Title: Synthesis of Highly Anisotropic Semiconducting GaTe Nanomaterials and Emerging Properties Enabled by Epitaxy,
Abstract: Pseudo-one dimensional (pseudo-1D) materials are a new-class of materials
where atoms are arranged in chain like structures in two-dimensions (2D).
Examples include recently discovered black phosphorus, ReS2 and ReSe2 from
transition metal dichalcogenides, TiS3 and ZrS3 from transition metal
trichalcogenides and most recently GaTe. The presence of structural anisotropy
impacts their physical properties and leads to direction dependent light-matter
interactions, dichroic optical responses, high mobility channels, and
anisotropic thermal conduction. Despite the numerous reports on the vapor phase
growth of isotropic TMDCs and post transition metal chalcogenides such as MoS2
and GaSe, the synthesis of pseudo-1D materials is particularly difficult due to
the anisotropy in interfacial energy, which stabilizes dendritic growth rather
than single crystalline growth with well-defined orientation. The growth of
monoclinic GaTe has been demonstrated on flexible mica substrates with superior
photodetecting performance. In this work, we demonstrate that pseudo-1D
monoclinic GaTe layers can be synthesized on a variety of other substrates
including GaAs (111), Si (111) and c-cut sapphire by physical vapor transport
techniques. High resolution transmission electron microscopy (HRTEM)
measurements, together with angle resolved micro-PL and micro-Raman techniques,
provide for the very first time atomic scale resolution experiments on
pseudo-1D structures in monoclinic GaTe and anisotropic properties.
Interestingly, GaTe nanomaterials grown on sapphire exhibit highly efficient
and narrow localized emission peaks below the band gap energy, which are found
to be related to select types of line and point defects as evidenced by PL and
Raman mapping scans. It makes the samples grown on sapphire more prominent than
those grown on GaAs and Si, which demonstrate more regular properties.