KR20200030817A - Photosensitive ferrite film and manufacturing method thereof - Google Patents

Abstract

Disclosed are a photosensitive ferrite film having high functionality and a manufacturing method thereof. According to the present invention, a method for manufacturing a photosensitive ferrite thin film comprises the steps: positioning a substrate on a rotating device; and spraying a raw material onto a rotating substrate to form an M-Ni-Zn ferrite thin film.

Description

Photosensitive ferrite film and manufacturing method thereof

The present invention relates to a photosensitive ferrite thin film and a method for manufacturing the same, and more particularly, to a photosensitive ferrite thin film capable of reacting to external stimuli and having high functionality, and a method for manufacturing the same.

Ferrite composed of iron oxide is a material that has various fields of application in terms of material, and has been researched and developed over the past decades. The application range of magnetic materials has been expanded to various fields that have electromagnetic functions, from integrated circuits in the high-frequency region to magnetic recording media. In particular, in recent years, due to the rapid development of micro-nano device-related technologies, miniaturization and weight reduction of various electric and electronic devices have been achieved, and the research from bulk to low-dimensional nano materials has been expanded for the purpose of simultaneously using high functionality and multi-function. However, demand for this is rapidly increasing.

In line with this, as ferrite materials are being developed into structures such as thin films or nanowires, the driving frequency band is increased to GHz, and research and development into materials having high thermal stability, high permeability and resonance frequency is actively underway.

In particular, according to recent ferrite thin film research trends, various ferrite thin film manufacturing methods, such as a sol-gel method, which is an aqueous solution-based synthesis method and a spin-spray synthesis method, which uses an electroless plating method based on an oxidation-reduction reaction, are used in methods such as traditional sputtering. It was developed. However, a manufacturing method such as a sputtering method or a chemical vapor deposition method has the advantage of being capable of forming a high-quality thin film, but is relatively unsuitable for controlling the properties of a ferrite thin film, and wastes cost and time for additional work for changing the composition. The disadvantage is that it is severe.

On the other hand, the spin-spray synthesis method based on the oxidation-reduction reaction has attracted attention in the production of ferrite thin films. The spin-spray synthesis method does not require high vacuum and can easily control the composition of the ferrite thin film itself through the mixing of a metal solvent in the reaction solution, thereby making it easy to control the magnetic and electrical properties of the film.

The typical spinel structure of Ni-Zn ferrite has a relatively high electrical resistivity, so it can be used up to a high frequency region (around 50 MHz) and is actively used as a magnetic material in the microwave region due to advantages such as high saturation magnetic flux density. However, Ni-Zn ferrite has a high electrical resistance and thus exhibits electrical insulator characteristics, making it difficult to utilize other than magnetic elements.

The present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a photosensitive ferrite thin film having high functionality and capable of reacting to external stimuli and a method for manufacturing the same.

A method of manufacturing a photosensitive ferrite thin film according to an aspect of the present invention for achieving the above object includes the steps of positioning a substrate on a rotating device; And forming a M-Ni-Zn ferrite thin film by spraying a raw material on a rotating substrate.

M may be any one of Cu ²⁺ , Cd ²⁺ , Co ²⁺ , Ca ²⁺ , Mg ²⁺ and Mn ²⁺ .

The raw material may be a chloride-based solvent.

The raw material may be at least one of MnCl ₂ , CoCl ₂ , MgCl ₂ , CuCl ₂ , NiCl ₂ , ZnCl ₂ and FeCl ₂ .

When the photosensitive ferrite thin film is a Cu-Ni-Zn ferrite thin film, the molar ratio of CuCl ₂ , NiCl ₂ , and ZnCl ₂ may be 2: 3: 50.

The substrate may include any one of polyimide and polydimethylsiloxane, a flexible polymer substrate, an oxide-based wafer of SiO ₂ and Al ₂ O ₃ , and a nitride-based wafer of GaN.

According to another aspect of the present invention, there is provided a photosensitive ferrite thin film prepared by positioning a substrate on a rotating device and spraying a raw material on a rotating substrate to form an M-Ni-Zn ferrite thin film. The photosensitive ferrite thin film may have photoreactivity.

According to the present invention, by adding metal ions to Ni-Zn ferrite, while maintaining the existing excellent magnetic properties, while controlling electrical resistance and other electrical properties and having photoreactivity, the effect of overcoming limitations on the use of ferrite elements There is.

