High strength vacuum deposited nitinol alloy films and method of making same
First Claim
1. A method for fabricating nitinol film using a vacuum sputter deposition apparatus having a magnetron, a cathode, a cooling device thermally coupled to the cathode and a deposition chamber capable of being selectively isolated from the atmosphere, the method comprising the steps of:
- a. disposing at least one cylindrical target selected from the group consisting of nickel, titanium and nickel-titanium alloy in the deposition chamber;
b. disposing a cylindrical substrate that is spatially separated from and concentric with the cylindrical target in the deposition chamber;
c. supplying a working gas to the deposition chamber;
d. sputter depositing material from the at least one cylindrical target to form a substantially non-columnar crystalline film under conditions where the mean free path of the sputtered particles is greater than about half the distance between the cylindrical target and the cylindrical substrate;
e. removing the deposited material from the cylindrical substrate.
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Abstract
A vacuum deposition method for fabricating high-strength nitinol films by sputter depositing nickel and titanium from a heated sputtering target, and controlling the sputter deposition process parameters in order to create high-strength nitinol films that exhibit shape memory and/or superelastic properties without the need for precipitation annealing to attenuate the transition conditions of the deposited material. A vacuum deposited nitinol film having high-strength properties equal to or better than wrought nitinol films and which are characterized by having non-columnar crystal grain structures.
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Citations
20 Claims
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1. A method for fabricating nitinol film using a vacuum sputter deposition apparatus having a magnetron, a cathode, a cooling device thermally coupled to the cathode and a deposition chamber capable of being selectively isolated from the atmosphere, the method comprising the steps of:
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a. disposing at least one cylindrical target selected from the group consisting of nickel, titanium and nickel-titanium alloy in the deposition chamber; b. disposing a cylindrical substrate that is spatially separated from and concentric with the cylindrical target in the deposition chamber; c. supplying a working gas to the deposition chamber; d. sputter depositing material from the at least one cylindrical target to form a substantially non-columnar crystalline film under conditions where the mean free path of the sputtered particles is greater than about half the distance between the cylindrical target and the cylindrical substrate; e. removing the deposited material from the cylindrical substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for fabricating nitinol film, comprising the steps of:
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a. providing a vacuum deposition apparatus; b. providing at least one cylindrical target selected from the group consisting of nickel, titanium, nickel-titanium alloy, nickel-titanium-X alloy wherein X is selected from the group consisting of copper, chromium, tantalum and zirconium; c. providing and heating a cylindrical substrate disposed concentrically with the cylindrical target before and during a deposition run; d. vacuum depositing nitinol metal from the at least one cylindrical target onto the cylindrical substrate to form a substantially non-columnar crystalline film; e. controlling at least one vacuum deposition processing parameter selected from the group of isothermally heating the cylindrical target, controlling the base vacuum pressure, deoxygenating the working gas, controlling the deposition pressure, controlling surface roughness of the cylindrical substrate, controlling the composition of the cylindrical substrate, applying a negative bias voltage to the cylindrical substrate and controlling the throw distance between the cylindrical substrate and the cylindrical target; f. removing the deposited nitinol film from the cylindrical substrate. - View Dependent Claims (18, 19)
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20. A method for fabricating nitinol film comprising the steps of:
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a. sputter depositing nitinol in a vacuum system having a magnetron, a cylindrical target, a cylindrical substrate disposed concentrically with the cylindrical target, a cooling device thermally coupled to a cathode and a deposition chamber capable of being selectively isolated from the atmosphere; and b. controlling the energy of particles emitted from the cylindrical target such that the mean free path of the emitted particles is greater than about one-half the throw distance between the cylindrical target and the cylindrical substrate.
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Specification