CN106906451B - A kind of electron irradiation preparation method of aluminum oxide quantum dots on thin film surface - Google Patents

Abstract

The invention relates to an electron irradiation preparation method of aluminum oxide quantum dots on the surface of thin films. The method includes the cleaning of the substrate; the preparation of the aluminum oxide amorphous film; the electron irradiation of the prepared amorphous film by a commercial electron electrostatic accelerator; and the annealing treatment of the irradiated amorphous film. Through the above steps, aluminum oxide quantum dots are prepared on the surface of the aluminum oxide amorphous thin film, and the distribution density and geometric structure characteristic parameters of the quantum dots can be regulated by controlling the parameters of electron irradiation and annealing. Compared with the prior art, the present invention grows aluminum oxide quantum dots in situ on the surface of the aluminum oxide film, without introducing impurities, and the process is simple; the obtained aluminum oxide film is in an amorphous state, so the circularity of the aluminum oxide quantum dots prepared by the present invention is Better, uniform size, good uniformity of morphological distribution. And the use of commercial electron electrostatic accelerator for electron irradiation can realize large-scale large-scale preparation and commercial application.

Description

A kind of electron irradiation preparation method of aluminum oxide quantum dots on thin film surface

technical field

The invention belongs to the technical field of quantum dot preparation, in particular to a preparation method of aluminum oxide quantum dots on the surface of thin films by electron irradiation.

Background technique

Alumina quantum dots are extremely small alumina particles formed by quasi-zero-dimensional nanostructures and closed electrons. Due to the small size structure of alumina quantum dots, the quasi-continuous energy band evolves into a discrete energy level structure, which has very different properties from bulk materials, including small size effect, quantum size effect, macroscopic quantum tunneling effect, and electron confinement. effect and unique surface effect; therefore, it exhibits a series of novel physical and chemical properties. At present, the preparation methods of alumina quantum dots mainly include template method, precipitation method, sol-gel method, hydrothermal method and so on. On the one hand, these methods are constantly improving and innovating; on the other hand, new preparation processes have been introduced one after another. Among them, the electron beam irradiation method is a promising candidate preparation process for quantum dots. The electron beam irradiation method acts on each part of the irradiated material by energy-carrying electrons, and the prepared quantum dots have uniform distribution and easy control of geometrical parameters. Furthermore, electron beam irradiation does not require auxiliary generating agents, which avoids the introduction of impurities, and the product has high purity. In addition, the preparation of quantum dots by electron beam irradiation is an in-situ growth method, and its technological process is simple and economical.

At present, there have been research reports on the preparation of other metal oxide quantum dots by electron beam irradiation, including zinc oxide quantum dots and titanium oxide quantum dots prepared by electron beam irradiation. However, the electron beam irradiation devices used in these processes are all transmission electron microscopes (transmission electron microscopes for short). It is suitable for scientific research, but difficult to commercialize on a large scale. At the same time, the electron beam intensity of TEM is limited, and the preparation efficiency is low. In particular, there are few reports on the preparation of quantum dots by electron irradiation of electron electrostatic accelerators, which are more suitable for industrial production. Further, there is no technology or research on preparing alumina quantum dots by electron irradiation method based on electron electrostatic accelerator in scientific and engineering circles. In view of this, the research group of the present invention intends to provide a preparation method of electron irradiation of aluminum oxide quantum dots on the surface of thin films based on electron electrostatic accelerator, so that the aluminum oxide quantum dots with novel physical and chemical properties can be more It is suitable for industrial production and commercial application, which is exactly the task of the present invention.

SUMMARY OF THE INVENTION

The purpose of the present invention is to aim at the defects and deficiencies existing in the prior art, to provide a method for preparing aluminum oxide quantum dots by electron irradiation on the surface of the film; the method adopts the reactive sputtering process to prepare the aluminum oxide amorphous film; Electron electrostatic accelerator irradiates the aluminum oxide amorphous film, and finally annealing the irradiated film; namely, aluminum oxide quantum dots are prepared on the surface of the film. The preparation method of the invention is to directly grow alumina quantum dots on the surface of the alumina film in situ, without introducing impurities, and the process is simple; because the electron electrostatic accelerator is used for electron irradiation, large-scale preparation of alumina quantum dots can be realized. point and commercial application.

