On-terrace graphoepitaxy for remarkable one-dimensional growth of 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene (C8-BTBT) nanowires

The demand has increased for an organic semiconducting material microfabrication process for photonic and electronic applications. However, conventional lithographic processes are not applicable to organic semiconductors because these techniques cause serious damage. The main purpose of this study is to address this issue by establishing a process for producing one-dimensional (1D) nanowires. In particular, a great advantage of graphoepitaxy is that the dimensions of the nanowire can be designed by employing pre-patterns formed on substrates. First, remarkable 1D growth guided by a pre-patterned substrate is described. Importantly, the 1D nanowires are grown only on patterned terraces. Second, a fundamental growth mechanism is discussed, where energy barriers at step edges play an essential role. The energy barriers confine the deposited molecules on the terraces to enhance the extended 1D evolution. Finally, a specific emphasis is placed on the merit of on-surface graphoepitaxy, namely it offers the wide-range controllability of nanowire width.