1. Department of Materials Sciences and Engineering City University of Hong Kong Kowloon Hong Kong
2. Department of Applied Physics Hong Kong Polytechnic University Kowloon Hong Kong
3. Department of Electrical and Computer Engineering University of California Davis Davis CA 95616 USA
4. Nanomaterials Research Institute Kanazawa University Kakuma Kanazawa 920-1192 Japan
5. Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
6. Department of Electrical Engineering and Computer Sciences University of California Berkeley Berkeley CA 94720 USA
7. Solar Energy Research Institute The National University of Malaysia 43600 Bangi Selangor Malaysia
8. Geballe Laboratory for Advanced Materials Department of Materials Science and Engineering Stanford University Stanford CA 94305 USA