CN102544366A - Resistance switch based on cobalt ferrite nano-film and preparation method therefor - Google Patents

Resistance switch based on cobalt ferrite nano-film and preparation method therefor Download PDF

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CN102544366A
CN102544366A CN2012100480048A CN201210048004A CN102544366A CN 102544366 A CN102544366 A CN 102544366A CN 2012100480048 A CN2012100480048 A CN 2012100480048A CN 201210048004 A CN201210048004 A CN 201210048004A CN 102544366 A CN102544366 A CN 102544366A
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film
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cofe
sputtering
resistance switch
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CN102544366B (en
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白海力
金朝
米文博
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Tianjin University
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Abstract

The invention relates to a resistance switch based on a cobalt ferrite nano-film and a preparation method therefor. A CoFe2O2 film is prepared by a method for sputtering a metal Fe target and a Co target through the reaction, the CoFe2O2 film is grown on a Si substrate plated with metal Pt, and silver conductive adhesive is coated on the upper surface of the CoFe2O2 film, so that a Ag/CoFe2O4/Pt sandwich structure is formed; and the resistance switch effect of the Ag/CoFe2O4/Pt sandwich structure is measured. The resistance switch based on the CoFe2O2 nano-film has high stability and can stably circulate for 200 times. The high-quality CoFe2O2 film is prepared by a reaction sputtering method successfully. Compared with other film preparation technologies, the target materials are simple. Compared with the radio frequency sputtering ceramic target method, the cobalt ferrite film is prepared by using metal Fe and Co targets as the target materials, so industrialized production is realized easily.

