CN112362623B - Physical and chemical adsorption method for identifying single-layer TMDs after laser radiation - Google Patents
Physical and chemical adsorption method for identifying single-layer TMDs after laser radiation Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6489—Photoluminescence of semiconductors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N2015/0866—Sorption
Abstract
The invention discloses a physical and chemical adsorption method in a single-layer TMDs after laser radiation; PL is obtained by respectively measuring photoluminescence intensity of single-layer TMDs under normal pressure and vacuum environment A0 And PL (PL) B0 The method comprises the steps of carrying out a first treatment on the surface of the Then performing laser irradiation on the material, and then testing the material in a vacuum environment to obtain PL B1 The method comprises the steps of carrying out a first treatment on the surface of the Then, the PL was obtained by test after backfilling with ambient air to normal pressure A1 The method comprises the steps of carrying out a first treatment on the surface of the PL is respectively to A0 And PL (PL) A1 ，PL B0 And PL (PL) B1 Normalizing to obtain ΔPL at normal pressure/vacuum 1 And DeltaPL 2 The method comprises the steps of carrying out a first treatment on the surface of the In the photoluminescence process, the physisorption proportion= (Δpl 1 ‑ΔPL 2 )/ΔPL 1 Chemisorption ratio = 1-physisorption ratio. The invention recognizes the components of chemical adsorption and physical adsorption which respectively contribute to fluorescence intensity, and judges by calculation who makes more main contribution in the laser irradiation enhanced single-layer TMDs photoluminescence process, and the study also reveals the synergistic effect of chemical and physical adsorption in enhancing single-layer TMDs photoluminescence intensity.
Description
Technical Field
The invention relates to a method for identifying physical and chemical adsorption in single-layer TMDs after laser irradiation; and more particularly to a method for identifying the ratio of physical and chemical adsorption during photoluminescence of single layer transition metal chalcogenides (transition metal dichalcogenides, TMDs).
Background
Spatially selective laser irradiation has proven to be an effective tool to achieve higher PL intensities for single-layer TMDs, i.e., to use gas molecules to form strong chemical bonds at defects to deactivate defects (chemisorption) to reduce non-radiative recombination channels, or to expose more gas molecule doping defects (physisorption) to reduce the weight of charged excitons. This is also currently two mainstream strategies to enhance the photoluminescent intensity of single-layer TMDs.
The synergistic effect of physical adsorption and chemisorption has always been to affect single layer WS 2 Important factors of photoluminescence intensity may cause charge transfer, defect passivation or serve directly as trapping centers for carriers and excitons, which have a great influence on the recombination lifetime of excitons and on the increase or decrease of non-radiative recombination processes. However, in the interaction of laser light and single-layer TMDs, the relationship between chemisorption and physisorption and which is the determining factor remain to be understood. Therefore, systematic studies on the chemisorption and physisorption processes of laser irradiated single-layer TMDs are necessary.
In the current research on chemisorption and physisorption, the two are discussed in parallel, and the adsorption effect of gas molecules on single-layer TMDs is generally attributed to the synergistic effect of chemisorption and physisorption. However, there is a clear difference in both time scale and ease of occurrence, so this understanding of the adsorption process is more shallow.
Through searching the prior patent literature, the Chinese patent with the application number of 201911059804.8 discloses a method and application for monitoring the defect influence exciton transmission in a few-layer two-dimensional material; however, in the work of researching various types of defects in some two-dimensional materials and performing subsequent significant modulation, similar to the work of enhancing the fluorescence thereof by laser modification, physical adsorption and chemical adsorption are usually mentioned at the same time, and are taken as the same defect types or the reasons for enhancing the fluorescence, but in practice, the two are the root causes of the fluorescence enhancement and the contribution degree are different. The defect related mentioned in other work should be chemisorption, the passivation process of the defect taking place by forming strong chemical bonds at the defect. However, more physical adsorption is to reduce the density of charges through the processes of charge transfer and the like at the defect part by gas molecule adsorption, reduce the weight of charged excitons, and relatively improve the weight of neutral excitons capable of carrying out radiation recombination, thereby improving the fluorescence intensity of the material. Thus by distinguishing the processes of physisorption and chemisorption, not only can the mechanism of formation of both be better explored, but also the root cause of fluorescence enhancement by both can be better explored. Meanwhile, the method can compare the contribution degree of the photoluminescence enhancement, and can carry out necessary researches on the sequence of the photoluminescence enhancement, the occurrence speed and the like for a series of related works, such as time resolution spectrum.