In order to achieve the above object, the present invention adopts the technical solution composed of the following technical measures.

The electron irradiation preparation method of aluminum oxide quantum dots on the surface of a thin film according to the present invention comprises the following process steps in sequence:

(1) Cleaning treatment of substrates

First, the used substrate is cleaned by removing impurities, oil, and decontamination, and then drying with nitrogen or oven; then, the cleaned and dried substrate is put into a magnetron sputtering coater for plasma reverse sputtering cleaning;

(2) Preparation of Alumina Amorphous Thin Films

The substrate after the plasma reverse sputtering cleaning is performed in step (1), and an amorphous aluminum oxide film is deposited on the substrate by a reactive sputtering process;

(3) Electron irradiation treatment of alumina amorphous film

The aluminum oxide amorphous thin film sample deposited on the substrate in step (2) is placed on an electrically insulating sample stage, and an accelerator is used to conduct electron irradiation treatment on the aluminum oxide amorphous thin film sample by a multi-step irradiation method; the irradiation atmosphere is In the atmospheric environment, the irradiation temperature is room temperature to ensure that the heating temperature of the aluminum oxide amorphous film sample is less than 300 °C; the aluminum oxide quantum dot array can be grown on the surface of the aluminum oxide amorphous film;

(4) Annealing treatment of alumina quantum dots

The alumina quantum dot sample prepared by electron irradiation in step (3) is annealed, and the specific method is to use a heating furnace for annealing treatment in the atmosphere or an oxygen atmosphere; 10°C/min, holding time for 5 to 20 minutes, and cooling to room temperature with the furnace; after annealing treatment, fully crystallized alumina quantum dots with standard stoichiometric chemical composition can be obtained.

In the above-mentioned technical scheme, in the step (1), the substrate is subjected to impurity removal, oil removal and decontamination cleaning, that is, nitric acid, acetone, absolute ethanol and deionized water are used successively to remove impurities from the substrate in an ultrasonic tank. , Degreasing and decontamination cleaning, cleaning time is 20 minutes.

In the above technical solution, the substrate in step (1) is made of single crystal silicon with a smooth surface, or a material with weak electrical conductivity of glass, and the surface roughness (Ra) of the substrate is less than 20 nm.

In the above technical solution, the plasma backsplash cleaning process parameters described in step (1) are: background vacuum degree <1×10 ^-4 Pa, working gas is Ar gas with a purity higher than 99.95%, backsplash cleaning bias voltage It is -100V～-500V, the air pressure of backsplash cleaning is 1.0Pa～5.0Pa, and the time of backsplash cleaning is 5～30 minutes.

In the above technical solution, the reactive sputtering deposition process parameters for depositing and preparing the alumina amorphous film on the substrate by the reactive sputtering process described in step (2) are: the purity of the used aluminum target is higher than 99.9%, the reactive sputtering gas It is a mixed gas of Ar and O ₂ , the purity of Ar and O ₂ gas is higher than 99.95%, the flow ratio of Ar/O ₂ gas is 1:1~5:1, the reactive sputtering power is 50W~500W, and the reactive sputtering power is 50W~500W. The jet pressure was 0.1Pa to 1.0Pa, and the deposition temperature was room temperature.

In the above technical solution, the thickness of the aluminum oxide amorphous thin film prepared in step (2) is 500 nm˜2 μm.

In the above-mentioned technical scheme, in the step (3), an accelerator is used to carry out electron irradiation treatment on the thin film sample, and the accelerator is an electron electrostatic accelerator, and the technical indicators that it satisfies are: the electron electrostatic accelerator electron energy is in the order of MeV, and the electron beam The current intensity is in the order of μA, and the electron energy and beam current intensity can be adjusted; the electron beam at the exit end is a divergent type, and is suitable for large-area irradiation treatment.

