ZnO Nanodot Arrays Research Articles

Highly efficient ultrathin-film amorphous silicon solar cells on top of imprinted periodic nanodot arrays

The addressing of the light absorption and conversion efficiency is critical to the ultrathin-film hydrogenated amorphous silicon (a-Si:H) solar cells. We systematically investigate ultrathin a-Si:H solar cells with a 100 nm absorber on top of imprinted hexagonal nanodot arrays. Experimental evidences are demonstrated for not only notable silver nanodot arrays but also lower-cost ITO and Al:ZnO nanodot arrays. The measured external quantum efficiency is explained by the simulation results. The Jsc values are 12.1, 13.0, and 14.3 mA/cm2 and efficiencies are 6.6%, 7.5%, and 8.3% for ITO, Al:ZnO, and silver nanodot arrays, respectively. Simulated optical absorption distribution shows high light trapping within amorphous silicon layer.

The effects of magnetic field on pulsed laser deposition of Mg-doped ZnO thin films

Mg-doped ZnO thin films were deposited on Si surfaces by laser ablation of a Zn:Mg target to shed light on the effects of magnetic field in pulsed laser deposition. Both crystalline and photoluminescence properties of the Mg-doped ZnO film were dramatically enhanced by performing laser ablation under transverse magnetic field at room temperature. The ablation wavelength turned out to be crucial to bring about optimum effects of the magnetic field on the laser-induced plasma plume. Besides, cylindrically phase-separated polystyrene-b-poly(methylmethacrylate) employed as a template facilitated fabrication of bandgap-engineered ZnO nanodot arrays.

Self-organized ZnO nanodot arrays: Effective control using SiNx interlayers and low-temperature plasmas

An advanced inductively coupled plasma (ICP)-assisted rf magnetron sputtering deposition method is developed to synthesize regular arrays of pear-shaped ZnO nanodots on a thin SiNx buffer layer pre-deposited onto a silicon substrate. It is shown that the growth of ZnO nanodots obey the cubic root-law behavior. It is also shown that the synthesized ZnO nanodots are highly-uniform, controllable by the experimental parameters, and also feature good structural and photoluminescent properties. These results suggest that this custom-designed ICP-based technique is very effective and highly-promising for the synthesis of property- and size-controllable highly-uniform ZnO nanodots suitable for next-generation light emitting diodes, energy storage, UV nanolasers, and other applications.

Fabrication of ZnO Nanodot Arrays by Sol-Gel within AAO Template

ZnO nanodot arrays were fabricated by using AAO template combining with sol-gel method. Structure and optical properties of ZnO/AAO composite structure were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL). The SEM results indicated that the pores in the template were arranged in a regular hexagonal lattice and ZnO nanodots were assembled into the AAO template. The XRD patterns demonstrated that the AAO template had an amorphous structure, and the ZnO nanodots had wurtzite structures. The PL spectrum revealed that ZnO/AAO composite structure had a strong ultraviolet emission at 390 nm.

Pulsed i‐PVD of Dielectric Nanodot Arrays Using a Nanoporous Template

AbstractThe results of multi‐scale numerical simulations of pulsed i‐PVD template‐assisted nanofabrication of ZnO nanodot arrays on a silicon substrate are presented. The ratios and spatial distributions of the ion fluxes deposited on the lateral and bottom surfaces of the nanopores are computed as a function of the external bias and plasma parameters. The results show that the pulsed bias plays a significant role in the ion current distribution inside the nanopores. The results of numerical experiments of this work suggest that by finely adjusting the pulse voltage, the pulse duration and the duty cycle of the external pulsed bias, the nanopore clogging can be successfully avoided during the deposition and the shapes of the deposited ZnO nanodots can be effectively controlled.magnified image

Self-assembly and optical properties of patterned ZnO nanodot arrays

Patterned ZnO nanodot (ND) arrays and a ND-cavity microstructure were realized on ananodic alumina membrane (AAM) surface through a spin-coating sol–gel process, whichbenefits from the morphology and localized negative charge surface of AAM as well as theoptimized sol concentration. The growth mechanism is believed to be a self-assemblyprocess. This provides a simple approach to fabricate semiconductor quantumdot (QD) arrays and a QD-cavity system with its advantage in low cost andmass production. Strong ultra-violet emission, a multi-phonon process, and itsspecial structure-related properties were observed in the patterned ZnO ND arrays.

