1. Plasma Processing and Technology Laboratory and Department of Electrical and Computer Engineering University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
2. North China University of Technology, Beijing 100144, People's Republic of China
3. IMEC, 3001 Leuven, Belgium
4. Logic Technology Development, Intel Corporation, Hillsboro, Oregon 97124, USA
5. National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
6. Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA