United States of America As Represented by the Secretary of the Air Force

Other

Michael J Suscavage

David F Bliss

John S Bailey

Michael J Callahan

Mikhail Klugerman

L Pierre De Rochemont

Vladimir L Tassev

Meckie T Harris

Daniel F Ryder, Jr

Gerald W Iseler

Daniel E Ryder

Pierre L deRochemont

Method and apparatus are provided for forming metal nitride (MN), wherein M is contacted with iodine vapor or hydrogen iodide (HI) vapor to form metal iodide (MI) and then contacting MI with ammonia to form the MN in a process of reduced or no toxicity. Such method is conducted in a reactor that is maintained at a pressure below one atmosphere for enhanced uniformity of gas flow and of MN product. The MN is then deposited on a substrate, on one or more seeds or it can self-nucleate on the walls of a growth chamber, to form high purity and uniform metal nitride material. The inventive MN material finds use in semiconductor materials, in nitride electronic devices, various color emitters, high power microwave sources and numerous other electronic applications.

Forming improved metal nitrides

Method and apparatus are provided for forming metal nitrides (MN) wherein M is contacted with iodine vapor or hydrogen iodide (HI) vapor to form metal iodide (MI) and contacting MI with ammonia to form the MN in a process of reduced or no toxicity. MN is then deposited on a substrate, on one or more seeds or it can self nucleate on the walls of a growth chamber, to form high purity metal nitride material. The inventive MN material finds use in semiconductor materials and in making nitride electronic devices as well as other uses.

Forming metal nitrides

This invention provides a process and apparatus for producing products of M-nitride materials wherein M&equals;gallium (GaN), aluminum (AlN), indium (InN), germanium (GeN), zinc (ZnN) and ternary nitrides and alloys such as zinc germanium nitride or indium aluminum gallium nitride. This process and apparatus produce either free-standing single crystals, or deposit layers on a substrate by epitaxial growth or polycrystalline deposition. Also high purity M-nitride powders may be synthesized. The process uses an ammonium halide such as ammonium chloride, ammonium bromide or ammonium iodide and a metal to combine to form the M-nitride which deposits in a cooler region downstream from and/or immediately adjacent to the reaction area. High purity M-nitride can be nucleated from the vapor to form single crystals or deposited on a suitable substrate as a high density material. High purity M-nitride single crystals can be grown by the direct reaction of the halide with the M-metal in a range of sizes from a few micrometers to centimeters, depending on the growth conditions. The small sized crystals are recovered as high purity M-nitride powder while the larger crystals can be prepared as substrates for electronic devices or UV/blue/green emitting diodes and lasers. The deposited layers can be used as M-nitride substrates, or targets for pulsed laser deposition (PLD), or other systems requiring high density targets. The deposition process, and subsequent density of the resulting component, is controlled by the reaction medium and by adjusting the temperature of the ammonium halide in an area near but separate from the reaction zone. Thickness of deposition on the substrates by the same process involves placement of the substrates in a suitable area in the reaction chamber and may be further controlled by the use of nitrogen, nitrogen-hydrogen mixtures or other suitable controlling gas to facilitate uniform distribution of the layer.

Process and apparatus for the growth of nitride materials

Using a GaN growth furnace, at least three different techniques can be used for forming the targets for the deposition of thin films. In the first, nitrides can be deposited as a dense coating on a target backing plate for use as a target. In this approach, the backing plate is placed near the Group III metal. During processing, the Group III metal or metal halide vaporizes and reacts with the nitrogen source to deposit a dense polycrystalline layer on the backing plate. To build up a thick layer on the backing plate, the backing plate is repeatedly placed in the processing furnace until a satisfactory thickness is attained. For the second approach, a properly shaped reaction vessel, the dense, thick Group III nitride crust that forms on top of the Group III metal during the process can be used directly or mechanically altered to meet the size requirements for a sputtering target holder. As a third approach, the Group III nitride material can be ground into a fine powder using traditional ceramic powder processing methods and then pressed to consolidate the powder into a sputtering target. The third processing option would typically lead to a low density target; however, this 'green' compact can then be reinserted into the same processing apparatus that the original powder was synthesized to infiltrate the open pores with the same or another group III metal nitride. This would produce a high density, thick target.

Process for the manufacture of group III nitride targets for use in

This invention permits superconducting ceramics, as well as other ceramic materials, to be spray deposited onto indefinitely large sheets of metallic substrate from a carboxylic acid salt solution. Elemental metal precursors of the superconductor are introduced into the solution as carboxylic acid salts. The deposit formed on the malleable metallic substrate is then thermomechanically calcined to form c-axis textured metal-superconductor composite sheet structures. These composite sheet structures can be formed by pressing together two ceramic-substrate structures, ceramic face-to-face, to form a metal-ceramic-metal sheet structure, or by overlaying a metal sheet over the deposited structure. Once the structure has been thermomechanically calcined, the c-axis of the superconductor is oriented parallel to the vector defining the plane of the metal sheet, i.e., perpendicular to the surface of the plane. These sheets of c-axis textured superconductor can then be mechanically worked as continuous superconducting filaments into larger composite structures with predetermined c-axis orientation. The fact that the c-axis of the superconductor is given predetermined orientation allows surface topologies to be mechanically constructed from these sheets that maximize the performance of the superconductor for a predetermined application or magnetic field environment.

Superconducting metal-ceramic laminate

The invention provides methods to manufacture dense, complex c-axis oriented ceramic oxide layers with thickness greater than 2.5 microns (.mu.m) on a metallic substrate (composites) without the use of an interfacial barrier, buffer, or surface layer using a metalorganic deposition process and thermomechanical reaction treatments is disclosed. A porous amorphous metal oxide ceramic deposit is formed directly on the substrate by spray pyrolyzing a mixed metalorganic precursor solution onto the metallic substrate. The metallic substrate has been previously heated to temperatures greater than the boiling point of the organic solvent and are high enough to initiate in situ decomposition of the metalorganic precursor salts. The process does not apply the precursor solution to the substrate as a liquid coating that is pyrolyzed in subsequent processing steps. The resultant porous amorphous oxide deposit is processed into a dense amorphous ceramic, or a fully crystallized c-axis oriented ceramic through a series of mechanical compression and short reaction treatments that are used to crystallize the amorphous ceramic layer. The inventive method applies to making complex ceramic oxides including superconducting compositions of bismuth cuprate ceramic, piezoelectric or insulating compositions. The composites so produced are useful in devices that include ceramic sputtering targets, heat shields, electrically conducting wires, magnetic solenoids, electromagnetic shielding, and energy storage devices. The invention also provides the ceramic-metal composites so made.

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Shirley, MA, United States of America

Michael J Suscavage