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This research work explored the growth of silicon nanowires with titanium catalysts and atmospheric pressure chemical vapor deposition (APCVD). A silicon nanowire is a one-dimensional structure having a diameter on the order of a few nanometers to hundreds of nanometers. Depending on the metal-catalyst used for a silicon nanowire growth experiment, traces of the metal catalyst may be incorporated within the wire, presenting a myriad of problems in terms of its end use in devices. Titanium is seen as a possible solution to these compatibility issues in grown silicon nanowires. Generally, the silicon nanowire growth has been described by the vapor-liquid- solid (VLS) mechanism, and through the vapor-solid-solid (VSS) mechanism, with titanium-catalyzed growth thought to follow a VSS mechanism. Titanium-catalyzed silicon nanowires were studied and their growth characterized in the range of 650°C to 1000°C in 7 4 growth experiments. In general, silicon deposition was observed at and above 800°C, with nanowires observed sometimes at 825°C to 975°C, and almost regularly from 950°C to 1000°C for a partial pressure of the silicon tetrachloride from 1.25 mbarr to 3.9 mbarr. Measured nanowire lengths were adjusted for rotation and tilt angle of the sample holder, to give growth rates, V, versus diameter, d. This gave a growth rate, V, from the plot of 1.58 nm/s to 3.92 nm/s, and diameter, d, from 189 nm to 347 nm with a critical diameter, dc, of70 nm. However, linear regression on the measured nanowire data showed a weak negative relation for the growth rate dependence for the 16 nanowires plotted. From these data it was found the 1/d growth relation due to diffusion from the substrate, and adsorption-limited growth with d-independent relation are not plausible for this growth study. Hence, we are left with the speculation that the growth relation may be crystallization-limited, in which case there is a (1 - dc/d) 2 diameter dependence, or diffusion through the solid catalyst interface where there is an upward trend for the growth rate, V, versus diameter, d, relation. Overall, it is seen from this study that catalyzed nanowire growths using titanium as the metal catalyst is a viable option with an APCVD setup. More data will be required to explore this relation.
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