A*STAR (Agency for Science, Technology, and Research), Institute of Materials Research and Engineering , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634.
Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543.
ACS Nano. 2017 Oct 24;11(10):9920-9929. doi: 10.1021/acsnano.7b03951. Epub 2017 Sep 26.
Nanostructures of metal sulfides are conventionally prepared via chemical techniques and patterned using self-assembly. This poses a considerable amount of challenge when arbitrary shapes and sizes of nanostructures are desired to be placed at precise locations. Here, we describe an alternative approach of nanoscale patterning of zinc sulfide (ZnS) directly using a spin-coatable and electron beam sensitive zinc butylxanthate resist without the lift-off or etching step. Time-resolved electron beam damage studies using micro-Raman and micro-FTIR spectroscopies suggest that exposure to a beam of electrons leads to quick disappearance of xanthate moieties most likely via the Chugaev elimination, and further increase of electron dose results in the appearance of ZnS, thereby making the exposed resist insoluble in organic solvents. Formation of ZnS nanocrystals was confirmed by high-resolution transmission electron microscopy and selected area electron diffraction. This property was exploited for the fabrication of ZnS lines as small as 6 nm and also enabled patterning of 10 nm dots with pitches as close as 22 nm. The ZnS patterns fabricated by this technique showed defect-induced photoluminescence related to sub-band-gap optical transitions. This method offers an easy way to generate an ensemble of functional ZnS nanostructures that can be arbitrarily patterned and placed in a precise way. Such an approach may enable programmable design of functional chalcogenide nanostructures.
金属硫化物的纳米结构通常通过化学技术制备，并通过自组装进行图案化。当需要将任意形状和大小的纳米结构精确放置在特定位置时，这就带来了相当大的挑战。在这里，我们描述了一种替代方法，无需使用剥离或蚀刻步骤，直接使用可旋转涂布和电子束敏感的丁基锌黄原酸盐抗蚀剂对硫化锌（ZnS）进行纳米级图案化。使用微拉曼和微傅里叶变换光谱的时间分辨电子束损伤研究表明，暴露在电子束下会导致黄原酸部分迅速消失，最有可能通过 Chugaev 消除，进一步增加电子剂量会导致 ZnS 的出现，从而使暴露的抗蚀剂在有机溶剂中不溶。高分辨率透射电子显微镜和选区电子衍射证实了 ZnS 纳米晶体的形成。该性质用于制造小至 6nm 的 ZnS 线，并且还能够以 22nm 的最小间距图案化 10nm 点。通过这种技术制造的 ZnS 图案显示出与子带隙光学跃迁相关的缺陷诱导光致发光。该方法提供了一种生成功能 ZnS 纳米结构的简便方法，可以以任意方式进行图案化并以精确的方式放置。这种方法可能能够实现功能硫属化物纳米结构的可编程设计。
