Conventional vapour deposition or epitaxial growth of two-dimensional (2D) materials and heterostructures is conducted in a large chamber in which masses transport from the source to the substrate. Here we report a chamber-free, on-chip approach for growing 2D crystalline structures directly in a nanoscale surface-confined 2D space. The method is based on the surprising discovery of the rapid, long-distance, non-Fickian transport of a uniform layer of atomically thin palladium on a monolayer crystal of tungsten ditelluride at temperatures well below the known melting points of all the materials involved. The nanoconfined growth realizes the controlled formation of a stable 2D crystalline material, Pd₇WTe₂, when the monolayer seed is either free-standing or fully encapsulated in a van der Waals stack. The approach is generalizable and compatible with nanodevice fabrication, promising to greatly expand the library of 2D materials and their functionalities.

二维 (2D) 材料和异质结构的传统气相沉积或外延生长是在大室中进行的，其中质量从源传输到基板。在这里，我们报告了一种无室、片上方法，用于直接在纳米级表面限制的 2D 空间中生长 2D 晶体结构。该方法基于以下令人惊讶的发现：在远低于所有相关材料的已知熔点的温度下，二碲化钨单层晶体上的均匀原子薄钯层可以快速、长距离、非菲克传输。当单层种子独立或完全封装在范德华堆叠中时，纳米限制生长实现了稳定的二维晶体材料 Pd ₇ WTe _{2的受控形成。}该方法具有通用性，并且与纳米器件制造兼容，有望大大扩展二维材料库及其功能。