Preparation method and application of high energy storage density ferroelectric thin film materials

Abstract

The invention discloses a preparation method and application of a high energy storage density ferroelectric thin film material, belonging to the field of electronic information materials and components, which comprises placing a composite substrate and a ceramic target material together in a sputtering chamber; adjusting the target-substrate distance; introducing a mixed gas of argon and oxygen into the sputtering chamber after evacuating the chamber; and sputtering under certain conditions to obtain a ferroelectric ceramic thin film. The composite substrate comprises Si, SiO2, Ti (20nm) and Pt (150nm) bottom electrodes from bottom to top, and the chemical structure of the ferroelectric thin film with ferroelectric effect is Ba(Zr 0.35 Ti 0.65 )O3(BZT35), with a thickness of 200‑400nm. By changing the ratio of argon to oxygen during the preparation process, the concentration of oxygen vacancies and other holes in the film is regulated, affecting the leakage current mechanism of the film, thereby producing a ferroelectric film with a large energy storage density. The ferroelectric film has good dielectric, ferroelectric and withstand voltage properties at room temperature, as well as good frequency stability.

Description

Technical Field

[0001] The invention belongs to the field of electronic information materials and components, and particularly relates to a ferroelectric film with high energy storage density based on ferroelectric effect and a preparation method thereof. Background Art

[0002] With the development of science and technology, pulse power technology is widely used in electronic weapons, hybrid electric vehicles, high-frequency inverters, lasers, radars, accelerators and other fields. As a key component of pulse power equipment, pulse capacitors need to have the characteristics of withstanding extremely high voltages and large discharge currents in a short period of time. In order to meet this demand, the dielectric materials used in pulse capacitors need to have a high energy storage density.

[0003] In recent years, ferroelectric materials have attracted more and more attention due to their excellent energy storage performance. Barium titanate (BaTiO3) is a typical lead-free perovskite ferroelectric material with excellent ferroelectric and dielectric properties. It is considered to have potential application prospects in infrared sensors, thin film capacitors, ferroelectric memories and tunable microwave devices. In addition, since barium titanate does not contain lead, the application of BaTiO3-based solid solutions has also attracted the attention of many researchers.

[0004] Barium zirconate titanate (BaZr x Ti 1-x O3) belongs to the barium titanate (BaTiO3) series, and is a new lead-free perovskite ferroelectric material obtained by substitution of the B position. 4+ With Ti 4+ Larger ionic radius, better chemical stability, and can inhibit Ti 4+ To Ti 3+ Compared with bulk materials, thin film materials have the advantages of small size, light weight, easy preparation, and dense surface, and the performance of thin films can be adjusted by changing the film thickness, substrate type, etc.

[0005] The main methods for preparing BZT thin films include magnetron sputtering, sol-gel method, pulsed laser deposition method, etc. Magnetron sputtering is a physical method that can prepare large-area thin films at low cost. When using magnetron sputtering to prepare BZT thin films, the volume ratio of argon and oxygen introduced during the preparation process is particularly important. When an inappropriate volume ratio of argon and oxygen is introduced, a ferroelectric thin film with high energy storage density cannot be prepared. Summary of the invention

[0006] The purpose of the present invention is to provide a ferroelectric film with high energy storage density based on the ferroelectric effect, and also provide a method for preparing the ferroelectric film. 0.35 Ti 0.65)O3 ceramic target is used as raw material and the ferroelectric thin film is prepared by magnetron sputtering. The thin film has the advantages of high energy storage density, high energy storage efficiency and low loss.

[0007] The present invention is achieved through the following technical solutions:

[0008] A ferroelectric film with high energy storage density based on ferroelectric effect is deposited on a Pt(111) / Ti / SiO2 / Si composite substrate, wherein the composite substrate is Si, SiO2, Ti (20nm) and Pt (150nm) bottom electrodes from bottom to top, and the chemical structure of the ferroelectric film with ferroelectric effect is Ba(Zr 0.35 Ti 0.65 )O3(BZT35), thickness is 200-400nm.

