CN110010342B

CN110010342B - Flexible thin film, device and method for regulating and controlling local magnetization direction of flexible thin film

Info

Publication number: CN110010342B
Application number: CN201910131434.8A
Authority: CN
Inventors: 安志强; 王海; 李英
Original assignee: Capital Normal University
Current assignee: Capital Normal University
Priority date: 2019-02-22
Filing date: 2019-02-22
Publication date: 2020-10-16
Anticipated expiration: 2039-02-22
Also published as: CN110010342A

Abstract

The invention provides a flexible film, a device and a method for regulating and controlling the local magnetization direction of the flexible film, wherein the method comprises the following steps: s1, cleaning the flexible substrate, and bending and fixing the flexible substrate with a curvature to form a substrate; s2, forming a magnetic nano film on the substrate in a magnetron sputtering mode; s3, flattening the magnetic nano film prepared in the S2 to obtain a flexible film with continuously changed magnetization direction from the center to the edge. The invention is based on the technology of preparing nano-film by magnetron sputtering, and adopts the method of depositing magnetic nano-film on the substrate. The local magnetization direction of the flexible film provided by the invention is continuously adjustable in a millimeter scale range; the film thickness, the magnetron sputtering power, the position of the bent substrate and other parameters can be conveniently regulated and controlled. The invention provides a large-scale preparation scheme for preparing the functional magnetic thin film device on the flexible substrate, and has certain commercial realization value.

Description

Flexible thin film, device and method for regulating and controlling local magnetization direction of flexible thin film

Technical Field

The invention belongs to the technical field of flexible thin films and thin film preparation, and particularly relates to regulation and control of local magnetization directions of flexible thin films and related technologies and products thereof.

Background

Flexible devices, typically comprise a flexible substrate and a functional building block. Because of its excellent space compatibility and environmental adaptability, it is closely related to people's daily life and has been the focus of research and application in the last two decades. The deformation of the flexible device is accompanied by a change in mechanical energy, which the functional unit on it can convert into an electrical/magnetic/optical signal, and vice versa. The former corresponds to a flexible detector/sensor and the latter corresponds to a micro-electromechanical system (MEMS). A device can be used as a structural element in a flexible display or information storage if it can maintain the stability of the output signal under deformation. Currently, with the global demand for flexible devices growing, a great deal of research is being devoted to developing these hybrid devices so as to create new material properties, providing convenient mass production processes for the industry.

In general, flexible devices are fabricated by manipulating the physical properties of the deposited ultrathin film by energy conversion or topographical modification using elastic deformation of a flexible support at macroscopic length or microscopic local regions. Its plastic deformation is usually compressed to a small or negligible extent. In the technology of preparing magnetic materials on a flexible substrate, the anisotropy of a magnetic thin film is one of the key basic problems for magnetic coding and driving. However, most of magnetostrictive materials in the prior art are rare earth intermetallic compounds, and have the disadvantages of low content, high price and high manufacturing cost. This seriously affects the marketability of conventional film materials of this type, and in the prior art, no adjustment of the same film about the easy axis direction is involved, and at present, the industrial mass production of such films cannot be effectively carried out, and the color developability and magnetic transferability are poor.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a flexible film, a device and a method for regulating and controlling the local magnetization direction of the flexible film. The method is to utilize local plastic deformation and macroscopic elastic deformation of the binding paper to adjust the magnetic anisotropy of the permalloy film. The 90 ° diversion of the magnetization direction was experimentally achieved for the first time in convex substrate deposition and demonstrated the high stability of the sample magnetic properties. The magnetic anisotropy of the film can be flexibly regulated and controlled by combining common binding paper and carrying out simple design through manufacturing parameters. In addition, due to the local residual stress and the characteristics of paper, the prepared film also has the advantages of industrial large-scale production, developable color, magnetic transferability and the like. Specifically, the invention provides the following technical scheme:

firstly, the invention provides a method for regulating and controlling the local magnetization direction of a flexible film, which comprises the following steps:

s1, cleaning the flexible substrate, and bending and fixing the flexible substrate with a curvature to form a substrate;

s2, forming a magnetic nano film on the substrate in a magnetron sputtering mode;

s3, flattening the prepared film in the S2 to obtain a flexible film with continuously changed magnetization directions from the center to the edge.

Preferably, the flexible substrate has a composite structure of an upper plastically deformable layer and a lower partially supporting layer.