Description

Resistance switch and preparation method based on the Conjugate ferrite nano thin-film
Technical field
Patent of the present invention relates to based on the resistance switch of Conjugate ferrite nano thin-film and preparation method, more specifically, is a kind of resistance switch and preparation method who relates to based on the Conjugate ferrite nano thin-film of reaction cosputtering preparation.
Background technology
The resistance switch effect can be applicable to resistance switch and stores (RRAM) at random, and this type device is made up of metal/insulator/metal sandwich structure.Because the metal ion of the variable valency that exists in the insulator, room etc., make the metal-insulator transition of part under the effect of electric field or Joule heat etc., to occur in the insulator, thereby cause the height resistance variations of sandwich structure, i.e. resistance switch.Seeking suitable insulation body material becomes people's research emphasis.Conjugate ferrite (CoFe 2O 4) have good insulating properties, and have complicated cube inverse spinel structure, wherein, lattice structure is made closs packing with oxygen atom, in the face-centered cubic lattice that 32 oxygen atoms constitute, 64 tetrahedral interstices (A position) and 32 octahedral interstices (B position) is arranged.Wherein, 64 tetrahedron A positions are occupied by 8 Fe, and 32 octahedral B positions are occupied by 8 Fe and 8 Co.CoFe 2O 4Contain Co, the Fe ion of variable valence state and form characteristics such as oxygen room easily, become the selection that we study resistance switch.
CoFe 2O 4Depress at the room temperature standard atmosphere and to have a cube inverse spinel structure, lattice constant does
Figure BDA0000139590450000011
In the unit cell of spinel structure, each unit cell has eight molecules, totally 56 ions.The crystal structure of this complicacy makes ferritic preparation very difficult.
Magnetically controlled sputter method is a kind of method for manufacturing thin film economical and practical and capable of being industrialized.When utilizing magnetron sputtering growth ferrite film, what each research group used all is the ceramic target of stoicheiometry, utilize radio frequency sputtering ferrite from target " transplanting " to substrate on film forming, used is the ceramic target of standard chemical proportioning.Utilize ceramic target radio frequency sputtering complex process, need preparation or buy ceramic target.
Summary of the invention
Utilize simple metal targets, reaction cosputtering method prepares CoFe 2O 4Nano thin-film, and utilize metal/insulator (CoFe2O4)/metal sandwich structure to prepare resistance switch.The present invention is promptly from above purpose, developed a kind of preparation method of the resistance switch based on the Conjugate ferrite nano thin-film.
Technical scheme based on CoFe2O4 nano thin-film and resistance switch among the present invention is following:
A kind of resistance switch based on the Conjugate ferrite nano thin-film utilizes the method for reactive sputtering metal Fe target and Co target to prepare CoFe 2O 4Film; And CoFe 2O 4Film growth is in the Si substrate that is coated with metal Pt, at CoFe 2O 4The film upper surface is coated with silver conductive adhesive, constitutes Ag/CoFe 2O 4/ Pt sandwich structure; Measure Ag/CoFe 2O 4/ Pt sandwich structure resistance switch effect.
The preparation method of the resistance switch based on the Conjugate ferrite nano thin-film of the present invention, concrete steps are following:
(1) adopts three target magnetic control sputtering devices; Metal purity be installed be 99.99% Fe target and purity respectively and be 99.99% Co target on two direct current sputtering target heads; All the make progress sample position at upright center of sputter equipment three targets tilts, with about 60 degree of the angle of horizontal plane;
(2) the Si sheet is fixed on specimen holder, and puts into sputtering chamber specimen holder position;
(3) unlatching sputtering equipment successively starts the one-level mechanical pump and the secondary molecular pump vacuumizes, and quickens vacuum pumping rate through the baking means, and vacuum degree is superior to 1 * 10-5Pa at the bottom of the back of the body of sputtering chamber;
(4) open substrate heating temperature control power supply, substrate is heated to 650 ℃ of panel displays temperatures, stablized 30 minutes;
(5) opening flowmeter and shielding power supply simultaneously and carry out preheating after 20 minutes, is 99.999% sputter gas Ar and O to vacuum chamber feeding purity 2, wherein Ar is 100sccm, oxygen is 1.8-8.0sccm, through regulating the opening degree of ultra high vacuum slide valve, the air pressure of sputtering chamber is controlled at 2.0Pa, and stablized 5 minutes;
(6) open shielding power supply, on the Fe target, apply the electric current of 0.2A and the direct voltage of 360V, apply the direct voltage of 0.1A and 360V on the Co target, sputter is 20 minutes in advance, waits sputtering current and voltage stable;
(7) control substrate at the uniform velocity rotation under 2 rev/mins rotating speed, and open the substrate baffle plate simultaneously, film growth 20 minutes obtains the thick film of 200nm;
(8) sputter finishes; Close baffle plate, shielding power supply and breather valve successively, and open slide valve chamber is continued to vacuumize, base reservoir temperature 650 ℃ stablize 1 hour after with 1 the degree/minute speed reduce to room temperature; Close pumped vacuum systems then; Charging into purity to vacuum chamber is 99.999% nitrogen, opens vacuum chamber, takes out CoFe 2O 4
