X‐ray photoelectron analysis of surface functional groups on diamond‐like carbon films by gas‐phase chemical derivatization method

Abstract

a Oxygen-related surface functional groups on diamond-like carbon (DLC) films were derivatized with fluorine-and nitrogenrelated groups by the gas-phase chemical derivatization (GCD) method, and the groups were analyzed quantitatively by X-ray photoelectron spectroscopy (XPS). It is desirable that a derivatization reaction is unique to the target group; however, it usually causes undesirable side reactions which affect other groups. This diversity of the reactions has complicated the analysis. In this report, we have overcome the problem by applying a mathematical treatment which takes the side reactions into account. This improved analysis shows that it is no longer necessary to have derivatization reactions unique to the target groups. As a result, it is demonstrated that the carbonyl (C O) group is the dominant surface functional group on both the DLC and its wet-oxidized films, the carboxyl (COOH) group plays a minor role, and the presence of the hydroxyl (OH) group is logically denied. Considering the oxidation steps of these oxygen-related surface functional groups, it is suggested that the C O group on the DLC films requires the cleavage of the carbon-carbon bond with a relatively high activation energy barrier to change into the COOH group.

Chemical conversion of self-assembled hexadecyl monolayers with active oxygen species generated by vacuum ultraviolet irradiation in an atmospheric environment

“…17,18 These active oxygen species, especially singlet state species, have a strong oxidative power; they oxidize the alkyl-terminated groups (-R) of SAMs and polymers to polar functional groups (OH, COOH and CHO), and convert their surfaces to become more hydrophilic. 31 These labeling reagents are not chemospecific for OH, CHO and COOH. [17][18][19] VUV irradiation of methyl-terminated organosilane SAMs showed that the active oxygen species gradually decayed the carbon skeleton of SAMs, by introducing new polar groups, until complete elimination of SAMs, and these chemical conversions were reflected on the surface properties, especially wettability.…”

“…With elongation of the VUV irradiation period, the backbone of SAMs and polymers is gradually degraded until complete dissociation. [31][32][33][34][35] Almost all previous reports have referred to chemical modifications of polymers and SAM molecules without discerning and realizing the method to achieve these modifications. These new polar groups on surface of SAMs act as anchor groups for multilayer assembly and biomolecule immobilization, [20][21][22][23] so that VUV irradiation offers a significant and accurate method for micro-nanoscale lithography, especially SAM patterning, 24 and such micro-nanopatterned SAMs will be enormously important for different technological applications.…”

Repressing oxidative wear within Si doped DLCs

“…XPS spectra were calibrated using the main C1s peak component, which is well characterised in the literature. Works in the literature specify spectra of DLC films should be calibrated to the hydrocarbon (CHx) peak at 284.4 eV (19)(20)(21)(22). Calibration shifted the spectrum by 1.2 eV, correcting for charging issues.…”

Surface oxidation process of a diamond-like carbon film analyzed by difference X-ray photoelectron spectroscopy

“…F 1 s and N 1 s ) are more sensitive than the C 1 s spectra, the evaluation of oxygen‐related surface functional groups becomes obvious. In addition, the authors improved the GCD‐XPS analysis by introducing a simple mathematical treatment to exclude the influence of side reactions . However, this improved GCD‐XPS analysis still has a drawback.…”