Double template electrosynthesis of ZnO nanodot array

This communication describes the preparation of highly-ordered nanodot arrays of ZnO, a technologically important material, by the double template approach developed by Bartlett and co-workers. Colloidal polystyrene spheres were used as the primary template, and electrodeposited polypyrrole was used as the secondary template in this study. The ZnO nanodot arrays were prepared on a polycrystalline Au substrate by electrodeposition using the pyrrole secondary template after making it insulating by potentiodynamically deactivating it. The ZnO nanodot array was characterized by scanning electron microscopy, energy-dispersive X-ray analyses, and laser Raman spectroscopy.

Fabrication and optical properties of highly ordered ZnO nanodot arrays

We report on the successful fabrication of highly ordered ZnO nanodots on Si(0 0 1) substrates under a low-cost and industrialized technique combining self-organized porous alumina membranes (PAMs) with reactive electron beam evaporation. Scanning electron microscope images reveal the copy of the ZnO nanodot arrays from the PAM masks without the aid of catalysts. In addition to the demonstration of ZnO crystallinity by transmission electron microscopy and micro-Raman measurements, temperature-dependent photoluminescence spectra of ZnO nanodot arrays show high intensity ratio of 400 between the ultraviolet and visible emission due to the low oxygen vacancies (resulting from the oxygen-full growth atmosphere and large surface-to-volume ratio in nanodots). The present technique provides the possibility of realizing good quality ZnO nanodot arrays on different substrates with tunable sizes and morphology.

Artificial control of ZnO nanodots by ion-beam nanopatterning

The use of focused ion-beam (FIB) nanopatterning for manipulating self-assembled ZnO nanodots is described. Highly aligned ZnO-nanodot arrays with various periodicities (e.g., 750, 190, and 100 nm) on FIB-nanopatterned SiO2∕Si substrates were prepared by metal-organic chemical-vapor deposition (MOCVD). The artificially assembled ZnO nanodots had an amorphous structure. Ga atoms incorporated into the surface areas of FIB-patterned nanoholes during FIB engraving were found to play an important role in the artificial control of ZnO, resulting in the production of ZnO nanodots on the FIB-nanopatterned areas. The nanodots evolved into single-crystalline dot clusters and rods with increasing MOCVD-growth time. In addition, microphotoluminescence measurements showed that the ZnO-nanodot arrays have low-dimensional quantum characteristics.

Artificial control of ZnO nanostructures grown by metalorganic chemical vapor deposition

Advantage and role of focused ion beam (FIB) for nanopatterning of the substrates toward the artificial control of self-assembly processes of semiconductor nanostructures are shown and discussed. Two-dimensional ZnO nanodot arrays well-ordered in size and position of the nanodots are demonstrated, for example, the nanodots with diameter of 130±10 and 18±5 nm were two dimensionally arrayed with periods of 750 and 100 nm, respectively. Gallium implanted in the FIB-nanopatterning is suggested as a plausible reason for the selective nucleation of ZnO nanodots on nanopatterned substrates.

Multidimensional ZnO nanodot arrays by self‐ordering on functionalised substrates

Highly ordered one- and two-dimensional ZnO nanodot arrays were realized by self-ordering on focused ion beam (FIB)-functionalised SiO2/Si substrates. Metalorganic chemical vapor deposition was used to deposit zero-dimensional ZnO nanostructures on nanopatterns acting as artificial traps for Zn adatoms. The quality of the multidimensional nanodot arrays depends on the FIB-introduced nanopattern morphologies and MOCVD growth conditions. Energy-dispersive X-ray measurements showed that Ga atoms incorporated in patterned areas during FIB-engraving play an important role for the initial nucleation of ZnO nanodots. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)