Temperature induced ordering of TEMPO thin films. Motivated by the consistent single layer growth observed on HOPG at low deposition times, we explored the ability to improve ordering by post-annealing single layer TEMPO:HOPG samples at 50 °C under atmospheric conditions. We once again note that the sublimation temperature of is relatively low, with temperatures in excess of 50 °C likely to remove the surface coating. Post-annealing at 50 °C is therefore expected to provide sufficient energy to the molecular system for the TEMPO layer to reach its minimum energy configuration. Before and after AFM images of annealed single layer TEMPO:HOPG and their corresponding height histograms are shown in Figure . Prior to annealing, the molecular layer height is measured as 0.6 ± 0.2 nm. Post-annealing, the height is found to increase to 0.9 ± 0.1 nm. We note that measured changes in height are consistent across a range of samples, and comfortably within the resolution of the AFM used (the measured difference of 0.3 nm is comparable, for instance, to the step height of HOPG). XPS data collected on the same samples are shown in Figure , and confirm that there is no significant difference in the binding energy or area of spectra measured in the N1s region, indicating that the amount of TEMPO on the surface is unchanged. These observations are now discussed within the context of computational modelling, from which we propose that the measured increase in height is a result of improved molecular ordering.