Vacuum Ultraviolet Treatment of Acid- and Ester-Terminated Self-Assembled Monolayers: Chemical Conversions and Friction Reduction

Abstract

We have prepared COOH- and COOCH-terminated self-assembled monolayers (SAMs) from undec-10-enoic acid (UDA) and methyl undec-10-enoate (MUDO) molecules on hydrogen-terminated silicon (H-Si) substrates through ultraviolet (UV) irradiation. The as-prepared UDA- and MUDO-SAMs were exposed to 172 nm vacuum-UV (VUV) light in a high vacuum environment (HV, <10 Pa) for different periods. The presence of COO components at the surfaces of these SAMs without prior oxidation would simplify the understanding of the origin of the chemical conversions and the changes of surface properties, as the prior oxidation would change the surface properties and generate different oxygenated groups. After the HV-VUV treatment, the abundance of COOH and COOCH components of these SAMs decreased without significant dissociation of their C-C backbones. Degradation of these components occurred through dissociating their C-O bonds, resulting in different C═O components. Also, the occurrence of Norrish type pathways resulted in a slight decrease of carbon content and produced CH components. We have applied the HV-VUV lithography to control the abundance of COOH and COOCH components in well-defined areas and to investigate the friction differences between the irradiated and masked areas. The irradiated areas exhibited lower friction than the masked areas without observing significant height contrasts between these areas. The reduction in friction was attributed to the conversion of the COOH and COOCH components to less adhesive components such as C═O and CH. These experiments suggest the HV-VUV treatments as an approach for low damage dry surface modifications and reductive lithographic techniques at surfaces terminated by acid and ester groups.

Hierarchical porous zeolitic imidazolate frameworks (ZIF-8) and ZnO@N-doped carbon for selective adsorption and photocatalytic degradation of organic pollutants

“…Peaks attributed to graphitic carbon, C–O or C–N and C O or C N were fixed at 284.5 eV, 286.2 eV, and 288.8 eV, respectively. 49 The FWHM of these peaks were 1.8 eV, 2.1 eV, and 2.9 eV, respectively. These deconvolution parameters were also applied during the deconvolution of the C 1s spectrum of ZnO@N-doped C before adsorption ( Fig.…”

Hierarchical Porous Zeolitic Imidazolate Frameworks (ZIF-8) and ZnO@N-doped Carbon for Selective Adsorption and Photocatalytic Degradation of Organic Pollutants

“…After adsorption, the XPS C1s spectrum envelope was deconvoluted, as illustrated in Figure 4b. Peaks attributed to graphitic carbon, C-O or C-N and C=O or C=N were fixed at 284.5 eV, 286.2 eV, and 288.8 eV, respectively 49 . The FWHM of these peaks were 1.8 eV, 2.1 eV, and 2.9 eV, respectively.…”

Controlled Growth of Organosilane Micropatterns on Hydrophilic and Hydrophobic Surfaces Templated by Vacuum Ultraviolet Photolithography

“…21,29 Also, the COOH and COOCH 3 terminated groups of SAMs obtained from undec-10-enoic acid (UDA) and methyl undec-10-enoate (MUDO) were trimmed after HV-VUV treatment as previously reported. 32 Trimming the oxygenated groups after HV-VUV lithography results in a friction decrease at the irradiated domains compared with that at the masked areas. 21,29,32 The C−O cleavage and Norrish-type pathways resulted in the generation of CO and CH 3 components.…”

“…32 Trimming the oxygenated groups after HV-VUV lithography results in a friction decrease at the irradiated domains compared with that at the masked areas. 21,29,32 The C−O cleavage and Norrish-type pathways resulted in the generation of CO and CH 3 components. 21,29,32 That is, the effect of VUV exposure was reversed from generating different oxygenated groups in an ambient environment at the surface of HD-SAM to trimming the COOH groups from the surface of UDA-SAM in an evacuated environment.…”