HOPG

HOPG (Highly Ordered Pyrolytic Graphite) is a highly ordered form of graphite that is commonly used as a calibration tool for probe microscopies such as Scanning Tunneling Microscopy or Atomic Force Microscopy.

HOPG behaves much like a pure metal. It is reflective, electrically conductive, but very brittle and flaky.

HOPG has been used as a substrate in many scientific experiments. See for example, Leitner et. al., Applied Spectroscopy, Volume 57, Number 12, 2003, pp 1502.