[0009] The preparation method of the ferroelectric thin film comprises the following steps:

[0010] The Pt(111) / Ti / SiO2 / Si substrate and the BZT35 ceramic target were placed in the sputtering chamber, the target-substrate distance was adjusted to 7 cm, and the vacuum was evacuated to 1×10 -4 ~2×10 -4 Pa, and then a mixed gas with a pressure of 1.2 Pa and a volume ratio of argon to oxygen of 40:0 to 40:15 is introduced, the substrate temperature is 500 to 700°C, the RF power is 100 to 140 W, the sputtering time is 20 to 120 min, and the chamber is kept warm in a pure oxygen atmosphere for 10 to 30 minutes. After cooling to room temperature, it is taken out from the sputtering chamber to obtain a ferroelectric ceramic film.

[0011] The advantages of the present invention are:

[0012] The present invention uses magnetron sputtering to prepare a ferroelectric thin film Ba(Zr) with high energy storage density. 0.35 Ti 0.65 )O3, and by adjusting the volume ratio of argon and oxygen during the preparation process, a ferroelectric film with the best energy storage density is obtained. The ferroelectric film has good dielectric, ferroelectric and voltage resistance properties at room temperature, as well as good frequency stability. The film obtained under the preparation process with an argon-oxygen ratio of 40:10 has a maximum energy storage density of 48.03 J / cm 3 , the energy storage efficiency is 87.7%. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the structure of the ferroelectric thin film of the embodiment.

[0014] Figure 2 XRD analysis shows that the film is composed of perovskite phase Ba(Zr 0.35 Ti 0.65)O3(110), (200), (210).

[0015] Figure 3 Graph of dielectric constant and dielectric loss for example.

[0016] Figure 4 It is the Weibull statistical distribution diagram of the breakdown field strength of the embodiment.

[0017] Figure 5 (a), (b), (c), and (d) are hysteresis loop diagrams of Examples 1, 2, 3, and 4, respectively.

[0018] Figure 6 Graph showing energy storage density and energy storage efficiency of an embodiment. DETAILED DESCRIPTION

[0019] The present invention uses Ba(Zr 0.35 Ti 0.65 )O3 ceramic target material is used as raw material, and a ferroelectric thin film is prepared by a magnetron sputtering method. The specific embodiment is as follows:

[0020] Embodiment 1:

[0021] 1. Pt(111) / Ti / SiO2 / Si substrate and Ba(Zr 0.35 Ti 0.65 )O3 ceramic target is placed in the sputtering chamber and the sputtering chamber is evacuated to 1×10 -4 ~2×10 -4 Pa;

[0022] 2. Heat the substrate to a substrate temperature of 600°C;

[0023] 3. Fill the sputtering chamber with a mixture of argon and oxygen to make the pressure in the sputtering chamber 1.2 Pa, and adjust the volume ratio of argon and oxygen to 40:0;

[0024] 4. Adjust the RF power source to 120W to start sputtering, and turn off the RF power source after sputtering for 60 minutes;

[0025] 5. Turn off the argon gas and fill only with oxygen until the pressure in the sputtering chamber is 100 Pa, and keep the substrate temperature at 600°C for 10 minutes;

[0026] 6. After naturally cooling to room temperature, a ferroelectric film with high energy storage density is obtained.

[0027] Figure 1 A schematic diagram of the structure of the ferroelectric thin film is given. Figure 2 XRD analysis shows that the film is composed of perovskite phase Ba(Zr 0.35 Ti 0.65 )O3(110), (200), (210). The dielectric constant and dielectric loss are as follows: Figure 3 As shown, the breakdown field strength is Figure 4 As shown, the hysteresis loop is Figure 5 As shown in (a), 22.48 J / cm was obtained at 3.20 MV / cm 3 It can be seen that the film obtained in this embodiment has a large breakdown field strength and energy storage density at room temperature.

