CN111722309B - Preparation method of two-dimensional crystal forbidden band fluorescence polarization modulation device - Google Patents
Preparation method of two-dimensional crystal forbidden band fluorescence polarization modulation device Download PDFInfo
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Abstract
The invention discloses a preparation method of a fluorescence polarization modulation device of a two-dimensional crystal forbidden band, which comprises the following steps: providing a high-conductivity material substrate; oxidizing an insulating layer on the high-conductivity material substrate; depositing a two-dimensional crystal monolayer on the insulating layer; evaporating a light-transmitting medium layer on the two-dimensional crystal single layer; spin-coating electron beam negative glue on the light-transmitting medium layer; carrying out electron beam exposure and development on the negative photoresist to obtain a nano-structure pattern on the negative photoresist; evaporating a metal layer on the developed negative glue; and removing the residual negative photoresist to obtain the metal nano metamaterial with the periodic unit structure on the light-transmitting medium layer. The device for modulating the fluorescence polarization of the two-dimensional crystal forbidden band, which is prepared by the invention, utilizes the metal nano metamaterial anisotropic resonance field to regulate and control the semiconductor fluorescence field, realizes polarized fluorescence and achieves the purpose of polarization adjustability, and effectively widens the linear adjustable range and the temperature application range of the two-dimensional crystal forbidden band fluorescence.
Description
Technical Field
The invention belongs to the technical field of nano photoelectrons, and particularly relates to a preparation method of a two-dimensional crystal forbidden band fluorescence polarization modulation device.
Background
The micro-nano light source with adjustable polarity has special advantages in the aspects of information safety, high-sensitivity sensing, structural analysis, pathogen diagnosis and the like. The novel two-dimensional crystal which is started in recent years has wide direct forbidden band selectivity, structural stability, photoelectric adjustability and substrate diversity and has excellent conditions of an on-chip micro-nano light source. However, the application range of the micro-nano light source is limited by the polarization randomness of fluorescence at room temperature, so that the light source on the chip needs to be subjected to polarization modulation.
The macroscopic light path modulates the polarization of light using a polarizer and a polarizing prism. The polaroid is mainly composed of a polyvinyl alcohol polarizing film and transparent cellulose triacetate protective films compounded on the upper and lower surfaces of the polyvinyl alcohol polarizing film. The main components of the polyvinyl alcohol polarizing film are polyvinyl alcohol and iodine, and the polyvinyl alcohol polarizing film is prepared by adopting a wet-process stretching process. The typical process is as follows: firstly, preparing a transparent polyvinyl alcohol thick film by a tape casting method or a melt extrusion method, immersing the transparent polyvinyl alcohol thick film into a compound solution containing iodine for reaction, and carrying out iodine dyeing on the thin film; and then, unidirectionally stretching the PVA film by 3-5 times in a certain direction between rollers rotating at different speeds to highly orient the molecular bonds of the polyvinyl alcohol, and simultaneously orienting the iodine molecules embedded therein to have dichroism, absorb light components with the polarization direction being the same as the stretching direction, and transmit the light components perpendicular to the stretching direction. The polyvinyl alcohol polarizing film is quickly deformed, shrunk, loosened, faded and the like in a warm environment, and has the advantages of low strength, brittle and breakable property and inconvenience in use and processing. Therefore, it is necessary to attach a triacetyl cellulose protective film having high light transmittance, good heat and temperature resistance, high strength, and optical isotropy to the upper and lower surfaces. This increases the thickness of the polarizer and prevents direct integration into the photonic device. In addition, the polarizer can be assembled from dichroic crystals, such as calcite, designed, cut, and polished according to specific aspect ratios and end face angle requirements. Although polarizers made with polarizing prisms have the advantages of high extinction ratio, high transmission, and high damage threshold. But the practicability and compatibility of the crystal in a micro-nano photonic system are very low due to the blocky crystal characteristics. Therefore, from a fabrication process perspective, none of the conventional polarizing elements are suitable for use in photonic chips.
Disclosure of Invention
Technical problem to be solved
In order to solve the problem that the traditional preparation process cannot be applied to a photonic chip, the invention provides a preparation method of a two-dimensional crystal forbidden band fluorescence polarization modulation device, so as to solve the problems that the polarization modulation strength of two-dimensional crystal forbidden band fluorescence is small and is limited by temperature.
