Niobium-Containing Nanorods Grown by Reactive Sputtering

Author(s):

Thomas C. Parker and Samuel G. Hirsch

Abstract:

In this work, we explore the deposition of nanorods using oblique-angle deposition while reactively sputtering niobium (Nb) targets with varying CH4 flow rates. X-ray diffraction and transmission electron microscopy showed that the highest flow rate, 4 standard cubic centimeters per minute (SCCM) CH4, resulted in nanorods that were amorphous, followed by 3 SCCM showing a transition to crystalline NbC nanorods, with a final transition at 0.1-SCCM CH4 forming nanorods with strained and highly oriented Nb crystallites. The lattice strain, 3.2%, is attributed to H interstitials. X-ray photoelectron spectroscopy (XPS) analysis indicated that, with the decreasing CH4 flow rate, there was a corresponding increase in carbide content and reciprocal decrease in graphitic content, with approximately 2%–52% for the former and approximately 80%–21% for the latter. Also, XPS showed that, with respect to atomic composition and decreasing CH4 flow rate, there was a decrease in carbon content, an increase in Nb content, and an increase in O content, measuring approximately 80%–20%, 15%–60%, and 12%–30%, respectively. The reduced O content is attributed to an increased growth rate and a gettering effect of excess carbon and H.