(9) at CoFe 2O 4Upper surface is coated with silver conductive adhesive, constitutes Ag/CoFe 2O 4/ Pt sandwich structure.
Measure Ag/CoFe 2O 4The voltage-current characteristic of/Pt sandwich structure is studied its resistance switch effect.
Respectively at the sticking copper wire of Pt and silver surface as lead, with the current-voltage characteristic curve of current source and voltmeter measuring samples, i.e. the resistance switch effect of measuring samples, the change in current process is 0 → 100 milliampere → 0 →-100 milliampere → 0.
Effect of the present invention is following:
1. find CoFe first 2O 4The resistance switch of nano thin-film has good stability (resistance switch can stable circulation 200 times);
2. the main method that present suitability for industrialized production thin-film material is adopted is a sputtering method, and we have successfully prepared high-quality CoFe with reaction cosputtering method first 2O 4Film is compared other film preparing technology, more easy realization of industrial production of magnetron sputtering;
3. target is selected simply to compare with radio-frequency sputtering ceramic target method, and we adopt metal Fe and Co target to prepare the Conjugate ferrite film as target, obtains more easily from industrial.
Description of drawings
Fig. 1 cosputtering equipment hit the head, sample position sketch map.
Fig. 2 is based on CoFe 2O 4The Ag/CoFe that nano thin-film constitutes 2O 4/ Pt sandwich structure sketch map.
The CoFe of Fig. 3 growth 2O 4XRD figure, from figure can see the CoFe of growth 2O 4Film is a polycrystal film.
Fig. 4 CoFe 2O 4The current-voltage characteristic curve of film can be seen from figure, and under identical voltage (as 1 volt), corresponding different electric current has shown different resistance values, and the low-resistance ratio of height is about 10, CoFe when oxygen flow is 3.0sccm 2O 4Nano thin-film shows good resistance switch effect.
Embodiment
According to the I-E characteristic analysis that we carry out sample prepared among the present invention, below will be based on CoFe 2O 4The preparation method's of the resistance switch of nano thin-film preferred forms is at length explained:
1. on the Si sheet of plating Pt, prepare CoFe 2O 4Film.
(1) adopt three target magnetic control sputtering devices, metal Fe (99.99%) and Co (99.99%) target are installed respectively on two direct current sputtering target heads, as shown in Figure 1, all RC sample position tilts sputter equipment three targets towards the top, with about 60 degree of the angle of horizontal plane;
The Si sheet that (2) will plate Pt is fixed on specimen holder, and puts into sputtering chamber specimen holder position, like sample position among Fig. 1
(3) unlatching sputtering equipment successively starts the one-level mechanical pump and the secondary molecular pump vacuumizes, and quickens vacuum pumping rate through means such as bakings, and vacuum degree is superior to 1 * 10-5Pa at the bottom of the back of the body of sputtering chamber;
(4) open substrate heating temperature control power supply, substrate is heated to 650 ℃ of panel displays temperatures, stablized 30 minutes;
(5) opening flowmeter and shielding power supply simultaneously and carry out preheating after 20 minutes, is 99.999% sputter gas Ar and O to vacuum chamber feeding purity 2, wherein Ar is 100sccm, O 2Gas is 3.0sccm, through regulating the opening degree of ultra high vacuum slide valve, the air pressure of sputtering chamber is controlled at 2.0Pa, and stablizes about 5 minutes.
(6) open shielding power supply, at electric current that applies 0.2A on the Fe target and the direct voltage about 360V, apply the direct voltage about 0.1A and 360V on the Co target, sputter is 20 minutes in advance, waits sputtering current and voltage stable;
(7) control substrate at the uniform velocity rotation under 2 rev/mins rotating speed, and open the substrate baffle plate simultaneously, film growth 20 minutes obtains the thick film of 200nm;
(8) sputter finishes, and closes baffle plate, shielding power supply and breather valve successively, and opens slide valve chamber is continued to vacuumize; Base reservoir temperature 650 ℃ stablize 1 hour after with 1 the degree/minute speed reduce to room temperature; Close pumped vacuum systems then, charging into purity to vacuum chamber is 99.999% nitrogen, opens vacuum chamber; Take out sample, can obtain being grown in the CoFe of the polycrystalline on the Si sheet that plates Pt 2O 4Film, as shown in Figure 2, judge the prepared CoFe of polycrystalline that is through X-ray diffraction 2O 4Film.
2. prepare Ag/CoFe 2O 4/ Pt sandwich structure.
At CoFe 2O 4Upper surface is coated with silver conductive adhesive, constitutes Ag/CoFe 2O 4/ Pt sandwich structure is shown in Fig. 3 sketch map.
3. measure Ag/CoFe 2O 4The voltage-current characteristic of/Pt sandwich structure is studied its resistance switch effect.Respectively at the sticking copper wire of Pt and silver surface as lead, with the current-voltage characteristic curve of current source and voltmeter measuring samples, i.e. the resistance switch effect of measuring samples; The change in current process is 0 → 100 milliampere → 0 →-100 milliampere → 0, and is as shown in Figure 4, under identical voltage (as 1 volt); Corresponding different electric current has shown different resistance values, and high low-resistance ratio is about 10 when oxygen flow is 3.0sccm; Show high low resistance state, i.e. CoFe 2O 4Nano thin-film shows good resistance switch effect.

