▎ 摘　　要

NOVELTY - A single crystal metal layer is produced by providing a metal source material (5); providing a single crystal deposition substrate (9) having a selected crystallographic orientation; arranging the metal source material and the deposition substrate in a closely-spaced relationship; and heating the metal source material and deposition substrate under vacuum to cause sublimation of the metal source material and heteroepitaxial deposition of sublimed metal atoms onto the deposition substrate, to form a single crystal metal layer on the deposition substrate. USE - Production of single crystal metal layer used as a catalyst layer in a process of 2D material growth (all claimed). ADVANTAGE - The use of 'close-space' sublimation allows for the production of a single crystal epitaxial metal layer to be formed on the deposition substrate within a fast process time, with the resulting layer being of high quality, in particular with respect to surface roughness and defect density of the layer. The method allows for the cost-efficient preparation of different single crystal film orientations and offers versatility to be expanded to a wide selection of materials. The method can be performed in a conventional CVD reactor, which allows for subsequent CVD processes utilizing the resulting single crystal layer to be performed without the need to transfer the single crystal metal layer between separate pieces of apparatus. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (1) production of a 2D material which involves producing single crystal metal layer and heating the deposition substrate (9) and single crystal metal layer in a selected gaseous atmosphere at a predetermined temperature Tgrowth to provide growth of the 2D material on the single crystal metal layer; and (2) single crystal metal layer comprising as-grown surface roughness value Ra of less than or equal to 5 nm. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic side-view of the deposition apparatus. First heater (1) Second heater (3) Metal source material (5) Deposition substrate (9) Deposition apparatus (100)