Area-selective growth of ruthenium dioxidenanorods on LiNbO3(100) and Zn/Si substrates

Abstract

Selective and blanket growth of ruthenium dioxide (RuO₂) nanorods have been achieved in chemical vapor deposition (CVD) using bis(ethylcyclopentadienyl)ruthenium. Area-selective growth is demonstrated on a substrate which consists of patterned SiO₂ as the non-growth surface and LiNbO₃(100) or Zn/Si as the growth surface. Regardless of blanket or selective CVD, the RuO₂ nanorods are grown in the [001] direction, of square cross section and 20–60 nm in diameter. The conditions for growing nanorods selectively are to deposit at 500 ± 10 °C, 2 mbar, with a deposition flux around 7.0 × 10⁻⁷ mol cm⁻² h⁻¹. Deposition outside the narrow growth temperature window results in either a patterned RuO₂ thin film without nanorods or growth without clean pattern definition. The RuO₂ nanorods are vertically aligned on LiNbO₃(100) in blanket CVD. When RuO₂ nanorods are grown selectively on a patterned LiNbO₃ substrate, their vertical growth habit is altered at the boundary between the masked and the unmasked area. The orientation of nanorods shifts from vertical to random directions, meanwhile the number density of rods diminishes towards the masked area in a narrow stripe along the border. These variations are shaped by the lateral movement of depositing species which collide on the masked area.