Ferroelectric domain regulated optical readout mode memory and preparing method thereof

Abstract

A ferroelectric domain regulated optical readout mode memory and a preparing method thereof. The memory has such a structure that a two-dimensional semiconductor and a ferroelectric film layer are sequentially arranged on a conductive substrate. The method for preparing the memory includes the steps of preparing the two-dimensional semiconductor on the conductive substrate, preparing a ferroelectric film, then writing a periodic positive-reverse domain structure into the ferroelectric film on the two-dimensional semiconductor by using a piezoresponse force microscopy technology, and regulating a photoluminescent intensity of the two-dimensional semiconductor WS.sub.2 by using a ferroelectric domain. A fluorescent picture taken by a fluorescent camera shows light and dark areas corresponding to polarization directions, the light and dark areas represent an on state (‘1’) and an off state (‘0’) of the memory respectively, and accordingly the purpose of storage is achieved.

Claims

1. A ferroelectric domain regulated optical readout mode memory, comprising, structurally sequentially from bottom to top, a substrate, a transition metal compound two-dimensional semiconductor and a polyvinylidene fluoride based ferroelectric functional layer, wherein the substrate is made from any conductive material; the transition metal compound two-dimensional semiconductor is a monolayer transition metal compound tungsten disulfide (WS.sub.2); and the polyvinylidene fluoride based ferroelectric functional layer is a polyvinylidene fluoride based ferroelectric polymer film; wherein the transition metal compound two-dimensional semiconductor is transferred to a surface of the substrate by a mechanical stripping transfer method; the polyvinylidene fluoride based ferroelectric functional layer is prepared by using a spin coating method, and annealed at a temperature of 135° C. for 2 hours to ensure crystallization characteristics of the polyvinylidene fluoride based ferroelectric functional layer; a polarization operation is carried out on a storage unit of the polyvinylidene fluoride based ferroelectric functional layer by using a piezo-response force microscope; and a fluorescent picture of the tungsten disulfide (WS.sub.2) is taken by using a fluorescent camera to obtain stored information.

2. A method for preparing a ferroelectric domain regulated optical readout mode memory, wherein, the ferroelectric domain regulated optical readout mode memory comprises, structurally sequentially from bottom to top, a substrate, a transition metal compound two-dimensional semiconductor and a polyvinylidene fluoride based ferroelectric functional layer, wherein the substrate is made from any conductive material; the transition metal compound two-dimensional semiconductor is a monolayer transition metal compound tungsten disulfide (WS.sub.2); and the polyvinylidene fluoride based ferroelectric functional layer is a polyvinylidene fluoride based ferroelectric polymer film, and the method comprises: transferring the transition metal compound two-dimensional semiconductor to a surface of the substrate by a mechanical stripping transfer method; preparing the polyvinylidene fluoride based ferroelectric functional layer by using a spin coating method, and annealing at a temperature of 135° C. for 2 hours to ensure crystallization characteristics of the polyvinylidene fluoride based ferroelectric functional layer; carrying out a polarization operation on a storage unit of the polyvinylidene fluoride based ferroelectric functional layer by using a piezo-response force microscope; and taking a fluorescent picture of the tungsten disulfide (WS.sub.2) by using a fluorescent camera to obtain stored information.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic structural cross-sectional view of a ferroelectric domain regulated monolayer WS.sub.2 optoelectronic memory;

(2) in the figure: 1 substrate made from any conductive material, 2 monolayer WS.sub.2, 3 ferroelectric film layer;

(3) FIG. 2 shows WS.sub.2 photoluminescent spectra in different polarization directions;

(4) FIG. 3 shows stored information extracted from a fluorescent picture of a PFM operating area.

(5) in the figure: “1” represents an area with strong fluorescence which corresponds to a downward polarization area of a ferroelectric layer; “0” represents an area with weak fluorescence which corresponds to an upward polarization area of the ferroelectric layer; and

(6) FIG. 4 shows stored information extracted from a fluorescent picture after the PFM is operated by applying a reverse voltage.

DESCRIPTION OF THE EMBODIMENTS

(7) The following describes a specific implementation mode of the present invention in details with reference to accompanying drawings.

(8) The present invention discloses a ferroelectric domain regulated optical readout mode memory and a preparing method thereof. The luminescent intensity of a two-dimensional material WS.sub.2 is changed through different polarization directions of a ferroelectric domain, a photoluminescent picture of the WS.sub.2 is taken by a fluorescent camera, and different storage states are represented by different luminescent areas of the WS.sub.2, so that a new storage mode of “electric writing and optical readout” is realized.

(9) The method includes the specific steps as follows:

(10) 1. Select a substrate.

(11) The substrate is made from any conductive material.

(12) 2. Prepare and transfer a two-dimensional semiconductor.

(13) A WS.sub.2 crystal is mechanically stripped with an adhesive tape and then transferred to the substrate, and a thickness of the WS.sub.2 is the same as that of a single molecular layer.

(14) 3. Prepare a ferroelectric functional layer.

(15) The P(VDF-TrFE) ferroelectric functional layer is prepared by applying a spin coating method and annealed at a temperature of 135° C. for 2 hours to ensure its crystalline characteristics.

(16) 4. Polarize the ferroelectric functional layer by utilizing a piezoresponse force microscope.

(17) The PFM is a microscope based on an atomic force microscope (AFM) to detect the electric deformation of a sample under an applied excitation voltage by using a conductive probe, the probe of the PFM scans the sample in a contact mode, a voltage generated by a signal generator is applied between the PFM probe and a sample electrode, and the electric deformation of a ferroelectric material is monitored by using a laser beam reflected by the back surface of a PFM microcantilever. The P(VDF-TrFE) is polarized by utilizing a voltage applied to the sample by the PFM tip, and a scanning voltage and a scanning frequency are respectively controlled to be ±25 V and 1 Hz preferably. In the scanning process, a positive voltage is applied to an area in which “1” needs to be written to make polarization downward; and a negative voltage for scanning is applied to a position where “0” needs to be written to make the polarization upward.

(18) 5. Take a fluorescent picture and extract stored information.

(19) A fluorescent camera is used for taking the fluorescent picture of the WS.sub.2 after domains are written, and the luminescent intensities of the WS.sub.2 under different polarizations are different so that the fluorescent picture can present light and dark areas with periodic changes corresponding to the written domains, as shown in FIG. 3. Besides, the polarization direction of the ferroelectric domain may be changed by applying a reverse voltage again so as to change a storage state corresponding thereto, as shown in FIG. 4.

(20) The present invention relates to the ferroelectric domain regulated optical readout mode memory and the preparing method thereof. The memory has the characteristics of being simple in structure, large in storage density, non-volatile, good in holding characteristic, capable of obtaining all stored information at one time and free of limitation of the conventional readout circuit, and accelerates application of a two-dimensional semiconductor material in the field of electronic devices.