Vapour–Solid Growth

Vapour–Solid Growth

The above equations representing decomposition reactions prompt the Si nanoparticles precipitation that functions as the nuclei of the silicon nanowires coated with silicon oxide. Nucleation, precipitation, and nanowire growth happen near the cold figure, hinting that the temperature gradient offers the extrinsic driving force for the formation and growth of the nanowires.

Vapour–Solid Growth

The process of vapor solid (VS) represented in whisker growth holds for nanowire development alike. The process entails evaporation, reduction of chemical, or reaction of gases that produces vapor. Afterward, the vapor is carried and condensed onto the substrate (Glaspell, Saoud & El-Shall, 2006). Previous research has used the VS method to prepare oxide whiskers and metals with micrometer diameters. Thus, it is possible to synthesize ID nanostructures based on the VS process provided it is possible to control the nucleation and succeeding processes of growth. Nanowires of various metal oxides have been obtained using the VS method.

Conclusion and Perspectives

Concluding Remarks

The paper has discussed the chemical methods that have been developed for generating nanostructures with 1-D morphologies, such as tubes, wires, rods, and belts. I explained the various techniques for making one-dimensional nanostructures based on building blocks of nanoscale and reduction of the size of the structures. Every technique discussed have its specific advantages along with unavoidable weaknesses. Case in point, methods founded on structural confinement can provide thin nanowires with constant cross-section over a length of hundreds of micrometers. However, these methods only function efficiently for a limited assortment of materials that consist of greatly anisotropic structures. On the flip side, the template-directed techniques offer efficient control over the dimensions and uniformity. The application of template, nonetheless, significantly reduces nanowire scales that one can produce in every sequence of synthesis. Elimination of integration based on the post-synthesis process may equally lead to damage to the resultant nanowire product. What’s more, most nanowires synthesized using template-based methods adopt a structure of polycrystalline, an unwanted feature that may deter their application in the fabrication of the device, and significant studies.

The vapor phase techniques founded on the control of supersaturation have the potential of providing nanowires as well as nanobelts of various materials, but only when used in moderately large volumes. Again, it remains challenging to control the uniformity and dimensions of the nanostructures. In connection to feasibility, the methods founded on the process of VLS appear to be most versatile in producing one-dimensional nanostructures using controllable compositions and sizes. Nonetheless, these metals are less suitable for application with metals, and the necessity of gold or other metals to function as a catalyst may equally lead to contamination for the resultant nanowires. Initial research from numerous experimental studies hints that the ultimate application of one-dimensional nanostructures is heavily dependent upon an individual’s ability to control their dimensions, surface properties, chemical compositions, crustal structure, and phase purity with absolute precision. Refereed alongside these metrics, all the methods discussed in this paper still need a significant amount of improvement before they gain popularity in commercial settings.

Summary of Recent Research

Preliminary research in the synthesis of metal nanowires using vapor-phase methods has studied the VLS process of development using the liquid binary metal cluster to speed up the absorption of gas-phase types of specific wire material. Reports from recent studies have depicted that during the process of growth involving nanowires, the favored orientation of crystallographic tends to change a barrier that is cooler than its environs situated immediately after the hot zone in the quartz tube and induces kinks as well as bends in the developing Ge wires. Similarly, researchers have reported the enlargement of the VLS growth concept that opens an additional pathway to fit complicated nano-heterostructures. Researchers have delivered growth materials successively to the droplets of liquid that catalyze the growth of nanowire to nucleate new phases that form as nanocrystal and can be included in the nanowires with epitaxially perfect edges (Yang, Ya & Fardy, 2010). The results of such studies present a promising result because the morphology of such nanostructures is easily tailored based on the application of liquid droplets that speed up the growth of nanowire as a mixing bowl where growth materials are sequentially supplied to new nuclear phases.

Additional work in the field has also sought to understand the VLS mechanisms of Si nanowire growth and the systematic encoding of nanoscale morphology. The researchers pointed towards the significance of specific patterning of semiconductor materials utilizing top-down lithographic methods to be important in the development of electronics used daily (Wang, 2009). Nonetheless, the persistent growth of these lithographic technologies usually leads to the trade-off of either low or throughput or high cost, and 3-D pattering can be challenging to attain. Previous research has also focused on the use of bottom-up chemical methods to control 3-dimensional nanoscale morphology of semiconductors and nanostructures as complementary methods. Nanoscale filaments, semiconductor nanostructures mateirials10-50 nm, and 1-50 microns long are some of the promising platform given that the composition of the wire can be modulated in the process of growth (Choi, 2012). The high aspect ratio makes 1-D structures able to integrate a variety of devices.

Previous experimental investigations have further studied the synthesis, characterization, ad physical properties of nanowires, putting specific emphasis on the properties of nanowires that vary from those of the bulk counterparts. The reviews have further documented the applications of the physical properties in nanowire that might result from individual structures (Pinion, Christesen & Cahoon, 2016). Such studies have shown that the emerging field of nanowire research has advanced speedily over the past years, catalyzed by the development of a number of complementary synthesis methods of nanowires well as useful tools for estimating the structure of nanowire and properties. Preliminary reports have further offered comprehensive reviews of present research events focusing on 1D nanostructures in the range of 1-100 nm. Most attention has been devoted to 1-D nanostructures synthesized in copious quantities with the application of chemical methods.

Future Challenges

One-dimensional materials have stimulated an enormous amount of industrial and scientific interests, given their tunable and varied chemical, physical, and mechanical properties. The production of scaled nanostructures has become significantly essential to bring the field of research closer to practical industrial applications, especially in electronic components. VLS provides attractive prospects for the synthesis of high quality and large area 1-D materials. However, the present challenges associated with chemically synthesized nanowires, such as their self-assembly into device architects. Future directions should address the challenges related to the chemical, thermal, and mechanical stability of 1D nanostructures for improved controlling and understanding. The weakened thermal stability of nanowires may ultimately mean a limited functionality or interconnectedness of the components. Thin worries often break into shorter segments even at room temperature. Besides, a step forward in the field of VSL requires the development of the mechanism from the perspective of the industrialization of nanowires. The desire to that would fuel various scientific research in the area of nanowires along with the formation of the progressive optoelectric market.

The field of 1-D nanostructures provides almost unlimited research opportunities for exploration by many scientists and laboratories globally. The technical and scientific potentials of such nanostructures are destined for great success, and the future of this science appears bright. Nevertheless, it is essential to note that some potential health and environmental issues may arise when new 1D nanostructures are produced in laboratories. In respect to previous studies on chrysolite, it is expected that many of these 1D nanostructures might present environmental hazards. Overall, there is need to provide a systemic evaluation of the impact of such nanostructures on health and environment.