In situ regrowth and purification of crystalline thin films
View Patent ↗Amorphous or polycrystalline films have been recrystallized into single-crystal thin films (of micrometer thickness) by a zone melting technique, in which an electrically heated wire generated a narrow heated or molten zone (0.5-2 mm wide) on the substrate sandwiched between two pieces of glass or indium-tin-oxide-coated glass. The substrate can be either an organic or inorganic compound. When the molten zone was moved slowly (3-120 μm/min) across the layer from one end of the cell to the other, a single-crystal film was produced after a single pass. This technique allows for thin film purification and an improvement in electronic, optical, and optoelectronic properties of the thin film. After this treatment, the steady-state short-circuit photocurrent can be improved by several orders of magnitude. These films are useful in the fields of optics and electronics for improving the performance in devices such as thin-film transistors and organic light-emitting diodes.
1. A method for treating a single material or amorphous thin film comprising:
(a) providing a substrate coated with a single material or amorphous thin film;
(b) positioning said substrate proximal to a heat source at a distance and for a time sufficient to form a heating zone in said film, wherein said heat zone is below the decomposition temperature of said film; and
(c) moving said substrate relative to said heater source at a speed sufficient to permit formation of a heating zone in said thin film proximal to said heat source.
2. The method of claim 1 , wherein said thin film comprises an organic compound.
3. The method of claim 1 , wherein said thin film comprises an inorganic compound.
4. The method of claim 1 , wherein said substrate is passed proximal to said heat source twice.
5. The method of claim 1 , wherein said substrate is passed proximal to said heat source three times.
6. The method of claim 1 , wherein said substrate is passed proximal to said heat source four times.
7. The method of claim 1 , wherein said substrate is passed proximal to said heat source multiple times.
8. The method of claim 7 , wherein at least two different speeds are used for different passes.
9. The method of claim 1 , wherein the film is melted by said heat source.
10. A crystalline thin film produced by a method comprising:
(a) providing a substrate coated with a single material or amorphous thin film;
(b) positioning said substrate proximal to a heat source at a distance and for a time sufficient to form a heating zone in said film, wherein said heat zone is below the decomposition temperature of said film; and
(c) moving said substrate relative to said heater source at a speed sufficient to permit formation of a heating zone in said thin film proximal to said heat source.
11. A method for producing an organic crystalline thin film comprising:
(a) providing an organic compound in a sample holder, said organic compound being provided in the form of a single material or amorphous thin film;
(b) positioning said sample holder proximal to a heat source at a distance and for a time sufficient to form a molten zone in said organic compound proximal to said heater source; and
(c) moving said sample holder relative to said heater source at a speed sufficient to permit formation of a molten zone in said organic compound proximal to said heat source,
wherein said organic compound forms an organic single-crystal thin film after exposure to said heat source.
12. The method of claim 11 wherein said sample holder comprises two parallel flat surfaces.
13. The method of claim 12 , wherein said flat surfaces are glass.
14. The method of claim 13 , wherein said glass is coated with indium-tin-oxide.
15. The method of claim 12 , wherein said parallel flat surfaces are separated by about 0.1 μm to about 50 μm.
16. The method of claim 15 , wherein said parallel flat surfaces are separated by about 1.5 μm to about 2.5 μm.
17. The method of claim 10 , wherein said crystalline thin film has an enhanced steady-state short-circuit photocurrent as compared to the corresponding amorphous thin film.
18. The method of claim 17 , wherein the enhancement is an order of magnitude.
19. The method of claim 18 , where in the enhancement is two orders of magnitude.
20. The method of claim 19 , where in the enhancement is three orders of magnitude.
21. The method of claim 11 , wherein said organic single-crystal thin film contains fewer impurities than said organic compound of step (a).
22. The method of claim 11 wherein said speed is about 3 μm/min to about 120 μm/min relative to said heating source.
23. The method of claim 11 , wherein said heating source is a wire.
24. The method of claim 23 , wherein said wire is in a linear configuration.
25. The method of claim 23 , wherein said wire is about 10 μm to about 3.0 mm in diameter.
26. The method of claim 25 , wherein said wire is about 50 μm to about 2.0 mm in diameter.
27. The method of claim 23 , wherein said wire is platinum.
28. The method of claim 23 , wherein said wire is nichrome.
29. The method of claim 23 , wherein said wire is heated electrically.
30. The method of claim 23 , wherein said wire is tightened after initiation of heating.
31. The method of claim 11 , wherein said molten zone is about 0.5 mm to about 2.0 mm wide.
32. The method of claim 11 , wherein said organic compound is a porphoryin.
33. The method of claim 32 , wherein said organic compound is 1,4-bis(butylamino)-9,10-anthraquinone.
34. The method of claim 32 , wherein said organic compound is zinc(II)meso-5,10,15,20-tetrakis-n-(undecyl)porphyrin.
35. The method of claim 32 , wherein said organic compound is zinc(II)2,3,7,8,12,13,17,18-octa-n-decylporphorin.
36. The method of claim 11 , wherein said sample holder is passed proximal to said heat source twice.
37. The method of claim 11 , wherein said sample holder is passed proximal to said heat source three times.
38. The method of claim 11 , wherein said sample holder is passed proximal to said heat source four times.
39. The method of claim 11 , wherein said sample holder is passed proximal to said heat source multiple times.
40. The method of claim 39 , wherein at least two different speeds are used for different passes.
41. The method of claim 11 , wherein said thin film is prepared by evaporation onto a surface.
42. The method of claim 11 , wherein said thin film is prepared by capillary filling.
43. The method of claim 11 , wherein said thin film is prepared by deposition onto a surface.
44. The method of claim 11 , wherein said thin film is prepared by spin coating.
45. An organic crystalline thin film produced by a method comprising, said organic compound being provided in the form of a single material or amorphous thin film:
(a) providing an organic compound in a sample holder;
(b) positioning said sample holder proximal to a heat source at a distance and for a time sufficient to form a molten zone in said organic compound proximal to said heater source; and
(c) moving said sample holder relative to said heater source at a speed sufficient to permit formation of a molten zone in said organic compound proximal to said heat source.