Specific geometric morphology and
improved crystalline properties
are of great significance for the development of materials in micro–nano
scale. However, for high-melting molybdenum (Mo), it is difficult
to get high-quality structures exhibiting a single-crystalline nature
and preconceived morphology simultaneously. In this paper, a pyramid-shaped
single-crystalline Mo nanostructure was prepared through a thermal
evaporation technique, as well as a series of experimental controls.
Based on detailed characterizations, the growth mechanism was demonstrated
to follow a sequential process that includes MoO2 decomposition
and Mo deposition, single-crystalline islands formation, layered nucleation,
and competitive growth. Furthermore, the product was measured to show
excellent physical properties. The prepared nanostructures exhibited
strong nano–indentation hardness, elastic modulus, and tensile
strength in mechanical measurements, which are much higher than those
of the Mo bulks. In the measurement of electronic characteristics,
the individual structures indicated very good electrical transport
properties, with a conductance of ∼0.16 S. The prepared film
with an area of 0.02 cm2 showed large-current electron
emission properties with a maximum current of 33.6 mA and a current
density of 1.68 A cm–2. Optical properties of the
structures were measured to show obvious electromagnetic field localization
and enhancement, which enabled it to have good surface enhanced Raman
scattering (SERS) activity as a substrate material. The corresponding
structure–response relationships were further discussed. The
reported physical properties profit from the basic features of the
Mo nanostructures, including the micro–nano scale, the single-crystalline
nature in each grain, as well as the pyramid-shaped top morphology.
The findings may provide a potential material for the research and
application of micro–nano electrons and photons.