Method for coating fluorescent powder with aluminum oxide through plasma-assisted atomic layer deposition

Abstract

The invention discloses a method for coating fluorescent powder with aluminum oxide through plasma-assisted atomic layer deposition, which comprises the following steps of: building an atomic layer deposition system, and placing a base station in a vacuum chamber of the atomic layer deposition system; fluorescent powder is placed on a base station, a vibration motor is turned on, and then the fluorescent powder is pretreated, including degassing treatment and oxygen plasma pretreatment; sequentially and alternately introducing two precursors into a vacuum chamber of the atomic layer deposition system, so that the two precursors are chemically adsorbed on the surface of the fluorescent powder and react to generate an aluminum oxide film; and after each precursor is introduced and reacts, the vacuum chamber needs to be cleaned by inert gas. According to the method, high-precision monoatomic-layer-level film control is achieved through the plasma-assisted atomic layer deposition technology, the defect that powder is prone to agglomeration in deposition is overcome through the vibration type fluidized bed technology, and therefore a high-quality aluminum oxide protection layer can be formed on the surface of the fluorescent powder; the water resistance and the luminescence property of the fluorescent powder are obviously improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of material surface treatment, and specifically relates to a method for plasma-assisted atomic layer deposition of aluminum oxide coated phosphor, which deposits a uniform aluminum oxide film on the surface of phosphor particles to improve the stability and luminescence performance of the phosphor. Background Art

[0002] With the rapid development of modern optoelectronic technology, phosphors are increasingly used in various optoelectronic devices, such as LED lighting, displays, lasers, and fluorescent displays. These devices rely on the optical properties of phosphors to achieve efficient light conversion and luminescence. However, phosphors are often exposed to harsh environments such as humidity, oxygen, and ultraviolet light, which may cause the performance of phosphors to deteriorate. For example, some phosphors are prone to light attenuation under humid conditions, which in turn affects their luminous efficiency and service life. In addition, oxidation and photodegradation are also one of the main factors that lead to the degradation of phosphor performance. These problems limit the stability and reliability of phosphors in long-term use.

[0003] In order to improve the environmental stability of phosphors, coating a layer of inorganic barrier film on the surface of the powder is a good solution. Many researchers have used sol-gel method, chemical vapor deposition method and other methods to oxidize aluminum, silicon, titanium and other oxides on the surface of phosphors to increase the life of phosphors or improve their luminescence performance. However, these methods have common disadvantages: the coating film has poor conformality and the thickness is difficult to accurately control; for powders with porous and rough surfaces, these methods are difficult to achieve good coating effects. Therefore, in view of the above problems, it is necessary to provide a new method for coating the surface of phosphors. Summary of the invention

[0004] The present invention provides a method for plasma-assisted atomic layer deposition of aluminum oxide coated phosphors, aiming to overcome the many shortcomings of the prior art when aluminum oxide, silicon oxide, titanium oxide, etc. are deposited on the surface of phosphors by sol-gel method or chemical vapor deposition method to increase the life of the phosphors or improve their luminous properties, such as poor conformality of the coating film and difficulty in precise thickness control.

[0005] The technical solution of the present invention to solve the above technical problem is as follows: a method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphor, comprising the following steps:

[0006] S1. Atomic layer deposition system installation: A base is fixedly installed at the bottom of the vacuum chamber of the atomic layer deposition system, and the base is driven to vibrate by a vibration motor. The vacuum chamber is connected to the first air inlet pipe and the second air inlet pipe;

[0007] S2. Phosphor treatment: placing the phosphor on the base, turning on the heating mechanism to heat the phosphor, starting the vibration motor, and then degassing the phosphor and pre-treating it with oxygen plasma;

[0008] S3. Atomic layer deposition coating film formation: Keep the vibration motor in the starting state, and introduce two precursors that can react with each other to produce aluminum oxide film into the vacuum chamber alternately through the first air inlet pipe and the second air inlet pipe in turn. After each precursor is introduced and the reaction is completed, an inert gas is introduced through the first air inlet pipe or the second air inlet pipe to purge the fluorescent powder in the vacuum chamber to take away the precursor free in the vacuum chamber. The two precursors are introduced alternately in this cycle for several times until an aluminum oxide film of a specific thickness is formed on the surface of the fluorescent powder.

