Strontium iridate thin film heterojunction with low-temperature abnormal hall effect, preparation method and application

Abstract

The application relates to the field of semiconductor technology and discloses an iridium strontium film heterojunction with low-temperature abnormal Hall effect, a preparation method and application, the heterojunction comprising an SrIrO3 single crystal film epitaxially grown on the surface of an SrTiO3 substrate with a crystal face orientation of (001) and a SmNiO3 single crystal film epitaxially grown on the surface of the SrIrO3 single crystal film; the application grows an SrIrO3 single crystal film on the pretreated SrTiO3 substrate through a pulse laser deposition system; a certain thickness of SmNiO3 single crystal film is epitaxially grown on the grown SrIrO3 epitaxial film by using the pulse laser deposition technology to obtain the SrTiO3 / SmNiO3 heterojunction; the obtained heterojunction has a continuous regulation and control effect on the signal size of the abnormal Hall effect at a temperature below 50 K.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically to a strontium iridium thin film heterojunction with low-temperature anomalous Hall effect, its preparation method, and its application. Background Technology

[0002] Thin-film heterojunctions are interfaces formed by the contact of two or more semiconductor materials with different band structures. Their properties mainly depend on the band structures of the constituent materials and the contact method between them. Therefore, such devices can achieve target performance by flexibly combining different types of thin-film materials. The anomalous Hall effect (AHE) is a quantum transport phenomenon that occurs in magnetic materials. It is generated without an external magnetic field and originates from the intrinsic Berry curvature or magnetization properties of the material. The anomalous Hall effect has broad application prospects in spintronics, and thin-film heterojunctions with low-temperature anomalous Hall effects have wide application and research value in low-energy-consumption spintronic devices. Currently, common materials for realizing the anomalous Hall effect include ferromagnetic metals, topological insulators, and their heterojunctions. However, ferromagnetic-based devices typically operate above room temperature, making it difficult to meet the requirements of low-temperature quantum devices. Furthermore, the anomalous Hall effect of topological insulator heterojunctions is sensitive to interface defects, and their fabrication processes are complex and have poor reproducibility.

[0003] Strontium iridium oxide (SrIrO3), a strongly spin-orbit coupled 5d transition metal oxide, exhibits a wealth of novel quantum states, most notably its electronic structure, which may possess both topological nontriviality and magnetoelectric coupling effects. This allows the nonmagnetic SrIrO3 to generate a topology-protected low-temperature anomalous Hall effect in heterojunction systems, making it an ideal platform for studying novel quantum transport phenomena. This characteristic of SrIrO3 heterojunctions makes them valuable for spintronics research, providing a material basis for developing novel low-power spintronic devices. The electronic transport properties of SrIrO3 are highly susceptible to interfacial magnetic exchange, lattice coupling, and charge transfer; therefore, related research places high demands on the interface quality, structural symmetry, and low-temperature stability of the heterojunction. Complete interfacial magnetic coupling may correspond to a quantum anomalous Hall state, while precisely controlled interfacial interactions can achieve a significant anomalous Hall effect. This phenomenon is significant in spintronics and can provide a new material platform for low-power, non-volatile spin memory and logic devices. SrIrO3 heterojunctions exhibiting anomalous Hall effect at low temperatures are beneficial for developing novel spintronic devices with high density, resistance to magnetic field interference, and optimized energy consumption. Currently, the realization of the anomalous Hall effect in SrIrO3 heterojunctions mainly relies on methods such as interface charge transfer, strain engineering, or magnetic manipulation. However, existing SrIrO3 heterojunction fabrication methods suffer from cumbersome fabrication processes and difficulty in controlling the anomalous Hall resistance.

[0004] In view of this, it is necessary to provide a method for the stable growth of SrIrO3 heterojunctions with high anomalous Hall effect at low temperatures and a controllable growth method thereof. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a strontium iridium thin film heterojunction with low-temperature anomalous Hall effect, its preparation method, and its application.

[0006] The technical solution adopted in this invention is:

[0007] A strontium iridium thin film heterostructure exhibiting a low-temperature anomalous Hall effect.

[0008] The SrIrO3 single crystal film epitaxially grown on the surface of a SrTiO3 substrate with a crystal orientation of (001), and the SmNiO3 single crystal film epitaxially grown on the surface of the SrIrO3 single crystal film.

