SEM images comparing the bright and dark sides of HfO2 nanosheets. (a) Wide view image of a curled sheet with a portion broken off. Bright and dark sides are both visible. (b) Close-up of the bright side. The surface has a lot of texture and contains micron scale clusters. Small dark circles can also be seen. (c) Close-up view of dark side. Surface is much smoother, although some particulate is attached. Small dark circles are again visible, measuring about 100 nm in diameter.
Kidd et al. Nanoscale Research Letters 2011 6:294 doi:10.1186/1556-276X-6-294