In the above technical solution, the electron electrostatic accelerator performs electron irradiation treatment on the alumina amorphous film sample, and the electron irradiation process parameters are: the electron energy is 1.0-3.0MeV, and the electron beam current density on the surface of the alumina amorphous film is The irradiation dose is 0.1 μA/cm ² -0.5 μA/cm ² , the irradiation dose is 1.0×10 ¹⁴ e/cm ² -1.0×10 ¹⁶ e/cm ² , and the total irradiation time is 60-120 minutes.

In the above technical solution, the multi-step irradiation method of the electron electrostatic accelerator means that the irradiation is interrupted once every 20 minutes, the interruption residence time is 10 minutes, and the irradiation is repeated for 20 minutes, and the cycle is repeated 3 to 6 times.

The electron irradiation preparation method of the aluminum oxide quantum dots on the surface of the thin film described in the present invention can control the distribution density and geometry of the aluminum oxide quantum dots by changing the electron beam current density, electron energy and electron irradiation dose of the electron electrostatic accelerator. Structural characteristic parameters, such as the size of quantum dots; at the same time, by changing the annealing temperature, heating rate and holding time, the distribution density and geometric structure characteristic parameters of alumina quantum dots, such as the size of quantum dots, can also be adjusted.

Compared with the prior art, the present invention has the following features and beneficial technical effects:

1. The electron irradiation preparation method of aluminum oxide quantum dots on a film surface of the present invention is to prepare aluminum oxide quantum dots on the surface of the aluminum oxide film by the electron electrostatic accelerator electron irradiation method. Compared with the prior art, it belongs to the in-situ method. The growth technology does not require auxiliary generators, and does not introduce impurities, and the prepared alumina quantum dots are of high purity.

2. The electron irradiation preparation method of aluminum oxide quantum dots on the surface of a thin film according to the present invention, because a commercial electron electrostatic accelerator is used to irradiate the aluminum oxide film to generate quantum dots, which is different from the transmission electron microscope in the prior art, In particular, electron irradiation is performed in an atmospheric environment, and a vacuum environment is not required, so the process is simpler and more economical; especially, the use of commercial electron electrostatic accelerators can achieve large-scale production, industrial production and more suitable for commercial use. application.

3. The electron irradiation preparation method of aluminum oxide quantum dots on the surface of a thin film according to the present invention adopts a commercial electron electrostatic accelerator, and its irradiation electron beam characteristic is that the electron energy is high in the order of MeV, and it is a divergent electron beam. ; Compared with the prior art, the growth mechanism of aluminum oxide quantum dots irradiated by this electron beam is an anisotropic transport mechanism caused by the surface charge layer formed by high-energy electrons; at the same time, the deposited aluminum oxide film is amorphous Therefore, the alumina quantum dots prepared by the method of the present invention have good circularity, uniform size and good uniformity of morphological distribution.

4. The electron irradiation preparation method of aluminum oxide quantum dots on the surface of a thin film according to the present invention, the aluminum oxide quantum dots irradiated by commercial electron electrostatic accelerators are annealed, and the process parameters of irradiation and annealing treatment can be changed, which is more convenient The distribution density and geometric structure characteristic parameters of alumina quantum dots can be controlled in a controlled manner.

Description of drawings

Fig. 1 adopts the SEM image of the surface morphology of the alumina quantum dots prepared by the electron irradiation preparation method of the alumina quantum dots on the thin film surface in Example 1 of the present invention;

FIG. 2 is an SEM image of the surface topography of the alumina quantum dots prepared by the electron irradiation preparation method of the alumina quantum dots on the surface of the thin film in Example 2 of the present invention.

Detailed ways

The method described in the present invention will be described in further detail below with specific examples, but it is not intended to limit the protection content of the present invention.

Example 1

In the present Example 1, the electron irradiation preparation method of the aluminum oxide quantum dots on the surface of the thin film is prepared in sequence according to the aforementioned process steps; the accelerator electron irradiation adopts a commercial electron electrostatic accelerator, a commercial electron electrostatic accelerator The model is JJ-2MV; the used magnetron sputtering coating machine is QX-500 type magnetron sputtering coating machine; the used heating furnace is a box-type heating furnace, and the substrate is a single crystal silicon wafer.