[0009] Furthermore, the thickness of the SrIrO3 single crystal film is 5 nm, and the thickness of the SmNiO3 single crystal film is 4–30 nm.

[0010] Furthermore, the heterojunction exhibits an anomalous Hall effect below 50K.

[0011] A method for preparing a strontium iridium thin film heterojunction with low-temperature anomalous Hall effect includes the following steps:

[0012] Step 1: Epitaxially grow a SrIrO3 single-crystal thin film on the surface of a SrTiO3 substrate using pulsed laser deposition;

[0013] Step 2: Using pulsed laser deposition, an epitaxial SmNiO3 single crystal film is grown on the surface of the SrIrO3 single crystal film obtained in Step 1 to obtain the desired heterojunction.

[0014] Furthermore, the SrTiO3 substrate in step 1 undergoes pretreatment before use. The pretreatment process is as follows:

[0015] First, use deionized water for ultrasonic cleaning for 600 seconds, then use anhydrous ethanol for ultrasonic cleaning for 600 seconds. Repeat the above cleaning process twice.

[0016] The cleaned SrTiO3 substrate was then etched and annealed.

[0017] The surface etching was performed using ammonium fluoride buffered hydrofluoric acid for 39 s, followed by annealing at 970 ℃ for 120 min.

[0018] Furthermore, the temperature during the pulsed laser deposition process in steps 1 and 2 is 700 ℃.

[0019] Furthermore, the SrIrO3 single-crystal thin film deposition process is carried out under oxygen conditions with an oxygen pressure of 100 mTorr; the pulsed laser conditions are as follows:

[0020] The laser repetition frequency is 2 Hz, and the laser energy density is 1.4 J / cm². 2 .

[0021] Furthermore, the SrIrO3 single crystal thin film in step 1 also includes heat treatment at a temperature of 700 °C for a time of 10 min.

[0022] Furthermore, the SmNiO3 single-crystal thin film deposition process in step 2 is carried out under oxygen conditions with an oxygen pressure of 100 mTorr; the pulsed laser conditions are as follows:

[0023] The laser repetition frequency is 2 Hz, and the laser energy density is 1.4 J / cm². 2 ;

[0024] After deposition, the oxygen pressure was maintained at 1 mTorr, and the mixture was cooled to room temperature at a rate of 10 °C / min.

[0025] Application of a strontium iridium thin film heterojunction with a low-temperature anomalous Hall effect, wherein the heterojunction is used to fabricate low-energy spintronic devices.

[0026] The beneficial effects of this invention are:

[0027] (1) The present invention uses pulsed laser deposition to achieve precise control over the growth process and interface structure of SrIrO3 and SmNiO3 single crystal thin films; the preparation method is simple and easy to control, and the obtained heterojunction has stable quality and high repeatability.

[0028] (2) The present invention uses SrTiO3 as a substrate. The lattice constant of SrTiO3 is similar to that of SmNiO3. The lattice mismatch of SrIrO3 and SmNiO3 single crystals is small, which ensures that SmNiO3 can be epitaxially grown on the surface of SrTiO3. The electronic transport characteristics of SrTiO3 are easily affected by interfacial magnetic exchange, which can obtain SrIrO3 and SmNiO3 heterojunctions with strong interfacial effects.

[0029] (3) The heterojunction obtained in this invention has antiferromagnetism in SmNiO3. It can induce the anomalous Hall effect with Berry curvature control through the interface exchange coupling between the antiferromagnetic order and the topological surface state of SrIrO3. The obtained heterojunction has the anomalous Hall effect at temperatures below 50 K, and the size of the anomalous Hall electron can be controlled with temperature changes. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the heterojunction obtained in this invention.

[0031] Figure 2 The image shows the XRD pattern of the SrIrO3 single crystal thin film obtained in step 1 of Example 1 of this invention.

[0032] Figure 3 The image shows the XRD pattern of the SmNiO3 single crystal thin film obtained in step 2 of Example 1 of this invention.

[0033] Figure 4 This is the curve showing the change in lateral resistance of the heterojunction with temperature obtained in Embodiment 1 of the present invention.

