Scanning probe microscopy of ZnO nanobelts (original) (raw)
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In situ probing of electromechanical properties of an individual ZnO nanobelt
Applied Physics Letters, 2009
We report here, an investigation on electrical and structural-microstructural properties of an individual ZnO nanobelt via in situ transmission electron microscopy using an atomic force microscopy ͑AFM͒ system. The I-V characteristics of the ZnO nanobelt, just in contact with the AFM tip indicates the insulating behavior, however, it behaves like a semiconductor under applied stress. Analysis of the high resolution lattice images and the corresponding electron diffraction patterns shows that each ZnO nanobelt is a single crystalline, having wurtzite hexagonal structure ͑a = 0.324 nm, c = 0.520 66 nm͒ with a general growth direction of ͓1010͔.
In situ probing of electromechanical properties of an individual ZnO nanobelt
Applied Physics Letters, 2009
We report here, an investigation on electrical and structural-microstructural properties of an individual ZnO nanobelt via in situ transmission electron microscopy using an atomic force microscopy ͑AFM͒ system. The I-V characteristics of the ZnO nanobelt, just in contact with the AFM tip indicates the insulating behavior, however, it behaves like a semiconductor under applied stress. Analysis of the high resolution lattice images and the corresponding electron diffraction patterns shows that each ZnO nanobelt is a single crystalline, having wurtzite hexagonal structure ͑a = 0.324 nm, c = 0.520 66 nm͒ with a general growth direction of ͓1010͔.
JURNAL FIZIK MALAYSIA
The thin film of ZnO nanowire and Sn-doped ZnO nanobelt were fabricated through physical vapor deposition (PVD) technique on Si (111) substrate. X-ray Diffaction (XRD) and Energy Dispersive X-ray (EDX) studies demonstrated that there are significant change in crystal structure and content of the elements as the nano structures change from nanowire to nanobelt when the ZnO thin film was doped with Sn. The morphological change in the shape of the nanostructure from nanowire to nanobelt and to nanoring can be observed from the Field Effect Scanning Electron Microscopy (FESEM) images. The high polarity of Sndoped ZnO has caused the formation of the spiral structure in the nanostructure of the ZnO thin film.
On the correlation of crystal defects and band gap properties of ZnO nanobelts
Applied Physics A: …, 2011
We report here investigations of crystal and electronic structure of as-synthesized and annealed ZnO nanobelts by an in-situ high-resolution transmission electron microscope equipped with a scanning tunneling microscopy probe. The in-situ band gap measurements of individual ZnO nanobelts were carried out in scanning tunneling spectroscopy mode using the differential conductance dI/dV -V data. The band gap value of the as-synthesized ZnO nanobelts was calculated to be ∼2.98 eV, while this property for the annealed nanobelts (∼3.21 eV) was close to the band gap value for bulk ZnO materials (∼3.37 eV). The difference in the band gap value of the as-synthesized ZnO nanobelts and annealed ones was attributed to the planar defects (e.g. stacking faults and twins). These defects can alter the electronic structure by producing localized resonant states that result in band gap reduction.
Poole-Frenkel Conduction Mechanism in ZnO:N Nanobelts
physica status solidi (a), 2018
In this paper, the authors demonstrate that the electrical conduction along ZnO:N nanobelts follow a conduction mechanism type Poole-Frenkel. Electrical measurements obtained using the conductive-AFM (C-AFM) technique and between two In/W electrodes of single ZnO:N nanobelts confirm this result. These measurements reveal that the dielectric constant, e r , of the ZnO nanobelts, is about 4.3. Cathodoluminescence (CL) spectra acquired from single ZnO:N nanobelts show a strong signal centered at 3.23, with two-phonon replicas at 3.15 and 3.08 eV, generated by a donor-acceptor pair (DAP) transition besides a signal centered at 3.29 eV corresponding with a free electron-acceptor (FA) transition. The authors propose the presence of N O as acceptor centers to explain the origin of these electronic transitions. Xray photoelectron spectroscopy measurements confirm the presence of this substitutional impurity, revealing an N 1s signal corresponding with Zn─N bonds. The authors propose that N O acceptor centers participate as defect traps that originate the Poole-Frenkel conduction mechanism.
