Methods for low-temperature p-CVD and thermal ALD of magnesium diboride
ALD and p-CVD methods to generate MgB 2 and MgB 2 -containing films in the growth temperature range of 250-300° C. The thermal ALD and p-CVD methods shown herein ensure that the high-temperature-induced roughening, which causes high surface resistances in MgB 2 coatings grown by the mentioned conventional techniques, is avoided. The MgB 2 and MgB 2 -containing films exhibit superconductive properties at above 20° K.
1. A method for forming a MgB 2 containing film comprising:
depositing a coating on a substrate via layer atomic layer deposition by X, where X is greater than 0, cycles of the steps of:
pulsing, for 0.75 to 5 seconds, a first precursor comprising Bis(cyclopentadienyl) Magnesium (II) (Mg(Cp) 2 ) at a first deposition temperature;
purging, 10 to 30 seconds, the first precursor;
pulsing, for 0.5 to 5 seconds, a second precursor comprising an oxidizer of the first precursor at a second deposition temperature;
purging , for 10 to 30 seconds, the second precursor; and
pulsing, for 0. 5 to 1 seconds, a third precursor comprising Trimethyl borate (B(OCH 3 ) 3 ) at a third deposition temperature, and
annealing, at a temperature below 450° C. the deposited coating in a reducing environment to remove oxygen from the film.
2. The method of claim 1 , wherein purging the first precursor and purging the second precursor both comprise ultra high purity nitrogen exposure.
3. The method of claim 1 , wherein the first precursor is pulsed via a carrier gas passed through a bubbler comprising liquid (Mg(Cp) 2 ).
4. The method of claim 1 , wherein the liquid (Mg(Cp) 2 is at a temperature of at least 70° C.
5. The method of claim 1 , wherein the liquid (Mg(Cp) 2 is at a temperature of about least 80° C.
6. The method of claim 1 , wherein the first reaction temperature, the second reaction temperature, and the third reaction temperature are from 125° C. to 250° C.
7. The method of claim 1 , wherein the annealing is in a 100% hydrogen plasma environment for 1 hour.
8. The method of claim 1 wherein the MgB 2 containing film comprises MgB 2 and B x Mg 1-x O.
9. A method for forming a MgB 2 -containing film comprising:
depositing a coating on a substrate via layer chemical vapor deposition by the steps of:
reacting decomposing, at a reaction temperature of 250° C. to 290° C., a vaporous first precursor pulse of at least 1 second comprising (Mg(H 3 BNMe 2 BH 3 ) 2 ), forming a solid MgB) 2 ,film on the substrate; and
applying a purge by a pulse of at least 15 seconds with ultra-high purity inert gas, removing the first precursor.
10. The method of claim 9 , wherein the chemical vapor deposition is pulsed chemical vapor deposition comprising a plurality of cycles, each cycle comprising pulsing of the vaporous precursor followed by application of the purge with ultra-high purity inert gas.
11. The method of claim 10 , wherein the MgB 2 -containing film is superconductive at temperatures above 20° K.
12. The method of claim 10 , wherein the MgB 2 -containing film has no more than 5-10 atomic % impurity.
13. The method of claim 9 , wherein the vaporous first precursor is formed by pulsing a carrier gas passed through a bubbler comprising liquid (Mg(H 3 BNMe 2 BH 3 ) 2 ) or Mg(DMADB) 2 ).
14. The method of claim 13 , wherein the liquid is at a temperature between 25° C. and 45° C.