[0034] Figure 5 This is a curve showing the anomalous Hall resistance of the heterojunction obtained in Example 1 of the present invention as a function of magnetic field.

[0035] Figure 6 This is a scanning tunneling microscope image of the interface of the heterojunction obtained in Example 1 of the present invention.

[0036] Figure 7 The curve showing the relationship between the longitudinal resistance of the SrIrO3 single-crystal thin-film heterojunction and the magnetic field obtained in the comparative example of this invention is shown. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0038] A strontium iridium oxide thin film heterojunction exhibiting a low-temperature anomalous Hall effect comprises a SrIrO3 single-crystal thin film epitaxially grown on the surface of a SrTiO3 substrate with a crystal plane orientation of (001), and an SmNiO3 single-crystal thin film epitaxially grown on the surface of the SrIrO3 single-crystal thin film, with the structure as follows: Figure 1 As shown. The SrIrO3 single crystal film is located on the (001)SrTiO3 substrate and is stacked by pulsed laser deposition. The SmNiO3 single crystal film and the SrIrO3 film are also stacked by pulsed laser deposition.

[0039] The thickness of the SrIrO3 single-crystal thin film is 5 nm, and the thickness of the SmNiO3 single-crystal thin film is 4–30 nm. The heterojunction exhibits an anomalous Hall effect below 50 K, and temperature has a continuous modulating effect on the signal magnitude of the anomalous Hall effect.

[0040] A method for preparing a strontium iridium thin film heterojunction with low-temperature anomalous Hall effect includes the following steps:

[0041] Step 1: Epitaxial growth of SrIrO3 single-crystal thin films is performed on the surface of a SrTiO3 substrate using pulsed laser deposition; the SrTiO3 substrate undergoes pretreatment before use, and the pretreatment process is as follows:

[0042] First, use deionized water for ultrasonic cleaning for 600 seconds, then use anhydrous ethanol for ultrasonic cleaning for 600 seconds. Repeat the above cleaning process twice.

[0043] The cleaned SrTiO3 substrate was then etched and annealed.

[0044] The surface etching was performed using ammonium fluoride buffered hydrofluoric acid for 39 s, followed by annealing at 970 ℃ for 120 min.

[0045] The temperature during pulsed laser deposition is 700 ℃.

[0046] The SrIrO3 single-crystal thin film deposition process was carried out under oxygen conditions at a pressure of 100 mTorr; the pulsed laser conditions were as follows:

[0047] The laser repetition frequency is 2 Hz, and the laser energy density is 1.4 J / cm². 2 .

[0048] The SrIrO3 single crystal thin film also includes heat treatment at a temperature of 700 °C for 10 min; after heat treatment, proceed to step 2.

[0049] Step 2: Using pulsed laser deposition, an epitaxial SmNiO3 single crystal film is grown on the surface of the SrIrO3 single crystal film obtained in Step 1 to obtain the desired heterojunction.

[0050] The deposition process was carried out under oxygen conditions at a pressure of 100 mTorr; the pulsed laser conditions were as follows:

[0051] The laser repetition frequency is 2 Hz, and the laser energy density is 1.4 J / cm². 2 ;

[0052] After deposition, the oxygen pressure was maintained at 1 mTorr, and the mixture was cooled to room temperature at a rate of 10 °C / min.

[0053] Example 1

[0054] A method for preparing a strontium iridium thin film heterojunction with low-temperature anomalous Hall effect includes the following steps:

[0055] Step 1: Using a (001)SrTiO3 substrate with a thickness of 0.5 mm, the SrTiO3 substrate is first ultrasonically cleaned with deionized water for 600 s, and then ultrasonically cleaned with anhydrous ethanol for 600 s. This process is repeated twice before surface etching is performed.

[0056] Surface etching was performed using an ammonium fluoride buffered hydrofluoric acid etching solution with a volume ratio of ammonium fluoride to hydrofluoric acid of 10:1 and an etching time of 39 s. After etching, the surface was placed in a tube furnace and annealed at 970 °C for 120 min.