[0028] Embodiment 2:

[0029] 1. Pt(111) / Ti / SiO2 / Si substrate and Ba(Zr 0.35 Ti 0.65 )O3 ceramic target is placed in the sputtering chamber and the sputtering chamber is evacuated to 1×10 -4 ~2×10 -4 Pa;

[0030] 2. Heat the substrate to a substrate temperature of 600°C;

[0031] 3. Fill the sputtering chamber with a mixture of argon and oxygen to make the pressure in the sputtering chamber 1.2 Pa, and adjust the volume ratio of argon and oxygen to 40:5;

[0032] 4. Adjust the RF power source to 120W to start sputtering, and turn off the RF power source after sputtering for 60 minutes;

[0033] 5. Turn off the argon gas and fill only with oxygen until the pressure in the sputtering chamber is 100 Pa, and keep the substrate temperature at 600°C for 10 minutes;

[0034] 6. After naturally cooling to room temperature, a ferroelectric film with high energy storage density is obtained.

[0035] Figure 1 A schematic diagram of the structure of the ferroelectric thin film is given. Figure 2 XRD analysis shows that the film is composed of perovskite phase Ba(Zr 0.35 Ti 0.65 )O3(110), (200), (210). The dielectric constant and dielectric loss are as follows: Figure 3 As shown, the breakdown field strength is Figure 4 As shown, the hysteresis loop is Figure 5 (b) shows that 28.93 J / cm2 was obtained at 3.81 MV / cm2. 3 .from Figure 6 It can be seen that the film obtained in this embodiment has a larger breakdown field strength and energy storage density at room temperature. Since the increase in the oxygen ratio reduces the oxygen vacancy concentration in the film, the energy storage performance of the film is slightly increased compared with Example 1.

[0036] Embodiment 3:

[0037] 1. Pt(111) / Ti / SiO2 / Si substrate and Ba(Zr 0.35 Ti 0.65 )O3 ceramic target is placed in the sputtering chamber and the sputtering chamber is evacuated to 1×10 -4 ~2×10 -4 Pa;

[0038] 2. Heat the substrate to a substrate temperature of 600°C;

[0039] 3. Fill the sputtering chamber with a mixture of argon and oxygen to make the pressure in the sputtering chamber 1.2 Pa, and adjust the volume ratio of argon and oxygen to 40:10;

[0040] 4. Adjust the RF power source to 120W to start sputtering, and turn off the RF power source after sputtering for 60 minutes;

[0041] 5. Turn off the argon gas and fill only with oxygen until the pressure in the sputtering chamber is 100 Pa, and keep the substrate temperature at 600°C for 10 minutes;

[0042] 6. After naturally cooling to room temperature, a ferroelectric film with high energy storage density is obtained.

[0043] Figure 1 A schematic diagram of the structure of the ferroelectric thin film is given. Figure 2 XRD analysis shows that the film is composed of perovskite phase Ba(Zr 0.35 Ti 0.65 )O3(110), (200), (210). The dielectric constant and dielectric loss are as follows: Figure 3 As shown, the breakdown field strength is Figure 4 As shown, the hysteresis loop is Figure 5 (c) shows that 48.03 J / cm was obtained at 4.50 MV / cm 3 .from Figure 6 It can be seen that the film obtained in this embodiment has the largest breakdown field strength and energy storage density of all the embodiments at room temperature. This is because an appropriate amount of oxygen is introduced during the preparation process to reduce the oxygen vacancy concentration of the film and the concentration of other holes does not increase significantly, so that the film obtained under this process has the best energy storage performance.

[0044] Embodiment 4:

[0045] 1. Pt(111) / Ti / SiO2 / Si substrate and Ba(Zr 0.35 Ti 0.65 )O3 ceramic target is placed in the sputtering chamber and the sputtering chamber is evacuated to 1×10 -4 ~2×10 -4 Pa;

[0046] 2. Heat the substrate to a substrate temperature of 600°C;

[0047] 3. Fill the sputtering chamber with a mixture of argon and oxygen to make the pressure in the sputtering chamber 1.2 Pa, and adjust the volume ratio of argon and oxygen to 40:15;

[0048] 4. Adjust the RF power source to 120W to start sputtering, and turn off the RF power source after sputtering for 60 minutes;

[0049] 5. Turn off the argon gas and fill only with oxygen until the pressure in the sputtering chamber is 100 Pa, and keep the substrate temperature at 600°C for 10 minutes;

[0050] 6. After naturally cooling to room temperature, a ferroelectric film with high energy storage density is obtained.

