Chemical modification of sputtered amorphous-carbon surfaces

Abstract

Methods to chemically passivate the surfaces of amorphous-carbon films (a-C) produced by dc magnetron sputtering were studied. The chemical composition of carbon surfaces produced via sputtering are dependent upon the environment to which the carbon is exposed immediately following deposition. When the sputtered film is vented to ambient conditions, free radicals produced at the surface during the deposition process are quenched by reaction with oxygen and/or water to form an oxidized, hydrophilic surface. If the sputtered carbon film is, however, exposed to a reactive gas prior to venting to ambient, the chemical nature of the resulting surface can be modified substantially. Specifically, a less highly oxidized and much more hydrophobic carbon surface is produced when the surface free radicals are quenched via either an addition reaction (demonstrated with a fluorinated olefin) or a hydrogen abstraction reaction (demonstrated with two alkyl amines). Chemical modification of amorphous-carbon films can also be accomplished by performing the sputtering in a reactive plasma formed from mixtures of argon with molecular hydrogen, amines, and perfluorocarbons. The elemental composition of these films, and the relative reactivity of the surfaces formed, were investigated via x-ray photoelectron spectroscopy and contact-angle goniometry, respectively. In the case of sputtering with a mixture of argon and hydrogen, increasing the hydrogen flow results in an increase in the amount of hydrogen incorporated into the carbon film and a decrease in the surface free energy. Sputtering in diethylamine produces an amorphous-carbon film into which nitrogen is incorporated. The free energies of the a-C:N surfaces produced in this process are similar to those of the a-C:H films. Sputtering in a fluorocarbon vapor results in the incorporation of fluorine into the film structure and the formation of very low free-energy surfaces. Increasing the concentration of the fluorocarbon in the sputtering plasma increases the amount of F incorporated into the film. At the highest fluorocarbon flow rates employed, a-C films were produced with stoichiometries and surface free energies comparable to those of bulk Teflon.

Laser‐Induced Direct Lithography for Patterning of Carbon with sp3 and sp2 Hybridization

“…The preliminary results raise the possibility of obtaining patterning of any desired carbon allotrope; pure diamond or graphite, by controlling the deposition conditions. Due to the involvement of radical formation in the process, addition of other components, such as nitrogen-reacting compounds, [12,33] to the precursor solution might alter the chemical composition, morphology, and structure of the deposited patterns.…”

“…Oxygen incorporation in carbon films is not uncommon and results from the presence of background oxygen in the deposition chamber. [12] Decomposition of the dibenzoyl peroxide precursor compound results in formation of oxygen, which can be absorbed within the carbon pattern. In addition, free radicals produced during the patterning process might be quenched by the oxygen to form oxidized material.…”

“…In addition, free radicals produced during the patterning process might be quenched by the oxygen to form oxidized material. [12] The use of 10 mW laser intensity at the sample spot probably produced enough heat to prevent the oxygen occlusion in the carbon pattern. In this case, the oxygen content decreased substantially to 0.9 %, and was similar to that found in HOPG.…”

Vacuum vapor deposition of PFPE molecules on CHxNy and CHxFy amorphous carbon surfaces

“…Comparison of the effects between the vapor deposition technique and dip-coating process will be discussed. In this study, the incorporation of nitrogen and fluorine contents into the DLC film is investigated in order to change the characteristics of the DLC surface (Yu et al 2003;Xin et al 2002;Cicala et al 2004;Kato et al 2003;Trippe et al 2004;Kawaguchi et al 2006;Choi et al 2006;Butter et al 1997;Prioli et al 2003;Leezeberg et al 2001;Stirniman and Falcone 2000). The PFPE lubricant molecules are deposited on the hydrogen, nitrogen or fluorine doped DLC surface using the vapor deposition technique.…”

Diamond‐like carbon coated polymer‐based targets in microscope slide format for MALDI mass spectrometry

“…A better adoption to the requirements of MALDI sample preparation could be reached by altering the surface properties via incorporation of other atoms such as nitrogen, hydrogen or fluorine, which would result in changes of the surface characteristics. [14] By increasing the contact angles of sample/matrix solution drops due to different DLC layer characteristics, smaller spot sizes resulting in higher analyte densities could be reached.…”