Directed Research & Development Annual Report

FY22 ANNUAL REPORT

UNDERSTANDING THE EFFECTS OF RADIATION ON RECONFIGURABLE PHASE CHANGE MATERIALS.

Chalcogenide thin films that undergo reversible phase changes show promise for next-generation nanophotonics, metasurfaces, and other emerging technologies. This general class of thin films can be switched rapidly between amorphous and crystalline phases which exhibit contrasted optical

that crystalline films can be amorphized by ion irradiation (metamictization) and quaternary addition affects radiation tolerance. This study provides new insight into chalcogenide phase stability offering design pathways for future applications. The project involved collaborations with students and faculty from Sandia Alliance partner Purdue University and National/Regional partner University of Florida. This work generated multiple publications including one extensive article in the Journal of Physics . PI David Adams was also recently elected Fellow and President of American Vacuum Society: Science and Technology of Materials, Interfaces and Processing. (PI: David Adams)

and electronic states. Despite the successful development of benchmark Ge 2 Sb 2 Te 5 for some applications, there is a desire to identify new materials with improved performance. The Sandia LDRD team focused on the behavior of sputter-deposited (Ge 2 Sb 2 Te 5 )xC1-x

David Adams was elected Fellow and President of American Vacuum Society: Science and Technology of Materials, Interfaces and Processing in 2023.

[0 < 1-x < 0.12] films and investigated the phase stability and key unknowns of several promising quaternary compositions. This study confirmed increased crystallization temperatures of C-doped Ge 2 Sb 2 Te 5 consistent with enhanced amorphous phase stability. Additional experiments involving high energy, and heavy ion irradiation explored the stability of films subjected to collision-induced disordering. Detailed characterization showed Plan view transmission electron micrographs and electron diffraction patterns comparing a non-doped film with three films of varied, doped composition. Films are shown after deposition, heating to crystallize, and MeV Au ion irradiation to high dose. Lack of distinct spots in the diffraction patterns post-irradiation is evidence of amorphization.

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