Coherent Josephson phase qubit with a single crystal silicon capacitor
  We have incorporated a single crystal silicon shunt capacitor into a Josephson phase qubit. The capacitor is derived from a commercial silicon-on-insulator wafer. Bosch reactive ion etching is used to create a suspended silicon membrane; subsequent metallization on both sides is used to form the capacitor. The superior dielectric loss of the crystalline silicon leads to a significant increase in qubit energy relaxation times. T1 times up to 1.6 micro-second were measured, more than a factor of two greater than those seen in amorphous phase qubits. The design is readily scalable to larger integrated circuits incorporating multiple qubits and resonators. 
U. Patel, Y. Gao, D. Hover, G. J. Ribeill, S. Sendelbach, and R.   McDermott
cond-mat.supr-con cond-mat.mes-hall quant-ph