1. Centre for Advanced Materials Research, University of Texas at El Paso, El Paso, Texas 79968, United States
2. Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968, United States
3. Department of Electrical and Computer Engineering and Petersen Institute of NanoScience and Engineering, University of Pittsburg, Pittsburgh, Pennsylvania 15261, United States
4. Department of Mechanical Engineering, University of California, Santa Barbara, California 93106-5070, United States
5. Materials Department, University of California, Santa Barbara, California 93016-5050, United States