Advanced unconventional techniques for sub‐100 nm nanopatterning

Patterned nanostructures with ultrasmall features endow functional devices with unique nanoconfinement and performance enhancements. The increasing demand for miniaturization has stimulated the development of sub-100 nm nanopatterning techniques. Beyond conventional lithography-which is limited by unavoidable factors-advanced patterning techniques have been reported to produce nanoscale features down to molecular or even atomic scale. In this review, unconventional techniques for sub-100 nm nanopatterning are discussed, in particular the principles by which to achieve the desired patterns (among other important issues). Such techniques can be classified into three categories: template-replica, template-induced, and template-free techniques. Moreover, multi-dimensional nanostructures consist of various building materials, the unique properties of which are summarized. Finally, the remaining challenges and opportunities for large-scale patterning, the improvement of device performance, the multi-dimensional nanostructures of biocompatible materials, molecular-scale patterning, and the carbon footprint requirements for future nanofabrication processes are discussed.