Hierarchical ZnO
Nanowire Growth with Tunable Orientations
on Versatile Substrates Using Atomic Layer Deposition Seeding
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Abstract
The ability to synthesize semiconductor
nanowires with deterministic
and tunable control of orientation and morphology on a wide range
of substrates, while high precision and repeatability are maintained,
is a challenge currently faced for the development of many nanoscale
material systems. Here we show that atomic layer deposition (ALD)
presents a reliable method of surface and interfacial modification
to guide nanowire orientation on a variety of substrate materials
and geometries, including high-aspect-ratio, three-dimensional templates.
We demonstrate control of the orientation and geometric properties
of hydrothermally grown single crystalline ZnO nanowires via the deposition
of a ZnO seed layer by ALD. The crystallographic texture and roughness
of the seed layer result in tunable preferred nanowire orientations
and densities for identical hydrothermal growth conditions. The structural
and chemical relationship between the ALD layers and nanowires was
investigated with synchrotron X-ray diffraction, high-resolution transmission
electron microscopy, and X-ray photoelectron spectroscopy to elucidate
the underlying mechanisms of orientation and morphology control. The
resulting control parameters were utilized to produce hierarchical
nanostructures with tunable properties on a wide range of substrates,
including vertical micropillars, paper fibers, porous polymer membranes,
and biological substrates. This illustrates the power of ALD for interfacial
engineering of heterogeneous material systems at the nanoscale, to
provide a highly controlled and scalable seeding method for bottom-up
synthesis of integrated nanosystems