1. Materials Physics Department, Sandia National Laboratories, 7011 East Avenue, Livermore, California 94550, United States
2. Nanoscale Sciences Department, Sandia National Laboratories, 1515 Eubank Blvd. SE, Albuquerque, New Mexico 87123, United States
3. Photovoltaics and Materials Technology Department, Sandia National Laboratories, 1515 Eubank Blvd. SE, Albuquerque, New Mexico 87123, United States