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Zhang et al. Soft Sci. 2026, 6, 16 Page 7 of 17

Figure 3. (A) XRD pattern of C-3; (B) XPS survey of the C-0 and C-3; (C) C 1s XPS spectra of C-1, C-2 and C-3; (D) O 1s XPS spectra of
C-0 and C-3; (E) Fe 2p XPS spectra of C-3; (F) Raman pattern of C-1, C-2 and C-3; (G) Comparison of I D /I G and conductivity. XRD: X-ray
diffraction; XPS: X-ray photoelectron spectroscopy; SS: stainless steel.

Table 1. XPS analysis results of C-0 (uncoated), C-1, C-2, and C-3 electrodes

C=C C–C C–O C=O and O–C=O Adsorbed oxygen Crystal oxygen
C-3 0.63 0.17 0.09 0.11 0.66 0.34
C-2 0.48 0.26 0.11 0.15 0.68 0.32
C-1 0.46 0.27 0.14 0.13 0.71 0.19
C-0 - - - 0.50 0.50

XPS: X-ray photoelectron spectroscopy.

the presence of layered sp2 nanosheets . Furthermore, the G peak shifts to higher wavenumbers with
[31]
increasing deposition bias voltage, which may be related to the higher sp2 content and the associated
reduction of residual stress in the carbon film [32,33] .

The resistivity of the three carbon films was measured using a four-probe method on samples deposited on
silica wafers, yielding 15.67, 9.06, and 6.47 mΩ·cm for C-1, C-2, and C-3, respectively. Figure 3G compares