This tutorial review describes recently developed methods for the growth of two-dimensional materials using liquid-metal based synthesis approaches. The integration of these materials and their potential applications are also reviewed and discussed.
High
dielectric constant (high-k) ultrathin films
are required as insulating gate materials. The well-known high-k dielectrics, including HfO2, ZrO2, and SrTiO3, feature three-dimensional lattice structures
and are thus not easily obtained in the form of distinct ultrathin
sheets. Therefore, their deposition as ultrathin layers still imposes
challenges for electronic industries. Consequently, new high-k nanomaterials with k in the range of
40 to 100 and a band gap exceeding 4 eV are highly sought after. Antimony
oxide nanosheets appear as a potential candidate that could fulfill
these characteristics. Here, we report on the stoichiometric cubic
polymorph of 2D antimony oxide (Sb2O3) as an
ideal high-k dielectric sheet that can be synthesized via a low-temperature, substrate-independent, and silicon-industry-compatible
liquid metal synthesis technique. A bismuth–antimony alloy
was produced during the growth process. Preferential oxidation caused
the surface of the melt to be dominated by α-Sb2O3. This ultrathin α-Sb2O3 was then
deposited onto desired surfaces via a liquid metal
print transfer. A tunable sheet thickness between ∼1.5 and
∼3 nm was achieved, while the lateral dimensions were within
the millimeter range. The obtained α-Sb2O3 exhibited high crystallinity and a wide band gap of ∼4.4
eV. The relative permittivity assessment revealed a maximum k of 84, while a breakdown electric field of ∼10
MV/cm was observed. The isolated 2D α-Sb2O3 nanosheets were utilized in top-gated field-effect transistors that
featured low leakage currents, highlighting that the obtained material
is a promising gate oxide for conventional and van der Waals heterostructure-based
electronics.
Two-dimensional (2D) metal oxides can be difficult to synthesise, and scaling up production using traditional methods is challenging. However, a new liquid metal-based technique, that utilises both “top-down” and “bottom-up”...
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