Preferably, the flexible substrate is binding paper, glossy paper, coated paper, laminated paper, plastic coated paper, weighing paper, A4 paper, polystyrene or cardboard.

Preferably, the magnetic thin film substance includes: iron, cobalt, nickel, and alloys containing the foregoing.

Preferably, in the magnetron sputtering in S2, the deposition power is 50W to 200W, the background vacuum is maintained at 10 "4 Pa, the working gas is Ar, and the gas flow rate is: 10sccm, and the sputtering working pressure is 0.3 Pa.

Preferably, the magnetic thin film material is common Ni₈₀Fe₂₀Permalloy.

Preferably, the thickness of the flexible film is 10-100 nm, and the bending curvature of the substrate is 5-9.4 mm.

Preferably, in the magnetron sputtering of S2, a flexible material is used to perform a mask, only a deposition area is left, and the control of the local magnetization direction of the flexible film is realized by adjusting the distance between the center of the flexible film and the center of the target.

Preferably, when the flexible film is magnetically transferred, the lower local support layer fiber paper is peeled off, a hydrophobic material is sprayed on the surface of the deposited magnetic nano film, and the magnetic film is transferred after drying.

Preferably, when the film substrate, the film thickness, the film bending curvature and the film deposition power are changed, a flexible film with good quality and continuously changing magnetization direction can be obtained in a certain range, and the easy axis of the film is changed by 90 degrees from the center along the stress direction of the film to the edge perpendicular to the stress direction of the film.

In addition, the invention also provides a flexible film, which comprises a substrate and a magnetic nano film, wherein the flexible film is prepared by adopting the method for regulating and controlling the local magnetization direction of the flexible film.

In addition, the invention also provides a flexible thin film device which comprises a flexible thin film, wherein the flexible thin film comprises a substrate and a magnetic nano thin film, and the flexible thin film is prepared by adopting the method for regulating and controlling the local magnetization direction of the flexible thin film.

Compared with the prior art, the invention has the following beneficial effects:

(1) the flexible substrate adopted by the invention is common commercial binding paper, and has great universality, wide source and strong economic applicability.

(2) The invention has simple process, easy modification of the engineering design structure of the production equipment by actual industrial production and equipment, and easy obtaining of the flexible nano film with continuously changed magnetization direction and large-scale production.

(3) The flexible nano film prepared by the method has stable magnetic anisotropy and no performance attenuation along with the time.

(4) The film prepared by the method can realize rich color development under the condition of not influencing the mechanical property of equipment, can prepare large-area magnetic films with the same color, can enhance the magneto-optical effect, and can be fitted by using colorimetry. Based on the method, double codes of magnetism and color can be designed, the double codes are applied to anti-counterfeiting, and the color of the double codes is unchanged at a wide angle. Besides, it can be applied to printing, painting, etc.

(5) The product of the invention can be directly used as a commercial product.

Drawings

Fig. 1a is a normalized kerr loop along the X-axis with each increase D of 0.5mm for an embodiment of the present invention;

fig. 1b is a normalized kerr loop along the Y-axis with each increase of 0.5mm for an embodiment of the present invention;

FIG. 1c is a graph of K versus D for multiple measurements of different samples according to an embodiment of the present invention, where each group of shapes is the same sample test result, and K is a magnetic anisotropy constant whose positive and negative can characterize the magnetization direction.

FIG. 2 is a normalized Kerr loop for different single layer substrates of an embodiment of the present invention;

FIG. 3 is a normalized Kerr curve for permalloys of varying thicknesses according to embodiments of the present invention;

FIG. 4 is a normalized Kerr angle for permalloy of varying curvature for the same thickness and power for an embodiment of the invention;

FIG. 5 shows the preparation of 50nm permalloy on a paper binding with r ≈ 9mm at power (a)200W, (b)150W, (c)50W, (d)30W, respectively, according to an embodiment of the present invention;

FIG. 6a is a photograph of a mask on a binding paper according to an embodiment of the present invention, the mask having a width of 1 mm;

FIG. 6b is a schematic diagram of a mask sputtering configuration according to an embodiment of the present invention;

fig. 6c is a normalized kerr plot along the X and Y axes for an embodiment of the present invention with D-7 mm;

fig. 6D is experimental data and fitted curves for an embodiment of the present invention where D is 7 mm;

fig. 6e is a normalized kerr plot along the X and Y axes for an embodiment of the present invention with D0 mm;

fig. 6f is experimental data and fitted curves for an embodiment of the present invention with D-0 mm;

