TRANSITION METAL-DOPED OXIDE SEMICONDUCTOR EXHIBITING ROOM-TEMPERATURE FERROMAGNETISM

• US 20100064771A1
• Filed: 09/01/2009
• Published: 03/18/2010
• Est. Priority Date: 07/30/2004
• Status: Abandoned Application

• Current Assignee: Boise State University
• Original Assignee: Boise State University
• Inventors: PUNNOOSE, ALEX
• Application Number:
  US12/552,276
• Publication Number:
  US 20100064771A1
• Time in Patent Office: Days
• US Class Current: 73/31.50
• CPC Class Codes: C01G 19/00 Compounds of tin
• CPC Class Codes: C01G 19/02 Oxides
• CPC Class Codes: C01G 49/06 Ferric oxide [Fe2O3]
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2002/82 by IR- or Raman-data
• CPC Class Codes: C01P 2006/42 Magnetic properties
• CPC Class Codes: G01N 27/74 of fluids G01N24/00 takes precedence
• CPC Class Codes: G01N 33/0027 concerning the detector
• CPC Class Codes: H01F 1/401 diluted
• CPC Class Codes: H01F 10/193 Magnetic semiconductor compounds in general H01F1/40; multilayers, e.g. superlattices H01F10/3213
• CPC Class Codes: H01L 29/24 including, apart from doping materials or other impurities, only semiconductor materials not provided for in groups H01L29/16, H01L29/18, H01L29/20, H01L29/22 including organic materials H10K99/00
• CPC Class Codes: H01L 29/26 including, apart from doping materials or other impurities, elements provided for in two or more of the groups H01L29/16, H01L29/18, H01L29/20, H01L29/22, H01L29/24 , e.g. alloys
• CPC Class Codes: Y10S 977/773 Nanoparticle, i.e. structure having three dimensions of 100 nm or less
• CPC Class Codes: Y10S 977/811 Of specified metal oxide composition, e.g. conducting or semiconducting compositions such as ITO, ZnOx

Abstract

An oxide semiconductor doped with a transition metal and exhibiting room-temperature ferromagnetism is disclosed. The transition metal-doped oxide semiconductor is preferably manufactured in powder form, and the transition metal is preferably evenly distributed throughout the oxide semiconductor. The preferred embodiments are iron-doped tin dioxide and cobalt-doped tin dioxide. Gases may be detected by passing them across a material and measuring the change in magnetic properties of the material; the preferred material is iron-doped tin dioxide.

Claims

1. An oxide semiconductor material comprising Fe-doped tin oxide nanoparticles, wherein the Fe-doped tin oxide nanoparticles exhibit room-temperature ferromagnetism.

2. The material of claim 1 wherein the Fe-doped tin oxide nanoparticles are Fe-doped SnO₂ nanoparticles wherein the Fe is evenly distributed through the SnO₂ lattice and the material of comprises no iron oxide phases.

3. The material of claim 1 wherein the Fe-doped tin oxide nanoparticles are Fe-doped SnO₂ nanoparticles wherein the Fe is evenly distributed through the SnO₂ lattice and the material of comprises no iron oxide phases of magnetite, hematite, maghemite, or goethite.

4. The material of claim 1 wherein no traces of iron, iron oxides, or tin metal are observable by X-ray diffraction studies utilizing the Debye-Scherrer technique.

5. The material of claim 1 having a Curie temperature of at least 850 K.

6. The material of claim 1 having a coercivity of at least 60 Oe.

7. The material of claim 1 wherein the Fe-doped tin oxide nanoparticles are Sn_0.95Fe_0.05O₂.

8. Oxide semiconductor powder comprising Fe-doped SnO₂ nanoparticles made by the process comprising:

adding SnCl₂, FeCl₂, and NH₄OH to water to produce at least one solution;

reacting the at least one solution together to produce a precipitate; and

annealing the precipitate.

9. The powder of claim 8 wherein the ratio of SnCl₂ to FeCl₂ is between 200 to 1 and 20 to 1.

10. The powder of claim 8 wherein the precipitate is annealed at a temperature between 350°

C. and 600°

C.

11. The powder of claim 10 wherein the ratio of SnCl₂ to FeCl₂ is between 200 to 1 and 20 to 1.

12. An oxide semiconductor material comprising Fe-doped tin oxide exhibiting room-temperature ferromagnetism, wherein the Fe atoms take the place of Sn atoms in the SnO₂ lattice so that the Fe atoms are substitutionally incorporated into the SnO₂ lattice at the Sn sites, and wherein the oxide semiconductor material comprises no iron oxide phases.

13. The oxide semiconductor material of claim 12, wherein said material is a film comprising said Fe-doped tin oxide exhibiting room-temperature ferromagnetism.

14. The oxide semiconductor material of claim 13, wherein said film is a thin film of Sn_0.95Fe_0.05O₂.

15. An oxide semiconductor material comprising Fe-doped SnO₂ particles, wherein the Fe-doped SnO₂ particles exhibit room-temperature ferromagnetism and 95% of which particles are less than 100 nm in length.

16. A method of detecting a gas comprising:

causing the gas to flow across a material that comprises transition-metal-doped tin oxide that exhibits room-temperature ferromagnetism; and

measuring a change in a magnetic property of the material.

17. The method of claim 16 wherein the transition-metal-doped tin oxide is Fe-doped SnO₂ nanoparticles, wherein Fe takes the place of Sn atoms in the SnO₂ lattice so that the Fe atoms are substitutionally incorporated into the SnO₂ lattice at the Sn sites.

18. The method of claim 17 wherein the nanoparticles comprise no iron oxide phases of magnetite, hematite, maghemite, or goethite.

19. The method of claim 17 wherein no traces of iron, iron oxides, or tin metal are observable in said nanoparticles by X-ray diffraction studies utilizing the Debye-Scherrer technique.

20. The method of claim 16, wherein said material is a film.

21. The method of claim 20, wherein said film is a thin film of Sn_0.95Fe_0.05O₂.

22. An apparatus for detecting a gas comprising a gas inlet, a flow controller, a device which is configured to measure magnetic properties, and a ferromagnetic material, wherein the ferromagnetic material comprises Fe-doped SnO₂ nanoparticles that exhibit room-temperature ferromagnetism.

23. The apparatus of claim 22 wherein the ferromagnetic material is Sn_0.95Fe_0.05O₂.