(II) technical scheme
The invention provides a preparation method of a two-dimensional crystal forbidden band fluorescence polarization modulation device, which comprises the following steps:
providing a high-conductivity material substrate;
oxidizing an insulating layer on the high-conductivity material substrate;
depositing a two-dimensional crystal monolayer on the insulating layer;
evaporating a light-transmitting medium layer on the two-dimensional crystal single layer;
spin-coating electron beam negative glue on the light-transmitting medium layer;
carrying out electron beam exposure and development on the negative photoresist to obtain a nano-structure pattern on the negative photoresist;
evaporating a metal layer on the developed negative glue; and
and removing the residual negative photoresist to obtain the metal nano metamaterial with the periodic unit structure on the light-transmitting medium layer.
Wherein the high conductive material substrate is a highly doped silicon or metal substrate with a thickness of 500 and 750 μm;
wherein the insulating layer is SiO2Or Al2O3The thickness is 270-310nm, and the high-conductivity material is formed on the substrate by a wet oxidation method;
wherein the two-dimensional crystal monolayer is transition metal chalcogenide MX2Wherein M ═ Mo, W; x is S, Se, Te;
wherein the thickness of the two-dimensional crystal monolayer is less than 1nm, and the two-dimensional crystal monolayer is deposited on the insulating layer by a chemical vapor deposition method;
wherein the light-transmitting dielectric layer is Al2O3Or SiO2The thickness is 10-50nm, and the two-dimensional crystal is evaporated on a single layer of the two-dimensional crystal by an electron beam evaporation method;
wherein the electron beam negative photoresist is MA 2403;
the metal nano-structure metamaterial is a gold, silver and aluminum nano-structure material, is 30-100nm thick and is prepared by an electronic direct writing technology;
the metal nano metamaterial with the periodic unit structure is provided with a linear, V-shaped or N-shaped air gap structure, and the included angle between the V-shaped or N-shaped structure and the horizontal direction is an air gap inclination angle theta.
(III) advantageous effects
According to the technical scheme, the device and the method for modulating the fluorescence polarization of the two-dimensional crystal forbidden band have the following beneficial effects:
(1) in the preparation method of the two-dimensional crystal forbidden band fluorescence polarization modulation device, the two-dimensional crystal forbidden band fluorescence polarization is modulated by the metamaterial, and the metamaterial surface plasmon resonance is a collective resonance behavior of light and metamaterial surface electrons and is not influenced by temperature, so that the polarization modulation method effectively widens the temperature application range.
(2) According to the preparation method of the two-dimensional crystal forbidden band fluorescence polarization modulation device, the coupling degree between the metamaterial resonant mode and the two-dimensional crystal fluorescence is adjusted through optimizing the structural design, so that fluorescence signals with different linearity degrees are generated, and the linearity adjustable range is widened.
(3) According to the preparation method of the two-dimensional crystal forbidden band fluorescence polarization modulation device, the adopted metamaterial is small in size, is not limited by the limit of optical diffraction, and is suitable for on-chip fixed-point integration, so that the device is flexible and adjustable in size and is suitable for on-chip integration and micro-nano light source modulation. The adjustable minimum area is determined by the metamaterial structure unit, and the device foundation is provided for chip-level photonic devices, systems and function development in the hundred nanometer square magnitude.
(4) In the preparation method of the fluorescence polarization modulation device for the forbidden band of the two-dimensional crystal, the two-dimensional crystal is isolated from the outside by the light-transmitting medium layer prepared by the evaporation method, so that the influence of factors such as water, oxygen and the like on the two-dimensional crystal is reduced, and the service life of a device is prolonged.
(5) In the preparation method of the two-dimensional crystal forbidden band fluorescence polarization modulation device, the substrate materials corresponding to the two-dimensional crystal are flexible and various, have multiple selectivity, and have good compatibility with a silicon-based photonic platform and a micro-nano preparation technology.
Drawings
Fig. 1 is a flow chart of a method for manufacturing a two-dimensional crystal forbidden band fluorescence polarization modulation device according to the present invention.
Fig. 2 is a flow chart of a manufacturing process of the two-dimensional crystal forbidden band fluorescence polarization modulation device according to the present invention.
Fig. 3 is a flowchart for testing a two-dimensional crystal bandgap fluorescence polarization modulation device based on the preparation method shown in fig. 1 to 2.
FIG. 4A is a block diagram of WS according to an embodiment of the present invention2Single layer optical imaging.
FIG. 4B is a schematic view of a computer program product according to the present inventionWS according to an embodiment of the present invention2Fluorescence intensity of the monolayer in the TE and TM directions.
FIG. 4C is a WS according to an embodiment of the present invention2Single layer fluorescence peak as a function of exit angle.
FIG. 4D is a block diagram of WS according to an embodiment of the present invention2Single layer fluorescence linearity as a function of fluorescence wavelength.