In addition, the method of manufacturing a photosensitive ferrite thin film according to the present invention is effective in that it is possible to synthesize a ferrite thin film of binary or ternary or more based on the stability of the spin-spray synthesis method, and is capable of producing a stable thin film with good productivity. .

Furthermore, when the photosensitive ferrite thin film according to the present invention is used, there is an effect that a relatively simple form of an optical switch element can be realized through a single ferrite film without complicated processes such as bonding of heterogeneous materials.

1 is a view showing a device for forming a ferrite layer by a spin spray method.
2 is a SEM image of the photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention.
3 is XRD results of the photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention.
4 is XPS results of the photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention.
Figure 5 shows the results of measuring the permeability (u ') at a frequency of 6.78 MHz for the photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention.
6 is an SEM image of a photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention and a Ni-Zn ferrite thin film without addition of metal ions.
7 is an XRD measurement result of a photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention and a Ni-Zn ferrite thin film without addition of metal ions.
8 is a result of measuring the magnetic properties of the photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention and a Ni-Zn ferrite thin film without addition of metal ions.
9 is a schematic view of an optical switching device according to the present invention.
10 is a graph showing a current-voltage characteristic in a channel irradiated with visible light in the optical switching device according to the present invention.
11 is a graph showing a result of measuring a current change by irradiating light on and off a ferrite channel in an optical switching device according to the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art. In the accompanying drawings, there may be components shown to have a specific pattern or have a predetermined thickness, but this is for convenience of explanation or distinction, so even if it has a specific pattern and a predetermined thickness, the features of the components shown in the present invention It is not limited to.

In the present invention, M-Ni-Zn ferrite is prepared. M may be any one of Cu ²⁺ , Cd ²⁺ , Co ²⁺ , Ca ²⁺ , Mg ²⁺ and Mn ²⁺ . Of the ferrites, the Ni-Zn ferrite of the spinel structure has a relatively high electrical resistivity, so it can be used in the high frequency region (around 50 MHz) and is used as a magnetic material in the microwave region due to advantages such as high saturation magnetic flux density. However, Ni-Zn ferrite has high electrical resistance and shows electrical insulator properties, so there is a limit to utilization other than magnetic elements. Thus, in the present invention, metal ions are added to Ni-Zn ferrite to improve the electrical properties of Ni-Zn ferrite.

The M-Ni-Zn ferrite according to the present invention is a divalent cation, Cu ²⁺ , Cd ²⁺ , Co ²⁺ , Ca ²⁺ , Mg ² , which can affect the composition and chemical bonding inside the Ni-Zn ferrite. Ni in the Ni-Zn ferrite is partially replaced by ⁺ and Mn ²⁺ . Ni-Zn ferrite can be structurally changed to change its electron behavior and physical and chemical properties.

The added metal ions have a large ionic radius compared to Ni ions and have a different preference for the spinel structure Ni-Zn ferrite. Accordingly, the incorporation of metal ions into the matrix of Ni-Zn ferrite can change many properties as an effect of modifying the cation distribution. In particular, the addition of metal ions can control the electrical distribution determined through the electron distribution of the valence state of ferrite and the electron exchange of Fe ²⁺ and Fe ³⁺ , and based on this, the use of Ni-Zn ferrite Various functionalities suitable for the purpose can be given.

A method of manufacturing a photosensitive ferrite thin film according to the present invention comprises the steps of positioning a substrate on a rotating device; And forming a M-Ni-Zn ferrite thin film by spraying a raw material on a rotating substrate.

M-Ni-Zn ferrite may be produced by a spin-spray synthesis method according to the method for manufacturing a photosensitive ferrite thin film according to the present invention. 1 is a view showing a device for forming a ferrite layer by a spin spray method. Referring to FIG. 1, a rotating table that is a rotating device capable of rotating while maintaining a constant temperature on a substrate, a batch storing a reaction solution and an oxidizing solution, and a pump connected in two batches are connected to each other to pump a constant solution over the substrate. A spin spray device consisting of two nozzles capable of spraying at a particle size is shown.

The spin-spray synthesis method does not require high vacuum, has the advantage of being easy to produce in the form of a membrane compared to the sol-gel method, and has no advantages such as post-heat treatment, and thus has advantages in processing time. The ferrite thin film manufactured using the spin-spray synthesis method has a thickness of hundreds of nanometers, grows in a columnar structure, and thus has a higher permeability at high frequencies, and has characteristics such as overcoming Sneok's limitations of existing bulk ferrites. .

