Vapor-liquid-solid mechanism

R. S. Wagner, and W. C. Ellis, Vapor—liquid—solid mechanism of single crystal growtti. Appl. Phys. 

Key words Cluster, whisker, columnar structure, vapor-liquid-solid mechanism... 

Choi and Shin et al. reported the fabrication of Si/Silica/Er2Si207 coreshell NWs of about 120 ran in diameter, grown vertically on Si substrates by the vapor-liquid-solid mechanism in an Si-Er-Cl-H2 system using Au catalyst, which is shovm in Eigure 54 (Choi et al., 2005). The NWs showed promising 1.54 pm Er + optical activity viable for light source applications. 

Wagner RS, Ellis WC (1964) Vapor-liquid-solid mechanism of single crystal growth. Appl Phys Lett 4 89-90... 

A second mechanism, the Vapor-Liquid-Solid mechanism (VLS) has also been investigated thoroughly and is used industrially today. A particular aspect of this process is the role of the liquid small droplets of metallic melts, e.g. of iron alloys which may exist as an impurity in the reactor or which are added to the process, act catalytically by dissolving gaseous species of Si and C in the first step. This solution becomes supersaturated with time and the precipitation of SiC begins. By continual dissolution and precipitation the whisker grows bearing the droplet like a head on its top. 

Nanowhiskers are very promising products of nanothechnology with broad applications in near future [1]. Nevertheless, there are several unsolved scientific problems related to formation and growth of nanowhiskers. The aim of our paper is to give more insight to these problems. The influence of substrate parameters and gas flow are under discussion. The scheme of nanowhisker growth developed in the frame of vapor-liquid-solid mechanism (VLS), is shown in Fig. 1. 

Microstructural observations have provided further evidence that the a-phase forms from the condensation of a vapor. Compos-Loriz and Riley (138) and Jennings (139) have proposed that ot-Si3N4 forms from reactions involving SiO, probably by a vapor-liquid-solid mechanism which tends to form needles or protruding crystals with high aspect ratios. It has also been observed on nitrided... 

Wagner, R.S. and Ellis, W.C. (1964) Vapor-liquid-solid mechanism of single crystal growth, Appl. Phys. Lett. 4, 89 (1965) Vapor-liquid-solid mechanism of crystal growth and its application to silicon, Trans. Met. Soc. AIME 233, 1053. The description of the VLS mechanism. Now used for more than Si. 

Wagner. R. S. 8t EQis, W. C. Vapor-liquid-solid mechanism of sii e crystal growth. AppI Phys. Lett. 4,89-90(1964). 

In our opinion, the phenomenon of the heterogeneous melting allows one to understand the vapor-liquid-solid mechanism of epitaxy, which occurs at a temperature below the reference melting temperature, and the mechanism of layer-by-layer growth of crystals. 

A CVD method via a vapor-liquid-solid mechanism has been further described to prepare boron nanobelts in both crystalline and amorphous forms by Ni and Li The boron source for the process... 

Ma and Bando reported a systemic investigation of the growth of boron carbide nanowires via a vapor-liquid-solid mechanism. A template- and catalyst-free carbothennal route of nanowire production has been employed with boron powder, boron oxide, and carbon black, mixed in a 2 1 1 ratio, as the precursor. The component mixture was subjected to 1650°C temperature for 2 h under an argon flow inside a high-frequency induction furnace and resulted in boron carbide nanowires of diameters ranging from 50 to 200 nm (Figure 20.17b). 

Lattice Dynamics of Icosahedral Alpha-Boron Under Pressure. Physical Review Letters, Vol. 78, No. 4, (January 1997), pp. 693-696, ISSN 0031-9007 Wang, Y.L. Gai, L. Xia, Y.N. (2005). Monodisperse Spherical Colloids of Pb and Their Use as Chemical Templates to Produce Hollow Particles. Advanced Materials, Vol. 17, No. 4, (February 2005), pp. 473-477, ISSN 0935-9648 Wang, Z.K. Shimizu, Y. Sasaki, T. Kawaguchi, K. Kimura, IC Koshizaki, N. (2003). Catalyst-Free Fabrication of Single Crystalline Boron Nanobelts by Laser Ablation. Chemical Physics Letters, Vol. 368, No. 5-6, Qanuary 2003), pp. 663-667, ISSN 0009-2614 Wagner, R.S. Ellis, W. C. (1964). Vapor-Liquid-Solid Mechanism of Single Crystal Growth. 

Many SiCNWs formation mechanisms such as vapor-solid mechanism (VS), vapor-liquid-solid mechanism (VLS) and oxide-assist growth (OAG) have been proposed. It is needed to clarify the formation mechanism of SiCNWs synthesized by thermal evaporation method for improvement of the product quantity, which leads to the sufficient amount of SiCNWs for the application researches. Various chemical reactions have been discussed but there are no experimental results about exhaust gas from the SiCNWs production system and no direct observation of the formation of SiCNWs. 

Y Chen, J Pan, X Huang. The effect of deposition temperature on the growth of TiC whiskers by the vapor-liquid-solid mechanism. J Cryst Growth 172 171, 1997. 

---