Fig. 5A is a SEM image of a nanowire grid according to an embodiment of the invention.
Fig. 5B is a fluorescence spectrum diagram of a device for modulating fluorescence polarization of a two-dimensional crystal forbidden band by a nanowire grid in TE and TM directions according to an embodiment of the invention.
Fig. 5C is a graph of the change of the fluorescence peak value with the exit angle of the device for modulating the fluorescence polarization of the two-dimensional crystal forbidden band by the nano-wire grid according to the embodiment of the invention.
Fig. 5D is a graph of the fluorescence linearity of a device for modulating the fluorescence polarization of a two-dimensional crystal forbidden band by a nanowire grid according to an embodiment of the invention as a function of the fluorescence wavelength.
Fig. 6 is a schematic view of a V-shaped nano-gate surface structure according to an embodiment of the invention.
Fig. 7A is an SEM image of a V-shaped metal nano-grid at 51 ° according to an embodiment of the present invention.
Fig. 7B is a TE-directional white light reflection spectrum of the V-shaped nano-grid when θ is 51 ° according to an embodiment of the present invention.
Fig. 7C is a fluorescence spectrum diagram of the device for modulating fluorescence polarization of two-dimensional crystal forbidden band by using the V-shaped nano-grid when θ is 51 ° according to the embodiment of the invention in TE and TM directions.
Fig. 7D is a graph of the change of the fluorescence peak value of the device for modulating the fluorescence polarization of the two-dimensional crystal forbidden band by the V-shaped nano-grid with the angle of emergence when θ is 51 ° according to the embodiment of the present invention.
Fig. 7E is a graph of the change of the fluorescence linearity of the device for modulating the fluorescence polarization of the two-dimensional crystal forbidden band by the V-shaped nano-grid with the fluorescence wavelength when θ is 51 °.
Fig. 8A is an SEM image of a V-shaped metal nano-grid at 63 ° according to an embodiment of the present invention.
Fig. 8B is a white light reflection spectrum of the V-shaped nano-grid TE direction at 63 ° according to an embodiment of the present invention.
Fig. 8C is a fluorescence spectrum diagram of the device for modulating fluorescence polarization of two-dimensional crystal forbidden band by using the V-shaped nano-grid when θ is 63 ° according to the embodiment of the invention in TE and TM directions.
Fig. 8D is a graph of the change of the fluorescence peak value of the device for modulating the fluorescence polarization of the two-dimensional crystal forbidden band by the V-shaped nano-grid according to the embodiment of the invention when θ is 63 °.
Fig. 8E is a graph of the fluorescence linearity of the device for modulating the fluorescence polarization of the two-dimensional crystal forbidden band by the V-shaped nano-grid according to the embodiment of the invention when θ is 63 °.
Fig. 9 is a schematic view of an N-type nano-gate surface structure according to an embodiment of the invention.
Fig. 10A is an SEM image of an N-type nano-gate at 30 ° θ according to an embodiment of the present invention.
Fig. 10B is a TE-directional white light reflection spectrum of the N-type nano-grid at 30 °.
Fig. 10C is a fluorescence spectrum diagram of a device for modulating fluorescence polarization of a two-dimensional crystal forbidden band by an N-type nano-grid in TE and TM directions when θ is 30 ° according to an embodiment of the present invention.
Fig. 10D is a graph of the change of the fluorescence peak value of the device for modulating the fluorescence polarization of the two-dimensional crystal forbidden band by the N-type nano-grid with the emission angle when θ is 30 ° according to the embodiment of the present invention.
Fig. 10E is a graph of the fluorescence linearity of the device for modulating the fluorescence polarization of the two-dimensional crystal forbidden band by the N-type nano-grid with the fluorescence wavelength when θ is 30 ° according to the embodiment of the present invention.
Fig. 11A is an SEM image of an N-type nano-gate at 45 ° θ according to an embodiment of the present invention.
Fig. 11B is a TE-directional white light reflection spectrum of the N-type nano-grid when θ is 45 ° according to an embodiment of the present invention.
Fig. 11C is a fluorescence spectrum diagram of a device for modulating fluorescence polarization of a two-dimensional crystal forbidden band by an N-type nano-grid in TE and TM directions when θ is 45 ° according to an embodiment of the present invention.
Fig. 11D is a graph of the variation of the fluorescence peak value of the device for modulating the fluorescence polarization of the two-dimensional crystal forbidden band by the N-type nano-grid with the emission angle when θ is 45 ° according to the embodiment of the present invention.
