Plan-view TEM image of an IrOx layer. With a typical thickness of approximately 3 nm on the SiO2/Si substrate. The IrOx metal is black and SiO2 is white. The IrOx metal layer contains pores that oxygen can readily migrate through.
Prakash et al. Nanoscale Research Letters 2013 8:220 doi:10.1186/1556-276X-8-220