FIG. 6g is a schematic diagram of a design of an industrial roller according to an embodiment of the present invention;

FIG. 7 shows (Si)/Ni in an example of the present invention₈₀Fe₂₀Model schematic diagram of absorption medium structure

FIG. 8a is a graph of 35nm Si deposited on a 50nm permalloy in accordance with an embodiment of the present invention;

FIG. 8b is a graph of Si optical coatings of varying thickness from left to right for an embodiment of the present invention, starting from colorless to bright yellow to purple and finally bright blue;

FIG. 9a is a schematic diagram of a magnetic thin film spray and transfer according to an embodiment of the present invention;

FIG. 9b is a normalized hysteresis loop for 50nm permalloy without sprayed hydrophobizing agent for an embodiment of the present invention;

FIG. 9c is a 50nm permalloy normalized hysteresis loop after stripping of the fiber paper after spraying the hydrophobizing agent according to the embodiment of the present invention;

wherein, BP means binding paper.

Detailed Description

The invention will be further described with reference to specific embodiments, and the advantages and features of the invention will become apparent as the description proceeds. The examples are illustrative only and do not limit the scope of the present invention in any way. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be made without departing from the spirit and scope of the invention.

Example 1:

in a specific embodiment, the method for preparing a magnetic flexible thin film with a continuously changing magnetization direction of the present invention can be implemented by the following method, in this embodiment, the substrate is made of flexible binding paper:

(1) cleaning and fixing of flexible binding paper substrate

Cleaning a binding paper substrate: with the common commercial colored binding paper, because the common commercial binding paper inevitably has a certain amount of dirt on the surface, the surface of the binding paper needs to be cleaned in order to prepare a good nano film. In view of the particularity of the binding paper, the cellulose paper at the bottom layer of the binding paper is prevented from being damaged by traditional cleaning, and the base is cleaned by dipping alcohol cotton into alcohol to repeatedly wipe the surface of the binding paper, so that the coating requirement is met.

Fixing the binding paper substrate: since the binding paper has the characteristic of being very soft and does not have the self-holding capacity of a certain shape, the binding paper with a proper size can be cut and fixed on a semi-cylindrical plastic bearing body (sample holder) with r ≈ 9mm curvature manufactured by 3D printing.

(2)Ni₈₀Fe₂₀Preparation of permalloy magnetic nano film

In the nano-film forming stage, a magnetic sputtering mode in a vacuum environment can be adopted. Putting the substrate into a vacuum cavity of a planar magnetron sputtering system device, wherein the background vacuum reaches 10 DEG^-4After Pa magnitude, Ni is adopted₈₀Fe₂₀Introducing Ar gas with 10SCCM flow rate to the alloy target material, and performing magnetron sputtering deposition on Ni with the thickness of 50nm under the working air pressure of 0.3Pa₈₀Fe₂₀A magnetic nano-film.

(3) Magneto-optical Kerr measurement

The normalized kerr curve was tested along the center of the film towards the edge, each time at a spacing of about 0.5mm, and tested and analyzed at each point along the X-axis and Y-axis, respectively, as shown in fig. 1a and 1 b. It was found that the direction of the easy axis of the magnetic anisotropy changed greatly, and the direction of the easy axis was shifted by 90 ° from the center along the stress direction of the film to the edge perpendicular to the stress direction of the film.

Example 2:

in this example, the influence of the substrate, the film thickness, the curvature, and the deposition power on the magnetization direction was examined on the film produced by the method for forming a flexible film according to the present invention

(1) Influence of different substrates on magnetic properties

At the same curvature (r ≈ 9mm) and power (80W), monolayer paper and plastic (20 μm weighed paper, 100 μm A4 paper, 150 μm polystyrene and 220 μm cardboard, respectively) of different thicknesses were chosen as substrates, onto which permalloy films of the same thickness, for example 50nm, were deposited, measured in succession along the direction of the stress (i.e. X-axis) and perpendicular to the direction of the stress (i.e. Y-axis) to obtain a normalized Kerr curve, with the abscissa as applied external field and the ordinate as normalized Kerr angle. We have found that anisotropy is generated and the easy axis directions of the magnetic anisotropy are all along the stress direction, as shown by comparison in fig. 2.

