Circularly polarized light photoelectric detector based on perovskite oxide heterostructure and preparation method thereof

Abstract

The invention relates to a circularly polarized light photoelectric detector based on a perovskite oxide heterostructure and a preparation method thereof, the photoelectric detector comprises a photoelectric conversion element and an optical element, the photoelectric conversion element comprises a substrate, a middle layer and an electrode layer, and the substrate, the middle layer and the electrode layer are sequentially arranged from bottom to top; the electrode layer is arranged on the upper surface of the middle layer, and the middle layer is used for being connected with a phase-locked photoelectric measurement system; the substrate is a LaAlO3 substrate, and the middle layer comprises a LaAlO3 layer, a SrTiO3 layer and a LaAlO3 layer which are sequentially arranged from bottom to top; the electrode layer comprises two Ti-Au double-layer electrodes, and the two Ti-Au double-layer electrodes are arranged on the upper surface of the middle layer at intervals; the optical element is used for emitting laser to the upper surface of the middle layer, an incidence point is located between the two Ti-Au double-layer electrodes, the photoelectric detector generates photoelectric responses with different intensities under the action of the middle layers (the LaAlO3 layer, the SrTiO3 layer and the LaAlO3 layer) and different optical rotations, polarized light with different optical rotations can be efficiently detected, and the photoelectric detector has huge application value in the field of circular vibration light detection.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic technology, and particularly relates to a circularly polarized light photodetector based on a perovskite oxide heterostructure and a preparation method thereof. Background Art

[0002] Circularly polarized light refers to light whose optical vector endpoint rotates with time and traces a circular trajectory on a plane perpendicular to the light propagation direction. Circularly polarized light has shown broad application prospects in fields such as photography, display, optical instruments, communication, aerospace, biomedicine, and security anti-counterfeiting.

[0003] Perovskite oxide is a semiconductor with excellent optoelectronic properties, having characteristics such as long carrier lifetime, high absorption coefficient for light, and long carrier diffusion length. It is suitable for the field of photodetection and is beneficial to improving the optoelectronic performance of circularly polarized light photodetectors.

[0004] The main principles of photodetectors are photoconductive effect, photovoltaic effect, photoemission effect, pyroelectric effect, etc. And the present invention realizes photoelectric conversion based on the basic principle of circular photoelectric effect. The circular photoelectric effect is that in materials with broken space inversion symmetry and strong Rashba spin-orbit coupling, the conduction band of the material will be degenerate lifted, and the momentum of photo-generated carriers depends on spin, that is, circularly polarized light will selectively excite electrons with a specific spin direction to transition (for example, light polarized clockwise will excite electrons with kz>0, and light polarized counterclockwise will excite electrons with kz<0), which will generate spin polarization. This spin polarization in turn leads to a change in the electron momentum along the direction perpendicular to the spin polarization direction, generating current in the case of a short circuit and voltage in the case of an open circuit. Based on the above principle, the present solution proposes a circularly polarized light photodetector based on a perovskite oxide heterostructure and a preparation method. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a circularly polarized light photodetector based on a perovskite oxide heterostructure and a preparation method thereof, which does not require an external bias voltage, not only has good discrimination for circularly polarized light with different polarities, but also has the characteristics of fast photoelectric response speed and high stability, and has good application prospects.

[0006] To solve the above technical problem, the technical solution adopted by the present invention is: a circularly polarized light photodetector based on a perovskite oxide heterostructure, including a photoelectric conversion element and an optical element. The photoelectric conversion element includes a substrate, an intermediate layer, and an electrode layer. The substrate, intermediate layer, and electrode layer are sequentially arranged from bottom to top. The electrode layer is disposed on the upper surface of the intermediate layer, and the intermediate layer is connected to a lock-in photoelectric measurement system;

[0007] The substrate is LaAlO 3 substrate, and the intermediate layer includes a LaAlO 3 layer, a SrTiO 3 layer, and a LaAlO 3 layer, which are sequentially arranged from bottom to top; the electrode layer is two Ti-Au double-layer electrodes, and the two Ti-Au double-layer electrodes are spaced apart on the upper surface of the intermediate layer;

[0008] The optical element is used to obliquely irradiate the laser passing through the polarizer, quarter-wave plate, and focusing lens once onto the upper surface of the intermediate layer, and the incident point is located between the two Ti-Au double-layer electrodes.

