1. Department of Physics University of California Berkeley Berkeley CA 94720 USA
2. Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
3. Department of Materials Science and Engineering University of California Berkeley Berkeley CA 94720 USA
4. The Molecular Foundry Lawrence Berkeley National Laboratory One Cyclotron Road Berkeley CA 94720 USA
5. Kavli Energy NanoSciences Institute University of California Berkeley and the Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
6. Department of Chemistry University of California Berkeley CA 94720 USA