Epindolidione (EPI) powder was synthesized following the procedure outlined by Jaffe and Matrick16 and taking account of the considerations of Kemp et al. 17 The powder was sublimation purified before use. EPI films of different thicknesses were deposited by physical vapor deposition onto 1 cm × 1 cm silicon substrates covered with a 150 nm thick layer of thermally grown oxide. Substrates were inserted into a vacuum chamber and cleaned by sputtering with Ar ions before being heated to ∼800 K to further remove contaminants. EPI was deposited from a Knudsen cell source in a vacuum with a base pressure of 2 × 10–8 mbar. Film thickness was monitored during deposition using a quartz microbalance where a conversion factor of Δ 1 Hz ≈ 0.083 nm was used.5 During deposition, the substrate temperature could be set to temperatures in the range of ∼120–800 K (cooling provided by liquid N2) and films were deposited at substrate temperatures of 200, 300, and 350 K. A detailed description of the experimental setup and sample mounting used is given elsewhere.18