Method of forming a crystalline thin film having the formula MY

1. A method of preparing, by atomic layer deposition (ALD), a crystalline thin film having a formula of MY 2 and having a crystal structure that is suitable for electronic applications, the method comprising:

a first step of preparing an amorphous film having a formula of MY x by atomic layer deposition on a surface of a substrate from at least one precursor of a metal M and at least one precursor of an element Y,

wherein x is in a range of 1.5 to 3.1,

wherein M is tungsten or molybdenum or a mixture thereof,

wherein a degree of oxidation of metal M in the at least one precursor of metal M is in the range from 3 to 6,

wherein the metal of the precursor of metal M has bonds consisting of single or multiple bonds M-Z and/or M-M, wherein Z=C, N or H,

wherein Y is sulfur, selenium, or a mixture thereof,

wherein the precursors of metal M and of element Y are halogen free, and

wherein the first step of preparing the amorphous film having the formula MY x comprises the steps of

a) introducing, by a single pulse, a first precursor of metal M or of element Y into a deposition chamber of an ALD reactor,

b) purging the deposition chamber with an inert gas,

c) introducing, by a single pulse, a second precursor into the deposition chamber, the second precursor being a precursor of metal M when the first precursor is a precursor of element Y, or a precursor of element Y when the first precursor is a precursor of metal M,

d) purging the deposition chamber with an inert gas,

e) repeating steps a) to d), wherein a substrate temperature is lower than or equal to 350° C. during steps a) to d) to avoid the formation of crystals that are randomly oriented with respect to the substrate, and

f) obtaining the amorphous film having the formula MY x ; and

a second step of annealing the amorphous film having the formula MY x to provide the crystalline film having crystal lattices whose basal planes are stacked in planes parallel to the surface of the substrate on which the crystalline film is formed, so that the crystalline film has a crystal structure suitable for electronic applications.

2. The method of claim 1 , wherein the atomic layer deposition comprises introducing into the deposition chamber the precursor of metal M, and then introducing the precursor of element Y, or introducing into the deposition chamber the precursor of element Y, and then introducing the precursor of metal M.

3. The method of claim 1 , wherein the substrate temperature is in a range from 0 to 350° C.

4. The method of claim 1 , wherein the substrate temperature does not change during steps a) to e).

5. The method of claim 1 , wherein the precursor of metal M is selected from the group consisting of Mo(NMe 2 ) 4 , M(=N—CMe 3 ) 2 (NMe 2 ) 2 , Mo(NEtMe) 4 , Mo(NEt 2 ) 4 , and M 2 (NMe 2 ) 6 , wherein M=molybdenum or tungsten, Me=—CH 3 , and Et=—CH 2 —CH 3 .

6. The method of claim 1 , wherein the precursor of element Y is selected from the group consisting of YR 2 , Y 2 R, Y 2 R 2 , Y 3 R 2 , and Y 2 R 3 , wherein R=H and/or alkyl and/or allyl and/or aryl, and wherein R=C for Y 2 R.

7. The method of claim 1 , wherein the precursor of element Y is selected from the group consisting of H 2 Y, 1,2-ethanedithiol, and a H 2 /Y 2 R 2 mixture, wherein R=H and/or alkyl and/or allyl and/or aryl.

8. The method of claim 1 , wherein a protective layer is deposited onto the amorphous film MY x after the first step but before the second step, or after the second step.

9. The method of claim 1 , wherein a pre-annealing stage is carried out after the first step but before the second step.

10. The method of claim 1 , wherein a pre-annealing stage is carried out after the first step but before the second step, and

wherein a protective layer is deposited onto the amorphous film MY x after the pre-annealing stage but before the second step.

11. The method of claim 1 , wherein an anneal temperature is 350° C. or more.

12. The method of claim 1 , wherein the surface of the substrate having the crystalline thin film deposited thereon is made of a material selected from the group consisting of a metal, a semiconductor, an inorganic oxide, an inorganic sulfide, and an inorganic selenide.

13. The method of claim 1 , wherein the amorphous film having the formula MY x has a thickness of less than 100 nanometers.

14. The method of claim 1 , wherein the precursor of metal M is selected from the group consisting of Mo(NMe 2 ) 4 , M(=N—CMe 3 ) 2 (NMe 2 ) 2 , Mo(NEtMe) 4 , Mo(NEt 2 ) 4 , and M 2 (NMe 2 ) 6 , wherein M=molybdenum or tungsten, Me=—CH 3 , and Et=—CH 2 —CH 3 , and

wherein the precursor of element Y is selected from the group consisting of YR 2 , Y 2 R, Y 2 R 2 , Y 3 R 2 , and Y 2 R 3 , wherein R=H and/or alkyl and/or allyl and/or aryl, and wherein R=C for Y 2 R.

