Epitaxial process of forming ferrite, Fe.sub.3 O.sub.4 and .gamma.Fe.sub.2 O.sub.3 thin films on special materials

• US 3,996,095 A
• Filed: 04/16/1975
• Issued: 12/07/1976
• Est. Priority Date: 04/16/1975
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Rosenberg, Robert, Tu, King-Ning, Ahn, Kie Yeung, Bajorek, Christopher Henry
• Primary Examiner(s): Mack, John H.
• Assistant Examiner(s): Weisstuch, Aaron
• Application Number:
  US05/568,540
• Time in Patent Office: 601 Days
• Field of Search: 204/192, 427/131, 427/129, 427/132, 340/174 TF, 360/113, 360/131, 428/469, 156/610, 156/612, 156/DIG. 74, 23/DIG. 1
• US Class Current: 204/192.2
• CPC Class Codes: H01F 10/18 being compounds
• CPC Class Codes: H01F 10/20 Ferrites
• CPC Class Codes: H01F 41/14 for applying magnetic films to substrates

Abstract

A first thin film of appropriate texture, lattice constant, and crystal structure, such as body centered cubic vanadium or chromium with (110) texture is deposited upon a rigid or flexible substrate forming a plurality of polycrystals. A ferrite such as magnetite (Fe₃ O₄) is sputtered from a target onto the first thin film forming a mixture of γFe₂ O₃ and Fe₃ O₄ substantially completely without formation of Fe or other oxides of iron, providing good magnetic characteristics and resistance to corrosion. The substrate temperature can be maintained as low as 200°C for both steps when sputtering or evaporation is employed.

Claims

1. A method of depositing magnetic ferrite films on a substrate comprising the sequential steps of:

placing a substrate having a surface to be coated in an evacuable deposition chamber,

vacuum depositing on said substrate a polycrystalline film of a first material having a crystal structure with lattice constants on the order of 8.35A by 8.35A square and

then epitaxially vacuum depositing on said polycrystalline film a magnetic ferrite film having a cubic spinel structure, said polycrystalline film providing characteristics favorable to epitaxial ferrite deposition.

2. The method of claim 1 wherein the steps of vacuum depositing are performed by sputtering.

3. The method of claim 1 wherein said polycrystalline film has a 110 cubic structure and a texture favoring growth of CoFe₂ O₄, Fe₃ O₄ and γ

Fe₂ O₃ and said ferrite is selected from CoFe₂ O₄, Fe₃ O₄ and γ

Fe₂ O₃.

4. The method of claim 1 wherein said magnetic ferrite film comprises magnetic iron-oxide which is deposited reactively upon said polycrystalline film by vacuum depositing iron from a source in an atmosphere containing oxygen.

5. A method in accordance with claim 1 wherein said polycrystalline material has lattice constants in the range between about 8.16A and 8.54A.

6. A method of depositing magnetic ferrite films on a substrate comprising the sequential steps of:

placing a substrate having a surface to be coated and comprising a substantially noncrystalline material in an evacuable deposition chamber,

vacuum depositing a polycrystalline film of a first material having b.c.c. crystal structure characteristics with a 110 texture consisting of a material selected from the group consisting of vanadium and chromium, and

then epitaxially vacuum depositing magnetic ferrite on said polycrystalline film.

7. The method of claim 6 wherein said first material is deposited in said chamber with a controlled atmosphere within said chamber by a method selected from the group consisting of sputtering in an inert gas atmosphere on the order of 10^-2 Torr and evaporation in a vacuum on the order of 10^-6 Torr.

8. The method of claim 7 wherein said ferrite material comprises magnetic iron-oxide which is deposited by sputtering.

9. The method of claim 8 wherein said iron-oxide comprises magnetite and is obtained by sputtering of a target comprising magnetite.

10. The method of claim 8 wherein the substrate is an organic polymer and the steps of depositing are performed at a substrate temperature below 225°

C.

11. The method of claim 7 wherein said ferrite material comprises magnetic iron-oxide which is deposited by evaporation.

12. A magnetic thin film ferrite epitaxially deposited upon a substrate coated with an intermediate thin film layer of a metal having a crystal structure with lattice constants yielding crystal structures on the order of about 8.35 ×

8.35A square, said metal having been deposited by a method selected from the group consisting of evaporation at a pressure on the order of 10^-6 Torr and sputtering in an inert atmosphere at a pressure on the order of 2 ×

10^-2 Torr, and

then epitaxially vacuum depositing said ferrite on said intermediate layer to form a cubic spinel structure upon said intermediate layer.

13. A method of forming an epitaxial magnetic ferrite film consisting of at least one of Fe₃ O₄ and γ

Fe₂ O₃ comprising the sequential steps of

sputtering a thin film of a metal selected from vanadium and chromium onto a substrate,

then vacuum depositing said epitaxial magnetic ferrite film on said film of a metal.

14. A low temperature method of forming an iron oxide magnetic film of material comprising γ

Fe₂ O₃ and Fe₃ O₄ comprising the sequential steps of vacuum depositing a 200A to 10,000A thick metal film of a metal selected from the group consisting of chromium and vanadium on a substrate held at a temperature between 200° and

250°

C to form a b.c.c. structure with 110 texture, and

thereafter sputtering a 100A to 10,000A thick epitaxial layer of magnetic iron oxide at a substrate temperature between 125°

to 225°

C in an inert gas atmosphere at a pressure of about 2 ×

10^-z Torr to form said magnetic iron oxide film on said metal film.