Fig. 11E is a graph of the change of the fluorescence linearity of the device, which modulates the fluorescence polarization of the two-dimensional crystal forbidden band by the N-type nano-grid when θ is 45 °, with the fluorescence wavelength.
Fig. 12A is an SEM image of an N-type nanogate at 55 °.
Fig. 12B is a white light reflection spectrum of the N-type nano-grid TE direction when θ is 55 °.
Fig. 12C is a fluorescence spectrum diagram of the device for modulating the fluorescence polarization of the two-dimensional crystal forbidden band by the N-type nano-grid in TE and TM directions when θ is 55 °.
Fig. 12D is a graph of the change of the fluorescence peak value with the emission angle of the device for modulating the fluorescence polarization of the two-dimensional crystal forbidden band by the N-type nano-grid when θ is 55 ° according to the embodiment of the present invention.
Fig. 12E is a graph of the fluorescence linearity of the device for modulating the fluorescence polarization of the two-dimensional crystal forbidden band by the N-type nano-grid at 55 ° according to the embodiment of the present invention, as a function of the fluorescence wavelength.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings.
The invention provides a preparation method of a two-dimensional crystal forbidden band fluorescence polarization modulation device, which is shown in figure 1, and the preparation process is shown in figure 2, and specifically comprises the following steps:
step S201: providing a high-conductivity material substrate;
step S202: oxidizing an insulating layer on the high-conductivity material substrate;
step S203: depositing a two-dimensional crystal monolayer on the insulating layer;
step S204: evaporating a light-transmitting medium layer on the two-dimensional crystal single layer;
step S205: spin-coating electron beam negative glue on the light-transmitting medium layer;
step S206: exposing the negative photoresist, and developing after exposure;
step S207: evaporating a metal layer on the developed negative glue; and
step S208: and removing the residual negative photoresist to obtain the metal nano metamaterial with the periodic unit structure on the light-transmitting medium layer.
Wherein the high conductive material substrate is a highly doped silicon or metal substrate with a thickness of 500 and 750 μm;
wherein the insulating layer is SiO2Or Al2O3The thickness is 270-310nm, and the high-conductivity material is formed on the substrate by a wet oxidation method;
wherein the two-dimensional crystal monolayer is transition metal chalcogenide MX2Wherein M ═ Mo, W; x is S, Se, Te;
wherein the thickness of the two-dimensional crystal monolayer is less than 1nm, and the two-dimensional crystal monolayer is deposited on the insulating layer by a chemical vapor deposition method;
wherein the light-transmitting dielectric layer is Al2O3Or SiO2The thickness is 10-50nm, and the two-dimensional crystal is evaporated on a single layer of the two-dimensional crystal by an electron beam evaporation method;
wherein the electron beam negative photoresist is MA 2403;
the metal nano-structure metamaterial is a gold, silver and aluminum nano-structure material, is 30-100nm thick and is prepared by an electronic direct writing technology;
wherein, the metal nanometer metamaterial with the periodic unit structure has an air gap between the unit structures for isolation;
the metal nano metamaterial with the periodic unit structure is provided with a linear, V-shaped or N-shaped air gap structure, and the included angle between the V-shaped or N-shaped structure and the horizontal direction is an air gap inclination angle theta.
In order to verify the modulation effect of the two-dimensional crystal forbidden band fluorescence polarization modulation device provided by the invention on the fluorescence polarization of the two-dimensional crystal forbidden band, the device provided by the invention is subjected to a test and calculation process shown in fig. 3, and the fluorescence linearity specifically comprises the following steps:
step S301: and converging the pump light on the sample by using a 50X objective lens, exciting the two-dimensional crystal monolayer to emit fluorescence, and collecting a fluorescence signal. Firstly, fluorescent image acquisition is carried out, and an excitation light path, a side-band light filter and a high-sensitivity imaging CCD (charge coupled device) are carried on a common optical microscope to form an imaging system for acquiring the fluorescent image.
Step S302: and collecting the emergent fluorescence spectrum of the sample in the TE/TM direction. Wherein the TE/TM direction refers to the direction parallel/perpendicular to the pump laser polarization. In the step, a fluorescence spectrometer (Andor SR-500) is adopted to collect fluorescence signals. During collection, an analyzer needs to be placed in front of the band-pass filter, and fluorescence collection in different polarization directions is completed by rotating the analyzer.
Step S303: measuring the spectrum of the fluorescence of the sample in the range of 0-360 degrees of exit angle, and drawing a graph of the change of the fluorescence peak value with the exit angle.