[0009] Furthermore, the thickness of the LaAlO 3 layer in the intermediate layer is 3-5 nm, and the thickness of the SrTiO 3 layer in the intermediate layer is 4-12 nm.

[0010] Furthermore, the thickness of the Ti electrode in the Ti-Au double-layer electrode is 4-6 nm, and the thickness of the Au electrode in the Ti-Au double-layer electrode is 49-51 nm

[0011] Furthermore, the distance between the two Ti-Au double-layer electrodes is 390-410 μm.

[0012] Furthermore, the optical element includes a laser emitter that emits a laser with a wavelength of 473 nm, a polarizer, a quarter-wave plate, and a focusing lens. The laser emitter emits a laser with a wavelength of 473 nm that sequentially passes through the polarizer, quarter-wave plate, and focusing lens and is obliquely incident on the upper surface of the intermediate layer.

[0013] A preparation method of a circularly polarized light photodetector based on a perovskite oxide heterostructure, which is used to prepare a circularly polarized light photodetector based on a perovskite oxide heterostructure, includes the following steps:

[0014] S1. Treat the LaAlO 3 substrate with an HF mixed solution or a BOE solution, and perform high-temperature annealing on the LaAlO 3 substrate;

[0015] S2. Deposit LaAlO 3 , SrTiO 3 and LaAlO 3 and LaAlO 3 thin films on the LaAlO

[0016] S3. Use maskless lithography to engrave an electrode pattern on the surface of the intermediate layer;

[0017] S4. Deposit two Ti-Au bilayer electrodes on the surface of the intermediate layer by means of vacuum thermal evaporation;

[0018] S5. Use N-methylpyrrolidone liquid for water bath heating to remove the photoresist on the surface of the photoelectric conversion element, and obtain the photoelectric conversion element.

[0019] Further, the LaAlO used in step 1 3 The substrate has a specification of 5 mm × 5 mm × 0.5 mm and is polished on one side. The LaAlO 3 The treatment time of the substrate in the HF solution is 20 seconds. The LaAlO 3 The substrate is annealed at a temperature of 1050 °C for 2.5 hours; the HF mixed solution is composed of an HF solution and an NH4F solution with a volume ratio of 6 to 1.

[0020] Further, the growth parameters of pulsed laser deposition in step S2 are: growth temperature 800 °C, growth oxygen pressure 10 - 4 Pa, laser energy density 1 J / cm -2 , laser frequency 1 HZ, and the distance from the target to the substrate is 56.6 mm.

[0021] Further, in step S4, the Ti electrode in the Ti-Au bilayer electrode is 5 nm, the Au electrode in the Ti-Au bilayer electrode is 50 nm, the electrode size of the Ti-Au bilayer electrode is 400 μm × 400 μm, and the channel length of the Ti-Au bilayer electrode is 400 μm.

[0022] Further, in step S5, the temperature of the water bath heating is 60 °C, and the time of the water bath heating is 28 - 35 min.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides a circularly polarized light photodetector based on a perovskite oxide heterostructure and its method. Based on the action of the intermediate layer (LaAlO 3 layer, SrTiO 3 layer, and LaAlO 3 layer), different optical rotations generate different intensities of photoelectric responses, and can efficiently detect polarized light with different polarizations, and has great application value in the field of circularly polarized light detection. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of the practical process of a circularly polarized light photodetector based on a perovskite oxide heterostructure of the present invention;

[0026] Figure 2 This is the preparation flow chart of a preparation method for a circularly polarized light photodetector based on a perovskite oxide heterostructure according to the present invention;

[0027] Figure 3 This is a schematic diagram of a fitting curve for circularly polarized light detection according to the present invention. Specific embodiments

[0028] In order to make the above features and advantages of the present invention more obvious and understandable, specific embodiments are hereinafter given and described in detail in conjunction with the accompanying drawings.

[0029] As Figure 1 shown, this embodiment provides a circularly polarized light photodetector based on a perovskite oxide heterostructure, including a photoelectric conversion element and an optical element.

