Mohacsi, Istvan, et al., Sci. Reports 7
 Li, Kenan, et al., J. of Vac. Sci. & Technol. B 35(6
Gleber, Sophie-Charlotte, et al., Optics express 22(23
Vila-Comamala, Joan, et al., J. of Synchrot. Rad 20(3
 Use of the Center for Nanoscale Materials and the Advanced Photon Source, Office of Science user facilities, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. We thank Ralu Divan, Leonidas Ocola, Liliana Stan, Bing Shi, and Stefan Vogt for their help during this research..