Supra 40 vp gemini column

The SEM (Zeiss-Supra 40 VP/Gemini Column, Carl Zeiss, Germany) was employed to observe the morphology of the samples at 2.00 kV. Samples were mounted on carbon adhesive discs attached to SEM specimen stubs and coated with gold ions in a sputter coater (K575X Sputter Coater, Quorum Technologies, UK).

We used a laboratory-built high-speed atomic force microscope (HS-AFM) as described previously (Ando et al., 2008; (link)Ngo et al., 2015; (link)Uchihashi et al., 2012) (link). HS-AFM imaging was carried out in solution using tapping mode with small cantilevers (BL-AC10DS-A2, Olympus, Tokyo, Japan) whose spring constant, resonant frequency in water, and quality factor in water were ∼0.1 N/m, ∼500 kHz, and ∼1.5, respectively. Our lab-made ferrocene tip on an original tip-less cantilever was grown through electron beam deposition (EBD) using scanning electron microscopy (ZEISS Supra 40 VP/Gemini column, Zeiss, Germany). Typically, the EBD tip was grown under vacuum (1 -5 x 10 -6 Torr), aperture size (10 µm), and EHT voltage (20 kV) for 30 s. The EBD ferrocene tip was further sharpened using a radio frequency plasma etcher (Tergeo Plasma Cleaner, Pie Scientific, CA, USA) under an argon gas atmosphere (typically at 180 mTorr and 20 W for 30 s). During HS-AFM imaging, the free-oscillation peak-to-peak amplitude of the cantilever (A0) was set to ∼1.6 -1.8 nm, and the feedback amplitude set-point was set at ~0.9A0.