Disclosure of Invention
The invention aims to provide a method for identifying physical and chemical adsorption in single-layer TMDs after laser irradiation. More particularly, a method for identifying the ratio of physical and chemical adsorption during photoluminescence of single layer transition metal chalcogenides (transition metal dichalcogenides, TMDs) is provided.
The embodiment of the invention is as follows: the photoluminescence intensity was measured under normal pressure and vacuum conditions, respectively, by subjecting single-layer TMDs (WS) 2 ) With laser treatment, the single-layer TMDs (WS) can be gradually enhanced in the treatment time range of the time node range before the fluorescence intensity starts to decrease 2 ) Until reaching the strongest point before the decrease in fluorescence intensity. Vacuum device built by oneself afterwardsRespectively carrying out photoluminescence test on the material under different processing time in the environment atmosphere of vacuum environment and normal pressure environment to identify the components of physical adsorption and chemical adsorption. This is to distinguish between the respective components of chemisorption and physisorption and explore the difference between the two for monolayer TMDs (WS 2 ) The extent of the contribution of the photoluminescence enhancement provides a clear comparison and explanation.
Specifically, the aim of the invention is achieved by the following technical scheme:
the invention relates to a method for identifying physical and chemical adsorption proportion in photoluminescence process of single-layer TMDs (TMDs) by laser irradiation, which comprises the following steps:
s1, performing fluorescence test on a single-layer TMDs sample in a vacuum device under normal pressure environment to obtain photoluminescence intensity data PL A0 The method comprises the steps of carrying out a first treatment on the surface of the Fluorescence test is carried out in a vacuum environment in a vacuum device to obtain photoluminescence intensity data PL B0 ；
S2, the fluorescence intensity of the single-layer TMDs sample is enhanced by laser irradiation in a normal gas environment (without being placed in a vacuum device);
s3, performing fluorescence test on the single-layer TMDs sample processed in the step S2 in a vacuum environment in a vacuum device to obtain photoluminescence intensity data PL B1 ；
S4, after backfilling to normal pressure by using ambient air, carrying out fluorescence test on the single-layer TMDs sample in a vacuum device under the normal pressure environment to obtain photoluminescence intensity data PL A1 ；
S5, PL is to A0 And PL (PL) A1 At the same time with PL A0 Normalization (i.e. divided by PL A0 Normalized PL A0 I.e., 1), normalized PL A1 Subtracting normalized PL A0 Obtaining the photoluminescence intensity increase Δpl under normal pressure 1 ；
PL is to B0 And PL (PL) B1 At the same time with PL B0 Normalization (i.e. divided by PL B0 Normalized PL B0 I.e., 1), normalized PL B1 Subtracting normalized PL B0 Obtaining an increase in photoluminescent intensity in a vacuum environmentQuantity DeltaPL 2 ；
S6, in the laser irradiation enhanced single-layer TMDs photoluminescence process, the physical adsorption proportion= (delta PL) 1 -ΔPL 2 )/ΔPL 1 Chemisorption ratio = 1-physisorption ratio.
As an embodiment of the present invention, the single layer TMDs are selected from two-dimensional transition metal sulfides or selenides.
As one embodiment of the present invention, the single layer TMDs include tungsten disulfide, molybdenum disulfide, or tungsten diselenide.
As one embodiment of the present invention, the wavelength of the laser irradiation is a wavelength corresponding to near ultraviolet to visible light; the irradiation power density is 700-900 mu W/mu m 2 . More preferably, the laser irradiation has a wavelength of 488nm; the irradiation power density is 700-900 mu W/mu m 2 . Further preferably, the wavelength of the laser irradiation is 488nm; the irradiation power density was 800. Mu.W/. Mu.m 2 。
As one embodiment of the present invention, the laser irradiation is the use of a laser to treat single-layer TMDs samples over a range of photoluminescent intensities to the corresponding time node at the highest point (i.e., the range before the fluorescence intensity begins to drop).
As one embodiment of the present invention, the laser irradiation is irradiation of a single layer TMDs sample within 100s using a laser.
In step S3, the vacuum environment corresponds to a vacuum degree of 0.1 Pa to 100Pa as an embodiment of the present invention.