(2) Influence of different thicknesses on magnetic properties

Ni is deposited at the same power (e.g., 80W) and curvature (r ≈ 9mm) for the same bound paper substrate₈₀Fe₂₀Thin film, the influence of the thickness of the thin film (from 10nm to 100nm) on the magnetism is studied, and the experimental result shows that: significant magnetic anisotropy occurs at film thicknesses between 10nm and 50nm and along the stress direction. When the film thickness is more than 75nm, the magnetic anisotropy disappears as shown in FIG. 3

(3) Influence of different curvatures on the magnetic properties

Ni was deposited at the same power (80W) and film thickness (50nm) for the same bound paper substrate₈₀Fe₂₀A thin film of a material selected from the group consisting of,the effect of curvature (r → ∞, r ∞ 9.4mm, r ≈ 9mm and r ≈ 5mm) on the magnetic properties was investigated. For r → ∞ the magnetic film shows isotropy; when the sample is deposited on a curved surface, its anisotropy gradually increases as the radius of curvature decreases, as shown in fig. 4.

(4) Influence of different powers on magnetism

Ni was deposited at the same curvature (r ≈ 9mm) and film thickness (50nm) for the same bound paper substrate₈₀Fe₂₀Thin film, the effect of power (from 30W to 200W) on magnetic properties was investigated. The experimental result shows that when the power is lower, the magnetic anisotropy is lower. When the power is too high, the anisotropy is also reduced. The maximum power at which anisotropy occurs is 80W. The anisotropy decreases, either by increasing or decreasing power. As shown in fig. 5.

Example 3:

in this example, an industrially producible way in which the method of the present invention can be performed is given.

We mask with a flexible paper sheet, leaving only the deposited areas, as shown in fig. 6a and 6 b. The magnetic properties at a distance D from the center of the film can also be accurately measured in the masked method. We discuss the center of the sputtering target (O), the center of the curved tray (O'), and the center of the mask (E) in fig. 6 b. In the discussion of deposition parameters, the focus is on the variation of the film center anisotropy. The middle part, OO', is parallel to the centerline of the target, with increasing D, oblique incidence deposition predominates. In one embodiment, a target size of 60mm is used, the target-to-substrate spacing is set to 60mm, and the sputtering zone is only 20mm, so that the sputtering zone is uniform for the deposition zone. We move the curved holder holding the substrate on the production equipment so that the mask center (E) is aligned with the center (O) of the target, as shown in fig. 6b, in other words, when the mask region is also the center region. As shown in fig. 6c and 6d, the easy axis direction of anisotropy is perpendicular to the stress direction for the edges of the film. A mask plate is prepared by using scissors or a nicking tool and is rectangular in shape. The limit of the mask is in the millimeter range, the long side is in the centimeter range, the length-width ratio is larger than 10, which is the size of the typical shape anisotropy, and the applicant finds through a large number of experiments that the direction of the easy axis of the anisotropy does not change, and here the shape-induced anisotropy is not the main cause, as shown in fig. 6e and 6f (D ═ 0mm), and for the central area, the easy axis of the anisotropy is along the direction of the stress. Therefore, by using the roller technology commonly used for industrially preparing the thin film, the large-scale production of the magnetic thin film with continuously adjustable magnetization direction can be realized only by changing the distance between the lower baffle and the center of the roller, as shown in fig. 6 f.

Example 4:

in this embodiment, the color developability of the prepared flexible film is discussed based on the technical solution of the present invention.

On flexible substrates, rich color development can be achieved by depositing optical coatings. The optical coating exhibits a corresponding color when the thickness of the optical coating (e.g., when Si is used) is an integer multiple of the wavelength of the incident light. The light can be reflected in the interference cavity for multiple stages, and the amplitude of the light is gradually weakened along with the gradual increase of the stages, and the schematic diagram is shown in fig. 7. The prior art has demonstrated that under appropriate conditions, a strong interference effect exists in a high-absorption ultra-thin optical coating, which can exhibit rich colors (application No. CN 201610535022.7: a color printing method of polarization information added by ultra-thin semiconductor nano-coating). Although the binding paper is rough, strong interference (i.e. first-order interference) still exists. For the same sample (r ≈ 9mm), 50nm permalloy was deposited, followed by 35nm Si deposition on a curved surface, showing different colors due to the different thicknesses of the middle and the edge, as influenced by the oblique deposition (i.e. the target is at an angle to the substrate), as shown in fig. 8a and 8 b. By selecting the deposition area in the center and controlling the thickness of the silicon, the colors from the background color, yellow, red and sky blue can be obtained. Experimental results show that the prepared film can realize rich color development under the condition of not influencing the mechanical property of equipment, and the color is not changed under a wide angle. The easy axis is well along its stress direction and its color develops as shown in fig. 8. By combining the design of roller sputtering, the magnetic film with the same color and large area can be prepared. The magnetic film can enhance the magneto-optical effect and can also be fitted using colorimetry. Based on the method, a magnetic and color double code can be designed, the anti-counterfeiting code is applied to anti-counterfeiting, and the color of the anti-counterfeiting code is unchanged at a wide angle. Besides, it can be applied to printing, painting, etc.