[0057] The cleaned (001)SrTiO3 substrate was placed in a laser pulse deposition vacuum system using a 3.8 cm diameter SrIrO3 target. The substrate temperature was maintained at 700 °C. Elemental oxygen was introduced into the pulsed laser deposition chamber, and the oxygen pressure was maintained at 100 mTorr. The laser repetition frequency was 2 Hz, and the laser energy density was 1.4 J / cm². 2 Under certain conditions, SrIrO3 target material was bombarded with pulsed laser. Epitaxial growth of SrIrO3 single crystal film on (001)SrTiO3 substrate was achieved, and the thickness of the obtained SrIrO3 single crystal film was 5 nm.

[0058] After pulsed laser bombardment, the substrate was kept at 700 ℃ for 10 min.

[0059] Step 2: Place the substrate with the SrTiO3 single crystal film obtained in Step 1 into a laser pulse deposition vacuum system, using a 3.8 cm diameter SmNiO3 target. Maintain the substrate temperature at 700 °C, introduce elemental oxygen into the pulsed laser deposition chamber, and maintain the oxygen pressure at 100 mTorr; the laser repetition frequency is 2 Hz, and the laser energy density is 1.4 J / cm². 2 Under suitable conditions, SmNiO3 target material was bombarded with a pulsed laser. Epitaxial growth of SmNiO3 single crystal film on the surface of SrIrO3 single crystal film was achieved, and the thickness of the obtained SmNiO3 single crystal film was 15 nm.

[0060] After obtaining the SmNiO3 single crystal thin film, the oxygen pressure was adjusted to 1 Torr, and the film was cooled from 700 °C to room temperature at a rate of 10 °C / min.

[0061] (001) The lattice constant of the SrTiO3 substrate is 3.905 Å. (001) The lattice mismatch between the SrTiO3 substrate and the SrIrO3 single crystal film is about 1.2%, which is beneficial for growing high-quality SrIrO3 single crystal films on this substrate. The lattice constant of SmNiO3 is 3.799 Å, and the lattice mismatch with SrIrO3 is about 3.9%, which is also beneficial for growing high-quality SmNiO3 single crystal films on this substrate. The anomalous Hall effect of the SmNiO3 / SrIrO3 heterojunction mainly comes from the interfacial interaction between the ferromagnetic insulator and the topological crystalline insulator in the film, which makes the single crystal film have an anomalous Hall effect.

[0062] The SrIrO3 single-crystal thin film obtained in step 1 of Example 1 was characterized, and its XRD pattern is shown below. Figure 2 As shown in the figure, the SrIrO3 single crystal thin film on the SrTiO3 substrate is along... <001> It is epitaxially grown in the direction and no impurity phase was detected in the XRD pattern.

[0063] The SmNiO3 single-crystal thin film obtained in step 2 of Example 1 was characterized, and its XRD pattern is shown below. Figure 3 As shown in the figure, it can be seen that the SmNiO3 single crystal film is along the (001)SrIrO3 single crystal film. <001> It is epitaxially grown in the direction and no impurity phase was detected in the XRD pattern.

[0064] The magnetoelectric transport properties of the SmNiO3 / SrIrO3 heterojunction obtained in Example 1 were characterized, and its lateral resistance was... ρ xx The curve of temperature change is as follows Figure 4 As shown, at a temperature of 2 The curve showing the relationship between the anomalous Hall resistance at 50 K, after removing the linear background, and the magnetic field is as follows: Figure 5 As shown.

[0065] from Figure 4 As can be seen, the lateral resistivity of the SrIrO3 single crystal thin film increases with decreasing temperature, exhibiting insulating behavior. From... Figure 5 As can be seen from the above, the thin film heterostructure obtained by the present invention has the characteristics of anomalous Hall effect.

[0066] Figure 6 The image shows the interface scanning tunneling microscope image of the SmNiO3 / SrIrO3 heterojunction obtained in Example 1 of the present invention. As can be seen from the image, the interface of the SmNiO3 / SrIrO3 epitaxial single crystal thin film heterojunction is clear, and both SrIrO3 and SmNiO3 single crystal epitaxial films are epitaxially grown.

[0067] Comparative Example 1 is set up to illustrate the effect of the present invention.

[0068] Comparative Example 1 includes only step 1, in which a single-crystal SrIrO3 thin film is epitaxially grown on a (001)SrTiO3 substrate to obtain a single-crystal thin film heterojunction. The thickness of the SrIrO3 single-crystal thin film is 5 nm.