Step S304: by the formula L ═ ITE-ITM)/(ITE+ITM) And calculating the fluorescence linearity, and drawing a curve graph of the fluorescence linearity with the fluorescence wavelength.
Example 1: WS2Single layer fluorescence polarization assay
First, in SiO2On a/Si substrate, by chemical vapor deposition to produce WS2Single layer: respectively heating sulfur and tungsten powder to generate vapor, and carrying the vapor to a clean substrate by using argon as carrier gas to deposit and grow to obtain WS2A single layer.
FIG. 4A is the WS2Optical microscopy of monolayers. Fig. 4B is the emission fluorescence spectrum in the TE, TM directions obtained by the test of step S302. As can be seen from FIG. 4B, the fluorescence intensities of the sample in the TE and TM directions are equal, WS2The single layer has a fluorescence peak of 630nm, a full width at half maximum of 30nm and a forbidden band width of 1.9-2.0 eV. Fig. 4C is a graph of the fluorescence spectrum obtained by the test of step S303 as a function of the exit angle. As can be seen from fig. 4C, the intensity of the sample at each exit angle is equal. FIG. 4D is a graph showing the linearity of fluorescence obtained by the test of step S304 as a function of the fluorescence wavelength, and it can be seen from FIG. 4D that the fluorescence line of the sample is within the forbidden bandThe degree of sex was-0.
Example 2: ag nano wire grating modulation two-dimensional crystal WS2Polarization of forbidden band fluorescence
The modulation method provided by the invention is based on the metamaterial surface plasmon resonance principle, which is influenced by the shape of the metamaterial, so that three shapes of metal nanometer metamaterials are designed in the example to modulate the fluorescence linearity, namely a nanometer wire grid, a V-shaped nanometer grid and an N-shaped nanometer grid.
The selection of the unit structure period is determined according to the fluorescence wavelength of the two-dimensional crystal. For example, the periods of the N, V-type nano-structure in the TE and TM polarization directions can be respectively set to 200nm and 400nm, so that the surface plasmon resonance of the metamaterial can be realized in the WS single layer2Fluorescence occurs at a wavelength around 630 nm. The inclination angle of the air gap in the structural unit is further adjusted, and the resonance response can be adjusted to the fluorescent wavelength, so that the metamaterial and the two-dimensional crystal are coupled to a higher degree.
The three structures of the unit structure of the metal nanometer metamaterial have different periods in TM and TE directions. Wherein the TM direction period of the wire grid structure is 600-800 nm; the period of the TE direction of the N, V type nano gate is 150-300nm, and the period of the TM direction is 300-600 nm. The N, V-shaped nanostructure has more adjustable structural dimensions than the wire grid structure, especially the air gap tilt angle theta in the structural unit. The invention can accurately adjust the resonance position by adjusting theta.
The two-dimensional crystal forbidden band fluorescence polarization modulation device and the fluorescence linearity test process are described in detail below for three structures of the nano wire grid, the V-shaped nano grid and the N-shaped nano grid.
Ag nanowire grid modulated WS2Polarization of forbidden band fluorescence
Firstly, a layer of SiO is obtained on a Si substrate by wet oxidation2An insulating layer; then, a layer of WS is grown on the insulating layer by chemical vapor deposition2A single layer; then evaporating and coating by an electron beam coating instrument on the single layer to obtain a layer of Al2O3A light-transmitting medium layer; spin-coating electron beam negative resist MA2403 on the light-transmitting dielectric layer; adopting electron beam direct writing technology to apply negative adhesive MA2403, exposing and writing the structure on negative glue by using a focused electron beam; exposed negative resist MA2403 is remained after development; finally, forming Ag nano metamaterial through metal evaporation and degumming processes to prepare the nano wire grid-WS2A single-layer fluorescence polarization modulation device, wherein fig. 5A is an SEM image of the Ag nanowire grid in the structure. The period and the line width b of the silver nanowire grid are 600nm, and w is 480 nm.
FIG. 5B is a nanowire grid-WS obtained by the test of step S3022The single-layer forbidden band fluorescence polarization modulation device emits fluorescence spectra in the TE and TM directions. As shown in FIG. 5B, the nanowire grid-WS2The fluorescence intensity of the single-layer forbidden band fluorescence polarization modulation device in the TM direction is 40% of that in the TE direction. Fig. 5C is a change law of the fluorescence peak value with the emission angle obtained by the test of step S303. As can be seen from FIG. 5C, the fluorescence exhibits linear polarization, with the polarization direction parallel to the nanowire grid. Fig. 5D is a graph showing the linearity of fluorescence according to the wavelength of fluorescence obtained by the test of step S304. As can be seen from fig. 5D, although the fluorescence peak is at 630nm, the fluorescence linearity is not enhanced at this position, but shows a broad spectrum response. This is caused by the wide spectrum resonance of the wire grid.
