1. Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA 94720, USA.
2. Berkeley Sensor and Actuator Center, University of California, Berkeley, Berkeley, CA 94720, USA.
3. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
4. Murata Manufacturing Co. Ltd., Nagaokakyo, Kyoto 617-8555, Japan.
5. Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan 30013, R.O.C.