Zhang Wenhao, Wu Xiqi, Li Liang, Zou Chongwen, Chen Yuhang
Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China.
Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, University of Science and Technology of China, Hefei 230027, China.
ACS Appl Mater Interfaces. 2023 Mar 15;15(10):13517-13525. doi: 10.1021/acsami.2c21935. Epub 2023 Mar 1.
Vanadium dioxide (VO) 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-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 etching strategy by direct writing on a VO 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 film were investigated systematically. The results show that VO 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-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.
二氧化钒（VO）因其在相变时光学和电学性质的显著变化而被广泛应用于可调谐光电器件的开发。为了制造出微纳尺度下基于VO的功能器件，需要一种高分辨率的加工技术。基于针尖诱导电场的扫描探针光刻（SPL）为原型制作提供了一种很有前景的方法。在此，我们展示了一种精确的VO蚀刻策略，即通过在VO薄膜上施加负针尖偏压进行直接写入，随后通过超声处理去除写入区域。系统地研究了偏压、超声处理、热处理以及针尖调制区域与原始VO薄膜之间的力学差异的影响。结果表明，通过交替重复针尖调制和超声处理，VO可以逐层蚀刻，并且可以写入任意图案。基于此方法，我们通过排列不同尺寸和高度的VO-金纳米块设计了一种超表面，用于近红外和中红外光谱选择性可调反射率。这种电场SPL方法展示了低至几十纳米的高分辨率、准三维图案化以及无抗蚀剂无掩模直接写入的突出优点，应适用于其他微纳器件的原型制作。