[0030] The photoelectric conversion element includes a substrate, an intermediate layer, and an electrode layer. The substrate is a LaAlO3 substrate. The intermediate layer includes a LaAlO 3 layer, a SrTiO3 layer, and a LaAlO 3 layer arranged in sequence from bottom to top; the electrode layer is two Ti-Au double-layer electrodes, and the two Ti-Au double-layer electrodes are spaced apart and arranged on the upper surface of the intermediate layer; the thickness of the LaAlO 3 layers is 3-5 nm. More preferably, the thickness of the LaAlO 3 layer is 4 nm for the best effect. The thickness of the SrTiO 3 layer is 4-12 nm. More preferably, the thickness of the SrTiO 3 layer is 12 m for the best effect.

[0031] A lock-in photoelectric measurement system is used to connect to the intermediate layer. The lock-in photoelectric measurement system uses an existing lock-in photoelectric measurement system, and its function is to extract and quantify the optical voltage signal with high precision.

[0032] The optical element includes a laser emitter that emits a laser with a wavelength of 473 nm, a polarizer, a quarter-wave plate, and a focusing lens. The laser emitter that emits a laser with a wavelength of 473 nm passes through the polarizer, the quarter-wave plate, and the focusing lens in sequence and obliquely irradiates the upper surface of the intermediate layer. The incident point is located in the middle of the two Ti-Au double-layer electrodes. The incident point is set in the middle of the two two Ti-Au double-layer electrodes, which can avoid the influence of thermal gradient on the experimental results. Setting it in the middle can avoid the thermal gradient on the experimental results to the greatest extent.

[0033] With the incident point in the middle of the two Ti-Au double-layer electrodes, the circular photoelectric effect will occur in the intermediate layer and a photocurrent will be generated (LaAlO 3 layer and SrTiO 3There is strong spin-orbit coupling at the heterointerfaces of the layers, which can directly convert the angular momentum (left-handed or right-handed) of circularly polarized light into a directional current of charge separation), and then a stable photovoltage can be measured. Then, by rotating a quarter-wave plate to adjust the helicity of the incident laser, different intensities of photovoltage generated by lasers with different helicities can be measured.

[0034] The thickness of the Ti electrode in the Ti-Au bilayer electrode is 4 - 6 nm. More preferably, when the thickness of the Ti electrode in the Ti-Au bilayer electrode is 5 nm, the effect is the best. The thickness of the Au electrode in the Ti-Au bilayer electrode is 49 - 51 nm. More preferably, when the thickness of the Au electrode in the Ti-Au bilayer electrode is 50 nm, the effect is the best. The distance between the two Ti-Au bilayer electrodes is 390 - 410 μm. More preferably, when the distance between the two Ti-Au bilayer electrodes is 400 μm, the effect is the best.

[0035] As Figure 2 shown, this solution also provides a preparation method of a circularly polarized light photodetector based on a perovskite oxide heterostructure for preparing a circularly polarized light photodetector based on a perovskite oxide heterostructure, including the following steps:

[0036] S1. Treat the LaAlO 3 substrate with an HF mixed solution and a BOE solution, and anneal the LaAlO 3 substrate at high temperature;

[0037] S2. Deposit LaAlO 3 , SrTiO 3 , and LaAlO 3 thin films on the LaAlO 3 substrate in sequence by the method of pulsed laser deposition;

[0038] S3. Engrave electrode patterns on the surface of the intermediate layer by maskless lithography;

[0039] S4. Deposit two Ti-Au bilayer electrodes on the surface of the intermediate layer by vacuum thermal evaporation;

[0040] S5. Use N-methylpyrrolidone liquid for water bath heating to remove the photoresist on the surface of the photoelectric conversion element to obtain the photoelectric conversion element.

[0041] Among them, the specification of the LaAlO 3 substrate used in step 1 is 5 mm × 5 mm × 0.5 mm and is polished on one side. LaAlO 3The substrate is treated with an HF solution for 20 seconds. The HF solution is a mixture of HF (hydrofluoric acid) and NH4F (ammonium fluoride) with a volume ratio of 6 to 1. Alternatively, a BOE solution (buffered oxide etchant) can be used for treatment., LaAlO 3 The substrate is annealed at a temperature of 1050 °C for 2.5 hours.