Compared with the prior art, the invention has the following beneficial effects:
1) By adopting the method, the problem that the chemical adsorption and physical adsorption components cannot be clearly distinguished all the time before is solved; by fluorescence tests under two different environmental atmospheres, the corresponding components of the two components are calculated, namely the two components are separated, so that a more rigorous analysis is provided for the reason that the different types of adsorption processes have an influence on the photoluminescence intensity of the single-layer TMDs;
2) By adopting the method, the effect of visually comparing the different proportions of the contribution of the chemical adsorption and the physical adsorption to the photoluminescence intensity of the single-layer TMDs is achieved; in order to distinguish the contribution of chemisorption and physisorption to photoluminescence enhancement, photoluminescence measurement is carried out in air and vacuum in sequence, and it is verified that more than two thirds of physisorption determines single-layer TMDs photoluminescence enhancement under laser irradiation, that is, the physisorption process plays a decisive role in PL enhancement of laser irradiation; the invention discloses the synergistic effect of chemical adsorption and physical adsorption in enhancing the photoluminescence intensity of single-layer TMDs, and identifies the components of the chemical adsorption and the physical adsorption respectively contributing to the fluorescence intensity, thereby providing a new visual angle for the interaction of laser and single-layer TMDs.
Drawings
Other features, objects and advantages of the present invention will become more apparent upon reading of the detailed description of non-limiting embodiments, given with reference to the accompanying drawings in which:
FIG. 1 is a graph of laser processing time versus normalized PL intensity under vacuum for various embodiments;
FIG. 2 is a graph of laser processing time versus normalized PL intensity without evacuation for various embodiments;
FIG. 3 is a schematic diagram showing the ratio of chemisorption and physisorption to PL enhancement at different laser irradiation times.
Detailed Description
The present invention will be described in detail with reference to examples. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that several modifications and improvements can be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.
The method for identifying physical and chemical adsorption in the photoluminescence process of the laser enhanced single-layer TMDs comprises the following steps:
step one: fluorescence test is carried out on the single-layer TMDs sample in a vacuum device under normal pressure environment to obtain photoluminescence intensity data PL A0 The method comprises the steps of carrying out a first treatment on the surface of the Fluorescence test under vacuum in vacuum devicePhotoluminescence intensity data PL B0 The method comprises the steps of carrying out a first treatment on the surface of the Then, the fluorescence intensity of the single-layer TMDs is enhanced by a laser modification method in a normal gas environment, fluorescence test is carried out in a vacuum environment in a vacuum device, and data acquisition is carried out to obtain photoluminescence intensity data PL B1 。
Step two: after backfilling to normal pressure by using ambient air, the single-layer TMDs are subjected to fluorescence test in a vacuum device under the normal pressure environment to obtain photoluminescence intensity data PL A1 。
Step three: and (3) comparing the fluorescence test data in the second and third steps, distinguishing the components of chemical adsorption and physical adsorption, and judging which of the chemical adsorption and physical adsorption plays a decisive role in PL enhancement after laser irradiation.
The method specifically comprises the following steps:
PL is to A0 And PL (PL) A1 At the same time with PL A0 Normalization (i.e. divided by PL A0 Normalized PL A0 I.e., 1), normalized PL A1 Subtracting normalized PL A0 Obtaining the photoluminescence intensity increase Δpl without vacuumizing 1 ；
PL is to B0 And PL (PL) B1 At the same time with PL B0 Normalization (i.e. divided by PL B0 Normalized PL B0 I.e., 1), normalized PL B1 Subtracting normalized PL B0 Obtaining the photoluminescence intensity increase Δpl at the time of vacuum pumping 2 ；
In the photoluminescence process of the laser enhanced single-layer TMDs, the physical adsorption proportion=delta PL 1 -ΔPL 2 /ΔPL 1 Chemisorption ratio = 1-physisorption ratio.
