| 摘要: | 近來，石墨烯因為它具有極高的電子遷移率而引起研究界大量的關注。在眾多製造石墨烯的製程中，現在公認最有效率的大量生產方式是還原氧化石墨烯，其中的方法包括熱還原、電化學還原等等。然而，還原氧化石墨烯的產物中殘存的大量氧化官能基卻造成電子遷移率的下降。在近期的研究中，有些團隊成功地利用各種技術移除還原氧化石墨烯中大部分殘存的氧化官能基。不幸的是，拉曼分析的結果卻顯示出儘管大部份的氧化官能基被移除了，石墨烯的晶格結構並沒有辦法被修復。
在我們的研究中，我們藉由拉曼光譜技術與X射線光電子能譜技術發現，若在無序的氧化結構下層加上一層晶格匹配的有序結構，即可以改善氧化的石墨烯的結構恢復。在實驗中，我們利用氧化掃描探針微影技術各別氧化一層石墨烯的區域、兩層石墨烯的區域、跟三層石墨烯的區域。藉由確認在一層石墨烯的區域、兩層石墨烯的區域、跟三層石墨烯的區域的氧化過程只氧化最上層的石墨烯，我們即可藉由此技術成功製造出下層沒有晶格模板的、有一層晶格模板的、有兩層晶格模板的一層微影氧化石墨烯。利用X射線光電子還原後，我們發現，若下層沒有晶格模板，微影氧化石墨烯的結構會在還原後變壞。值得注意的是，若是下層有晶格模板，微影氧化石墨烯的結構能夠往化學氣相沉積石墨烯的結構恢復。
這項發現讓還原的氧化石墨烯能夠同時擁有足夠能隙，又能保有相對好的結構與電性。讓有「下一代電子材料」之稱的石墨烯能夠實至名歸。;Recently, graphene has attracted a great number of attentions due to its high electron mobility. However, the honeycomb structure makes it a material with zero bandgap. Researchers have found a lot of ways to open the bandgap for further applications. Among all of the methods, the reduction of graphene oxide through thermal, electrochemical, or other reduction methods is the most well-recognized efficient way to produce bandgap-opened graphene in large scale. However, in the end product, which is called reduced graphene oxide (rGO), there are too many irremovable oxygen functional groups including C-O, C=O, and COOH. These oxygen functional groups worsen its good properties. In recent publications, although some groups have successfully removed most of oxygen functional groups on rGO, Raman analysis showed that there was no way to reconstruct its lattice structure toward graphene despite the removal of oxygen functional groups. Hence, it is crucial to find a way to improve lattice reconstruction of disordered graphene.
In our work, we found that a lattice-matching ordered template underneath disordered oxidized graphene could improve the structure restoration of oxidized graphene though characterizations of μ-Raman spectroscopy (μ-RS) and μ-X-ray photoelectron microscopy (μ-XPS). In the experiment, we oxidized graphene in regions with 1 layer, 2 layer, and 3 layer through oxidation scanning probe lithography (o-SPL). The oxidation process on 1-layer, 2-layer, and 3-layer graphene of o-SPL was made sure to be top-layer oxidation only so that 1-layer o-SPL graphene without a template, with a 1-layer template, and with a 2-layer template were successfully produced. After XPS reduction, if there was no template underneath, the structure of o-SPL graphene got worse. Noticeably, the structure of o-SPL graphene with a template could successfully be restored to approach the structure of pristine CVD graphene.
It is a finding which provides a way to solve the problem of the worsened conductivity of band-gap opened graphene. The preservation of a better structure for rGO can make it deserve the title of “the anticipated candidate for electronics in the next generation.” |
