Considering that Φ sample = Φ tip − eVCPD, we obtained: Figure 6 AFM topography, KPFM scan, and selleck chemical Comparison of height and CPD value profiles. AFM topography (a) and KPFM scan (b) of a pattern made in both polarizations: oxide (left) and graphitic (right) body contours are clearly resolved by CPD difference. Comparison of height profile and CPD value profile (five-point average along the black line) (c). The difference in work function measured allows
to clearly resolve patterned graphitic bodies and partially confirms the prevalent graphitic composition of the features although it was not possible to get a quantitative explanation Blasticidin S mw of the local work functions measured. The use of fluorocarbon resist patterns fabricated by SPL as mask for silicon dry plasma etching has been already
reported [6]. Due to the better control achieved through oxidation in this work, we tested standard silicon dry etching only on fabricated oxide patterns. The plasma gases employed were a SF6 and SF6/C4F8 (pseudo Bosch). Exposure times ranged from 5 to 30 s. The different etch rate between Si substrate and oxide features result in a gain in features’ height. A maximum enhancement (final and initial average height ratio ≈ 40:1) occurs after Selleck GDC 0068 8 s of exposure to SF6 (Figure 7a), while pseudo Bosch plasma quickly consumes the mask, and the ratio between final and initial average height remains
constant around 5:1 for different etching times. We calculated an etch rate of 22 nm min−1 leading to a selectivity ≈ 42 over p-doped Si(100), relative to a measured attack rate of SF6 over Si of Lck 940 nm min−1. Those values are compatible with what was reported for SF6 dry etching of wet and dry oxides. The etch rate is slightly influenced by several factors: single lines resist less than dense areas patterned by multiple lines, higher voltages during lithography produce features more resistant to etching, and any shape defect produced during deposition will affect the etching process. Imaging of grooves and protrusions can be affected by artifacts. A tip with a relatively large cone angle overestimate the real width of steep vertical features and fails to penetrate into deep and narrow grooves. That error is negligible for thin films as-deposited but is maximized for features with rectangular section between 50- and 100-nm tall; in order to minimize such effect for the topographies, we used a high aspect ratio tip. To prove the potentiality of the process, we prepared a Si mold intended for nanofluidic applications (Figure 7); to verify that we can create junctions between micro- and nanostructures, we fabricated aluminum micropatterns (approximately 300-nm thick) by vapor deposition with a conventional masking made by laser writing.
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