One-step growth of ZnO from film to vertically well-aligned nanorods and the morphology-dependent Raman scattering

Abstract

We observed a transition from film to vertically well-aligned nanorods for ZnO grown on sapphire (0001) substrates by metalorganic chemical vapor deposition. A growth mechanism was proposed to explain such a transition. Vertically well-aligned homogeneous nanorods with average diameters of ∼30, 45, 60, and 70nm were grown with the c-axis orientation. Raman scattering showed that the E2 (high) mode shifted to high frequency with the decrease of nanorod diameters, which revealed the dependence of nanorod diameters on the stress state. This dependence suggests a stress-driven diameter-controlled mechanism for ZnO nanorod arrays grown on sapphire (0001) substrates.

Growth and characterization of seed layer-free ZnO thin films deposited on porous silicon by hydrothermal method

“…For wurtzite structure crystals, stress induced in the crystals obviously affects the E 2 (high) phonon frequency, from which information on the stress can be extracted. [30] E 2 (high) mode in the Raman spectra is usually used to probe the in-plane strain. The residual stress of the ZnO thin films was calculated using the 439 cm −1 in the stress-free bulk a-plane ZnO and the pressure coefficient.…”

Substrate effect of hydrothermally grown ZnO nanorods and its luminescence properties

“…Earlier, there were many reports, showing different architectonically nanostructures of ZnO, i.e. flower, tetrapod, hierarchically ordered, pyramid like growth on different polymer and other conducting and non-conducting substrates [11][12][13][14][15]. Haldar et al [22] observed densely spaced and multi-stacked ZnO NRs grown radially outward from a common nucleation centre and oriented isotropically, forming an architecture with the resemblance to a flower on Ge substrates by chemical vapour deposition (CVD) technique.…”

“…In all our samples we observed a strong sharp UV emission peak which varies from 371 to 396 nm depending on the samples. There are many reports [1][2][3][4][5][6][12][13][14][15][16][17][18][26][27][28] on near band edge (NBE) emission peak at 381 nm and assigned to free exciton emission. Park et al [28] reported that at low temperature (40 K) three peaks at 373, 381 and 391 nm correspond to the ZnO seed layer on which ZnO nanowires were grown, an NBE peak responsible for recombination of free excitons, and a donor-acceptor pair (DAP) respectively.…”

“…The report on UV lasing action of well aligned ZnO nanorod arrays [2,9] stimulate the researchers to synthesise ZnO-based nanowires and rods of different shapes and size on various substrates. Several physical and chemical approaches have been employed to fabricate high quality ZnO NRs, such as the template assisted growth [10], plasma-molecular beam epitaxy [11], vapour liquid solid method [2], chemical vapour deposition [12], electrochemical deposition [13], pulsed laser deposition [14] and surfactant assisted hydrothermal growth [15][16][17]. The physical methods [2,[11][12][13][14] required expensive sophisticated equipments with rigorous conditions like good quality single crystal substrates and high temperature (up to 900 C).…”

Fabrication of Diameter-tunable Well-aligned ZnO Nanorod Arrays via a Sonochemical Route

“…[5][6][7] By adjusting the growth conditions, including reaction temperature, oxygen-to-zinc flux ratio, and size of metal catalysts, vapor-phase methods can produce highly-crystalline and well-aligned 1D ZnO nanostructures with different diameters, however, they require sophisticated equipments due to rigorous environmental conditions, such as high temperature (up to 1400 o C) and low pressure. Such severe environmental conditions are inadequate for nanoelectronic circuit integration in glassbased transparent electrode devices or polymer-based flexible devices.…”