In the first step, the laser modification and fluorescence enhancement method adopts the method of prolonging the laser irradiation time to treat the sample and uses laser irradiation (the wavelength of the laser irradiation is 488nm; the irradiation power density is 800 mu W/mu m) 2 ). Single layer TMDs samples were processed over a time range using a laser at a corresponding time node at the peak of photoluminescence intensity. It is noted that the photoluminescence intensity increases with the irradiation time from enhancement to quenchingThe change in extinction, and thus the data collected, is at and before the point where fluorescence is enhanced to peak. The fluorescence enhancement is due to the fact that under the irradiation of laser, the number of non-radiative recombination channels (chemisorption) is reduced due to passivation of defect states, meanwhile, surface pollutants are removed under the action of laser irradiation, existing sulfur vacancies are exposed, gas molecular doping is enhanced, the weight of charged excitons (physisorption) is reduced, and the PL intensity of single-layer TMDs is enhanced through the combination of chemisorption and physisorption. However, the increasing chemisorption and physisorption are not always advantageous for their PL strength, and excessive chemisorption and physisorption also reduces single layer WS 2 The quality and structure of the crystal reduces its fluorescence efficiency, where quenching of PL is a result of structural degradation accompanied by oxidation. Therefore, in order to explore the enhancement effect of physical adsorption and chemical adsorption on the photoluminescence intensity, the invention controls the time within 100 seconds for treatment.
In the second step, the components of the vacuum device are as follows: the vacuum drying oven for injection molding of ordered polycarbonate has an internal dimension required to be a specific dimension for coupling into a raman spectrometer and a vacuum of 0.1 to 100Pa. After being connected to a small vacuum pump through an external hose with the outer diameter of 8mm and an external adapter, the vacuum pump is grounded through three plugs for 30 min. After the sample is vacuumized, the gas molecules in the vacuum drying oven are basically pumped out of the oven, the PL intensity contributed by the chemical adsorption process is almost unchanged due to the strong interaction of chemical bonds on the passivated defects, and the PL intensity contribution by physical adsorption is obviously weakened due to the removal of the weakly adsorbed gas molecules. The physical adsorption process is therefore substantially eliminated even if all gas molecules cannot be completely removed. At this time, the fluorescence intensity is tested under vacuum, so that only a very weak enhancement of fluorescence can be found, and the enhancement result is that the chemical adsorption derived from gas molecules leads to sulfur vacancies and H 2 O or O 2 Equivalent passivation reduces the non-radiative recombination process, thereby increasing the photoluminescent intensity of the material.
In the third step, the process of processing and comparing the test data is that the PL intensity data in the vacuum environment and the normal pressure environment are normalized according to the PL intensity in the vacuum environment and the normal pressure environment when not irradiated, so that the photoluminescence intensity in the vacuum is slightly increased along with the increase of the irradiation time, and even if the irradiation time reaches 100s, the increase of the photoluminescence intensity is weak. Under normal pressure, when the irradiation time is increased to 100s, the photoluminescence intensity increases more obviously. As described above, the increase in PL intensity observed in vacuum and normal pressure is caused by contribution of the chemisorption process and synergy of the chemisorption and physisorption processes, respectively, and thus chemisorption and physisorption components can be intuitively separated by this process. Meanwhile, the ratio of PL enhancement caused by the chemical adsorption and physical adsorption processes at different irradiation times (the ratio refers to the ratio of physical adsorption and chemical adsorption to photoluminescent enhancement part after laser treatment respectively) can be calculated by subtracting the contribution of chemical adsorption from the synergistic enhancement of the two, and the ratio of physical adsorption is far higher than that of chemical adsorption when each irradiation is performed, and the huge difference between the two is caused by the different activation energies. This result therefore shows that the physisorption process plays a decisive role in the PL enhancement of laser irradiation.
See the following examples for specific applications:
further, fig. 1 is a graph showing the relationship between the laser processing time and the normalized PL intensity in the vacuum environment in each example, and it is understood from fig. 1 that the photoluminescence intensity in the vacuum increases only slightly with the increase of the irradiation time, and the increase of the photoluminescence intensity is only about-6% even when the irradiation time is 100 seconds.
FIG. 2 is a graph of laser processing time versus normalized PL intensity in a vacuum environment for each example, and it can be seen from FIG. 2 that the photoluminescence intensity increases by about 60% when the irradiation time is increased to 100 seconds in an air condition. The results indicate that the physisorption process plays a decisive role in the PL enhancement of laser irradiation.
FIG. 3 depicts the proportion of PL enhancement caused by chemisorption and physisorption processes at different irradiation times. It can be seen that the proportion of physical adsorption per irradiation is above 74%, and more up to 89% after 60 seconds.