(II) V-type Ag nano-grid modulation WS2Polarization of forbidden band fluorescence
Firstly, a layer of SiO is obtained on a Si substrate by wet oxidation2As an insulating layer; then, a layer of WS is grown on the insulating layer by chemical vapor deposition2A single layer; then evaporating a layer of Al on the single layer by using an electron beam coating instrument2O3A light-transmitting medium layer; spin-coating electron beam negative resist MA2403 on the light-transmitting dielectric layer; exposing the negative photoresist MA2403 by adopting an electron beam direct writing technology, and writing a structure on the negative photoresist by using a focused electron beam; exposed negative resist MA2403 is remained after development; and finally, forming an Ag nano structure through metal evaporation and glue removal processes to obtain the device, wherein fig. 6 is a structural diagram of a V-shaped Ag nano wire grid in the structure. Wherein, the period and line width a of the nano grid is 200nm, and b is 400 nm; s is 50nm and the angle of inclination theta of the air gap is variable.
In the following, V-shaped nanograting-WS was performed for θ 51 ° and θ 63 °2Single layer coupling device fluorescence polarizationAnd (5) vibration measurement.
(1)θ＝51°
Fig. 7A is an SEM image of a V-shaped nanogate when θ is 51 °. FIG. 7B is the white light reflectance spectrum of the device in the TE direction, with the reflection valley of 600-650nm representing the surface plasmon resonance position of the device. Fig. 7C is the fluorescence spectrum of the device in the TE, TM directions obtained by the test of step S302. As can be seen from FIG. 7C, the fluorescence intensity in the TM direction is only 25% of that in the TE direction, compared to the nanowire grid-WS2The difference in TE and TM intensities of the coupling device is increased. Fig. 7D is a change law of the fluorescence peak value with the emission angle obtained by the test of step S303. As can be seen from FIG. 7D, the fluorescence exhibits strong linear polarization, with the polarization direction parallel to the long axis of the V-shaped grating. FIG. 7E is a plot of fluorescence linearity as a function of fluorescence wavelength, with a peak at 625nm, aligned with the surface plasmon resonance position, up to 60%, as measured in step S304. The linearity of the fluorescence is still high after 650nm wavelength, which is caused by the metamaterial modulation of the impurity fluorescence of the two-dimensional crystal in the range.
(2)θ＝63°
Fig. 8A is an SEM image of the V-shaped nanogate when θ is 63 °. Fig. 8B is a white light reflection spectrum of the device in the TE direction, and reflection valleys around 650nm represent surface plasmon resonance positions of the V-shaped nanogate structure. Fig. 8C shows the fluorescence spectrum of the device in TE and TM directions obtained by the test in step S302, and the spectrum result shows that the fluorescence intensity in two perpendicular directions has a large difference. Fig. 8D shows the change rule of the fluorescence peak value with the emission angle obtained by the test in step S303, and it can be seen from fig. 8D that the fluorescence has strong linear polarization, and the polarization direction is parallel to the long axis of the V-shaped grating. FIG. 8E is a curve showing the change of the linearity of fluorescence with the fluorescence wavelength obtained by the test in step S304, and it can be seen from FIG. 8E that the linearity has a distinct peak at about 640nm, the peak value is 60%, and the external linearity of the peak is rapidly reduced. This is because when θ is 63 °, surface plasmon resonance of the V-shaped nanogrid in the TE direction occurs in the vicinity of 650nm, and only strong modulation is exerted on the fluorescence signal there. The reason for the high background fluorescence may be caused by poor glue removal process and residual glue luminescence.
(III) N type Ag nano grid modulation WS2Polarization of forbidden band fluorescence
Firstly, a layer of SiO is obtained on a Si substrate by wet oxidation2An insulating layer; then, a layer of WS is grown on the insulating layer by chemical vapor deposition2A single layer; then evaporating a layer of Al on the single layer by using an electron beam coating instrument2O3A light-transmitting medium layer; spin-coating electron beam negative photoresist MA2403 on the transparent medium layer, and writing the structure on the negative photoresist by using the focused electron beam; exposing the negative photoresist MA2403 by adopting an electron beam direct writing technology; exposed negative resist MA2403 is remained after development; and finally, forming an Ag nano structure through metal evaporation and glue removal processes to obtain the device, wherein fig. 9 is a structural diagram of an N-type Ag nano wire grid in the structure. The period and line width a of the nano grid in the structure are 200nm, and b is 400 nm; s is 50nm and the angle of inclination theta of the air gap is variable.