In order to prepare a ferrite layer by spin-spray synthesis, a reaction solution containing a raw material to which a metal ion is added and a reaction solution for an oxidation reaction are used. In order to control the composition of the ferrite thin film, a chloride-based solvent based on a metal ion may be used as the reaction solution.

Therefore, the raw material may be at least one of MnCl ₂ , CoCl ₂ , MgCl ₂ , CuCl ₂ , NiCl ₂ , ZnCl ₂ and FeCl ₂ .

When the metal ion contained in the Ni-Zn ferrite is copper, since the photosensitive ferrite thin film is a Cu-Ni-Zn ferrite thin film, the raw materials used are CuCl ₂ , NiCl ₂ , and ZnCl ₂ and FeCl ₂ . At this time, the molar ratio of CuCl ₂ , NiCl ₂ , and ZnCl ₂ may be 2: 3: 50.

The substrate has good insulating properties, and a substrate having high utilization as an electronic device can be used. The substrate may be a flexible polymer substrate such as polyimide and polydimethylsiloxane, an oxide-based wafer such as SiO ₂ and Al ₂ O ₃ , or a nitride-based wafer such as GaN.

Hereinafter, a method for manufacturing a photosensitive ferrite thin film according to the present invention will be described through specific test examples. However, the following test examples do not limit the present invention.

[Production of Cu-Ni-Zn ferrite thin film by spin-spray synthesis method]

Using a device for spin-spray synthesis as shown in FIG. 1, when a substrate on which a ferrite thin film is grown is placed on a rotating table, and a reaction solution and an oxidizing liquid sprayed onto the rotating substrate together with the rotating table are supplied, the ferrite thin film is a substrate. Grow on top.

CuCl ₂ , NiCl ₂ , ZnCl ₂ and FeCl ₂ were used as the reaction liquid as a raw material, and NaNO ₂ solution was used for the oxidation-reduction reaction with the metal chloride solvent, and CH ₃ COOHN ₄ buffer was mixed. Used. In order to induce the reduction reaction of each metal ion, the pH of the whole oxidizing solution was adjusted between 7.5 and 8.5 using ammonia water. At this time, in order to prevent oxidation in an external atmospheric environment during the reaction, an experiment was conducted by making the reaction chamber inside a nitrogen atmosphere.

The temperature of the rotary table was fixed at 90 ° C so that the reaction solution and the oxidizing solution reacted well and the ferrite film could grow, and in addition, the table was used to improve the uniformity of the synthesized ferrite film and increase the reaction efficiency of the sprayed solution. It was rotated at 150 to 200 rpm.

The amount of the solvent added to the reaction solution is 20 mMol / L of FeCl ₂ , 5 mMol / L of NiCl ₂ , and 0.3 mMol / L of ZnCl ₂ with tertiary deionized water. The amount of the solvent added in the oxidizing solution was 4.4 mMol / L of NaNO _{2 and} 65 mMol / L of CH ₃ COOHN ₄ buffer was mixed with deionized water, and the pH was fixed to 8.0 using ammonia water.

In this experiment, copper ions are added to control the electrical properties of the Ni-Zn ferrite film, and for this purpose, a CuCl ₂ solvent is additionally added to the reaction solution to control the composition of the grown ferrite film.

In order to minimize the effect of impurities generated by overreaction of the metal ions to be added, a method of manufacturing a ferrite film having a stable composition is provided, and a decrease in the permeability of the ferrite film is minimized.

The content of CuCl ₂ was 0.1 mMol / L in Example 1, 0.2 mMol / L in Example 2, 0.3 mMol / L in Example 3, and 0.4 mMol / L in Example 4.

2 is a SEM image of the photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention. In the case of Examples 1 and 2, it grows showing clear columnar structure properties. However, in Examples 3 and 4 in which the CuCl ₂ content is 0.3 mMol / L or more, ferrite thin films having poor quality without showing columnar structure characteristics were synthesized because growth conditions were not met due to excessive inclusion of copper ions and non-uniformity of the reduction reaction.

3 is XRD results of the photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention. In Examples 1 to 4, peaks of (220), (311), (400), (511) and (440) were observed in the range of 2θ = 20 to 80 °. As a result, it was found that the Cu-Ni-Zn ferrite thin film grown by varying the CuCl ₂ content had a spinel structure. In Example 1 and Example 2, a structurally stable Cu-Ni-Zn ferrite film was grown, and spinel peaks were observed in all regions. In Examples 3 and 4, peaks other than the peaks of the spinel structures were observed, or The size of the XRD signal with respect to the peak was small, so it was not observed.

