Abstract
By understanding the growth mechanism of nanomaterials, the morphological features of nanostructures can be rationally controlled, thereby achieving the desired physical properties for specific applications. Herein, the growth habits of aluminum nitride (AlN) nanostructures and single crystals synthesized by an ultrahigh-temperature, catalyst-free, physical vapor transport process were investigated by transmission electron microscopy. The detailed structural characterizations strongly suggested that the growth of AlN nanostructures including AlN nanowires and nanohelixes follow a sequential and periodic rotation in the growth direction, which is independent of the size and shape of the material. Based on these experimental observations, an helical growth mechanism that may originate from the coeffect of the polar-surface and dislocation-driven growth is proposed, which offers a new insight into the related growth kinetics of low-dimensional AlN structures and will enable the rational design and synthesis of novel AlN nanostructures. Further, with the increase of temperature, the growth process of AlN grains followed the helical growth model.
Highlights
The elucidation of the growth mechanism of nanomaterials is one of the most critical topics in nanoscience community, because it is the cornerstone of materials research and applications
The X-ray diffraction (XRD) pattern confirms the high crystallinity of the as-prepared products, corresponding to the well-indexed WZ crystal structure of aluminum nitride (AlN) (a = 0.3114 nm and c = 0.4981 nm, ICDD-PDF-4 + N o. 00-025-1133, Fig. S2a)
After tilting at a small angle, a wave-type surface was observed in the two sections (Fig. 3e). These novel helical morphologies raise a basic question that whether it was induced by dislocations or twins? we present a convincing answer to this question by high-resolution TEM (HRTEM) characterizations
Summary
The elucidation of the growth mechanism of nanomaterials is one of the most critical topics in nanoscience community, because it is the cornerstone of materials research and applications. Diverse well-known and extensively investigated nanomaterials with simple morphologies such as nanoparticles (NPs), nanorods (NRs), nanocubes (NCs), and nanotubes (NTs) have been synthesized using two general approaches: bottom-up (growth) and top-down (decomposition) by template-assisted and template-free methods[1]. These anisotropic nanostructures have demonstrated novel physical features and promising utility in nanoelectronics, nanophotonics, solar energy conversion, and electrochemical energy storage, which are strongly dependent on their morphologies and geometries[2,3,4,5]. The AlN nanohelixes add a new member to the growing family of 1D NWs
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