[0069] Figure 7 Longitudinal resistance at different temperatures, as shown in Comparative Example 1 of this invention. R xy The curve shows the relationship between the thin film and the magnetic field. As can be seen from the figure, this thin film does not exhibit the dual-carrier characteristics of the Hall effect, but rather shows a linear Hall effect curve.

[0070] The vacuum system in the above embodiments refers to a system with a pressure of less than or equal to 10. -7 Torr's closed system.

[0071] This invention utilizes a pulsed laser deposition system to epitaxially grow a SrIrO3 single-crystal thin film on a pretreated SrTiO3 substrate; then, using pulsed laser deposition, a SmNiO3 single-crystal thin film of a certain thickness is epitaxially grown on the grown SrIrO3 film to obtain an SrTiO3 / SmNiO3 heterojunction. The heterojunction obtained by this invention exhibits continuous temperature modulation of its anomalous Hall effect signal magnitude below 50 K.

Claims

1. A SrIrO3 thin film heterojunction with low temperature abnormal Hall effect, characterized in that, comprising a SrIrO3 single crystal thin film epitaxially grown on the surface of a SrTiO3 substrate with a crystal face orientation of (001), and a SmNiO3 single crystal thin film epitaxially grown on the surface of the SrIrO3 single crystal thin film.

2. The strontium iridate thin film heterojunction with low temperature anomalous Hall effect of claim 1, wherein, The thickness of the SrIrO3 single crystal thin film is 5 nm, and the thickness of the SmNiO3 single crystal thin film is 4-30 nm.

3. The strontium iridate thin film heterojunction with low temperature anomalous Hall effect of claim 1, wherein, The heterojunction has an abnormal Hall effect below 50 K.

4. The method of claim 1 to 3 for the preparation of a strontium iridate thin film heterojunction with low temperature anomalous Hall effect, characterized in that, comprising the following steps: Step 1: epitaxially growing a SrIrO3 single crystal thin film on the surface of a SrTiO3 substrate by pulsed laser deposition; Step 2: epitaxially growing a SmNiO3 single crystal thin film on the surface of the SrIrO3 single crystal thin film obtained in Step 1 by pulsed laser deposition, thereby obtaining the required heterojunction.

5. The method of claim 4, wherein the method further comprises: The SrTiO3 substrate in Step 1 is pretreated before use, and the pretreatment process is as follows: First, ultrasonic cleaning with deionized water for 600 s, ultrasonic cleaning with anhydrous ethanol for 600 s, and repeating the above cleaning twice; the cleaned SrTiO3 substrate is surface etched and then annealed; surface etching uses buffered hydrofluoric acid with ammonium fluoride, etching for 39 s, annealing temperature is 970 ℃, and annealing time is 120 min.

6. The method of claim 4, wherein the method further comprises: The temperature during the pulsed laser deposition process in Step 1 and Step 2 is 700 ℃.

7. The method of claim 4, wherein the method further comprises the step of: The deposition process of the SrIrO3 single crystal thin film is carried out in an oxygen atmosphere with an oxygen pressure of 100 mTorr; the pulsed laser conditions are as follows: ​ The laser repetition frequency was 2 Hz, and the laser energy density was 1.4 J / cm 2 .

8. The method of claim 4, wherein the method further comprises the step of: The SrIrO3 single crystal thin film in Step 1 also includes heat treatment, the heat treatment temperature is 700 ℃, and the treatment time is 10 min. ​ 9. The method of claim 4, wherein the method further comprises the step of: The deposition process of the SmNiO3 single crystal thin film in Step 2 is carried out in an oxygen atmosphere with an oxygen pressure of 100 mTorr; the pulsed laser conditions are as follows: ​ The laser repetition frequency is 2 Hz, and the laser energy density is 1.4 J / cm 2 ; After deposition, the oxygen pressure is maintained at 1 mTorr, and the temperature is cooled to room temperature at a rate of 10 ℃ / min.

10. Use of a strontium iridate thin film heterojunction having a low temperature anomalous Hall effect according to any one of claims 1 to 3, characterized in that, The heterojunction is used to prepare low-energy-consumption spintronic devices.

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