二溴-联二蒽分子在bi(111)表面上的聚合化及多层分子链
首发时间:2023-10-31
摘要:本文利用低温扫描隧道显微镜(lt-stm)研究了合成石墨烯纳米带的前驱体分子二溴-联二蒽(dbba)在半金属bi(111)表面上的脱溴及聚合化过程。实验发现,dbba分子在120k的衬底温度下可实现完全脱溴,由此形成一维的聚合蒽共价分子链,这是目前发现的dbba分子的最低脱溴温度。随着分子覆盖度的逐渐增加,衬底表面出现了双层的和三层厚的聚合蒽分子链阵列。但是,第二层和第三层的聚合蒽分子链之间存在较大的间隙。有趣的是,第三层分子链的间隙几乎是第二层分子链间隙的二倍。在第三层聚合蒽链的基础上继续沉积dbba分子,发现未脱溴的dbba分子出现在聚合蒽链的缝隙内,并通过范德瓦尔斯作用形成自组装的dbba单链和双链。随分子数的增加,由于聚合蒽链之间宽大的沟槽阻碍了分子的表面扩散运动,使得直立的dbba分子未能形成有序的自组装结构。上述研究结果对探索dbba分子与bi(111)表面之间的相互作用,dbba的脱溴及聚合化过程,以及聚合蒽分子链对dbba自组装结构的影响提供了研究基础和参考意义。
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polymerization and multilayers of dbba chains on bi(111) surface
abstract:the debromination and polymerization of dibromo-bianthryl (dbba), a precursor of graphene nanoribbons, on the surface of semi-metal bi(111) surface was studied by low temperature scanning tunneling microscopy (lt-stm). it is found that dbba molecules can be debrominated at a substrate temperature of 120 k, thus forming a one-dimensional polyanthracene covalent chains. this is the lowest debromination temperature of dbba molecules on metal surfaces found so far. with the increase of molecular coverage, two-layer thick and three-layer thick polyanthracene chain arrays appeared on bi(111) surface. however, there is large inter-chain gaps in the second and third polyanthracene layers. interestingly, the inter-chain gap of the latter is almost twice as large as the former. after further deposition of dbba onto the third polyanthracene layer, it was found that the undebrominated dbba molecules appeared in the large gap of polyanthracene chains and formed self-assembled single and double chains by van der waals interaction. as the number of dbba increases, the wide grooves between the polyanthracene chains hinder the surface diffusion of dbba, so that the upright dbba molecules cannot form the ordered self-assembly structure. these results provide the essential information for understanding of the interaction between dbba molecule and bi(111) surface, the debromination and polymerization process of dbba, and the interplay between the polymerizationand self-assembly of dbba molecules on semi-metal surface.
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