15. The method of claim 1 , wherein the annealing step is carried out under an inert atmosphere.

16. The method of claim 1 , wherein, before the first step, the surface of the substrate has —OH groups.

17. The method of claim 1 , wherein the precursor of metal M is free of cyclopentadienyl ligand.

18. The method of claim 1 , wherein the precursor of metal M is M(=N—CMe 3 ) 2 (NMe 2 ) 2 or Mo(NEtMe) 4 , wherein M=molybdenum or tungsten, Me=—CH 3 , and Et=—CH 2 —CH 3 .

19. A method of preparing, by atomic layer deposition (ALD), a crystalline thin film having a formula of MY 2 , the method comprising:

a first step of preparing an amorphous film having a formula MY x by ALD on a surface of a substrate from at least one precursor of a metal M and at least one precursor of an element Y,

wherein x is in a range of 1.5 to 3.1,

wherein M is tungsten, molybdenum or a mixture thereof,

wherein a degree of oxidation of metal M in the at least one precursor of metal M is in a range of 3 to 6,

wherein the metal of the precursor of metal M exclusively has bonds selected from the group consisting of metal nitrogen single bonds, metal nitrogen double bonds, and mixtures thereof,

wherein Y is sulfur, selenium or a mixture thereof,

wherein the precursors of metal M and of element Y are halogen free, and

wherein the first step of preparing the amorphous film having the formula MY x comprises the steps of

a) introducing, by a single pulse, a first precursor of metal M or element Y into a deposition chamber of an ALD reactor,

b) purging the deposition chamber with an inert gas,

c) introducing, by a single pulse, a second precursor into the deposition chamber, the second precursor being a precursor of metal M when the first precursor is a precursor of element Y, or a precursor of element Y when the first precursor is a precursor of metal M,

d) purging the deposition chamber with an inert gas,

e) repeating steps a) to d) in order to obtain the amorphous film having the formula MY x , wherein a substrate temperature is lower than or equal to 350° C. during steps a) to d) to avoid the formation of crystals that are randomly oriented with respect to the substrate, and

f) obtaining the amorphous film having the formula MY x ; and

a second step of annealing the amorphous film having the formula MY x to provide a crystalline film having crystal lattices whose basal planes are stacked in planes parallel to the surface of the substrate on which the crystalline film is formed, so that the crystalline film has a crystal structure suitable for electronic applications.

20. The method of claim 19 , wherein the element Y consists of selenium.

21. A method of preparing, by atomic layer deposition (ALD), a crystalline thin film having a formula of MY 2 , the method comprising:

a first step of preparing an amorphous film having a formula MY x by ALD on a surface of a substrate from at least one precursor of a metal M and at least one precursor of an element Y,

wherein x is in a range of 1.5 to 3.1,

wherein M is tungsten, molybdenum or a mixture thereof,

wherein a degree of oxidation of metal M in the at least one precursor of metal M is in a range of 3 to 6,

wherein the metal M of the precursor of metal M has bonds consisting of single or multiple bonds M-Z and/or M-M, wherein Z=C, N or H,

wherein Y is selenium,

wherein the precursors of metal M and of element Y are halogen free, and

wherein the first step of preparing the amorphous film having the formula MY x comprises the steps of

a) introducing, by a single pulse, a first precursor of metal M or of element Y into a deposition chamber of an ALD reactor,

b) purging the deposition chamber with an inert gas,

c) introducing, by a single pulse, a second precursor into the deposition chamber, the second precursor being a precursor of metal M when the first precursor is a precursor of element Y, or a precursor of element Y when the first precursor is a precursor of metal M,

d) purging the deposition chamber with an inert gas,

e) repeating steps a) to d) in order to provide the amorphous film having the formula MY x , wherein a substrate temperature is lower than or equal to 350° C. during steps a) to d) to avoid the formation of crystals that are randomly oriented with respect to the substrate, and

f) obtaining the amorphous film having the formula MY x ; and

a second step of annealing the amorphous film having the formula MY x to provide the crystalline film having the formula MY 2 , wherein the crystalline film has crystal lattices whose basal planes are stacked in planes parallel to the surface of the substrate on which the crystalline film is formed, so that the crystalline film has a crystal structure suitable for electronic applications.