Fabrication of a VO₂-Based Tunable Metasurface by Electric-Field Scanning Probe Lithography with Precise Depth Control

Abstract

Vanadium dioxide (VO 2 ) is widely employed in developing tunable optoelectronic devices due to its significant changes in optical and electric properties upon phase transition. To fabricate the VO 2 -based functional devices down to the micro/ nanoscale, a high-resolution processing technique is in demand. Scanning probe lithography (SPL) on the basis of a tip-induced electric field provides a promising approach for prototyping. Here, we demonstrated a precise VO 2 etching strategy by direct writing on a VO 2 film with a negative tip bias and subsequent sonication removal of the written area. The effects of bias voltage, sonication, and thermal treatment as well as the mechanical difference between the tip-modulated area and the pristine VO 2 film were investigated systematically. The results show that VO 2 can be etched layer by layer via alternately repeating tip modulation and sonication, and arbitrary patterns can be written. Based on this route, we designed a kind of metasurface by arranging VO 2 −gold nanoblocks with different sizes and heights for spectrally selective tunable reflectivity in near-and mid-infrared. This electric-field SPL method demonstrates the prominent advantages of high resolution down to several tens of nanometers, quasi-3D patterning, and resist-free maskless direct writing, which should be applicable for prototyping other micro/nanodevices.

Advanced manufacturing of dielectric meta-devices

“…Schematic representation of the main steps in fabricating the designed metasurface (right). [241] Fig. 12 The utilization of UV lithography in the fabrication of all-dielectric metasurfaces.…”

“…As depicted in the left image of Fig. 11(c), the results indicate that VO2 can be etched layer by layer through alternately repeating tip modulation and sonication, allowing for the creation of arbitrary patterns [241] . Leveraging this approach, a metasurface was designed by arranging VO2–gold nanoblocks with varying sizes and heights, enabling spectrally selective tunable reflectivity in the near- and mid-IR, as shown in the right image of Fig.…”

Anisotropic Effects in Local Anodic Oxidation Nanolithography on Silicon Surfaces: Insights from ReaxFF Molecular Dynamics

“…6 Compared with other nanomanufacturing techniques, such as optical lithography, electron beam lithography, and nanoimprint lithography, LAO has advantages in atomiclevel resolution, direct surface patterning ability, and low instrument cost. 7,8 It has found broad applications in the manufacturing of quantum devices, 9 synaptic devices, 10 metasurfaces, 11 memristors, 12 transistors, 13 Schottky junctions, 14 gas sensors, 15 photoluminescence enhancement, 16 and optical devices. 17 Despite the promise of this approach, several challenges impede its further development and industrial implementations.…”

“…Local anodic oxidation (LAO) nanolithography is a promising nanofabrication technique to accommodate fast and flexible prototyping of functional nanostructures. − It relies on the controlled oxidation of conductive surfaces in anodic solutions, which is induced by an enhanced local electric field created by applying a bias between the nanoscale probes/electrodes and substrate . Compared with other nanomanufacturing techniques, such as optical lithography, electron beam lithography, and nanoimprint lithography, LAO has advantages in atomic-level resolution, direct surface patterning ability, and low instrument cost. , It has found broad applications in the manufacturing of quantum devices, synaptic devices, metasurfaces, memristors, transistors, Schottky junctions, gas sensors, photoluminescence enhancement, and optical devices …”

Dimension-Controlled VO2 Film for Optoelectronic Logic Gates and Information Encryption

“…For example, many researchers have exploited VO 2 for various applications, including near-sensor computing, ASCII code encryption, neuromorphic computing, and optical switching . While the performance of a VO 2 -based device is not only closely associated with its phase transition property but also depends on its dimensional characteristics and grain size, especially for the infrared light or THz modulations with 3D-like VO 2 film or VO 2 meta-surface structures. − Thus, the 3D dimension-induced spectrum modification in VO 2 film should have great potential to expand new applications. However, the traditional 3D-like porous VO 2 structures are normally prepared by sol–gel or hydrothermal methods, ,− which always lead to randomly distributed VO 2 particles and inhomogeneous grain size, resulting in the degraded localized surface plasmon resonance (LSPR) properties.…”