Control over the Number Density and Diameter of GaAs Nanowires on Si(111) Mediated by Droplet Epitaxy
ABSTRACT We present a novel approach for the growth of GaAs nanowires (NWs) with controllable number density and diameter, which consists of the combination between droplet epitaxy (DE) and self-assisted NW growth. In our method, GaAs islands are initially formed on Si(111) by DE and subsequently, GaAs NWs are selectively grown on their top facet, which acts as nucleation site. By DE we can successfully tailor number density and diameter of the template of initial GaAs islands and the same degree of control is transferred to the final GaAs NWs. We show how, by a suitable choice of V/III flux ratio, a single NW can be accommodated on top of each GaAs base island. By transmission electron microscopy, as well as cathodo- and photo-luminescence spectroscopy we confirmed the high structural and optical quality of GaAs NWs grown by our method. We believe that this combined approach can be more generally applied to the fabrication of different homo- or hetero-epitaxial NWs, nucleated on the top of predefined islands obtained by DE.
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ABSTRACT: In this report, self-organized GaN nanodots have been grown on Si (111) by droplet epitaxy method, and their density can be controlled from 1.1 × 10 10 to 1.1 × 10 11 cm −2 by various growth parameters, such as substrate temperatures for Ga droplet formation, the pre-nitridation treatment of Si substrate, the nitridation duration for GaN crystallization, and in situ annealing after GaN formation. Based on the characterization of in situ RHEED, we can observe the surface condition of Si and the formation of GaN nanodots on Si. The surface nitridaiton treatment at 600°C provides a-SiNx layer which makes higher density of GaN nanodots. Crystal GaN nanodots can be observed by the HRTEM. The surface composition of GaN nanodots can be analyzed by SPEM and μ-XPS with a synchrotron x-ray source. We can find GaN nanodots form by droplet epitaxy and then in situ annealing make higher-degree nitridation of GaN nanodots.Nanoscale Research Letters 12/2014; 9:682. DOI:10.1186/1556-276X-9-682 · 2.48 Impact Factor
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ABSTRACT: We report on the recent progress in electronic applications using III?V nanowires (NWs) on Si substrates using the selective-area growth method. This method could align vertical III?V NWs on Si under specific growth conditions. Detailed studies of the III?V NW/Si heterointerface showed the possibility of achieving coherent growth regardless of misfit dislocations in the III?V/Si heterojunction. The vertical III?V NWs grown using selective-area growth were utilized for high performance vertical field-effect transistors (FETs). Furthermore, III?V NW/Si heterointerfaces with fewer misfit dislocations provided us with a unique band discontinuity with a new functionality that can be used for the application of tunnel diodes and tunnel FETs. These demonstrations could open the door to a new approach for creating low power switches using III?V NWs as building-blocks of future nanometre-scaled electronic circuits on Si platforms.Journal of Physics D Applied Physics 09/2014; 47(39):394001. DOI:10.1088/0022-3727/47/39/394001 · 2.52 Impact Factor
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ABSTRACT: In this paper, we report the effect of Au thickness on the self-assembled Au droplets on GaAs (111)A and (100). The evolution of Au droplets on GaAs (111)A and (100) with the increased Au thickness progress in the Volmer-Weber growth mode results in distinctive 3-D islands. Under an identical growth condition, depending on the thickness of Au deposition, the self-assembled Au droplets show different size and density distributions, while the average height is increased by approximately 420% and the diameter is increased by approximately 830%, indicating a preferential lateral expansion. Au droplets show an opposite evolution trend: the increased size along with the decreased density as a function of the Au thickness. Also, the density shifts on the orders of over two magnitude between 4.23 × 10(10) and 1.16 × 10(8) cm(-2) over the thickness range tested. At relatively thinner thicknesses below 4 nm, the self-assembled Au droplets sensitively respond to the thickness variation, evidenced by the sharper slopes of dimensions and density plots. The results are systematically analyzed and discussed in terms of atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), cross-sectional surface line profiles, and Fourier filter transform (FFT) power spectra.Nanoscale Research Letters 08/2014; 9(1):407. DOI:10.1186/1556-276X-9-407 · 2.52 Impact Factor