Depositions were performed with an Asylum MFP-3D
(Asylum Research, Santa Barbara, AR-13324 CA, USA) operating in contact mode in liquid with integrated software to control lithographic parameters (Microangelo). The liquid environment (1,3,5-trimethylbenzene, ≥99.0%; Sigma-Aldrich) was exposed to typical ambient humidity (35% to 40%). The probe employed during the fabrication tests was SiN Au-coated Olympus OMLC-RC 800 (k = 0.042 Nm−1, typical tip radius 430 nm), and the maximum bias applicable is ±20 V. It was possible to achieve a writing speed of 10 μm s−1, but the process is better controlled with a speed ranging from 0.2 to 5 μm s−1. Tip’s wear does not compromise writing up to 10-mm continuous writing. Raman spectra have been collected with a micro-Raman spectrometer Horiba T64000 (Edison, NJ, USA). Spectra have been recorded at room temperature, using an incoming laser light line linearly polarized at 514.5 nm from an Argon/Krypton ion laser (Ar/Kr Stabilite 2018-RM, Spectra-Physics, Mountain View, CA, USA), and a power density of about 2 mW μm−2 is used (×100 objective, Olympus SLM plan). The spectrometer resolution was determined by curve fitting the silicon 520 cm−1 band using a linear combination of Gaussian and Lorentian curves achieving full width at half eFT-508 maximum (FWHM)
less than 2 cm−1. This silicon band was used for the precise calibration of energy scale. Kelvin probe force microscopy measures have been performed with Asylum MFP-3D in air at room temperature (RH ≈ 35%) with Pt-coated probe Olympus OMCL-AC240TM. The work function of one reference tip (Φ tip = 4.93 ± 0.05 eV) was calibrated by Kelvin Adenylyl cyclase probe force microscopy (KPFM) on freshly cleaved highly oriented pyrolytic graphite (HOPG). Si dry etching was conducted with a Sentech ICP-RIE SI 500 plasma etcher (Sentech Instruments
GmbH, Berlin, Germany). Working parameters for SF6 were as follows: gas flow 30 sccm, 1 Pa, RF/ICP power 600, and RF plate power 18 W. For pseudo Bosch (SiF6 + C4F8), gas SiF6 flow 30 sccm, C4F8 flow 32 sccm, 1 Pa, RF/ICP power 600, and RF plate power 18 W. Each sample has been finally cleaned by oxygen plasma. Fabricated masters have been imaged in tapping mode with standard Si cantilevers (Nanosensors PPP-NCH, Nanoworld AG, Neuchâtel, Switzerland; nominal resonant frequency ca. 330 kHz, force constant ≈ 42 Nm−1, polygon-based pyramidal tip with half cone angles of 20° to 30° with a tip apex radius below 10 nm). To minimize tip’s convolution artifacts, some buy AG-881 samples have been imaged using high aspect ratio tips (Nanosensors AR5-NCHR; nominal resonant frequency ca. 330 kHz, force constant ≈ 42 Nm−1) with half cone angle smaller than 2.8°. Energy diffraction spectroscopy (EDS) elemental analysis was performed by a X-Max large area analytical EDS silicon drift detector (Oxford Instruments, Oxford, UK) with (Mn Kα typically 125 eV) mounted on a JEOL 7500 FA SEM (Akishima, Tokyo, Japan).