Process for producing a crystalline layer
A method for manufacturing a crystal layer includes using a substrate having a surface film made of a dichalcogenide of a transition metal, designated MX 2 , where “M” denotes a transition metal and “X” denotes a chalcogen, the surface film including a set of monolayers bonded together by van der Waals bonds; forming a polycrystalline aluminium nitride AlN film, having grain boundaries, on the surface film; and diffusing metal elements into the surface film, through the grain boundaries of the polycrystalline aluminium nitride AlN film, the metal elements being chosen to react chemically with MX 2 by a redox reaction so as to convert the van der Waals bonds into covalent bonds. A crystalline layer is formed on the polycrystalline aluminium nitride AlN film after the diffusing.
1 . A method for manufacturing a crystalline layer, comprising:
a) using a substrate comprising a surface film made of a dichalcogenide of a transition metal, designated MX 2 , where “M” denotes a transition metal and “X” denotes a chalcogen, the surface film comprising a set of monolayers bonded together by van der Waals bonds;
b) forming a polycrystalline aluminium nitride AlN film, having grain boundaries on the surface film;
c) diffusing metal elements into the surface film, through the grain boundaries of the polycrystalline aluminium nitride AlN film, the metal elements being chosen to react chemically with MX 2 by a redox reaction so as to convert the van der Waals bonds into covalent bonds; and
d) forming a crystalline layer on the polycrystalline aluminium nitride AlN film after stage c).
2 . The method according to claim 1 , wherein c) is preceded by exposing the metal elements on the polycrystalline aluminium nitride AlN film.
3 . The method according to claim 1 , wherein c) is preceded by forming a material, comprising the metal elements, on the polycrystalline aluminium nitride AlN film.
4 . The method according to claim 3 , d) is preceded by removing residues of the material which are formed on the polycrystalline aluminium nitride AlN film, after the diffusion of the metal elements into the surface film on conclusion of c).
5 . The method according to claim 1 , wherein the metal elements diffused during c) are atoms chosen as a reducing agent for the MX 2 .
6 . The method according to claim 1 , wherein a) is carried out so that MX 2 is chosen to have a crystal lattice mismatch with the polycrystalline aluminium nitride AlN of less than or equal to 1.5%.
7 . The method according to claim 6 , wherein a) is carried out so that MX 2 is chosen from molybdenum disulfide MoS 2 , tungsten disulfide WS 2 or vanadium disulfide VS 2 .
8 . The method according to claim 7 , wherein a) is carried out so that MX 2 is molybdenum disulfide MoS 2 ; the method further comprising:
the metal elements diffused during c) are atoms chosen as a reducing agent for molybdenum disulfide MoS 2 , the atoms being chosen from gallium Ga, aluminium Al or manganese Mn.
9 . The method according to claim 1 , wherein d) is carried out so that the crystalline layer is made of a crystalline material having a crystal lattice mismatch with the polycrystalline aluminium nitride AlN of less than or equal to 1.5%.
10 . The method according to claim 1 , wherein d) is carried out so that the crystalline layer is made of a crystalline material chosen from silicon carbide SiC and an alloy of III-N type.
11 . The method according to claim 10 , in which the alloy of III-N type is chosen from aluminium nitride AlN, gallium nitride GaN or aluminium-gallium nitride AlGaN.
12 . The method according to claim 1 , wherein b) is carried out so that the polycrystalline aluminium nitride AlN film exhibits a thickness of less than or equal to 5 nm.
13 . The method according to claim 1 , wherein d) is carried out so that the crystalline layer exhibits a thickness of greater than or equal to 200 nm.