Example 1
Enhancement of monolayer WS by laser modification treatment 2 The chemisorbed and physisorbed components were separated and compared by the method of the invention at 20s, comprising the steps of:
1. will single layer WS 2 Fluorescence test (wherein fluorescence test uses Raman spectrometer with equipment of Horiba brand, excitation light source is 488nm semiconductor laser with power of 1mW, laser spot size is focused on spot with spot diameter of 1 μm by 100 times objective lens with 0.9 Numerical Aperture (NA), test parameters are collection time: 3 s), and photoluminescence intensity data PL is obtained A0 The method comprises the steps of carrying out a first treatment on the surface of the Fluorescence test is carried out in a vacuum environment (the vacuum degree is pumped to 50 Pa) in a vacuum device to obtain photoluminescence intensity data PL B0 The method comprises the steps of carrying out a first treatment on the surface of the Then, a single layer WS 2 The fluorescence intensity is enhanced by a laser irradiation method (wavelength is 488 nm) in a normal gas environment, after the treatment is carried out for 20 seconds, fluorescence test is carried out in a vacuum environment (the vacuum degree is pumped to 50 Pa) in a vacuum device, and data acquisition is carried out to obtain photoluminescence intensity data PL B1 。
2. Backfilling the vacuum device to normal pressure by using ambient air, and then carrying out the single-layer WS test in the step one 2 Fluorescence test is carried out in a vacuum device built by oneself under normal pressure environment to obtain photoluminescence intensity data PL A1 。
3. The process of processing and comparing the test data is to normalize the PL integral intensity data in vacuum and normal pressure according to the PL integral intensity in vacuum and normal pressure when not irradiated; the method specifically comprises the following steps:
PL is to A0 And PL (PL) A1 At the same time with PL A0 Normalization (i.e. divided by PL A0 Normalized PL A0 I.e., 1), normalized PL A1 Subtracting normalized PL A0 Obtaining a non-vacuumized productPhotoluminescence intensity increase Δpl 1 The method comprises the steps of carrying out a first treatment on the surface of the PL is to B0 And PL (PL) B1 At the same time with PL B0 Normalization (i.e. divided by PL B0 Normalized PL B0 I.e., 1), normalized PL B1 Subtracting normalized PL B0 Obtaining the photoluminescence intensity increase Δpl at the time of vacuum pumping 2 . It can be seen that the photoluminescence intensity in vacuum increases only slightly with increasing irradiation time, and at 20s the photoluminescence intensity increases by-2.5%. Under normal pressure, the photoluminescence intensity increased by-10.7% when the irradiation time increased to 20 s. As can be seen from the calculation method described above, the proportion of physical adsorption at 20s of irradiation time was-77%. This result not only separated the chemisorbed and physisorbed components, but clearly demonstrated by comparison that the physisorption process plays a decisive role in the PL enhancement of laser irradiation.
Example 2
Enhancement of monolayer WS by laser modification treatment 2 The chemisorbed and physisorbed components were separated and compared by the method of the invention at 40s, comprising the steps of:
1. will single layer WS 2 Fluorescence test is carried out in a vacuum device built by oneself under normal pressure environment to obtain photoluminescence intensity data PL A0 The method comprises the steps of carrying out a first treatment on the surface of the Fluorescence test is carried out in a vacuum environment (the vacuum degree is pumped to 50 Pa) in a vacuum device to obtain photoluminescence intensity data PL B0 The method comprises the steps of carrying out a first treatment on the surface of the Then, a single layer WS 2 The fluorescence intensity is enhanced by laser irradiation (wavelength is 488 nm) in normal gas environment, after treatment for 40s, fluorescence test is carried out in vacuum environment (vacuumized to 50 Pa) in vacuum device, and data acquisition is carried out to obtain photoluminescence intensity data PL B1 。
2. Backfilling the vacuum device to normal pressure by using ambient air, and then carrying out the single-layer WS test in the step one 2 Fluorescence test is carried out in a vacuum device built by oneself under normal pressure environment to obtain photoluminescence intensity data PL A1 。
3. The process of processing and comparing the test data is to normalize the PL integral intensity data in vacuum and normal pressure according to the PL integral intensity in vacuum and normal pressure when not irradiated; the method specifically comprises the following steps:
PL is to A0 And PL (PL) A1 At the same time with PL A0 Normalization (i.e. divided by PL A0 Normalized PL A0 I.e., 1), normalized PL A1 Subtracting normalized PL A0 Obtaining the photoluminescence intensity increase Δpl without vacuumizing 1 The method comprises the steps of carrying out a first treatment on the surface of the PL is to B0 And PL (PL) B1 At the same time with PL B0 Normalization (i.e. divided by PL B0 Normalized PL B0 I.e., 1), normalized PL B1 Subtracting normalized PL B0 Obtaining the photoluminescence intensity increase Δpl at the time of vacuum pumping 2 . It can be seen that the photoluminescence intensity in vacuum increases only slightly with increasing irradiation time, and at 40s the photoluminescence intensity increases by-3.4%. Under normal pressure, the photoluminescence intensity increased by-12.9% when the irradiation time increased to 40 s. As can be seen from the calculation method described above, the proportion of physical adsorption at 40s of irradiation time was-74%. This result not only separated the chemisorbed and physisorbed components, but clearly demonstrated by comparison that the physisorption process plays a decisive role in the PL enhancement of laser irradiation.