Probing nano-scale mechanical characteristics of individual semi-conducting nanobelts
Materials Science and Engineering: A, 2005
Quasi-one-dimensional (1D) solid nanostructures, such as nanobelts of semi-conducting oxides, have stimulated considerable interest for scientific research due to their importance in mesoscopic physics studies and their potential applications as nano-devices, nanocantilevers, nanoactuators and nanosensors. A key challenge to today's research is the experimental difficulty in fabricating, manipulating and testing the physical properties of a single nanowire/cantilever whose size is in the nano-to micro-meter range, because the small size (diameter and length) of the object prohibits the applications of the well-established testing techniques.
Aspect ratio dependence of the elastic properties of ZnO nanobelts
Nano Letters
The Young's modulus of ZnO nanobelts was measured with an atomic force microscope by means of the modulated nanoindentation method. The elastic modulus was found to depend strongly on the width-to-thickness ratio of the nanobelt, decreasing from about 100 to 10 GPa, as the width-to-thickness ratio increases from 1.2 to 10.3. This surprising behavior is explained by a growth-direction-dependent aspect ratio and the presence of stacking faults in nanobelts growing along particular directions.
Nanotechnology, 2006
ZnO nanowires and nanobelts are two representatives of one-dimensional semiconductor nanomaterials possessing potential applications as optoelectronic and sensor devices. In this study, we applied a vapour-transport-deposition method to synthesize both types of nanostructures using relatively low temperatures (860 • C) by controlling the source materials. We found that the resulting product under similar growth conditions can be switched between [0001]-axial nanowires and 1120-axial nanobelts simply by adding indium to the source. The former appear as ordered vertical arrays of pure ZnO while the latter are belts without spatial ordering. Both represent defect-free single crystals grown via the vapour-liquid-solid mechanism using nanosphere lithography-fabricated catalyst Au templates. Examination of the early growth stage suggests that the dissolution of In into Au influences the nucleation of ZnO at the solid-liquid interface, and subsequently defines the structure and crystallographic orientation of the nanobelts. The optical properties of both nanostructures are studied by photoluminescence and resonant Raman scattering, which indicate consistently that the doped nanobelts have a higher carrier concentration than the nanowires.
Acta Physica Polonica A, 2007
Scanning tunneling spectroscopy was used to check the tunneling I−V characteristics of junctions formed by n-ZnO nanowires deposited on Si substrates with n-and p-type electrical conductivity (i.e. n-ZnO nanowire/ n-Si and n-ZnO nanowire/p-Si junctions, respectively). Simultaneously, several phenomena which influence the measured I−V spectra were studied by atomic force microscopy. These influencing factors are: the deposition density of the nanowires, the possibility of surface modification by tip movement (difference in attraction forces between nanowires and the p-Si and n-Si) and the aging of the surface.
Mesoporous single-crystal ZnO nanobelts: supported preparation and patterning
We demonstrate that highly porous ZnO nanobelts can be prepared by thermally decomposing ZnS(en) 0.5 hybrid nanobelts (NBs) synthesized through a solvothermal route using Zn layers deposited on alumina substrates as both the Zn substrate and source. Hybrid decomposition by thermal annealing at 400 C gives porous ZnS NBs that are transformed by further annealing at 600 C into wurtzite single crystal ZnO nanobelts with an axial direction of [0001]. The evolution of the morphological and structural transformation ZnS(en) 0.5 / ZnS / ZnO is investigated at the nanoscale by transmission and scanning electron microscopy analyses. Control of the ZnO NB distributions by patterning the Zn metallization on alumina is achieved as a consequence of the parent hybrid NB patterned growth. The presence of NBs on alumina in a 100 mm wide region between Zn stripes allows us to fabricate two contact devices where contact pads are electrically connected through a porous ZnO NB entanglement. Such devices are suitable for employment in photodetectors as well as in gas and humidity sensors. IMEM-CNR, Parco Area delle Scienze 37/A,