The electron irradiation preparation method of the aluminum oxide quantum dots on the surface of the thin film described in the present embodiment 1, specifically adopts the following process steps in sequence:

Step (1), cleaning of the substrate

Firstly, the surface-polished single-crystal silicon wafers were sequentially cleaned with analytically pure nitric acid, acetone, anhydrous ethanol and deionized water in an ultrasonic tank for impurity removal, oil removal and decontamination cleaning. The cleaning time was 20 minutes, and then nitrogen was used for cleaning. Blow dry; then, put the single crystal silicon wafer into ^QX -500 magnetron sputtering coating machine for plasma reverse sputtering cleaning; The backsplash cleaning bias voltage is -100V, the Ar gas with the purity of 99.95% is used as the working gas, the backsplash pressure is 1.0Pa, and the cleaning time is 5 minutes; and the surface roughness of the single crystal silicon wafer used is less than 20nm;

Step (2), preparation of aluminum oxide amorphous thin film

For the single crystal silicon wafer after the plasma reverse sputtering cleaning in step (1), an amorphous aluminum oxide film is deposited on the single crystal silicon wafer by a reactive sputtering process, and the deposition process parameters are: the purity of the aluminum target used is 99.99 %, using a mixture of Ar and O ₂ with a purity of 99.95% as the sputtering gas, the flow ratio of Ar:O ₂ gas is 1:1, the reactive sputtering power is 50W, the reactive sputtering gas pressure is 0.1Pa, and the deposition temperature is is room temperature; finally, an amorphous aluminum oxide film with a thickness of 2 μm must be deposited;

(3) step, electron irradiation treatment of aluminum oxide amorphous film

Place the aluminum oxide amorphous film sample deposited on the single crystal silicon wafer in step (2) on an electrically insulating sample stage, and use a JJ-2MV commercial electron electrostatic accelerator to test the aluminum oxide amorphous film sample in an atmospheric environment. Electron irradiation treatment was carried out in a multi-step irradiation method. The irradiation treatment parameters were: electron energy of 1.0 MeV, electron beam current density of 0.1 μA/cm ² , irradiation temperature of room temperature, and the sample of alumina amorphous film placed on a wooden board. On the base, the electron irradiation dose is 1.0×10 ¹⁴ e/cm ² , and the total electron irradiation time is 60 minutes. The residence time is 10 minutes, and then irradiated for 20 minutes, and this cycle is repeated 3 times, which can ensure that the heating temperature of the aluminum oxide amorphous film sample is not higher than 300 °C; the aluminum oxide quantum can be grown on the surface of the aluminum oxide amorphous film. array of points;

Step (4), annealing treatment of alumina quantum dots

The alumina quantum dot sample prepared by electron irradiation in step (3) is annealed. The specific method is to use a box-type heating furnace for annealing in an atmospheric environment. The process parameters are: annealing temperature of 300 ° C, heating rate of 5 ℃/min, hold for 5 minutes, and then cool to room temperature with the furnace; standard stoichiometric ratio, crystalline structure alumina quantum dot samples can be obtained by annealing treatment.

The structure and morphology of the alumina quantum dot sample prepared in Example 1 was detected, including the following test techniques, indicators and results:

A JSM-7500F field emission scanning electron microscope (SEM) was used to observe the structure and morphology of the aluminum oxide quantum dots on the surface of the film. The test process parameters were: acceleration voltage of 200kV and resolution of 1nm. The results show that aluminum oxide quantum dots are formed on the surface of the aluminum oxide amorphous film deposited on the single crystal silicon wafer, and the geometric shape of the quantum dots is circular; the quantum dots are uniformly distributed on the surface of the film, and the distribution density is about 1450μm ^-2 ; The quantum dot size distribution is relatively uniform, with an average diameter of about 12.3 nm; as shown in Figure 1.

