Nematic-type Structure of the SnO2 (110) Surface at Room Temperature.

The most exposed (110) surface of SnO2 plays an important role in practical applications like gas sensors and catalysts. It has previously been considered to be amorphous at room temperature. In this study, the structure of the (110) surface stabilized at room temperature is determined using aberration-corrected transmission electron microscopy and first-principles calculations. The (110) surface has local order and is made of Sn2 O2 strands that partially cover underlying unsaturated Sn rows. The results indicate that the Sn2 O2 strands assemble as building blocks on the surface to form a partially ordered structure, quite like the nematic liquid crystal. Partial occupation of the Sn2 O2 strands along the [ 1 1 ‾ ${1\bar{1}}$ 0] direction avoids the interaction between neighboring Sn2 O2 strands and therefore makes the surface more stable. The novel phenomenon of the surface provides insight for understanding and developing catalysts and gas sensors based on SnO2 .