[0042] Among them, the growth parameters of pulsed laser deposition in step S2 are: growth temperature 800 °C, growth oxygen pressure 10 -4 Pa, laser energy density 1 J / cm -2 , laser frequency 1 HZ, and the distance from the target to the substrate is 56.6 mm.

[0043] Among them, the photoresist models in step S3 are S1805 and LOR3A.

[0044] Among them, in step S4, the Ti electrode in the Ti-Au double-layer electrode is 5 nm, the Au electrode in the Ti-Au double-layer electrode is 50 nm, the electrode size of the Ti-Au double-layer electrode is 400 μm × 400 μm, and the channel length of the Ti-Au double-layer electrode is 400 μm.

[0045] Among them, in step S5, the temperature of water bath heating is 60 °C, the time of water bath heating is 28 - 35 min, and more preferably, the time of water bath heating is 30 min for the best effect.

[0046] The circularly polarized light photodetector based on the perovskite oxide heterostructure prepared by this preparation method is based on LaAlO 3 layer, SrTiO 3 layer and LaAlO 3 layer. Different optical rotations of the three thin film layers generate different intensities of photoelectric responses, which can efficiently detect polarized light with different polarizations. It has great application value in the field of circularly polarized light detection. The prepared photodetector has the advantages of fast response speed and high detection result accuracy.

[0047] Application Example 1

[0048] The circularly polarized light photodetector based on the perovskite oxide heterostructure is pasted onto the base with double-sided tape. The base is connected to the device using an ultrasonic aluminum wire bonder, and the base is connected to the base of the lock-in photoelectric measurement system, as Figure 1 shown, Figure 1 is a schematic structural diagram of the circularly polarized light photodetector based on the perovskite oxide heterostructure. In the figure, the bottom layer LAO represents LaAlO 3 substrate, and the meanings of LAO, STO, and LAO on the LaAlO 3 substrate in the middle are, respectively, LaAlO 3 layer, SrTiO3 Layer and LaAlO 3 layer. The two yellow areas represent two Ti-Au double-layer electrodes, and the blue light represents a laser with a wavelength of 473 nm that passes through a polarizer, a quarter-wave plate, and a focusing lens in sequence.

[0049] The laser (λ = 473 nm and P = 6 mW) passes through a polarizer, a quarter-wave plate, and a focusing lens in sequence, and is obliquely incident on the sample surface. The position of the light spot is observed through a CCD, and the laser spot is adjusted to the center position between the corresponding electrodes by adjusting the knob of the displacement stage, and the laser is blocked with a baffle.

[0050] Turn on the instruments such as the source meter and chopper used for measurement, start the measurement program on the computer, and measure the photocurrents at the positions where the quarter-wave plate scale is 0°, 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, 165°, 180°, 195°, 210°, 225°, 240°, 255°, 270°, 285°, 300°, 315°, 330°, 345°, 360° respectively. Each angle is measured for 100 seconds, and the average value within 100 seconds for each angle is taken. After processing the data, plot the photocurrent response intensity diagram related to the circular polarization degree (quarter-wave plate scale) ( Figure 3 ) Figure 3 In, the abscissa Angle represents the angle (unit: degree), the ordinate Voltage represents the voltage (unit: microvolt), the red curve represents the fitting curve of the voltage change under different incident angles of the light beam, and the black dots represent the incident angle of 30°.

[0051] As Figure 3 can be seen, the detector shows significantly different photocurrent response intensities to polarized light with different polarizations, that is, the LaAlO 3 layer, SrTiO 3 layer and LaAlO 3 layer made of photodetector generates different optical responses to polarized light with different polarizations (90°, 180°, 270° and 360° are linearly polarized light; 45° and 225° are left circularly polarized light; 135° and 315° are right circularly polarized light). According to the above description, the photodetector of this scheme can be used for the detection of circularly polarized light.