Example 2

The preparation method, process steps and the used electron irradiation instrument of the present embodiment 2 are the same as those of the embodiment 1, wherein the process parameters are different, and the substrate is a glass sheet; specifically, the following process steps are adopted in sequence:

Step (1), cleaning of the substrate

First of all, the surface-polished glass sheets were cleaned in an ultrasonic tank with analytically pure nitric acid, acetone, anhydrous ethanol and deionized water in order for impurity removal, oil removal and decontamination cleaning. The cleaning time was 20 minutes, and then dried in an oven; Subsequently, the glass sheet was placed in a QX-500 magnetron sputtering coating machine for plasma back-sputter cleaning. The process parameters of the back-sputter cleaning were: the background vacuum was 5×10 ^-5 Pa, and the back-sputter cleaning bias was -500V, Ar gas with a purity of 99.95% is used as the working gas, the backsplash pressure is 5.0Pa, and the cleaning time is 30 minutes; and the surface roughness of the glass sheet used is less than 20nm;

Step (2), preparation of aluminum oxide amorphous film

For the glass sheet cleaned by plasma reverse sputtering in step (1), an amorphous aluminum oxide film is deposited on the glass sheet by a reactive sputtering process. A mixture of 99.95% Ar and O ₂ was used as the reactive sputtering gas, the flow ratio of Ar:O ₂ gas was 5:1, the reactive sputtering power was 500W, the reactive sputtering gas pressure was 1.0Pa, and the deposition temperature was room temperature; Deposit an amorphous aluminum oxide film with a thickness of 500 nm;

(3) step, electron irradiation treatment of aluminum oxide amorphous film

The aluminum oxide amorphous film sample deposited on the glass plate in step (2) was placed on an electrically insulating sample stage, and the aluminum oxide amorphous film sample was subjected to multi-step irradiation using a JJ-2MV commercial electron electrostatic accelerator in an atmospheric environment. The electron irradiation treatment was carried out by irradiation method, and the irradiation process parameters were: electron energy was 3.0MeV, electron beam current density was 0.5μA/cm ² , irradiation temperature was room temperature, and the alumina amorphous film sample was placed on the wooden base, The electron irradiation dose is 4.0×10 ¹⁵ e/cm ² , the total electron irradiation time is 120 minutes, and the irradiation method is a multi-step irradiation method, that is, the irradiation is interrupted once every 20 minutes, and the pause time is 10 minutes, and then irradiated for 20 minutes, and this cycle is repeated 6 times, so that the heating temperature of the film sample can be guaranteed not to be higher than 300 °C; the aluminum oxide quantum dot array can be grown on the surface of the aluminum oxide amorphous film;

Step (4), annealing treatment of alumina quantum dots

The alumina quantum dot samples prepared by electron irradiation in step (3) are annealed. The specific method is to use a box heating furnace for annealing treatment in an atmospheric environment. The process parameters are: annealing temperature of 400 ° C and heating rate of 10 ° C. /min, the holding time is 20 minutes, and then cooled to room temperature with the furnace; the standard stoichiometric ratio, crystalline structure of alumina quantum dot samples can be obtained by annealing treatment.

Example 2 adopts the same detection method for the structure and morphology of alumina quantum dots as in Example 1. The results show that alumina quantum dots are also formed on the surface of the alumina thin film prepared in Example 2, and the geometric shape of the quantum dots is also circular, and the size and distribution are relatively uniform. However, compared with the sample in Example 1, the quantum dots in Example 2 have a smaller distribution density of about 850 μm ⁻² , and a larger average diameter of about 18.1 nm, as shown in FIG. 2 .

It can be confirmed by the above examples that the geometric structure parameters of the prepared alumina quantum dots, the distribution density on the surface of the alumina thin film and the The irradiation process parameters are closely related; that is, the distribution density and geometric structure characteristics of alumina quantum dots can be effectively controlled by changing the electron irradiation process parameters.

