A study on one-step laser nanopatterning onto copper–hydrazone-complex thin films and its mechanism

Abstract

Semiconductor diode-based laser patterning with visible light has been extensively applied to the fabrication of arbitrary structures. However, recently, the technique has faced a great challenge because it cannot meet nanoscale-resolved patterning fabrication due to the optical diffraction limit, which is an inherent drawback in the field of optics. To attack the question, copper(II)–hydrazone-complex (CuL₂) thin films are used as laser patterning materials. Under the heating of a writing laser spot, one-step laser nanopatterning on the CuL₂ thin films is obtained. The convex-type and concave-type pattern structures are directly written without wet-etching and developing processes. The minimum pattern feature size is about 31 nm, which is far smaller than the diffraction limit and only ∼1/20 the writing spot size. Analysis indicates that the laser nanopatterning originates from obvious photothermal localization responses to the writing spot. Compared with common organic resists, the exposure dose of CuL₂ is several orders higher than that of the polymer; thus CuL₂ thin film materials are suitable for maskless direct laser writing lithography. This work also provides an effective method for one-step nanopatternings through diode-based laser writing at visible light wavelengths.