[0009] On the basis of the above technical solutions, the present invention can also make the following further specific options.

[0010] Specifically, the first air inlet pipe in S1 is used to deliver a precursor into the vacuum chamber in a gas pulse manner, and the second air inlet pipe is used to deliver another precursor into the vacuum chamber in a gas pulse manner.

[0011] Specifically, the vibration frequency of the vibration motor in S1 is set to 50-60 Hz.

[0012] Specifically, the temperature of the phosphor after heating in S2 is 50-70°C.

[0013] Specifically, the degassing treatment of the phosphor in S2 is to evacuate the vacuum chamber to a pressure of 0.1 Pa.

[0014] Specifically, during the oxygen plasma pretreatment in S2, the generation power of the oxygen plasma is 40-50 W, the pretreatment time is 8-20 min, and the oxygen plasma flow rate is 10-15 sccm.

[0015] Specifically, the two precursors in S3 that can react with each other to form an aluminum oxide film are oxygen plasma and trimethylaluminum.

[0016] Specifically, the pulse times of oxygen plasma and trimethylaluminum in S3 are 5-10 s and 1-2 s, respectively.

[0017] Specifically, the inert gas used in S3 is argon or nitrogen, with a flow rate of 90-110 sccm, and each purge lasts for 30-40 seconds.

[0018] Specifically, the phosphor is a silicon-based nitride phosphor with a particle diameter of 9±1 μm or a silicate phosphor with a particle diameter of 12±1 μm.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention combines plasma-assisted atomic layer deposition technology with a vibrating fluidized bed powder processing technology, and successfully applies it to coating the surface of phosphor with an aluminum oxide film, thereby forming a high-quality aluminum oxide film layer on the surface of the phosphor, which not only effectively protects the phosphor from the influence of the external environment, but also improves its optical properties to a certain extent, thereby enhancing the stability and light emission efficiency of the phosphor. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure shows a flow chart of a method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphors provided by the present invention;

[0022] Figure 2 FIG. 1 is a schematic diagram of the structure of an atomic layer deposition system in one embodiment of the present invention.

[0023] Description of reference numerals:

[0024] 1. Vacuum chamber; 2. Base; 3. First air inlet pipe; 4. Second air inlet pipe; 5. Air extraction pipe. DETAILED DESCRIPTION

[0025] The principles and features of the present invention are described below in conjunction with the accompanying drawings and specific embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0026] like Figure 1 and 2 As shown, the present invention provides a method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphors, which comprises the following steps:

[0027] S1. Atomic layer deposition system installation: A base is fixedly installed at the bottom of the vacuum chamber of the atomic layer deposition system, and the base is driven to vibrate by a vibration motor. The vacuum chamber is connected to the first air inlet pipe and the second air inlet pipe;

[0028] S2. Phosphor treatment: placing the phosphor on the base, turning on the heating mechanism to heat the phosphor, starting the vibration motor, and then degassing the phosphor and pre-treating it with oxygen plasma;

[0029] S3. Atomic layer deposition coating: Keep the vibration motor started, and introduce two precursors that can react with each other to form an aluminum oxide film into the vacuum chamber alternately through the first air inlet pipe and the second air inlet pipe. After each precursor is introduced and the reaction is completed, an inert gas is introduced through the first air inlet pipe or the second air inlet pipe to purge the fluorescent powder in the vacuum chamber to take away the precursor free in the vacuum chamber. The two precursors are introduced alternately several times in this cycle until an aluminum oxide film of a specific thickness is formed on the surface of the fluorescent powder.

