Wafer-scale synthesis of large-area black phosphorus material heterostructures
A scalable approach for the synthesis of black phosphorus (BP) material thin films over large areas is described. A red phosphorus (RP) material thin film may be deposited on a substrate followed by conversion to a BP material thin film using high-pressure alone or high pressure and high temperature. A thin-film of dielectric material such as hexagonal boron nitride (hBN) can be formed on a RP material film before the conversion is performed to improve the crystalline quality and stability of the converted BP material. Surprisingly, an atomically sharp and defect-free interface can be formed between the converted BP material and hBN. The BP material has high crystalline uniformity and can be used to fabricate thin-film transistors and optoelectronic devices such as infrared photodetectors.
1. A wafer comprising:
a substrate;
a layer of crystalline black phosphorous material formed over a first area of the substrate; and
a layer of dielectric material formed over the black phosphorous material in the first area, wherein a first interface between the black phosphorous material and the dielectric material extending for as much as one micron across the first area has fewer than 5 stacking faults in the black phosphorous material, wherein the layer of black phosphorous material covers at least 75% of a surface of the substrate.
2. The wafer of claim 1 , wherein the layer of black phosphorous material has regions of continuous coverage as large as 600 microns across a surface of the substrate.
3. The wafer of claim 1 , wherein the first area comprises a single crystal grain and has a minimum span across a surface of the substrate of 2 microns.
4. The wafer of claim 1 , wherein the first area comprises a single crystal grain and has a span across a surface of the substrate as large as 100 microns.
5. The wafer of claim 1 , wherein the dielectric material comprises hexagonal boron nitride or silicon nitride.
6. The wafer of claim 5 , wherein the black phosphorus material is uniformly crystalline throughout its thickness.
7. The wafer of claim 1 , wherein the dielectric material comprises aluminum oxide or hafnium oxide.
8. The wafer of claim 1 , wherein the black phosphorous material is uniformly crystalline from the first interface to a second interface between the crystalline black phosphorous material and the substrate.
9. The wafer of claim 8 , wherein a thickness of the black phosphorous material is between two atomic layers and 100 nanometers.
10. The wafer of claim 8 , wherein the first area comprises a single crystal grain and has a minimum span across a surface of the substrate of 2 microns.
11. The wafer of claim 10 , wherein a defect density in atomic layers of the black phosphorous material is between 10 cm −2 and 100 cm −2 .
12. The wafer of claim 1 , wherein the black phosphorous material exhibits electron or hole mobilities as much as 170 cm 2 V 4 s −1 .
13. The wafer of claim 1 , further comprising:
a drain electrode formed in electrical contact with the black phosphorous material at a first location within the first area;
a source electrode formed in electrical contact with the black phosphorous material at a second location within the first area; and
a gate electrode formed between the drain electrode and the source electrode for controlling current flow between the drain electrode and the source electrode.
14. The wafer of claim 1 , wherein the layer of black phosphorous material exhibits electron and hole mobilities between 100 cm 2 V −1 s −1 and 10,000 cm 2 V −1 s −1 .
15. The wafer of claim 1 , further comprising at least one additional layer of dielectric material or black phosphorous material formed over the first area to form a heterostructure stack of at least three layers.
16. The wafer of claim 15 , wherein the heterostructure stack comprises hBN/BP/hBN where hBN represents a film of hexagonal boron nitride and BP represents a film of black phosphorus material.
17. A wafer comprising:
a substrate;
a layer of crystalline black phosphorous material formed over a first area of the substrate; and
a layer of dielectric material formed over the black phosphorous material in the first area, wherein a first interface between the black phosphorous material and the dielectric material extending for as much as one micron across the first area has fewer than 5 stacking faults in the black phosphorus material, wherein the first area comprises a single crystal grain and has a span across a surface of the substrate as large as 100 microns.
18. The wafer of claim 17 , wherein the dielectric material comprises hexagonal boron nitride or silicon nitride.
19. The wafer of claim 17 , wherein a thickness of the black phosphorous material is between two atomic layers and 100 nanometers.
20. The wafer of claim 17 , further comprising at least one additional layer of dielectric material or black phosphorous material formed over the first area to form a heterostructure stack of at least three layers.
21. A wafer comprising:
a substrate;
a first layer of crystalline black phosphorous material formed over a first area of the substrate;
a layer of first dielectric material formed over the black phosphorous material in the first area, wherein a first interface between the black phosphorous material and the first dielectric material extending for as much as one micron across the first area has fewer than 5 stacking faults in the black phosphorus material; and
at least one additional layer of dielectric material or black phosphorous material formed over the first area to form a heterostructure stack of at least three layers.
22. The wafer of claim 21 , wherein the first dielectric material comprises hexagonal boron nitride or silicon nitride.
23. The wafer of claim 21 , wherein the first layer of black phosphorous material has regions of continuous coverage as large as 600 microns across a surface of the substrate.
24. The wafer of claim 23 , wherein a thickness of the black phosphorous material is between two atomic layers and 100 nanometers.
25. The wafer of claim 21 , wherein the first layer of black phosphorous material exhibits electron and hole mobilities between 100 cm 2 V −1 s −1 and 10,000 cm 2 V −1 s −1 .