Anomalous scaling during glancing angle deposition

Metallic nanorods grown by glancing angle deposition at T(s)=300-1123 K exhibit self-affine scaling, where the average rod width w increases with height h according to w(proportional to)h(p). The growth exponent p for the investigated metals (Ta, Nb, and Cr) varies with temperature and material but collapses onto a single curve when plotted against the homologous temperature theta=T(s)/T(m). It decreases from p=0.5 at theta=0 to 0.39 at theta=0.22, consistent with reported theoretical predictions, but exhibits a transition to an anomalous value of p=0.7 at theta=0.26, followed by a decrease to 0.33 at theta=0.41. The cause for the anomalous scaling at 0.24 <= theta <= 0.34 is unknown but may be due to a gradual transition from two-dimensional to three-dimensional surface island growth. (C) 2009 American Institute of Physics. [doi:10.1063/1.3257377]