4 is XPS results of the photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention. The XPS results for Examples 1 to 4 also reflected the structural characteristics of the generated examples similar to the XRD results of FIG. 3.

Figure 5 shows the results of measuring the permeability (u ') at a frequency of 6.78 MHz for the photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention. In Examples 1 and 2, the permeability (u ') increased from 570 to 680, and as the content of copper ions increased as in Examples 3 and 4, the permeability rapidly decreased from 530 to 400. This is considered to be because the proportion of copper ions increases in the overall structure, and the crystallinity and magnetic properties decrease.

The Ni-Zn ferrite film containing copper ions was prepared in the Cu-Ni-Zn ferrite film having the best magnetic properties in Example 2 in which 0.2 mMol / L of CuCl ₂ was added according to the above experimental results, and the prepared ferrite thin film was structural It has the characteristics of hundreds of nano-sized grains and a uniform columnar structure, so it has a high magnetic permeability even in the high frequency region, and can be utilized as a magnetic element and an electronic element based on its characteristics. Hereinafter, further experiments were performed using the ferrite thin film of Example 2 in which CuCl ₂ was added to 0.2 mMol / L.

6 is an SEM image of a photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention and a Ni-Zn ferrite thin film without addition of metal ions. Comparative example is a Ni-Zn ferrite thin film without copper ions added, and it can be confirmed that the SEM image showed very clear columnar structure characteristics and grew. The Cu-Ni-Zn ferrite film of Example 2 also exhibited clear columnar structure properties. Therefore, it was confirmed that the production conditions of the Cu-Ni-Zn ferrite film were sufficiently stable compared to the production method of the stable Ni-Zn ferrite film.

7 is an XRD measurement result of a photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention and a Ni-Zn ferrite thin film without addition of metal ions. In Comparative Example and Example 2, peaks of (220), (311), (400), (511) and (440) corresponding to the spinel structure were observed in the range of 2θ = 20 to 80 °. As a result of this, it was found that the Cu-Ni-Zn ferrite thin film prepared by adding copper ions had a spinel structure like the Ni-Zn ferrite thin film. Based on these results, it was confirmed that the ferrite thin film grown by adding copper ions has stable crystallinity that can be used for magnetic and electronic devices.

8 is a result of measuring the magnetic properties of a photosensitive ferrite thin film prepared by the method for manufacturing a photosensitive ferrite thin film according to the present invention and a Ni-Zn ferrite thin film without addition of metal ions. From FIG. 8, it can be confirmed that the magnetic properties of the ferrite film of Comparative Example and Example 2 show a difference in the real number of complex permeability. In particular, it can be seen that the Ni-Zn ferrite film of the comparative example has a permeability value of about 700 at a frequency of 6.78 MHz. The ferrite thin film of Example 2 produced through the method of the present invention exhibited a permeability value of about 680 at a frequency of 6.78 MHz. It was confirmed that copper ions were added to the ferrite film for optical switching prepared by adding CuCl ₂ to the reaction solution, but the reduction in magnetic properties and structural properties was small compared to the comparative example.

[Production of optical switching elements]

In the present invention, based on the experiment method and environment described above, a basic binary Ni-Zn ferrite film (comparative example) and a ternary ferrite film for optical switching with metal ions added (Example 2) are prepared and used. Thus, an optical switching element was produced.

By using the photosensitive ferrite thin film according to the present invention, it is possible to manufacture a single material-based optical switching electronic device, not an optical switching device using a complex structure such as the use and bonding of dissimilar materials. A typical optical switching element implements an optical switching element through junction of n-type p-type semiconductor materials and the like and current movement thereof. The optical switching device of the present invention has a feature of realizing optical switching characteristics by controlling the flow of current when irradiated with light using a high-quality Cu-Ni-Zn ferrite thin film. The optical switching device manufactured according to the present invention can secure the stability and uniformity of operation by using a single material and simplify the manufacturing process.

An insulating substrate is used for the optical switching element according to the present invention. For example, SiO ₂ / Si, SiNx / Si, Al ₂ O ₃ , MgO, or GaN may be used as the substrate. In addition, the substrates are based on silicon-based oxide, carbide substrates, group III-V compound semiconductors such as gallium arsenide and gallium phosphide, group II-IV compound semiconductors such as zinc oxide, group IV compound semiconductors, organic semiconductors, and glass. Substrates such as compounds can be used.