Example 5:

in this embodiment, based on the technical solution of the present invention, the magnetic transferability of the flexible thin film is discussed.

In order to overcome the disadvantages, a method is proposed in which a paper for binding is composed of an upper layer of PVC (Polyvinyl chloride, hereinafter abbreviated as Polyvinyl chloride) and a lower layer of paper for binding, the lower layer of paper is peeled off, and the magnetic stability of permalloy is ensured, as shown in FIG. 9 a. the super-hydrophobic surface made of new material or metamaterial is one of the hottest topics for several decades². We found that the magnetic properties after spraying were almost unchanged from the magnetic properties before spraying, as shown in fig. 9b and 9 c. In addition, the wetting angle was measured with a contact angle meter (Biolin, AAN11455) and was approximately 142 °, as shown in fig. 9 c. Thus, a thin superhydrophobic covering significantly improves the environmental compatibility of the sample without losing its steric compatibility and magnetic properties. Ultralight (2.4 mg/cm)²) The ultra-thin (30 μm) magnetic thin film has ultra-high magnetic sensitivity. In solution, the magnetic film can move directionally under low magnetic field even geomagnetic field, and the design has certain significance to the motion of nano-/micro-robot in liquid.

Example 6:

in another embodiment, the method of the present invention can further prepare a flexible thin film, where the flexible thin film includes a substrate and a magnetic nano-thin film, and the flexible thin film is prepared by the method for regulating and controlling the local magnetization direction of the flexible thin film as in any one of embodiments 1 to 5.

In addition, the method of the present invention can also assist in the preparation of a flexible thin film device, where the device includes a flexible thin film, the flexible thin film includes a substrate and a magnetic nano-thin film, and the flexible thin film is prepared by the method of controlling the local magnetization direction of the flexible thin film as in any one of embodiments 1 to 5.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A method for regulating and controlling the local magnetization direction of a flexible film is characterized by comprising the following steps:

s3, flattening the magnetic nano film prepared in the S2 to obtain a flexible film with continuously changed magnetization direction from the center to the edge;

in the magnetron sputtering of S2, a flexible material is used for masking, only a deposition area is left, and the control of the local magnetization direction of the flexible film is realized by adjusting the distance between the center of the flexible substrate and the center of the target material;

in the magnetron sputtering in the S2, the deposition power is 50-200W;

the thickness of the flexible film is 10-50 nm, and the bending curvature of the substrate is 5-9.4 mm.

2. The method of claim 1, wherein the flexible substrate has a composite structure of an upper plastically deformable layer and a lower partially supporting layer.

3. The method of claim 2, wherein the flexible substrate is a binding paper, a glossy paper, a coated paper, a laminated paper, a plastic coated paper, a weight paper, a4 paper, polystyrene, or cardboard.

4. The method of claim 1, wherein the magnetic nanofilm comprises: iron or cobalt or nickel, or an alloy comprising iron or cobalt or nickel.

5. The method of claim 1, wherein in the magnetron sputtering in S2, the background vacuum is maintained at 10^-4Pa, Ar as working gas, and the gas flow rate is as follows: 10sccm, and the sputtering working pressure is 0.3 Pa.

6. The method of claim 1, wherein the magnetic nano-film is Ni₈₀Fe₂₀Permalloy.

7. The method as claimed in claim 2, wherein when the flexible film is magnetically transferred, the lower partial supporting layer fiber paper is peeled off, the hydrophobic material is sprayed on the surface of the deposited magnetic nano film, and the magnetic nano film is dried and then transferred.

8. A flexible film comprising a substrate and a magnetic nano-film, wherein the flexible film is prepared by the method of any one of claims 1 to 7.

9. A flexible thin film device comprising a flexible thin film comprising a substrate, a magnetic nanofilm, wherein the flexible thin film is prepared by the method of any one of claims 1-7.