Direct formation of hexagonal boron nitride on silicon based dielectrics
A scalable process for fabricating graphene/hexagonal boron nitride (h-BN) heterostructures is disclosed herein. The process includes (BN) X H y -radical interfacing with active sites on silicon nitride coated silicon (Si 3 N 4 /Si) surfaces for nucleation and growth of large-area, uniform and ultrathin h-BN directly on Si 3 N 4 /Si substrates (B/N atomic ratio=1:1.11±0.09). Further, monolayer graphene van der Waals bonded with the produced h-BN surface benefits from h-BN's reduced roughness (3.4 times) in comparison to Si 3 N 4 /Si. Because the reduced surface roughness leads to reduction in surface roughness scattering and charge impurity scattering, therefore an enhanced intrinsic charge carrier mobility (3 folds) for graphene on h-BN/Si 3 N 4 /Si is found.
1. A multilayer structure comprising:
a single crystal semiconductor wafer comprising two major, generally parallel surfaces, one of which is a front surface of the single crystal semiconductor wafer and the other of which is a back surface of the single crystal semiconductor wafer, a circumferential edge joining the front and back surfaces of the single crystal semiconductor wafer, a central plane between the front surface and the back surface of the single crystal semiconductor wafer, and a bulk region between the front and back surfaces of the single crystal semiconductor wafer;
a layer comprising N-terminated (100) silicon nitride in interfacial contact with the front surface of the single crystal semiconductor wafer;
a layer comprising hexagonal boron nitride in interfacial contact with the layer comprising silicon nitride; and
a layer comprising graphene in interfacial contact with the layer comprising hexagonal boron nitride, the layer comprising graphene characterized by a ratio I 2D /I G of at least about 3, wherein I G is a full-width at half maxima of G-band, I 2D is a full-width at half maxima of 2D-band position, and the ratio of the intensities of the 2D and G bands (I 2D /I G ) is determined via confocal Raman spectroscopy.
2. The multilayer structure of claim 1 wherein the single crystal semiconductor wafer comprises a material selected from the group consisting of silicon, silicon carbide, silicon germanium, gallium arsenide, gallium nitride, indium phosphide, indium gallium arsenide, germanium, and combinations thereof.
3. The multilayer structure of claim 1 wherein the single crystal semiconductor wafer comprises silicon.
4. The multilayer structure of claim 1 wherein the layer comprising N-terminated (100) silicon nitride is neutrally charged.
5. The multilayer structure of claim 1 wherein the hexagonal boron nitride has a molar ratio of B:N is between about 1.3:1 and 1:1.3.
6. The multilayer structure of claim 1 wherein the hexagonal boron nitride has an atomic concentration ratio of nitrogen and boron is 1:1.11±0.09.
7. The multilayer structure of claim 1 wherein the layer comprising graphene has a field effect mobility from about 500 cm 2 V −1 s −1 to about 1300 cm 2 V −1 s −1 .
8. The multilayer structure of claim 1 wherein the layer comprising graphene has an intrinsic charge carrier mobility of at least about 1200 cm 2 /Vs.
9. The multilayer structure of claim 1 further comprising a metal film in interfacial contact with the layer comprising graphene.
10. The multilayer structure of claim 9 wherein the metal film comprises a metal selected from the group consisting of nickel, copper, iron, platinum, palladium, ruthenium, aluminum, cobalt and alloys thereof.
11. The multilayer structure of claim 9 wherein the metal film comprises nickel, cobalt, or nickel and cobalt.
12. The multilayer structure of claim 9 wherein the metal film comprises copper.
13. The multilayer structure of claim 1 , wherein the layer comprising hexagonal boron nitride is prepared by a process comprising:
contacting a front surface of the layer comprising silicon nitride with (i) a boron-containing gas or a boron-containing vapor and (ii) a nitrogen-containing gas or nitrogen-containing vapor at a temperature sufficient to directly deposit the layer comprising hexagonal boron nitride in interfacial contact with the front surface of the layer comprising silicon nitride.