| 1. |
- Baer, Donald R., et al.
(författare)
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XPS guide: Charge neutralization and binding energy referencing for insulating samples
- 2020
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 38:3
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Tidskriftsartikel (refereegranskat)abstract
- This guide deals with methods to control surface charging during XPS analysis of insulating samples and approaches to extracting useful binding energy information. The guide summarizes the causes of surface charging, how to recognize when it occurs, approaches to minimize charge buildup, and methods used to adjust or correct XPS photoelectron binding energies when charge control systems are used. There are multiple ways to control surface charge buildup during XPS measurements, and examples of systems on advanced XPS instruments are described. There is no single, simple, and foolproof way to extract binding energies on insulating material, but advantages and limitations of several approaches are described. Because of the variety of approaches and limitations of each, it is critical for researchers to accurately describe the procedures that have been applied in research reports and publications.
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| 2. |
- Liu, Li, et al.
(författare)
-
Surface and interface control on photochemically initiated immobilization
- 2006
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 128:43, s. 14067-14072
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Tidskriftsartikel (refereegranskat)abstract
- Surface and interface properties are important in controlling the yield and efficiency of the photochemically initiated immobilization. Using a silane-functionalized perfluorophenyl azide (PFPA-silane) as the photoactive cross-linker, the immobilization of polymers was studied by adjusting the density of the surface azido groups. Dilution of the photolinker resulted in a gradual decrease in the density of surface azido groups as well as the thickness of the immobilized film. When a nonphotoactive silane was added to PFPA-silane, the film thickness decreased more rapidly, suggesting that the additive competed with PFPA-silane and effectively reduced the density of the surface azido groups. The effect of surface topography was studied by adding a nonphotoactive silane with either a shorter (n-propyltrimethoxysilane (PTMS)) or a longer spacer (n-octadecyltrimethoxysilane (ODTMS)). In most cases the long chain ODTMS shielded the surface azido groups, resulting in a more rapid decrease in film thickness as compared to PTMS treated under the same conditions. As the density of the surface azido groups decreased, the immobilized polymer changed from smooth films to patched structures and, eventually, single polymer molecules.
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| 3. |
- Uppalapati, Suji, et al.
(författare)
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Photochemical Reactions of Poly(4-vinylphenol) Thin Films
- 2010
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 211:4, s. 461-470
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism involved in the photochemical immobilization of poly (4-vinylphenol) (PVP) thin. films was investigated. The films were fabricated by a simple procedure of UV irradiation and solvent extraction. A combination of ellipsometry, IR, and high-resolution X-ray photoelectron spectroscopy (XPS) was used to provide detailed and quantitative analysis of the composition of the photochemical reaction products. Upon irradiation at 260 nm, benzyl and phenoxy radicals are generated in the polymer. In the absence of oxygen, PVP films crosslinked via the combination of the benzyl radicals or phenoxy radicals. At lower irradiation doses, the photochemical process was dominated by cross-linking of the polymer backbone via the combination of benzyl radicals. At higher exposure doses, cross-linked quinoid structures were generated, and the concentration increased with the irradiation time. No oxidation or degradation products were observed. In the presence of oxygen, additional reactions of oxidation and degradation occurred. At lower doses, oxidation at the benzyl position produced the ketone structure evidenced by the drastic increase in the 0 content in the irradiated films. As the irradiation doses increased, further oxidation at the methylene position occurred, and in addition, volatile and degradation products were also generated. This photochemical process was successfully employed to fabricate patterned PVP structures.
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