Claims (2)

1. the resistance switch based on the Conjugate ferrite nano thin-film is characterized in that utilizing the method for reactive sputtering metal Fe target and Co target to prepare CoFe 2O 4Film; And CoFe 2O 4Film growth is in the Si substrate that is coated with metal Pt, at CoFe 2O 4The film upper surface is coated with silver conductive adhesive, constitutes Ag/CoFe 2O 4/ Pt sandwich structure; Measure Ag/CoFe 2O 4/ Pt sandwich structure resistance switch effect.
2. the preparation method of the resistance switch based on the Conjugate ferrite nano thin-film as claimed in claim 1 is characterized in that concrete steps are following:
(1) adopts three target magnetic control sputtering devices; Metal purity be installed be 99.99% Fe target and purity respectively and be 99.99% Co target on two direct current sputtering target heads; All the make progress sample position at upright center of sputter equipment three targets tilts, with about 60 degree of the angle of horizontal plane;
(2) the Si sheet is fixed on specimen holder, and puts into sputtering chamber specimen holder position;
(3) unlatching sputtering equipment successively starts the one-level mechanical pump and the secondary molecular pump vacuumizes, and quickens vacuum pumping rate through the baking means, and vacuum degree is superior to 1 * 10-5Pa at the bottom of the back of the body of sputtering chamber;
(4) open substrate heating temperature control power supply, substrate is heated to 650 ℃ of panel displays temperatures, stablized 30 minutes;
(5) opening flowmeter and shielding power supply simultaneously and carry out preheating after 20 minutes, is 99.999% sputter gas Ar and O to vacuum chamber feeding purity 2, wherein Ar is 100sccm, oxygen is 1.8-8.0sccm, through regulating the opening degree of ultra high vacuum slide valve, the air pressure of sputtering chamber is controlled at 2.0Pa, and stablized 5 minutes;
(6) open shielding power supply, on the Fe target, apply the electric current of 0.2A and the direct voltage of 360V, apply the direct voltage of 0.1A and 360V on the Co target, sputter is 20 minutes in advance, waits sputtering current and voltage stable;
(7) control substrate at the uniform velocity rotation under 2 rev/mins rotating speed, and open the substrate baffle plate simultaneously, film growth 20 minutes obtains the thick film of 200nm;
(8) sputter finishes; Close baffle plate, shielding power supply and breather valve successively, and open slide valve chamber is continued to vacuumize, base reservoir temperature 650 ℃ stablize 1 hour after with 1 the degree/minute speed reduce to room temperature; Close pumped vacuum systems then; Charging into purity to vacuum chamber is 99.999% nitrogen, opens vacuum chamber, takes out CoFe 2O 4
(9) at CoFe 2O 4Upper surface is coated with silver conductive adhesive, constitutes Ag/CoFe 2O 4/ Pt sandwich structure.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105679931A (en) * 2016-01-28 2016-06-15 青岛大学 Heterojunction and preparation method therefor
CN108149195A (en) * 2017-12-25 2018-06-12 中建材蚌埠玻璃工业设计研究院有限公司 A kind of preparation method of super abrasive high transmittance zirconia film
CN109355625A (en) * 2018-12-04 2019-02-19 吉林师范大学 A kind of CoFe2O4The preparation method of thin magnetic film
CN112349834A (en) * 2020-10-16 2021-02-09 华东师范大学 Sandwich-structure giant magneto-impedance effect composite material and preparation method thereof

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6242584A (en) * 1985-08-20 1987-02-24 Matsushita Electric Ind Co Ltd Nonlinear resistance element and manufacture of same
CN1738051A (en) * 2005-07-06 2006-02-22 中国科学院上海硅酸盐研究所 Non-volatility memorizer, changing method and preparation method based on resistance variations
CN1920088A (en) * 2006-09-14 2007-02-28 电子科技大学 Preparation method of metal oxide nano array-inverse thin film
CN101335326A (en) * 2008-07-24 2008-12-31 中国科学院上海硅酸盐研究所 Electrically inducted resistor material for resistor type memory and preparing method thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6242584A (en) * 1985-08-20 1987-02-24 Matsushita Electric Ind Co Ltd Nonlinear resistance element and manufacture of same
CN1738051A (en) * 2005-07-06 2006-02-22 中国科学院上海硅酸盐研究所 Non-volatility memorizer, changing method and preparation method based on resistance variations
CN1920088A (en) * 2006-09-14 2007-02-28 电子科技大学 Preparation method of metal oxide nano array-inverse thin film
CN101335326A (en) * 2008-07-24 2008-12-31 中国科学院上海硅酸盐研究所 Electrically inducted resistor material for resistor type memory and preparing method thereof

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105679931A (en) * 2016-01-28 2016-06-15 青岛大学 Heterojunction and preparation method therefor
CN105679931B (en) * 2016-01-28 2018-01-02 青岛大学 A kind of hetero-junctions and preparation method thereof
CN108149195A (en) * 2017-12-25 2018-06-12 中建材蚌埠玻璃工业设计研究院有限公司 A kind of preparation method of super abrasive high transmittance zirconia film
CN109355625A (en) * 2018-12-04 2019-02-19 吉林师范大学 A kind of CoFe2O4The preparation method of thin magnetic film
CN112349834A (en) * 2020-10-16 2021-02-09 华东师范大学 Sandwich-structure giant magneto-impedance effect composite material and preparation method thereof
CN112349834B (en) * 2020-10-16 2023-02-03 华东师范大学 Sandwich-structure giant magneto-impedance effect composite material and preparation method thereof

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