The formation of semiconductor heterojunctions and their high-density integration are foundations of modern electronics and optoelectronics. To enable two-dimensional crystalline semiconductors as building blocks in next-generation electronics, developing methods to deterministically form lateral heterojunctions is crucial. Here we demonstrate an approach for the formation of lithographically patterned arrays of lateral semiconducting heterojunctions within a single two-dimensional crystal. Electron beam lithography is used to pattern MoSe₂ monolayer crystals with SiO₂, and the exposed locations are selectively and totally converted to MoS₂ using pulsed laser vaporization of sulfur to form MoSe₂/MoS₂ heterojunctions in predefined patterns. The junctions and conversion process are studied by Raman and photoluminescence spectroscopy, atomically resolved scanning transmission electron microscopy and device characterization. This demonstration of lateral heterojunction arrays within a monolayer crystal is an essential step for the integration of two-dimensional semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin devices.

Modern three-dimensional nanofabrication requires both additive and subtractive processes. However, both processes are largely isolated and generally regarded as incompatible with each other. In this study, we developed simultaneous additive and subtractive fabrication processes using two-photon polymerization followed by femtosecond (fs) laser multiphoton ablation. To demonstrate the new capability, submicrometer polymer fibers containing periodic holes of 500-nm diameter and microfluidic channels of 1-µm diameter were successfully fabricated. This method combining both two-photon polymerization and fs laser ablation improves the nanofabrication efficiency and enables the fabrication of complex three-dimensional micro-/nanostructures, promising for a wide range of applications in integrated optics, microfluidics and microelectromechanical systems.