AFM measurements of sub-monolayer TEMPO films are shown in Figure -c for SiO2, HOPG, and Au(111), respectively, each showing clearly distinct surface morphology following 5 seconds of growth. Reference images of the pristine substrates pre-deposition can be found in Figure . On SiO2 (Figure ) molecular growth appears uneven, with AFM images revealing a preference for TEMPO to collect in small molecular clusters with heights < 2 nm. In contrast, on HOPG, we observe large atomically flat single layer islands 0.6 ± 0.2 nm in height (orange in Figure ) suggesting layer by layer growth. Finally, on sputter-annealed Au(111) substrates, molecular growth again appears flat, with AFM images revealing a higher coverage of TEMPO compared to HOPG (see Figure ). By operating the AFM with a high loading force on TEMPO:Au(111), a scratch test was performed, resulting in a measured layer thickness of 3 ± 1 nm. This is supported by XPS measurements (discussed in detail below), which show a significant increase in the measured N 1s signal on Au(111), with measured peak areas of 190, 105, and 370, for SiO2, HOPG, and Au(111) respectively. We note that despite many attempts, it was not possible to prepare a sub-monolayer coverage on Au(111). We attribute this to the higher surface binding of Au(111) compared to SiO2 and HOPG, and the difficulty in preparing a stable plasma for deposition times lower than 5 seconds.