Low loss superconducting titanium nitride coplanar waveguide resonators

Thin films of TiN were sputter-deposited onto Si and sapphire wafers with and without SiN buffer layers. The films were fabricated into rf coplanar waveguide resonators, and internal quality factor measurements were taken at millikelvin temperatures in both the many photon and single photon limits, i.e., high and low electric field regimes, respectively. At high field, we found the highest internal quality factors (similar to 10(7)) were measured for TiN with predominantly a (200)-TiN orientation. The (200)-TiN is favored for growth at high temperature on either bare Si or SiN buffer layers. However, growth on bare sapphire or Si(100) at low temperature resulted in primarily a (111)-TiN orientation. Ellipsometry and Auger measurements indicate that the (200)-TiN growth on the bare Si substrates is correlated with the formation of a thin, approximate to 2 nm, layer of SiN during the predeposition procedure. On these surfaces we found a significant increase of Q(i) for both high and low electric field regimes. (C) 2010 American Institute of Physics. [doi:10.1063/1.3517252]