A facile and non-destructive quartz fiber shadow mask process for the sub-micrometer device fabrication on two-dimensional semiconductors

Abstract

The normal fabrication process for electronic and optoelectronic devices can bring in significant modifications on two-dimensional (2D) semiconductors’ intrinsic properties. To address this issue, some dry methods have been developed, such as ‘‘transfer contact’’ method and ‘‘shadow mask technology’’. However, the method that can combine the advantages of low cost, non-destruction, and high reliability at sub-micrometer scale is rarely reported. Here, we demonstrate a fabrication technique using ultrafine quartz fibers as shadow masks. In this technique, sub-micrometer scale devices can be ‘‘all dry’’ fabricated facilely, and the intrinsic properties of 2D semiconductors are preserved. Meanwhile, the masking effect can be evaluated in situ based on the light interference between the quartz fiber and the substrate to increase the fabrication reliability. Furthermore, such method is flexible enough for fabrication of multiple devices on one chip or even on a single crystal flake. This technology provides a facile, nondestructive and reliable alternative method for fabricating sub-micrometer devices. Two-dimensional (2D) semiconductor materials show great potential in electronics and optoelectronics application due to their unique properties, such as high mobility in atomically thin scale [1–4], layerdependent band structure [5, 6], strong photon–electron interaction [7–9], and ability to form heterostructure without the limitation of lattice matching [10–12]. In order to explore the emerging new 2D semiconductors, normal ultraviolet (UV) lithography and electron beam lithography (EBL) techniques are often utilized to fabricate nanodevices. However, owing to the traditional mask technique, contaminants and damages can easily be introduced to the material surface. Since the pristine electronic states of 2D semiconductors are extremely sensitive to the surface conditions, significant modifications can be brought to the materials’ intrinsic properties during these processes. This may hinder the exploration of novel 2D materials, both in fundamental research and industrial applications. To reserve the intrinsic properties of 2D semiconductors, many new fabrication technologies have been developed. ‘‘Dry method’’ seems to be one of the most effective ways, where the 2D semiconductor usually contacts nothing except air or inert gas. For example, in the ‘‘transfer contact’’ method [13–17], patterned electrodes are directly aligned and laminated onto freshly exfoliated 2D materials and therefore avoid any contaminants and damages. Thanks to the super-gentle nature of this method, near ideal metal–semiconductor junctions [13], high performance and reliable transistors [14, 15], and vertical Schottky-junction solar cells [16] were realized. Nevertheless, costly and complicated operations such as EBL, UV lithography, and reactive ion etching (RIE) are indispensable for preparation of the electrodes. In addition, some desired metal Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007/s12598021-01787-0.