Low Damage Reductive Patterning of Oxidized Alkyl Self-Assembled Monolayers through Vacuum Ultraviolet Light Irradiation in an Evacuated Environment

Abstract

Through 172 nm vacuum ultraviolet light irradiation in a high vacuum condition (HV-VUV), well-defined micropatterns with a varied periodic friction were fabricated at the surface of self-assembled monolayers (SAMs) terminated with oxygenated groups. No apparent height contrast between the HV-VUV-irradiated and -masked areas was observed, which indicated the stability of the C-C skeleton of the assembled molecules. The trimming of oxygenated groups occurred through dissociating the C-O bonds and promoting the occurrence of α- and β-cleavages in the C═O-containing components. Hence, the HV-VUV treatment trimmed the oxygenated groups without degrading the C-C skeleton. The HV-VUV treatment influenced the order of the assembled molecules, and the step-terrace structure was distorted. The decrease in friction at the HV-VUV-irradiated domains was attributed to the dissociation of oxygenated groups. (3-Aminopropyl)trimethoxysilane (APTMS) aggregated at the masked areas of the HV-VUV-patterned SAM, where the oxygenated groups worked as anchors. APTMS aggregations did not exist at the irradiated areas, indicating the trimming of the oxygenated groups at these areas. The direct assembling of APTMS on the Si substrate at the irradiated areas was prevented by the remaining C-C skeleton.

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

“…22,24,29 These conditions were selected on the basis of the abundance of oxygenated groups and retaining the step−terrace structure of H−Si, as previously reported. 21,22,29 The UDA-SAM was HV-VUV patterned for 300 s at a 10 mm distance to the light source as illustrated in Figure 1, where the intensity of VUV light was ≈13.8 mW/cm 2 . 21,29 Fabrication of APTMS Patterns.…”

“…21 The height of these micropatterns and the existence of NH 2 and H 3 N + ions indicated the formation of APTMS multilayers. 21 Ultimate thickness control of organosilane micropatterns through adjusting the moisture and temperature during the CVD has not been investigated yet, to the best of our knowledge. Also, the influence of functional groups at the surfaces on the thicknesses of APTMS micropatterns can be examined.…”

“…21,29−32 The HV-VUV treatment of the oxidized hexadecyl (HD)-SAM decayed the C−OH, C−O−C, COO−C, and COOH components. 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.…”

“…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.…”

“…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. 21,22,29,32 On the other hand, the grafting of organosilanes on polymers would enhance the crystallinity, luminescence, water resistance, flame retardancy, and thermal and mechanical properties of these polymers to be applicable in different applications such as CO 2 capture, metal ion sensing, and antifouling.…”