Example 3
Enhancement of monolayer WS by laser modification treatment 2 The chemisorbed and physisorbed components were separated and compared by the method of the invention at 60s, comprising the steps of:
1. will single layer WS 2 Fluorescence test is carried out in a vacuum device built by oneself under normal pressure environment to obtain photoluminescence intensity data PL A0 The method comprises the steps of carrying out a first treatment on the surface of the Fluorescence test is carried out in a vacuum environment (the vacuum degree is pumped to 50 Pa) in a vacuum device to obtain photoluminescence intensity data PL B0 The method comprises the steps of carrying out a first treatment on the surface of the Then, a single layer WS 2 The fluorescence intensity is enhanced by laser irradiation (wavelength of 488 nm) in normal gas environment, and the obtained product is processed to 60s and then placed in a vacuum deviceFluorescence test under vacuum (vacuum degree of 50 Pa) and data acquisition to obtain photoluminescence intensity data PL B1 。
2. Backfilling the vacuum device to normal pressure by using ambient air, and then carrying out the single-layer WS test in the step one 2 Fluorescence test is carried out in a vacuum device built by oneself under normal pressure environment to obtain photoluminescence intensity data PL A1 。
3. The process of processing and comparing the test data is to normalize the PL integral intensity data in vacuum and normal pressure according to the PL integral intensity in vacuum and normal pressure when not irradiated; the method specifically comprises the following steps:
PL is to A0 And PL (PL) A1 At the same time with PL A0 Normalization (i.e. divided by PL A0 Normalized PL A0 I.e., 1), normalized PL A1 Subtracting normalized PL A0 Obtaining the photoluminescence intensity increase Δpl without vacuumizing 1 The method comprises the steps of carrying out a first treatment on the surface of the PL is to B0 And PL (PL) B1 At the same time with PL B0 Normalization (i.e. divided by PL B0 Normalized PL B0 I.e., 1), normalized PL B1 Subtracting normalized PL B0 Obtaining the photoluminescence intensity increase Δpl at the time of vacuum pumping 2 . It can be seen that the photoluminescence intensity in vacuum increases only slightly with increasing irradiation time, and that at 60s the photoluminescence intensity increases by-4%. And under normal pressure, when the irradiation time is increased to 60s, the photoluminescence intensity is increased by-35%. As can be seen from the calculation method described above, the proportion of physical adsorption at 60s irradiation time was 89%. This result not only separated the chemisorbed and physisorbed components, but clearly demonstrated by comparison that the physisorption process plays a decisive role in the PL enhancement of laser irradiation.