9 is a schematic view of an optical switching device according to the present invention. The optical switching element in the present invention is fabricated based on a two-terminal element, and the electrode is composed of a cathode and an anode. The cathode and anode are connected to both ends of a channel composed of a ferrite thin film. The current and voltage are provided to the ferrite channel through the anode, and the light is irradiated to the channel to measure the current flow and thereby drive the switching element. The cathode and the anode may be formed of a conductor, for example, a double layer of titanium and gold (Ti / Au), or copper, nickel, or the like.

Referring to FIG. 9, the switching device of the present invention includes a substrate, a ferrite thin film channel, a cathode, and an anode. Device fabrication consists of growing a ferrite film for optical switching on a substrate, forming a ferrite channel, and forming an electrode. The ferrite thin film for optical switching is prepared as in Example 2 described above, and can be patterned into a dimension of W 10 um * L 20 um using a photolithography method. An electrode composed of a double layer (Ti / Au) of titanium and gold is formed on the ferrite channel pattern by using a common DC and e-beam evaporation method at both ends of the ferrite channel pattern.

10 is a graph showing a current-voltage characteristic in a channel irradiated with visible light in the optical switching device according to the present invention. It is a curve that irradiates light to the optical switching element perpendicular to the channel and measures current-voltage. By changing the voltage from -4V to + 4V through the electrode, the corresponding current characteristics were measured, and the intensity of the light was adjusted to 1, 3, 5 and 10 mW by adjusting the power of the visible light lamp, and The size was analyzed. Referring to FIG. 10, as the power of the irradiated light increased, the magnitude of the current increased, and when irradiating light of 5 mW or more, it was confirmed that the magnitude of the measured current appeared saturated.

11 is a graph showing a result of measuring a current change by irradiating light on and off a ferrite channel in an optical switching device according to the present invention. A constant voltage is applied to the electrode, and light is periodically turned on and off to the channel for irradiation. When light is irradiated to the channel, the light and light switching ferrite film react to lower the resistance, generate a carrier, and the current level rises. When the application of light is removed, the current characteristic is lowered to the existing low level current level. It is implemented in the form of On-Off switching by the light. As a result, as described above, by controlling the light applied to the ferrite channel, the optical switching system operates.

The photosensitive ferrite thin film manufactured according to the present invention is easy to use as a magnetic property material such as electromagnetic shielding of a magnetic element such as a thin film type inductor and an integrated device, and also based on a characteristic in which electrical properties change by light Therefore, it can be used as a material for electronic devices for optical switches.

The embodiments of the present invention have been described above, but those skilled in the art can add, change, delete, or add components without departing from the spirit of the present invention as set forth in the claims. The present invention may be variously modified and changed by the like, and it will be said that this is also included within the scope of the present invention.

Claims (8)

Positioning the substrate on a rotating device; And
And forming a M-Ni-Zn ferrite thin film by spraying a raw material on a rotating substrate. The method according to claim 1,
M is Cu ²⁺ , Cd ²⁺ , Co ²⁺ , Ca ²⁺ , Mg ²⁺ and Mn ²⁺ is any one of the methods for manufacturing a photosensitive ferrite thin film. The method according to claim 1,
The raw material is a method of manufacturing a photosensitive ferrite thin film, characterized in that a chloride-based solvent. The method according to claim 1,
The raw material is MnCl ₂ , CoCl ₂ , MgCl ₂ , CuCl ₂ , NiCl ₂ , ZnCl ₂ And FeCl ₂ Photosensitive ferrite thin film production method characterized in that at least one. The method according to claim 4,
When the photosensitive ferrite thin film is a Cu-Ni-Zn ferrite thin film, the molar ratio of CuCl ₂ , NiCl ₂ , and ZnCl ₂ is 2: 3: 50. The method according to claim 1,
The substrate comprises any one of a polyimide and a polydimethylsiloxane flexible polymer substrate, SiO ₂ and Al ₂ O ₃ oxide-based wafer, and GaN nitride-based wafer, any one of the photosensitive ferrite. Thin film manufacturing method. Light-sensitive ferrite thin film prepared according to the manufacturing method according to claim 1. The method according to claim 7,
Light-sensitive ferrite thin film, characterized in that by controlling the current according to the applied voltage when irradiated with light.

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