Stoichiometric Epitaxial Strontium Titanate Thin Films on Silicon by High-Temperature Sr Segregation

Andries Boelen; Marina Baryshnikova; Maxim Korytov; Sean R. C. McMitchell; Felix Cahyadi; Christian Haffner; Clement Merckling

arXiv · 2606.09574

Stoichiometric Epitaxial Strontium Titanate Thin Films on Silicon by High-Temperature Sr Segregation

Andries Boelen·Marina Baryshnikova·Maxim Korytov·Sean R. C. McMitchell·Felix Cahyadi·Christian Haffner·Clement Merckling

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Abstract

Thin-film strontium titanate (SrTiO$_3$, STO) layers grown on silicon require accurate stoichiometry and single-crystalline order to exploit their functional properties optimally. Oxide molecular beam epitaxy can provide an epitaxial interface, but suffers from source oxidation and resulting flux instabilities, yielding only a narrow growth process window for cationic stoichiometry control. Here, we investigate post-growth annealing in oxygen as a pathway to drive the STO layer toward stoichiometry in intentionally Sr-rich epitaxial STO films on silicon (001). Annealing over a broad temperature range revealed two distinct Sr-segregation mechanisms. Below 800 {\deg}C, excess Sr segregates toward the surface, forming SrO outgrowths that progressively sublimate at elevated temperatures. Above 800 {\deg}C, a second mechanism dominates: Sr accumulates within the interfacial SiO$_2$ layer formed by oxygen diffusion at the STO/Si interface. Together, these mechanisms effectively remove excess Sr from the STO lattice, yielding a more stoichiometric perovskite layer. Our results demonstrate that growing slightly Sr-rich STO templates followed by controlled annealing provides a practical route to improve crystalline quality, offering a scalable strategy for high-quality STO integration on silicon.

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Andries Boelen, Marina Baryshnikova, Maxim Korytov, Sean R. C. McMitchell, Felix Cahyadi, Christian Haffner, Clement Merckling. 2026-06-08. Stoichiometric Epitaxial Strontium Titanate Thin Films on Silicon by High-Temperature Sr Segregation. https://arxiv.org/abs/2606.09574

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