[0052] The above has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A circularly polarized light photodetector based on a perovskite oxide heterostructure, characterized in that: It includes a photoelectric conversion element and an optical element, wherein the photoelectric conversion element includes a substrate, an intermediate layer and an electrode layer, wherein the substrate, the intermediate layer and the electrode layer are arranged in sequence from bottom to top, the electrode layer is arranged on the upper surface of the intermediate layer, and the intermediate layer is used to connect with a phase-locked photoelectric measurement system; The substrate is a LaAlO3 substrate, the middle layer includes a LaAlO3 layer, a SrTiO3 layer and a LaAlO3 layer arranged in sequence from bottom to top; the electrode layer is two Ti-Au double-layer electrodes, and the two Ti-Au double-layer electrodes are arranged at intervals on the upper surface of the middle layer; The optical element is used for obliquely projecting the laser light that has passed through the polarizing plate, the quarter wave plate and the focusing lens once to the upper surface of the intermediate layer, and the incident point is located between the two Ti-Au double-layer electrodes.

2. The circularly polarized light photodetector based on perovskite oxide heterostructure according to claim 1, characterized in that: The thickness of the LaAlO3 layer in the middle layer is 3-5 nm, and the thickness of the SrTiO3 layer in the middle layer is 4-12 nm.

3. The circularly polarized light photodetector based on perovskite oxide heterostructure according to claim 1, characterized in that: The thickness of the Ti electrode in the Ti-Au double-layer electrode is 4-6 nm, and the thickness of the Au electrode in the Ti-Au double-layer electrode is 49-51 nm.

4. The circularly polarized light photodetector based on perovskite oxide heterostructure according to claim 1, characterized in that: The distance between the two Ti-Au double-layer electrodes is 390-410 μm.

5. The circularly polarized light photodetector based on perovskite oxide heterostructure according to claim 1, characterized in that: The optical element includes a laser emitter emitting a wavelength of 473nm, a polarizer, a quarter wave plate and a focusing lens. The laser emitter emits a laser with a wavelength of 473nm which passes through the polarizer, the quarter wave plate and the focusing lens in sequence and is obliquely projected onto the upper surface of the intermediate layer.

6. A method for preparing a circularly polarized light photodetector based on a perovskite oxide heterostructure, characterized in that: The method for preparing a circularly polarized light photodetector based on a perovskite oxide heterostructure as claimed in any one of claims 1 to 5 comprises the following steps: S1, treating the LaAlO3 substrate with a HF mixed solution or a BOE solution, and performing high temperature annealing on the LaAlO3 substrate; S2, sequentially depositing LaAlO3, SrTiO3 and LaAlO3 thin films on a LaAlO3 substrate by a pulsed laser deposition growth method; S3, engraving an electrode pattern on the surface of the intermediate layer by maskless photolithography; S4, depositing two Ti-Au double-layer electrodes on the surface of the intermediate layer by vacuum thermal evaporation; S5. Using N-methylpyrrolidone liquid to perform water bath heating to remove the photoresist on the surface of the photoelectric conversion element, so as to obtain the photoelectric conversion element.

7. The method for preparing a circularly polarized light photodetector based on a perovskite oxide heterostructure according to claim 6, characterized in that: The LaAlO3 substrate used in the step 1 has a specification of 5mm×5mm×0.5mm and is polished on one side. The LaAlO3 substrate is treated in the HF solution for 20 seconds. The LaAlO3 substrate is annealed at a temperature of 1050°C for 2.5 hours. The HF mixed solution is a mixture of HF solution and NH4F solution in a volume ratio of 6 to 1.

8. The method for preparing a circularly polarized light photodetector based on a perovskite oxide heterostructure according to claim 6, characterized in that: The growth parameters of the pulsed laser deposition in step S2 are: growth temperature 800°C, growth oxygen pressure 10 -4 Pa, laser energy density 1J / cm -2 , laser frequency 1HZ and target to substrate distance 56.6mm.

9. The method for preparing a circularly polarized light photodetector based on a perovskite oxide heterostructure according to claim 6, characterized in that: In the step S4, the Ti electrode in the Ti-Au double-layer electrode is 5nm, the Au electrode in the Ti-Au double-layer electrode is 50nm, the electrode size of the Ti-Au double-layer electrode is 400μm×400μm, and the channel length of the Ti-Au double-layer electrode is 400μm.

10. The method for preparing a circularly polarized light photodetector based on a perovskite oxide heterostructure according to claim 6, characterized in that: The water bath heating temperature in step S5 is 60° C., and the water bath heating time is 28-35 min.

Images