Example 4
Enhancement of monolayer WS by laser modification treatment 2 The chemisorbed and physisorbed components were separated and compared by the method of the invention at 80s, comprising the steps of:
1. will single layer WS 2 Fluorescence test is carried out in a vacuum device built by oneself under normal pressure environment to obtain photoluminescence intensity data PL A0 The method comprises the steps of carrying out a first treatment on the surface of the Fluorescence test is carried out in a vacuum environment (the vacuum degree is pumped to 50 Pa) in a vacuum device to obtain photoluminescence intensity data PL B0 The method comprises the steps of carrying out a first treatment on the surface of the Then, the monolayer-WS 2 The fluorescence intensity is enhanced by laser irradiation (wavelength is 488 nm) in normal gas environment, after treatment for 80s, fluorescence test is carried out in vacuum environment (vacuumizing degree is 50 Pa) in a vacuum device, and data acquisition is carried out to obtain photoluminescence intensity data PL B1 。
2. Backfilling the vacuum device to normal pressure by using ambient air, and then carrying out the single-layer WS test in the step one 2 Fluorescence test is carried out in a vacuum device built by oneself under normal pressure environment to obtain photoluminescence intensity data PL A1 。
3. The process of processing and comparing the test data is to normalize the PL integral intensity data in vacuum and normal pressure according to the PL integral intensity in vacuum and normal pressure when not irradiated; the method specifically comprises the following steps:
PL is to A0 And PL (PL) A1 At the same time with PL A0 Normalization (i.e. divided by PL A0 Normalized PL A0 I.e., 1), normalized PL A1 Subtracting normalized PL A0 Obtaining the photoluminescence intensity increase Δpl without vacuumizing 1 The method comprises the steps of carrying out a first treatment on the surface of the PL is to B0 And PL (PL) B1 At the same time with PL B0 Normalization (i.e. divided by PL B0 Normalized PL B0 I.e., 1), normalized PL B1 Subtracting normalized PL B0 Obtaining the photoluminescence intensity increase Δpl at the time of vacuum pumping 2 . It can be seen that the photoluminescence intensity in vacuum increases only slightly with increasing irradiation time, and at 80s the photoluminescence intensity increases by-5%. While under normal pressure, when the irradiation time was increased to 80s, the photoluminescence intensity increased by-49%. As can be seen from the calculation method described above, the proportion of physical adsorption at 80s irradiation time was 89%. This result not only separates the chemisorbed and physisorbed componentsFrom this, and by contrast, clearly demonstrate that the physisorption process plays a decisive role in the PL enhancement of laser irradiation.
Example 5
Enhancement of monolayer WS by laser modification treatment 2 The chemisorbed and physisorbed components were separated and compared by the method of the invention at 100s, comprising the steps of:
1. will single layer WS 2 Fluorescence test is carried out in a vacuum device built by oneself under normal pressure environment to obtain photoluminescence intensity data PL A0 The method comprises the steps of carrying out a first treatment on the surface of the Fluorescence test is carried out in a vacuum environment (the vacuum degree is pumped to 50 Pa) in a vacuum device to obtain photoluminescence intensity data PL B0 The method comprises the steps of carrying out a first treatment on the surface of the Then, a single layer WS 2 The fluorescence intensity is enhanced by a laser irradiation method (wavelength is 488 nm) in a normal gas environment, after the treatment is carried out for 100 seconds, fluorescence test is carried out in a vacuum environment (the vacuum degree is pumped to 50 Pa) in a vacuum device, and data acquisition is carried out to obtain photoluminescence intensity data PL B1 。
2. Backfilling the vacuum device to normal pressure by using ambient air, and then carrying out the single-layer WS test in the step one 2 Fluorescent test is carried out in a vacuum device under normal pressure environment to obtain photoluminescence intensity data PL A1 。
3. The process of processing and comparing the test data is to normalize the PL integral intensity data in vacuum and normal pressure according to the PL integral intensity in vacuum and normal pressure when not irradiated; the method specifically comprises the following steps:
PL is to A0 And PL (PL) A1 At the same time with PL A0 Normalization (i.e. divided by PL A0 Normalized PL A0 I.e., 1), normalized PL A1 Subtracting normalized PL A0 Obtaining the photoluminescence intensity increase Δpl without vacuumizing 1 The method comprises the steps of carrying out a first treatment on the surface of the PL is to B0 And PL (PL) B1 At the same time with PL B0 Normalization (i.e. divided by PL B0 Normalized PL B0 I.e., 1), normalized PL B1 Subtracting normalized PL B0 Obtaining the photoluminescence intensity increase Δpl at the time of vacuum pumping 2 . Can seeThe photoluminescence intensity in vacuum increased only slightly with increasing irradiation time, and at 100s irradiation time, the photoluminescence intensity increased by-6%. While under normal pressure, when the irradiation time was increased to 100s, the photoluminescence intensity was increased by-56%. As can be seen from the calculation method described above, the proportion of physical adsorption at 100s irradiation time was 89%. This result not only separated the chemisorbed and physisorbed components, but clearly demonstrated by comparison that the physisorption process plays a decisive role in the PL enhancement of laser irradiation.