In the following, for the case where θ is 30 °, θ is 45 °, and θ is 55 °, N-type nanogrid-WS2The single layer coupling device was tested for fluorescence polarization.
(1)θ＝30°
Fig. 10A is an SEM image of an N-type nanogate at θ ═ 30 °. Fig. 11B shows a white light reflection spectrum of the device in the TE direction, from which it is understood that the surface plasmon resonance position is at 570 nm. Fig. 10C is the fluorescence spectrum of the device in the TE, TM directions obtained by the test of step S302. As can be seen from FIG. 10C, the fluorescence intensity in the two perpendicular directions is greatly different, and the background fluorescence is very high. Fig. 10D is a graph showing the change of the fluorescence peak value with the emission angle obtained by the test in step S303, and it can be seen that the fluorescence exhibits linear polarization, but is not strong, and the polarization direction is parallel to the long axis of the N-type grating. Fig. 10E is a graph of the change in the fluorescence linearity with the fluorescence wavelength obtained by the test in step S304, and the linearity in the vicinity of the fluorescence peak 630nm is less than 40%, because when θ is 30 °, the surface plasmon resonance position of the N-type grating is at 570nm, and the deviation from the fluorescence peak position is large, and therefore the polarization effect of the resonance field on the fluorescence field is weak. The reasons for the high background fluorescence are that θ is small, the emitted fluorescence is weak, and the signal-to-noise ratio is low.
(2)θ＝45°
Fig. 11A is an SEM image of an N-type nanogate at θ ═ 45 °. Fig. 11B shows a white light reflection spectrum of the device in the TE direction, from which it is understood that the surface plasmon resonance position is 630 nm. Fig. 11C shows the fluorescence spectra of the device in TE and TM directions obtained by the test in step S302. As can be seen from FIG. 11C, the maximum difference in fluorescence intensity occurred in the two perpendicular directions. Meanwhile, the emergent fluorescence signal is strong, the background is weak, and the signal-to-noise ratio is high. Fig. 11D is a graph of the variation of the fluorescence peak value with the emission angle obtained by the test in step S303, and it can be seen that the fluorescence has super-strong linear polarization, and the polarization direction is parallel to the long axis of the N-type grating. FIG. 11E is a graph showing the linearity of fluorescence with the wavelength of fluorescence measured in step S304. From this change curve, the linearity at around 630nm of the fluorescence peak was found to be 80%. The reason why the structure has super-strong linearity is that when theta is 45 degrees, the surface plasmon resonance of the N-type nano grid in the TE direction is just positioned at the fluorescent wavelength, and the modulation capability to the fluorescent field is strongest. In this mode driving, the fluorescence in the TE direction smoothly passes through the nanovoids, while the fluorescence in the TM direction is suppressed, so that high fluorescence linearity occurs.
(3)θ＝55°
Fig. 12A is an SEM image of a 55 ° N-type nanogate. Fig. 12B shows a white light reflection spectrum of the device in the TE direction, from which it is understood that the surface plasmon resonance position is 660 nm. Fig. 12C shows the emission fluorescence spectrum of the device in the TE and TM directions obtained by the test in step S302. As can be seen from FIG. 12C, the intensity of the fluorescence light in two perpendicular directions is greatly different, and the fluorescence signal emitted from the fluorescence light is strong, the background is weak, and the signal-to-noise ratio is high. Since the TM-direction fluorescence suppression ability is reduced, the difference in the TE/TM direction of the fluorescence intensity is reduced compared to an N-type grid having θ equal to 45 °. Fig. 12D is a graph of the variation of the fluorescence peak value with the emission angle obtained by the test in step S303, and it can be seen that the fluorescence exhibits strong linear polarization, and the polarization direction is parallel to the long axis of the N-type grating. FIG. 12E is a graph showing the linearity of fluorescence with the wavelength of fluorescence measured in step S304. As is clear from the graph, the linearity in the vicinity of the fluorescence peak at 630nm is 60%, and the linearity outside the fluorescence peak decreases rapidly. The surface plasmon resonance position of the structure is 660nm and WS2The linearity of fluorescence generated after integration is between N-type grids when theta is 30 degrees and theta is 45 degrees, which shows that changing the angle can change the resonance position of the surface plasmon and adjust the resonance position of the surface plasmon simultaneouslyLinearity of fluorescence.
