Khatri Om P, Sano Hikaru, Murase Kuniaki, Sugimura Hiroyuki
Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
Langmuir. 2008 Oct 21;24(20):12077-84. doi: 10.1021/la8021613. Epub 2008 Sep 27.
Photopatterning of a hexadecyl (HD) monolayer has been demonstrated using vacuum ultraviolet (VUV; lambda = 172 nm) light under controlled vacuum pressure with the objective of minimizing the pattern dimension. X-ray photoelectron spectroscopy (XPS) and lateral force microscopy (LFM) studies reveal that photodegradation of the HD monolayer not only is limited to the regions exposed to VUV but also spreads under the masked regions. The strong oxidants generated by VUV irradiation to atmospheric oxygen and water vapor diffuse toward the masked regions through the nanoscopic channels and photodissociate the monolayer under the masked area, near the photomask apertures, resulting in broadening of the photopattern. Such broadening decreases with decreased vacuum pressure inside the VUV chamber, associated with a decrease of oxidant concentration and reduction of their diffusion. Gold nanoparticles (AuNPs) were immobilized on the VUV patterned features to probe the dimension of the chemically active pattern. Field emission electron microscopy reveals the construction of 565 nm wide pattern features at a vacuum pressure of 10 Pa. This pattern widens to 1,030 nm at 10 (4) Pa using the same size apertures (500 nm) as printed on the photomask. This study provides insight for fabricating submicron patterns with high reproducibility and its exploitation for different applications, which includes the patterning of nanoparticles, biopolymers, and other nano-objects at submicron dimensions.
在可控真空压力下，利用真空紫外线（VUV；波长λ = 172 nm）对十六烷基（HD）单分子层进行光图案化，目的是最小化图案尺寸。X射线光电子能谱（XPS）和侧向力显微镜（LFM）研究表明，HD单分子层的光降解不仅限于暴露于VUV的区域，还会在掩膜区域下扩散。VUV照射大气中的氧气和水蒸气产生的强氧化剂通过纳米通道向掩膜区域扩散，并使掩膜区域下方、靠近光掩膜孔径处的单分子层发生光解离，导致光图案变宽。随着VUV腔内真空压力的降低，这种变宽现象会减弱，这与氧化剂浓度的降低及其扩散的减少有关。金纳米颗粒（AuNP）被固定在VUV图案化特征上，以探测化学活性图案的尺寸。场发射电子显微镜显示，在10 Pa的真空压力下构建了宽度为565 nm的图案特征。使用与光掩膜上相同尺寸（500 nm）的孔径，在10⁴ Pa时该图案宽度扩展到1030 nm。这项研究为制造具有高重现性的亚微米图案及其在不同应用中的开发提供了思路，这些应用包括亚微米尺寸的纳米颗粒、生物聚合物和其他纳米物体的图案化。
