Fabrication of two-dimensional semiconductors on the surface of ferroelectric films by means of gold-assisted mechanical exfoliation

Objectives. The aim of this study is to develop and demonstrate an effective method for obtaining large-area, high-quality monolayers of molybdenum disulfide (MoS₂) on the surface of ferroelectric lead zirconate titanate (PZT) films which exhibit pronounced granularity and texturing. Conventional mechanical exfoliation techniques are inefficient for transferring two-dimensional materials onto nonplanar surfaces. This is due to local height variations and substrate granularity which hinder the formation of continuous monolayers and high-defect-density transferred structures. A particular challenge is the transfer onto functional substrates with surface topography characterized by heterogeneities ranging from tens of nanometers to micrometers.

Methods. A gold-assisted exfoliation (GAE) method was employed, including: magnetron sputtering of a 50 nm gold film; mechanical delamination of monolayers using thermally cleavable tape; and subsequent gold etching. The characterization was performed using X-ray diffraction, optical confocal microscopy, atomic force microscopy, and second harmonic generation techniques. The efficiency of the transfer process was compared for Si/SiO₂ and PZT substrates.

Results. MoS₂ crystallites with areas up to 3000 µm² were obtained on PZT and over 65000 µm² on standard Si/SiO₂ substrates, both of which exhibit minimal defect densities. Conventional mechanical exfoliation is shown to be unable to ensure transfer onto textured surfaces, whereas the GAE method preserves the monolayer character of the transferred crystallites even on nonplanar substrates.

Conclusions. This work demonstrates for the first time the possibility of obtaining large-area, high-quality MoS₂ monolayers on substrates with pronounced grainy and textured structures, such as ferroelectric PZT films, using the gold-assisted exfoliation method. The work also shows that gold-assisted exfoliation is an effective technique for fabricating extended two-dimensional films with controlled morphological and structural properties, including on substrates previously considered unsuitable for such applications.

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