[0030] It should be noted that the plasma-assisted atomic layer deposition used in the present invention can form a uniform and dense film on the surface of the substrate, which has high deposition accuracy and control ability, and can achieve high-quality film deposition at a relatively low temperature, which is particularly important for heat-sensitive phosphors. There is currently no precedent for using plasma-assisted atomic layer deposition technology to coat phosphors, especially no precedent for combining vibrating fluidized bed technology with atomic layer deposition technology. The saturated vapor pressure (1.65 kPa) of trimethylaluminum at room temperature is high enough to keep it in a gaseous state and enter the reaction chamber. The amount of trimethylaluminum introduced can be monitored by a flow meter. In the alternating ventilation link, trimethylaluminum is introduced first in each cycle. The vibration of the vibration motor is conducive to the dispersion of the phosphor, preventing powder aggregation from affecting the uniformity of the deposited film; the pulsed introduction of the precursor can ensure that the amount of the precursor injected each time is limited, avoiding the precursor from aggregating in the chamber and affecting the uniformity of the deposition.

[0031] The present invention adopts the above technology to form a high-quality film layer of aluminum oxide on the surface of the phosphor, effectively protecting the phosphor from the influence of the external environment, and can also improve its optical properties to a certain extent, and enhance the stability and light emission efficiency of the phosphor.

[0032] exist Figure 2 In the figure, the vacuum chamber 1 (quartz tube) and the base 2 are connected by a vacuum sealing flange and six screws. Each time the phosphor is added or removed, the quartz tube must be removed from the base, the phosphor must be placed on the base, and then the quartz tube must be put back. The bottom of the vacuum chamber is connected to the first air inlet pipe 3, the top is connected to the second air inlet pipe 4, and the exhaust pipe 5 is also connected to the top of the vacuum chamber. In order to prevent powder from entering the pipes, a dust filter can be set at the pipe opening.

[0033] Example 1

[0034] A method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphors, comprising the following steps:

[0035] S1. Build and install the atomic layer deposition system. The schematic diagram of the system is shown in the figure. Figure 2 As shown;

[0036] S2. Select silicon-based nitride phosphor with a particle diameter of about 9±1μm. Start the vibration motor with a vibration frequency of 50Hz, and degas the silicon-based nitride phosphor at 50℃ for 1h to remove the gas adsorbed on the surface. After degassing, the pressure in the vacuum chamber is 0.1Pa. Use 40W oxygen plasma to pretreat the powder for 10min to improve the surface activity of the powder.

[0037] S3. Keep the vibration motor started, set the pulse time of TMA (trimethylaluminum) and oxygen plasma to 2s and 10s respectively, the flow rate of argon gas to 100sccm, the purge time to 30s, and the flow rate of oxygen gas introduced when generating oxygen plasma to 12sccm. During the deposition process, each cycle is divided into four steps: 1) Pulse TMA into the vacuum chamber to allow it to be fully adsorbed on the surface of the phosphor; 2) Use argon gas to purge the chamber to remove unreacted precursors and by-products, ensure the monolayer adsorption characteristics of the reaction, and evacuate the vacuum chamber; 3) Pulse oxygen into the vacuum chamber while turning on the RF power supply to form oxygen plasma, which reacts with the adsorbed TMA to form an aluminum oxide film; 4) Pass argon gas again to purge the residues and gases after the reaction to complete a deposition cycle.

[0038] 400 deposition cycles were performed in an atomic layer deposition system. The thickness of the deposited aluminum oxide film was measured using an ellipsometer and TEM, and it was observed that the film thickness was uniform, about 61nm, and the deposition rate was 0.15nm / cyc le. The luminescence performance before and after coating was tested using a steady-state fluorescence spectrometer. The results showed that the luminescence intensity of the coated phosphor was significantly improved and the color temperature was slightly reduced. The water resistance of the silicon-based nitride phosphor after 400 cycles of coating was tested, and the pH value of the solution remained almost unchanged, indicating the good barrier properties of the aluminum oxide film.

[0039] Example 2

[0040] S1. Build and install the atomic layer deposition system. The schematic diagram of the system is shown in the figure. Figure 2 As shown;

[0041] S2. Silicate phosphors were selected, with a particle diameter of about 12±1μm. The silicon-based nitride phosphors were degassed at 50°C for 1h to remove the gas adsorbed on the surface. The pressure in the vacuum chamber after degassing was 0.1Pa. The powders were pretreated with 40W oxygen plasma for 10min to improve the surface activity of the powders.

