CN-121976302-A - Low-voltage ferroelectric domain regulation and control method based on lithium niobate single crystal film

Abstract

The invention discloses a low-voltage ferroelectric domain regulating and controlling method based on a lithium niobate single crystal film, which utilizes the characteristic of asymmetric positive and negative coercive fields of the lithium niobate single crystal film and realizes domain inversion with low voltage and quick response by carrying out domain regulation and control twice on the surface of the film. Firstly, a piezoelectric microscope is used for carrying out initialization regulation and control on a patterned ferroelectric domain in a selected area, and then a low-voltage and short-pulse signal is applied to a specific position of a turned domain, so that secondary turning of the ferroelectric domain is realized, and the problem that lithium niobate is difficult to be applied to a low-power-consumption and quick-response ferroelectric device due to overhigh coercive field is effectively solved.

Inventors

• ZHANG YONG
• LU HAO
• CHEN PENGCHENG
• XU XIAOYI
• Fan Weiwen
• YANG XINZHE
• LIU MANMAN
• WANG XIANGMEI
• ZHU SHINING

Assignees

• 南京大学

Dates

Publication Date

20260505

Application Date

20260319

Claims (10)

1. 1. The low-voltage ferroelectric domain regulating method based on the lithium niobate single crystal film is characterized by comprising the following steps of: Step 1, selecting a clean area on the surface of a lithium niobate single crystal film; Step 2, performing ferroelectric domain patterning regulation and control on the selected area in the step 1 by using a piezoelectric microscope PFM; step 3, replacing a conductive probe holder, and scanning a c-AFM image of the region; step 4, drawing a pulse voltage signal by using a custom waveform mode; and 5, applying the pulse voltage to the inverted ferroelectric domain area to realize secondary domain inversion.
2. 2. The method according to claim 1, wherein the lithium niobate single crystal thin film in step 1 is a Z-cut lithium niobate single crystal thin film.
3. 3. The method according to claim 2, wherein the structure of the lithium niobate single crystal thin film in the step 1 is 495 μm-505 μm lithium niobate substrate, 0.2 μm-2 μm silicon dioxide layer, metal layer, 300-700 nm z cut lithium niobate, and the metal layer is 10 nm-30 nm Cr, 50 nm-200 nm Au, 10 nm-30 nm Cr from bottom to top.
4. 4. The method of claim 1, wherein the lithium niobate single crystal thin film selected in step 1 is connected to a small iron sheet through conductive silver paste, and after being connected to the ground terminal of the PFM device, the lower metal layer of the lithium niobate thin film is grounded.
5. 5. The method according to claim 1, characterized in that in step2, a region of not more than 30 μm gamma 30 μm and not less than 1 μm gamma 1 μm is selected under a piezo-electric microscope PFM, and the first ferroelectric domain modulation is performed using a gray scale map.
6. 6. The method of claim 5, wherein when using gray scale to maximize ferroelectric domain inversion, a negative voltage of-150V to 0V and a positive voltage of 0V to 150V is applied, wherein the positive voltage is a voltage to achieve ferroelectric domain inversion.
7. 7. The method of claim 1, wherein the c-AFM image of step 3 is a region of not greater than 30 μm x 30 μm and not less than 1 μm x 1 μm.
8. 8. The method of claim 1, wherein the pulsed voltage in step 4 is a voltage applied from a sample bottom electrode structure through a PFM apparatus mount.
9. 9. The method of claim 1, wherein the custom waveform in step 4 is a pulse voltage of 0V- (5V-10V) -0V, wherein the pulse width of the pulse is not less than 10 ms and not more than 15 minutes.
10. 10. The method of claim 1, wherein after step 5 is completed, the c-AFM image is scanned to verify the flipping effect.