In summary, the invention has two obvious advantages: (1) The chemical adsorption and physical adsorption components are separated, so that the judgment on the influence of the chemical adsorption and the physical adsorption on the fluorescence of the material from which way can be more accurately pointed out, and more intensive researches can be performed, for example, the sequence and the degree of speed of the chemical adsorption and the physical adsorption on the time scale and the contribution degree of the chemical adsorption and the physical adsorption to the fluorescence enhancement can be more simply and conveniently tested and calculated, so that more rigorous and rich researches are realized. (2) By simple calculation means, different contribution degrees of chemical adsorption and physical adsorption to obtain higher photoluminescence intensity of single-layer TMDs respectively are clearly shown. From this comparison, it was confirmed that the physical adsorption process plays a decisive role in the PL enhancement by laser irradiation. The invention can provide proper supplement for the deep understanding of the interaction between the laser and the single-layer TMDs; and a better platform can be provided for the detailed process of deep chemical adsorption and physical adsorption.
The foregoing describes specific embodiments of the present invention. It is to be understood that the invention is not limited to the particular embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the claims without affecting the spirit of the invention.
Claims (7)
1. A method for identifying a proportion of physical and chemical adsorption during laser irradiation of a monolayer of TMDs to enhance photoluminescence thereof, said method comprising the steps of:
s1, performing fluorescence test on a single-layer TMDs sample in a vacuum device under normal pressure environment to obtain photoluminescence intensity data PL A0 The method comprises the steps of carrying out a first treatment on the surface of the Fluorescence test is carried out in a vacuum environment in a vacuum device to obtain photoluminescence intensity data PL B0 ；
S2, the fluorescence intensity of the single-layer TMDs sample is enhanced by laser irradiation in a normal gas environment; the laser irradiation is to process a single-layer TMDs sample in a time range from the photoluminescence intensity to a corresponding time node at the highest point by using laser;
s3, performing fluorescence test on the single-layer TMDs sample processed in the step S2 in a vacuum environment in a vacuum device to obtain photoluminescence intensity data PL B1 ；
S4, after backfilling to normal pressure by using ambient air, carrying out fluorescence test on the single-layer TMDs sample in a vacuum device under the normal pressure environment to obtain photoluminescence intensity data PL A1 ；
S5, PL is to A0 And PL (PL) A1 At the same time with PL A0 Normalization is carried out, and PL after normalization A0 1, normalized PL A1 Subtracting normalized PL A0 Obtaining the photoluminescence intensity increase Δpl under normal pressure 1 ；
PL is to B0 And PL (PL) B1 At the same time with PL B0 Normalization is carried out, and PL after normalization B0 1, normalized PL B1 Subtracting normalized PL B0 Obtaining the photoluminescence intensity increase Δpl under vacuum 2 ；
S6, in the laser irradiation enhanced single-layer TMDs photoluminescence process, the physical adsorption proportion= (delta PL) 1 -ΔPL 2 )/ΔPL 1 Chemisorption ratio = 1-physisorption ratio.
2. A method of identifying a suitable proportion of physical and chemical adsorption during photoluminescence enhancement by laser irradiation of single layer TMDs as claimed in claim 1 wherein the single layer TMDs are selected from two-dimensional transition metal sulfides or selenides.
3. A method of identifying a proportion of physical and chemical adsorption suitable for use in laser irradiation of monolayers of TMDs to enhance their photoluminescence as claimed in claim 2 wherein the monolayers of TMDs comprise tungsten disulphide, molybdenum disulphide or tungsten diselenide.
4. The method of claim 1, wherein the laser radiation has a wavelength corresponding to near ultraviolet to visible light; the irradiation power density is 700-900 mu W/mu m 2 。
5. The method of identifying physical and chemical adsorption ratios during photoluminescence enhancement by laser irradiation of monolayer TMDs according to claim 4, wherein the laser irradiation has a wavelength of 488nm; the irradiation power density is 700-900 mu W/mu m 2 。
6. A method of identifying a proportion of physical and chemical adsorption during photoluminescence enhancement of a single layer TMDs laser irradiation as claimed in claim 1 wherein the laser irradiation is irradiation of a single layer TMDs sample within 100s using a laser.
7. The method of claim 1, wherein in step S3, the vacuum environment corresponds to a vacuum of 0.1 Pa to 100Pa.
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