Engineering surface reactions with polyatomic ions

Lau, Woon‐Ming; Kwok, R. W. M.

doi:10.1016/s0168-1176(97)00305-4

Cited by 15 publications

(9 citation statements)

References 17 publications

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“…Unlike photon and electron irradiation which can promote reactivity with chemical selectivity through their direct coupling to the electronic structures of the reactants, the reaction driving forces of atom/molecule projectiles are more complex and typically influenced by charge exchange and translation−potential (T−V) energy conversion among all parties in the collision events induced by the entry of the projectile into the reaction system. − Typically, projectile chemistry and energy are the key reaction attributes for improving chemical selectivity and reactivity in the design of collision-induced chemistry. The recent successes in controlled soft-landing 4,5 of hyperthermal polyatomic molecules or molecular ions fully exploit the projectile chemistry in the yield of reaction products with specific chemical functionalities.…”

Section: Introductionmentioning

confidence: 99%

Ultrathin Polymer Film Formation by Collision-Induced Cross-Linking of Adsorbed Organic Molecules with Hyperthermal Protons

Zheng

Fan

et al. 2004

J. Am. Chem. Soc.

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A new synthetic approach for the formation of ultrathin polymer films with customizable properties was developed. In this approach, the kinematic nature of proton collisions with simple organic molecules condensed on a substrate is exploited to break C-H bonds preferentially. The subsequent recombination of carbon radicals gives a cross-linked polymer thin film, and the selectivity of C-H cleavage preserves the chemical functionalities of the precursor molecules. The nature and validity of the method are exemplified with theoretical results from ab initio molecular dynamics calculations and experimental evidence from a variety of characterization techniques. Its applicability is demonstrated by the synthesis of ultrathin polymer films with precursor molecules such as dotriacontane, docosanoic acid, poly(acrylic acid) oligomer, and polyisoprene. The approach is fundamentally different from conventional chemical synthesis as it involves an unusual mix of physical and chemical processes including charge exchange, projectile penetration, kinematics, collision-induced dissociation, inelastic energy transfer, chain transfer, and chain cross-linking.

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Section: Introductionmentioning

confidence: 99%

Ultrathin Polymer Film Formation by Collision-Induced Cross-Linking of Adsorbed Organic Molecules with Hyperthermal Protons

Zheng

Fan

et al. 2004

J. Am. Chem. Soc.

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“…Ion beam processing for surface modification has drawn substantial interest due to its experimental flexibility and controllability. , For example, the decomposition of self-assembled monolayers by atomic ions has been used for lithographic patterning . The soft landing of intact individual polyatomic ions on self-assembled monolayers has also been demonstrated. − The chemical modification or growth of thin films on polymer surfaces has also been achieved by hyperthermal polyatomic ions. − We have previously examined the chemistry, morphology, and stability of fluorocarbon films formed on polystyrene by hyperthermal polyatomic ion deposition. − We found that the fluorocarbon film chemistry depends on projectile ion energy, structure, and fluence. We observed mostly intact projectile ions deposited onto the surface at low kinetic energy (25 eV) while mostly projectile fragments deposited at higher energy (100 eV).…”

Section: Introductionmentioning

confidence: 99%

“…[6][7][8] The chemical modification or growth of thin films on polymer surfaces has also been achieved by hyperthermal polyatomic ions. [9][10][11] We have previously examined the chemistry, morphology, and stability of fluorocarbon films formed on polystyrene by hyperthermal polyatomic ion deposition. [12][13][14][15] We found that the fluorocarbon film chemistry depends on projectile ion energy, structure, and fluence.…”

Section: Introductionmentioning

confidence: 99%

Preparation of Chemical Gradient Surfaces by Hyperthermal Polyatomic Ion Deposition: A New Method for Combinatorial Materials Science

2001

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C3F5 + ion deposition at 50 eV is used to produce chemical gradient surfaces on poly(methyl methacrylate) (PMMA) by systematic variation of the fluence across the surface. The gradient is characterized by recording small spot X-ray photoelectron spectra and air/water contact angles along the sample length. The fluorine content grows with ion fluence toward the modified end of the sample while the oxygen content decreases simultaneously. These two effects are attributed to the formation of a fluorocarbon film on top of the PMMA surface, which increases in coverage with C3F5 + ion fluence. The air/water contact angle increases in parallel with the fluorine content along the surface gradient. These results clearly indicate that a chemical and wettability gradient is produced on PMMA by mass-selected hyperthermal ion deposition. C3F5 + ion deposition can also be used to produce chemical gradient surfaces on polystyrene, aluminum, and silicon substrates. It is shown that hyperthermal polyatomic ion deposition is a general method for a wide range of surface chemical gradients on various substrates including polymers, metals, semiconductors, and ceramics.

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“…The low-energy hydrogen bombardment was performed with a home-built and low-cost mass-separated low energy ion beam system, 16,18,40,41 which delivers a hydrogen beam to the target substrate in a high vacuum chamber. Hydrogen gas with the purity of 99.8% was used in the bombardments.…”

Section: Experimental Design and Methodsmentioning

confidence: 99%

Study of a hydrogen-bombardment process for molecular cross-linking within thin films

Liu¹,

Yang²,

Nie³

et al. 2011

The Journal of Chemical Physics

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A low-energy hydrogen bombardment method, without using any chemical additives, has been designed for fine tuning both physical and chemical properties of molecular thin films through selectively cleaving C-H bonds and keeping other bonds intact. In the hydrogen bombardment process, carbon radicals are generated during collisions between C-H bonds and hydrogen molecules carrying ∼10 eV kinetic energy. These carbon radicals induce cross-linking of neighboring molecular chains. In this work, we focus on the effect of hydrogen bombardment on dotriacontane (C(32)H(66)) thin films as growing on native SiO(2) surfaces. After the hydrogen bombardment, XPS results indirectly explain that cross-linking has occurred among C(32)H(66) molecules, where the major chemical elements have been preserved even though the bombarded thin film is washed by organic solution such as hexane. AFM results show the height of the perpendicular phase in the thin film decreases due to the bombardment. Intriguingly, Young's modulus of the bombarded thin films can be increased up to ∼6.5 GPa, about five times of elasticity of the virgin films. The surface roughness of the thin films can be kept as smooth as the virgin film surface after thorough bombardment. Therefore, the hydrogen bombardment method shows a great potential in the modification of morphological, mechanical, and tribological properties of organic thin films for a broad range of applications, especially in an aggressive environment.

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Engineering surface reactions with polyatomic ions

Cited by 15 publications

References 17 publications

Ultrathin Polymer Film Formation by Collision-Induced Cross-Linking of Adsorbed Organic Molecules with Hyperthermal Protons

Ultrathin Polymer Film Formation by Collision-Induced Cross-Linking of Adsorbed Organic Molecules with Hyperthermal Protons

Preparation of Chemical Gradient Surfaces by Hyperthermal Polyatomic Ion Deposition: A New Method for Combinatorial Materials Science

Study of a hydrogen-bombardment process for molecular cross-linking within thin films

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