Formation mechanism of SiGe nanorod arrays by combining nanosphere lithography and Au-assisted chemical etching
© Lai et al; licensee Springer. 2012
Received: 30 November 2011
Accepted: 18 February 2012
Published: 18 February 2012
The formation mechanism of SiGe nanorod (NR) arrays fabricated by combining nanosphere lithography and Au-assisted chemical etching has been investigated. By precisely controlling the etching rate and time, the lengths of SiGe NRs can be tuned from 300 nm to 1μm. The morphologies of SiGe NRs were found to change dramatically by varying the etching temperatures. We propose a mechanism involving a locally temperature-sensitive redox reaction to explain this strong temperature dependence of the morphologies of SiGe NRs. At a lower etching temperature, both corrosion reaction and Au-assisted etching process were kinetically impeded, whereas at a higher temperature, Au-assisted anisotropic etching dominated the formation of SiGe NRs. With transmission electron microscopy and scanning electron microscopy analyses, this study provides a beneficial scheme to design and fabricate low-dimensional SiGe-based nanostructures for possible applications.
KeywordsGe nanorod self-assembly nanosphere lithography
Over the past few decades, intensive research efforts have been devoted to the fabrication and characterization of Si-based nanostructures due to their intrinsic physical properties, high packing density, and compatibility with current Si technology . Self-assembled Si-based nanostructures are of particular interest because self-assembly provides a possible way to realize nanostructures without process-induced damages, which are frequently observed in the samples defined by electron (e)-beam lithography or reactive ion etching (RIE) [2, 3]. Ge/Si has become a model system for the fabrication and investigation of nanometer-scale heteroepitaxy due to their moderate lattice mismatch (4.2%) [4, 5]. The fabrication of SiGe nanowire arrays is one of the most interesting topics [6, 7]. Recently, the use of Si-based nanowires as high-performance devices or sensors has been extensively reported [8–12]. There are several methods to fabricate nanowire structures, such as e-beam lithography  and vapor-liquid-solid growth [14–16], and metal-assisted chemical etching [17–20]. Previous works have demonstrated that nanosphere lithography (NSL) provides an efficient way to fabricate self-organized, ordered, and close-packed sphere arrays [21, 22]. However, there have been few studies paying attention on the formation mechanism of SiGe NRs. In this work, we fabricated SiGe NR arrays by combing NSL and Au-assisted chemical etching. The influences of chemical etching conditions on the morphologies of as-etched SiGe NRs were investigated to clarify their formation mechanism.
Results and discussion
In this study, the formation mechanism of SiGe NR arrays fabricated by combining NSL and Au-assisted chemical etching has been investigated. By precisely controlling the etching rate and time, the lengths of the SiGe NRs can be tuned. The morphologies of SiGe NRs changed dramatically by varying the etching temperatures. We propose a mechanism involving a locally temperature-sensitive redox reaction to explain this strong temperature dependence of the morphologies of SiGe NRs. At a lower etching temperature, both corrosion reaction and Au-assisted etching process were kinetically hindered, whereas at a higher temperature, Au-assisted anisotropic etching dominated the formation of SiGe NRs. With TEM and SEM analyses, this study provides a beneficial scheme to design and fabricate low-dimensional SiGe-based nanostructures for possible applications.
The research is supported by the National Science Council of Taiwan under contract numbers NSC 100-2221-E-008-016-MY3, NSC 100-2622-E-008-009-CC3, and NSC-98-2112-M-032-003-MY3. The authors also thank the National Nano Device Laboratories and Center for Nano Science and Technology at National Central University for the facility support.
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