[0051] Figure 1 A schematic diagram of the structure of the ferroelectric thin film is given. Figure 2 XRD analysis shows that the film is composed of perovskite phase Ba(Zr 0.35 Ti 0.65 )O3(110), (200), (210). The dielectric constant and dielectric loss are as follows: Figure 3 As shown, the breakdown field strength is Figure 4 As shown, the hysteresis loop is Figure 5 (d) shows that 27.60 J / cm was obtained at 3.90 MV / cm 3 .from Figure 6 It can be seen that the film obtained in this embodiment has a large breakdown field strength and energy storage density at room temperature, but due to excess oxygen in the preparation process, the concentration of positively charged holes increases while the concentration of oxygen vacancies decreases, causing the energy storage performance of the film to be slightly lower than that of Example 3.

[0052] The relevant process parameters and energy storage performance of the specific embodiment are shown in Table 1.

[0053] Table 1

[0054]

[0055] It can be seen from the above embodiments that the energy storage film involved in the present invention is a single-layer ferroelectric film. By changing the ratio of argon to oxygen during the preparation process to control the concentration of oxygen vacancies and other holes in the film, the leakage current mechanism of the film is affected, thereby obtaining a ferroelectric film with a large energy storage density. The present invention uses BZT35 ferroelectric material with a large polarization difference and high withstand voltage to prepare an energy storage film, which is conducive to obtaining better energy storage performance. Compared with other energy storage films, BZT35 film has the advantages of large dielectric constant, large energy storage density, high energy storage efficiency and good pressure resistance, which is of great significance for meeting the actual needs of future energy storage films. Ferroelectric films are prepared by magnetron sputtering, and the process is simple and compatible with other semiconductor processes. The ferroelectric film obtained by the present invention has good dielectric, ferroelectric and withstand voltage properties at room temperature, as well as good frequency stability. The film obtained under the preparation process with an argon-oxygen ratio of 40:10 has a maximum energy storage density of 48.03 J / cm 3 The energy storage efficiency is 87.7%. The high energy storage density ferroelectric thin film material obtained by the present invention can be applied to the fields of electronic weapons, hybrid electric vehicles, high-frequency inverters, lasers, radars, accelerators, etc.

Claims

1. A method for preparing a ferroelectric thin film material with high energy storage density, characterized in that: placing the composite substrate and the ceramic target together into a sputtering chamber; Adjust the target-substrate distance; adjust the target-substrate distance to 7 cm, and evacuate to 1×10 -4 ~2×10 -4 Pa; After the sputtering chamber is evacuated, a mixture of argon and oxygen is introduced; the pressure of the mixture of argon and oxygen is 1.2 Pa and the volume ratio is 40:10; Ferroelectric ceramic thin film was obtained by sputtering under certain conditions; the substrate temperature was set to 500-700°C, the radio frequency power was set to 100-140W, and the sputtering time was set to 20-120min; the argon gas was turned off and only oxygen was filled in, and the temperature was kept in the sputtering chamber for 10-30 minutes; The ceramic target is Ba(Zr 0.35 Ti 0.65 )O3(BZT35).

2. The method for preparing a ferroelectric thin film material with high energy storage density according to claim 1, characterized in that: The composite substrate is Pt(111) / Ti / SiO2 / Si.

3. The method for preparing a ferroelectric thin film material with high energy storage density according to claim 1, characterized in that: The composite substrate is Si, SiO2, 20nm thick Ti and 150nm thick Pt bottom electrode from bottom to top.

4. A high energy storage density ferroelectric thin film material, characterized in that: Prepared by the method according to any one of claims 1 to 3.

5. The high energy storage density ferroelectric thin film material according to claim 4, characterized in that: The invention comprises a ferroelectric film deposited on a Pt(111) / Ti / SiO2 / Si composite substrate, wherein the composite substrate comprises Si, SiO2, Ti with a thickness of 20 nm and a Pt bottom electrode with a thickness of 150 nm from bottom to top, and the chemical structure of the ferroelectric film having a ferroelectric effect is Ba(Zr 0.35 Ti 0.65 )O3(BZT35), thickness is 200-400nm.

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