Monolayer films of semiconducting metal dichalcogenides, methods of making same, and uses of same
Metal-chalcogenide films disposed on a substrate comprising at least one monolayer (e.g., 1 to 10 monolayers) of a metal-chalcogenide. The films can be continuous (e.g., structurally and/or electrically continuous) over 80% or greater of the substrate that is covered by the film. The films can be made by methods based on low metal precursor concentration relative to the concentration of chalcogenide precursor. The methods can be carried out at low water concentration. The films can be used in devices (e.g., electrical devices and electronic devices).
1. A method of making a metal-chalcogenide film on a substrate, the film comprising 1 to 10 monolayers of the metal-chalcogenide comprising:
contacting a metal precursor, a chalcogenide precursor, a reducing gas, and a substrate in a reactor such that the metal-chalcogenide film is formed,
wherein the metal precursor and the metal chalcogenide precursor are each present in a gas phase and the metal precursor is present at a pressure of 1×10 −2 Torr or less and the chalcogenide precursor is present at a pressure of 1×10 −1 Torr or less, wherein the contacting is carried out in the presence of a desiccant.
2. The method of claim 1 , wherein the contacting is carried out at a water concentration of less than 1×10 −2 Torr.
3. The method of claim 1 , wherein the metal precursor has a concentration lower than a concentration of the chalcogenide precursor.
4. The method of claim 1 , wherein partial pressures of the metal precursor and the chalcogenide precursor are controlled such that grains of a first monolayer are connected laterally until the first monolayer is formed across about 80% or greater of the substrate covered by the film.
5. The method of claim 4 , further comprising forming a second monolayer on the first monolayer after the first monolayer is formed on about 80% or greater of the substrate covered by the film.
6. The method of claim 5 , wherein the second monolayer is formed on the first monolayer after the first monolayer is formed on about 95% or greater of the substrate covered by the film.
7. The method of claim 1 , wherein the desiccant is a salt.
8. The method of claim 7 , wherein the salt is NaCl, KCl, or NaBr.
9. A method of making a metal-chalcogenide film on a substrate, the film comprising 1 to 10 monolayers of the metal-chalcogenide comprising:
contacting a metal precursor, a chalcogenide precursor, a reducing gas, and a substrate in a reactor such that the metal-chalcogenide film is formed,
wherein the metal precursor is present in a gas phase and the metal precursor is present at a pressure of 1×10 −2 Torr or less,
wherein the contacting is carried out in the presence of a desiccant.
10. The method of claim 9 , wherein the contacting is carried out at a water concentration of less than 1×10 −2 Torr.
11. The method of claim 9 , wherein the metal precursor has a concentration lower than a concentration of the chalcogenide precursor.
12. The method of claim 9 , wherein partial pressures of the metal precursor and the chalcogenide precursor are controlled such that grains of a first monolayer are connected laterally until the first monolayer is formed across about 80% or greater of the substrate covered by the film.
13. The method of claim 12 , further comprising forming a second monolayer on the first monolayer after the first monolayer is formed on about 80% or greater of the substrate covered by the film.
14. The method of claim 13 , wherein the second monolayer is formed on the first monolayer after the first monolayer is formed on about 95% or greater of the substrate covered by the film.
15. The method of claim 9 , wherein the desiccant is a salt.
16. The method of claim 15 , wherein the salt is NaCl, KCl, or NaBr.