Example 3:
in addition to the above systems, two-dimensional crystals which may be preferred have a single layer of WSe2。WSe2The monolayer has higher quantum efficiency and longer fluorescence wavelength of 750 nm. From the WSe2The structure and process of preparing the metamaterial-two-dimensional crystal forbidden band fluorescence polarization modulation device by a single layer are the same as those of the embodiment 2, the period of the selected nanostructure is determined according to the fluorescence wavelength, the thickness of the selected dielectric layer is determined by the wavelength of the excitation light, and the establishment principle is explained in the technical scheme introduction. Generally, the wavelength is increased, the metal dissipation is reduced, the surface plasmon resonance response is enhanced, and the modulation effect on the fluorescence linearity is better.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A preparation method of a two-dimensional crystal forbidden band fluorescence polarization modulation device comprises the following steps:
providing a high-conductivity material substrate;
oxidizing an insulating layer on the high-conductivity material substrate;
depositing a two-dimensional crystal monolayer on the insulating layer;
evaporating a light-transmitting medium layer on the two-dimensional crystal single layer;
spin-coating electron beam negative glue on the light-transmitting medium layer;
carrying out electron beam exposure and development on the negative photoresist to obtain a nano-structure pattern on the negative photoresist;
evaporating a metal layer on the developed negative glue; and
removing the residual negative photoresist to obtain the metal nano metamaterial with the periodic unit structure on the light-transmitting medium layer;
wherein the two-dimensional crystal monolayer is transition metal chalcogenide MX2, where M ═ Mo, W; x is S, Se, Te.
2. The method as claimed in claim 1, wherein the substrate of high conductivity material is a highly doped silicon or metal substrate with a thickness of 500-750 μm.
3. The method for preparing the fluorescence polarization modulation device of the two-dimensional crystal forbidden band according to claim 1, wherein the insulation layer is SiO2Or Al2O3The thickness is 270-310nm, and the high-conductivity material is formed on the substrate by a wet oxidation method.
4. The method for preparing the fluorescence polarization modulation device of the two-dimensional crystal forbidden band according to claim 1, wherein the thickness of the two-dimensional crystal single layer is less than 1nm, and the two-dimensional crystal single layer is grown on the insulating layer by a chemical vapor deposition method.
5. The method for preparing the fluorescence polarization modulation device of the two-dimensional crystal forbidden band according to claim 1, wherein the light-transmitting medium layer is Al2O3Or SiO2The thickness is 10-50nm, and the two-dimensional crystal is evaporated on the two-dimensional crystal single layer by an electron beam evaporation method.
6. The method for preparing a fluorescence polarization modulation device of a two-dimensional crystal forbidden band according to claim 1, wherein the electron beam negative glue is MA 2403.
7. The preparation method of the fluorescence polarization modulation device of the two-dimensional crystal forbidden band according to claim 1, wherein the metal nano-structured metamaterial is a nano-structured material of gold, silver and aluminum, has a thickness of 30-100nm, and is prepared by an electronic direct writing technology.
8. The preparation method of the fluorescence polarization modulation device of the two-dimensional crystal forbidden band according to claim 1, wherein the metal nano metamaterial with the periodic unit structure is provided with a linear, V-shaped or N-shaped air gap, and an included angle between the V-shaped or N-shaped air gap and the horizontal direction is an air gap inclination angle theta.
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| JP2003131003A (en) * | 2001-10-29 | 2003-05-08 | Lintec Corp | Manufacturing method of three dimensional photonic crystal |
| CN101183158A (en) * | 2007-11-26 | 2008-05-21 | 华中科技大学 | Wire grating wideband polarizer and method of producing the same |
| CN103869389A (en) * | 2014-04-08 | 2014-06-18 | 太原理工大学 | Photonic crystal cascade structure improving far field emission efficiency of quantum dots |
| CN108761617A (en) * | 2018-03-23 | 2018-11-06 | 中国科学院上海光学精密机械研究所 | Cavity-enhanced high reflection wave plate of medium and preparation method thereof |
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| JP2003131003A (en) * | 2001-10-29 | 2003-05-08 | Lintec Corp | Manufacturing method of three dimensional photonic crystal |
| CN101183158A (en) * | 2007-11-26 | 2008-05-21 | 华中科技大学 | Wire grating wideband polarizer and method of producing the same |
| CN103869389A (en) * | 2014-04-08 | 2014-06-18 | 太原理工大学 | Photonic crystal cascade structure improving far field emission efficiency of quantum dots |
| CN108761617A (en) * | 2018-03-23 | 2018-11-06 | 中国科学院上海光学精密机械研究所 | Cavity-enhanced high reflection wave plate of medium and preparation method thereof |
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