Description

Low-voltage ferroelectric domain regulation and control method based on lithium niobate single crystal film Technical Field The invention relates to a semiconductor technology, in particular to a low-voltage ferroelectric domain regulating and controlling method based on a lithium niobate single crystal film. Background In recent years, flip ferroelectric domains have become increasingly popular in the fields of memory, nonlinear optics, and the like. Therefore, the ferroelectric domain inversion technology with high performance and strong stability is extremely important for the development of ferroelectric materials. Lithium niobate (LiNbO 3, LN) crystals belong to a trigonal system, and the coercive field E c is 21 kV/mm, so that the lithium niobate always plays a difficult role in the field of ferroelectric domain engineering devices due to the extremely large coercive field. To meet the development needs of the age, how to develop a ferroelectric domain regulating technology with quick response and low power consumption becomes a problem to be solved in the development of lithium niobate crystals. Currently, piezo-electric microscopy (Piezoelectric Force Microscope, PFM) is one of the main approaches to ferroelectric domain modulation, and PFM probe polarization has been attracting attention thanks to its ability to operate in the micro-region. At present, as the thin film technology of ferroelectric materials is more mature, the high coercive field lithium niobate block can effectively reduce the flip voltage under the technology of the thin film technology. Although the application of the thin film lithium niobate in the fields of storage devices, nonlinear photonic crystals and the like is quite mature, the lithium niobate domain engineering device can not meet the time requirements of low power consumption and quick response. At present, the polarization success rate of the ferroelectric film can be effectively improved by doping MgO to reduce the coercive field, sputtering a metal layer on the lower surface of the lithium niobate film, and the like. However, the modes of structure optimization, material modification and the like are complex to operate, and the sample preparation is not easy to change. The problem of how to achieve low voltage, fast responding ferroelectric domain modulation on lithium niobate single crystal thin films remains an urgent issue. Disclosure of Invention The invention aims to provide a low-voltage ferroelectric domain regulating and controlling method based on a lithium niobate single crystal film, which effectively reduces the polarization voltage of PFM probe polarization, improves the ferroelectric domain regulating and controlling response speed, so as to obtain a ferroelectric domain with high performance and strong stability, and solves the problem that the lithium niobate single crystal film has too large coercive field, so that the lithium niobate single crystal film is difficult to develop in the field of low-power consumption ferroelectric domain engineering devices. The low-voltage ferroelectric domain regulating method based on the lithium niobate single crystal film comprises the following steps: Step 1, selecting a clean area (the surface root mean square Roughness (RMS) is not more than 800 pm) on the surface of a lithium niobate single crystal film; Step 2, performing ferroelectric domain patterning regulation and control on the selected area in the step 1 by using a piezoelectric microscope PFM; Step3, replacing a conductive probe holder (Ocra Holder), and scanning a c-AFM image of the region; step 4, drawing a pulse voltage signal by using a custom waveform mode; and 5, applying the pulse voltage to the inverted ferroelectric domain area to realize secondary domain inversion. After the above steps are completed, the c-AFM image is scanned to verify the flipping effect. Preferably, the lithium niobate single crystal film in the step 1 is a Z-cut lithium niobate single crystal film. Preferably, the structure of the lithium niobate single crystal film in the step 1 is composed of a lithium niobate substrate with the thickness of 495 mu m-505 mu m, a silicon dioxide layer with the thickness of 0.2 mu m-2 mu m, a metal layer and lithium niobate cut with the thickness of 300-700 nm z, wherein the metal layer is composed of Cr with the thickness of 10 nm-30 nm Cr, 50 nm-200 nm Au and 10 nm-30 nm from bottom to top. More preferably 500 μm lithium niobate substrate, 2 μm silicon dioxide layer, metal layer (30 nm Cr, 100 nm Au, 10 nm Cr), 500 nm z cut lithium niobate. Preferably, the lithium niobate single crystal film selected in the step 1 is connected with a small iron sheet through conductive silver colloid, and is grounded after being connected to the ground end of the PFM equipment. Preferably, in step 2, a region of no more than 30 μm and no less than 1 μm is selected under a piezoelectric microscope PFM, and the first ferroelectric domain is modulated u