Department of Materials Science and Engineering , Kyoto University , Yoshida-Hommachi , Sakyo-ku, Kyoto 606-8501 , Japan.
Langmuir. 2018 Mar 13;34(10):3228-3236. doi: 10.1021/acs.langmuir.7b04327. Epub 2018 Feb 28.
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.
我们通过紫外线（UV）照射，在氢终止硅（H-Si）衬底上制备了由十一碳烯酸（UDA）和甲基十一碳烯酸甲酯（MUDO）分子组成的-COOH 和-COOCH 末端自组装单层（SAM）。在高真空环境（HV，<10 Pa）中，将制备的 UDA 和 MUDO-SAM 用 172nm 真空紫外（VUV）光照射不同时间。这些 SAM 表面没有预先氧化的 COO 成分的存在将简化对化学转化起源和表面性质变化的理解，因为预先氧化会改变表面性质并产生不同的含氧基团。在 HV-VUV 处理后，这些 SAM 中 COOH 和 COOCH 成分的丰度降低，而其 C-C 主链没有明显解离。这些成分的降解是通过其 C-O 键的解离来实现的，导致不同的 C═O 成分。此外，Norrish 型途径的发生导致碳含量略有下降，并产生 CH 成分。我们已经将 HV-VUV 光刻应用于控制 COOH 和 COOCH 成分在明确定义区域的丰度，并研究了照射和掩蔽区域之间的摩擦差异。照射区域的摩擦小于掩蔽区域，而这些区域之间没有观察到显著的高度对比。摩擦的降低归因于 COOH 和 COOCH 成分转化为较少粘附的成分，如 C═O 和 CH。这些实验表明，HV-VUV 处理是一种在酸和酯基团终止的表面进行低损伤干式表面改性和还原光刻技术的方法。
