  2D-layered tin (II) oxide (SnO) has recently emerged as a promising bipolar
channel material for thin-film transistors and complementary
metal-oxide-semiconductor devices. In this work, we present a first-principles
investigation of the mechanical properties of ultrathin SnO, as well as the
electronic implications of tensile strain ($\epsilon$) under both uniaxial and
biaxial conditions. Bulk-to-monolayer transition is found to significantly
lower the Young's and shear moduli of SnO, highlighting the importance of
interlayer Sn-Sn bonds in preserving structural integrity. Unprecedentedly,
few-layer SnO exhibits superplasticity under uniaxial deformation conditions,
with a critical strain to failure of up to 74% in the monolayer. Such
superplastic behavior is ascribed to the formation of a tri-coordinated
intermediate (referred to here as h-SnO) beyond $\epsilon$ = 14%, which
resembles a partially-recovered orthorhombic phase with relatively large work
function and wide indirect band gap. The broad structural range of tin (II)
oxide under strongly anisotropic mechanical loading suggests intriguing
possibilities for realizing novel hybrid nanostructures of SnO through strain
engineering. The findings reported in this study reveal fundamental insights
into the mechanical behavior and strain-driven electronic properties of tin
(II) oxide, opening up exciting avenues for the development of SnO-based
nanoelectronic devices with new, non-conventional functionalities.
