Self-aligned formation of superconducting sub-5 nm PtSi films

Yao, Yao and Fernandes, Daniel F. and Košutová, Tereza and Kubart, Tomas and Zhang, Zhen and Lefloch, François and Gustavo, Frédéric and Leblanc, Axel and Lábár, János and Pécz, Béla and Zhang, Shi-Li (2024) Self-aligned formation of superconducting sub-5 nm PtSi films. APL Quantum, 1 (2). ISSN 2835-0103

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Abstract

Platinum silicide (PtSi) presents a promising superconductor for achieving silicon-based Josephson field-effect transistors (JoFETs). In a viable process flow to realize self-aligned PtSi formation, thermal oxidation at 600 °C is required to form a protective oxide layer on the surface of the as-formed PtSi selectively against Pt to facilitate subsequent selective etch in aqua regia. However, sub-10 nm PtSi films tend to agglomerate and even break into discrete PtSi islands upon thermal treatments above 500 °C. To achieve nanoscale JoFETs, we have developed a simple alternative with chemical oxidation at room temperature leading to the formation of homogeneous sub-5 nm PtSi films. The critical temperature of the resultant superconducting PtSi films is found to increase from 0.66 to 0.90 K when the PtSi thickness is raised from 3.1 to 12.7 nm, while, concurrently, the PtSi grains grow larger in thicker films. The critical temperature also increases from 0.53 to 0.66 K for the 3.1 nm PtSi film when the formation temperature is raised from 400 to 500 °C.

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