Plasma-assisted molecular beam epitaxy and characterization of SnO(2) (101) on r-plane sapphire

Plasma-assisted molecular beam epitaxy has been shown to be a viable and practical method for producing high quality tin oxide, SnO(2). Phase-pure epitaxial single crystalline SnO(2) (101) thin films of 1 mu m in thickness were reproducibly grown on r-plane sapphire Al(2)O(3) (10 (1) over bar2) substrates. The SnO(2) epitaxy progressed in the Volmer-Weber growth mode. A minimum on-axis omega-scan full width at half maximum of 0.22 S for the SnO(2) (101) peak was measured indicating relatively low film mosaic. An epitaxial relationship of (010)(SnO2) parallel to[(1) over bar2 (1) over bar0](sapphire) and [(1) over bar 01](SnO2) parallel to[(1) over bar 011](sapphire) was determined between the film and substrate. A SnO(2) film tilt of 1.3 degrees S around the [010]SnO(2) toward [0001](sapphire) was measured. A dislocation density of 8 x 10(9) cm(-2) was measured. Hall effect measurements quantified an unintentionally doped electron concentration for different samples in a range (0.3-3.0) x 10(17) cm(-3) with a corresponding electron mobility range of 20-100 cm(2)/V s. The SnO(2) growth behavior was determined to be in one of the two distinct growth regimes. An oxygen-rich regime was characterized by a linear increase in the film growth rate with increasing Sn flux; whereas, the films grown entirely in the Sn-rich regime showed a decrease in the growth rate with increased Sn flux. (C) 2008 American Vacuum Society.