Claims (7)

1. an electron irradiation preparation method of film surface aluminum oxide quantum dots is characterized in that comprising following processing steps successively: (1) Cleaning treatment of substrates First, the used substrate is cleaned by removing impurities, oil, and decontamination, and then drying with nitrogen or oven; then, the cleaned and dried substrate is put into a magnetron sputtering coater for plasma reverse sputtering cleaning; (2) Preparation of Alumina Amorphous Thin Films The substrate after the plasma reverse sputtering cleaning is performed in step (1), and an amorphous aluminum oxide film is deposited on the substrate by a reactive sputtering process; (3) Electron electrostatic accelerator irradiation treatment of alumina amorphous film The aluminum oxide amorphous film sample deposited on the substrate in step (2) is placed on an electrically insulating sample stage, and an electron electrostatic accelerator is used to irradiate the aluminum oxide amorphous film sample with a multi-step irradiation method; The atmosphere is the atmospheric environment, and the irradiation temperature is room temperature, so as to ensure that the heating temperature of the aluminum oxide amorphous film sample is less than 300 °C; the aluminum oxide quantum dot array can be grown on the surface of the aluminum oxide amorphous film; (4) Annealing treatment of alumina quantum dots The alumina quantum dot sample prepared by irradiation with the electron electrostatic accelerator in step (3) is annealed, and the specific method is to use a heating furnace for annealing treatment in the atmosphere or an oxygen atmosphere; /～10℃/min, holding time for 5～20 minutes, cooling to room temperature with the furnace; after annealing treatment, alumina quantum dots with standard stoichiometric ratio and complete crystallization can be obtained; The electron electrostatic accelerator meets the technical indicators: the electron energy of the electron electrostatic accelerator is in the order of MeV, the electron beam intensity is in the order of μA, and the electron energy and beam intensity can be adjusted; for large-area irradiation treatment; The irradiation process parameters of the electron electrostatic accelerator are as follows: the electron energy is 1.0～3.0MeV, the electron beam current density on the surface of the alumina amorphous film is 0.1μA/cm ² ～ 0.5μA/cm ² , and the irradiation dose is 1.0× 10 ¹⁴ e/cm ² ～1.0×10 ¹⁶ e/cm ² , and the irradiation time is 60-120 minutes. 2. the electron irradiation preparation method of film surface aluminum oxide quantum dots according to claim 1, is characterized in that described in step (1), substrate is carried out impurity removal, degreasing and decontamination cleaning, namely use nitric acid successively , acetone, anhydrous ethanol and deionized water in the ultrasonic tank to remove impurities, degreasing and decontamination cleaning of the substrate, the cleaning time is 20 minutes. 3. the electron irradiation preparation method of film surface aluminum oxide quantum dots according to claim 1 and 2 is characterized in that the substrate described in step (1) adopts the weak conductivity of monocrystalline silicon with smooth surface or glass material, and the surface roughness of the substrate is less than 20nm. 4. The electron irradiation preparation method of aluminum oxide quantum dots on thin film surface according to claim 1 or 2, characterized in that the plasma backsplash cleaning process parameter described in step (1) is: background vacuum degree＜1× 10 ^-4 Pa, the working gas is Ar gas with a purity higher than 99.95%, the backsplash cleaning bias is -100V～-500V, the backsplash cleaning pressure is 1.0Pa～5.0Pa, and the backsplash cleaning time is 5～30 minutes. 5. The electron irradiation preparation method of aluminum oxide quantum dots on film surface according to claim 1, characterized in that described in step (2), utilizing reactive sputtering process to deposit and prepare reactive sputtering of aluminum oxide amorphous film on substrate The parameters of the sputtering deposition process are: the purity of the aluminum target used is higher than 99.9%, the reactive sputtering gas is a mixture of Ar and O ₂ , the purity of Ar and O ₂ gas are both higher than 99.95%, and the flow ratio of Ar/O ₂ gas It is 1:1-5:1, the reactive sputtering power is 50W-500W, the reactive sputtering pressure is 0.1Pa-1.0Pa, and the deposition temperature is room temperature. 6 . The method for preparing aluminum oxide quantum dots on the surface of thin film by electron irradiation according to claim 1 or 5 , wherein the prepared aluminum oxide amorphous thin film has a thickness of 500 nm to 2 μm. 7 . 7. the electron irradiation preparation method of aluminum oxide quantum dots on film surface according to claim 1, it is characterized in that the multi-step irradiation mode of described electron electrostatic accelerator refers to interrupt once after every irradiation 20 minutes, interrupt dwell time For 10 minutes, then irradiate for 20 minutes, and so on 3-6 times.