[0042] S3 sets the deposition temperature to 50°C, the pulse times of TMA (trimethylaluminum) and oxygen plasma to 2s and 10s respectively, the flow rate of argon gas to 100sccm, the purge time to 30s, and the flow rate of oxygen gas introduced when generating oxygen plasma to 12sccm. The deposition process is the same as in Example 1.

[0043] 400 deposition cycles were performed in the atomic layer deposition system. The luminescence performance was measured and it was observed that the luminescence intensity of the coated phosphor was stable and maintained good performance under high temperature conditions. The water resistance test results showed that the pH value of the coated phosphor in water changed by less than 0.5, indicating that its water resistance was significantly improved.

[0044] Through the above embodiments, the present invention can draw the following conclusions:

[0045] Plasma-assisted atomic layer deposition technology can effectively deposit uniform and high-quality aluminum oxide films on the surface of phosphors, improving their stability in high humidity and high temperature environments. In addition, the aluminum oxide coating effectively extends the service life of phosphors, providing new ideas for future product design in the LED lighting industry.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphors, characterized in that: The steps include: S1. Atomic layer deposition system installation: A base is fixedly installed at the bottom of the vacuum chamber of the atomic layer deposition system, and the base is driven to vibrate by a vibration motor. The vacuum chamber is connected to the first air inlet pipe and the second air inlet pipe; S2. Phosphor treatment: placing the phosphor on the base, turning on the heating mechanism to heat the phosphor, starting the vibration motor, and then degassing the phosphor and pre-treating it with oxygen plasma; S3. Atomic layer deposition coating film formation: Keep the vibration motor in the starting state, and introduce two precursors that can react with each other to produce aluminum oxide film into the vacuum chamber alternately through the first air inlet pipe and the second air inlet pipe in turn. After each precursor is introduced and the reaction is completed, an inert gas is introduced through the first air inlet pipe or the second air inlet pipe to purge the fluorescent powder in the vacuum chamber to take away the precursor free in the vacuum chamber. The two precursors are introduced alternately in this cycle for several times until an aluminum oxide film of a specific thickness is formed on the surface of the fluorescent powder.

2. The method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphor according to claim 1, characterized in that: The first gas inlet pipe in S1 is used to deliver a precursor into the vacuum chamber in a gas pulse manner, and the second gas inlet pipe is used to deliver another precursor into the vacuum chamber in a gas pulse manner.

3. The method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphor according to claim 1, characterized in that: The vibration frequency of the vibration motor in S1 is set to 50-60Hz.

4. The method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphor according to claim 1, characterized in that: The temperature of the phosphor in S2 after heating is 50-70°C.

5. The method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphor according to claim 1, characterized in that: In S2, the degassing treatment of the phosphor is to evacuate the vacuum chamber to a pressure of 0.1Pa.

6. The method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphor according to claim 1, characterized in that: During oxygen plasma pretreatment in S2, the generation power of oxygen plasma is 40-50W, the pretreatment time is 8-20min, and the oxygen plasma flow rate is 10-15sccm.

7. The method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphor according to claim 1, characterized in that ,The two precursors in S3 that can react with each other to form aluminum oxide film are oxygen plasma and trimethylaluminum.

8. The method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphor according to claim 7, characterized in that: The pulse times of oxygen plasma and trimethylaluminum in S3 are 5-10 s and 1-2 s, respectively.

9. The method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphor according to claim 1, characterized in that: The inert gas used in S3 is argon or nitrogen with a flow rate of 90-110 sccm and each purge lasts for 30-40 seconds.

10. The method for plasma-assisted atomic layer deposition of aluminum oxide-coated phosphor according to any one of claims 1 to 9, characterized in that: The phosphor is a silicon-based nitride phosphor with a particle diameter of 9±1 μm or a silicate phosphor with a particle diameter of 12±1 μm.

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