Solid precursor feed system for thin film depositions
A dry powder MOCVD vapor source system is disclosed that utilizes a gravimetric powder feeder, a feed rate measurement and feeder control system, an evaporator and a load lock system for continuous operation for thin film production, particularly of REBCO type high temperature superconductor (HTS) tapes.
1. A method for manufacturing a high temperature superconductor, the method comprising:
providing a vapor deposition reactor comprising a reactor deposition chamber operating under vacuum conditions and configured for depositing a high-temperature superconductor thin film;
loading an initial charge of precursor powder to a powder vessel maintained under vacuum and coupled to a scale and a mechanically driven powder feeder, wherein the scale is configured to provide continuous mass data of precursor powder in the powder vessel;
coupling a load lock assembly to the powder vessel, wherein the load lock assembly is located outside the powder vessel and comprises a pressure isolated chamber for reloading the powder vessel, wherein a plurality of gas control valves and a gate valve pressure isolate the load lock assembly from the powder vessel, and a flow control orifice to equalize pressure between the load lock assembly and powder vessel;
coupling an evaporator in between the powder feeder and the reactor deposition chamber;
introducing a substrate to the reactor deposition chamber;
monitoring the precursor powder vessel weight in the powder vessel;
controlling the powder feeder based upon the powder vessel weight in order to provide a target precursor powder feed rate to the evaporator;
evaporating the precursor powder and transporting the evaporated precursor into the reactor for deposition as a thin film upon the substrate; and
recharging the powder vessel with powder precursor via the load lock assembly while the reactor operates continuously under vacuum.
2. The method of claim 1 , wherein the reactor is a Photo-Assisted Metal Organic Chemical Vapor Deposition (PAMOCVD) reactor.
3. The method of claim 1 , wherein the powder feeder is a feed screw.
4. The method of claim 1 , wherein the deposited thin film has a growth rate of 1.0 μm/min or greater.
5. The method of claim 1 , wherein the superconductor layer further comprises a lift factor at 4K, 20 T (Ic (4K, 20 T)/Ic (77K, self-field)) of 2 or greater.
6. The method of claim 1 , wherein the superconductor layer further comprises a lift factor at 4K, 20 T (Ic (4K, 20 T)/Ic (77K, self-field)) of 3 or greater.
7. The method of claim 1 , wherein the powder precursor is comprised of more than one thin film component.