1. Physics, Applied Physics and Astronomy Department, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
2. The Center for Materials, Devices, and Integrated Systems, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
3. Materials Science and Engineering Department, Rensselaer Polytechnic Institute, Troy, New York 12180, USA