CN106011794B - The preparation method of superslide nanocrystalline and amorphous C film under atmospheric environment - Google Patents

Abstract

The invention discloses a method for preparing an ultra-smooth nanocrystalline-amorphous carbon film in an atmospheric environment. The preparation method includes the following steps: putting the pre-cleaned silicon chip into acetone and ethanol for ultrasonic cleaning, and then transferring it to a plasma On the bottom plate of the vacuum chamber of the enhanced chemical vapor deposition equipment, the base plate is connected to a negative bias power supply; vacuumize until it is less than 1.0×10 ^‑3 Pa; pass in argon gas, and conduct plasma under the condition of a DC bias voltage of 500~800 V Body cleaning to remove residual impurities and pollutants on the surface; Methane and nitrogen are introduced, and the film is deposited for 20 to 40 minutes at a DC bias of 780~820 V; Methane and hydrogen are fed, and the DC bias is 780~820V Coating under the conditions of 90~120 minutes. The film obtained by the present invention presents nanocrystalline-amorphous characteristics, has high hardness and elasticity, and excellent tribological properties (the friction coefficient can be maintained at about 0.005, and the wear rate can reach ~ ^10-17 m ³ / N/m level).

Description

Preparation method of ultra-smooth nanocrystalline-amorphous carbon film in atmospheric environment

technical field

The invention relates to a preparation method of a nano-crystal-amorphous carbon film exhibiting super-slip behavior in an atmospheric environment.

Background technique

Friction and wear is one of the main ways in mechanical systems that leads to energy dissipation and failure of mutually moving parts. It is estimated that the energy consumption caused by friction accounts for about one-third of the global energy resources, and about 60% of mechanical material losses are attributed to wear. Designing a mechanical system with an ultra-low friction coefficient and wear and establishing a super-slip system are of epoch-making significance for saving energy to the greatest extent and reducing the emission of harmful substances in the mechanical system to the atmospheric environment, and will surely produce revolutionary economic and social benefits. So far, the realization of superlubricity has mainly focused on some experiments related to layered materials, such as molybdenum disulfide (MoS ₂ ), highly oriented pyrolytic graphite (HOPG), and multi-walled carbon nanotubes (MWCNT). The slip is mainly attributed to the incommensurate contact between two crystallographic planes on the nanometer or micrometer scale, which requires high vacuum and ultra-clean environment. On a macroscopic scale, structural defects and distortions are difficult gaps for materials to exhibit superslip properties. Therefore, exploring the macroscopic superslip system has become one of the hot research topics for scientific and technological personnel.

At present, the most promising typical material capable of achieving macroscopic superslip behavior is hydrogen-containing diamond-like carbon (DLC) film. Because the dangling bonds on its smooth surface are saturated and passivated by hydrogen, and there is no chemical and physical interaction between the sliding surfaces, it can exhibit superslip behavior in vacuum and special atmosphere. However, its high internal stress and its friction performance are greatly affected by the environment, which limits its engineering application, especially in the case of high contact stress and atmospheric environment, it is difficult to achieve super slipperiness. Therefore, it is necessary to develop some new technologies and methods to strengthen the mechanical properties of carbon films and their tribological properties in the atmospheric environment, so that they can also exhibit super-slip properties in engineering applications.

Contents of the invention

The purpose of the present invention is to provide a method for preparing an ultra-smooth nano-crystal-amorphous carbon film in an atmospheric environment.

The invention adopts plasma-enhanced chemical vapor deposition technology to introduce nano-diamond particles (less than 10 nm) into the amorphous carbon grid, thereby releasing the internal stress of the film and strengthening the mechanical properties of the film. Nanoparticles can promote the formation of onion carbon structure (fullerene-like structure) transfer film at the friction interface, thus endowing the film with super slippery behavior. Based on this idea, we prepared a nanocrystalline-amorphous carbon film with a different structure from the conventional diamond-like carbon film. The film exhibits high hardness (~18.94GPa), elastic recovery coefficient (~84%) and ultra-low friction coefficient (~0.005) and wear (~10 ^-17 m ³ /N/m ). The method has the characteristics of mature vapor deposition system technology, simple equipment, low deposition temperature, uniform film formation, good repeatability and the like. This has greatly broadened the potential application prospects of carbon-based thin films and provided a new possibility for the application of carbon-based thin films. type society.

The preparation method of ultra-smooth nanocrystalline-amorphous carbon film under atmospheric environment is characterized in that the preparation method comprises the following steps:

1) Put the pre-cleaned silicon wafer into acetone and ethanol for ultrasonic cleaning, and then transfer it to the base plate at the lower part of the vacuum chamber of the plasma-enhanced chemical vapor deposition equipment, and the base plate is connected to the negative bias power supply;

2) Vacuum until less than 1.0×10 ^-3 Pa;

3) Introduce argon gas and perform plasma cleaning under the condition of DC bias voltage 500~800 V to remove impurities and pollutants remaining on the surface;

4) Introduce methane and nitrogen, and coat for 20 to 40 minutes at a DC bias of 780 to 820 V; inject methane and hydrogen, and coat for 90 to 120 minutes at a DC bias of 780 to 820 V.

The power supply is a DC power supply.

The flow ratio of the methane and nitrogen is 0.8:1.0~1.2:1.0; the flow ratio of the methane and hydrogen is 1:1.8~1:2.2.

The film obtained by the present invention has nanocrystalline-amorphous characteristics, that is, the film contains diamond nanoparticles (less than 10nm); this kind of film has high hardness and elasticity, and its nano-hardness is 18.94 GPa, and the elastic recovery coefficient is 84%. ; The obtained nanocrystalline-amorphous carbon film has excellent tribological properties, and the friction coefficient can be continuously maintained at about 0.005 when the contact stress reaches 2.89GPa in the air (relative humidity is 20%).

The preparation method of the present invention is simple and easy, and methane and hydrogen gas are introduced into the vacuum chamber, and ionization is generated under the induction of a DC power supply, so that a plasma atmosphere with various groups such as electrons, ions, and free radicals is generated, wherein Various positively charged carbon-containing groups (CH ₃ ⁺ , CH ₂ ⁺ , etc.) are accelerated under the action of negative bias, and deposited on the substrate to form a thin film.

The films prepared in the present invention were characterized by infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that the film is a hydrocarbon film containing diamond nanoparticles, which has the characteristics of nanocrystalline-amorphous structure.

Description of drawings

Figure 1: (A) High-resolution transmission electron microscope image (HRTEM) of nanocrystalline-amorphous carbon film; (B) XRD data map of nanocrystalline-amorphous carbon film and amorphous carbon film.

Figure 2: (A) Infrared spectrum of nanocrystalline-amorphous thin film (FTIR); (B) C1s binding spectrum of nanocrystalline-amorphous carbon film and amorphous carbon film.

Detailed ways

In order to better understand the present invention, it is illustrated by examples.

Example 1

First, select three silicon wafers with a smooth surface, put them into acetone and ethanol for ultrasonic cleaning, take out the silicon wafers, dry them with ear cleaning balls, and quickly transfer them into the vacuum chamber of the plasma-enhanced chemical vapor deposition equipment, place them On the base plate, start vacuuming. When the vacuum is less than 1.0×10 ^-3 Pa, argon gas is introduced, the air pressure is adjusted to 6.0 Pa, and plasma cleaning is carried out under the condition of a DC voltage of 800 volts. After the cleaning is completed, methane and nitrogen (flow ratio is 1.0) are introduced to deposit the film under the condition of DC bias voltage of 800 volts, and the deposition time is 0.5 hours; The film was deposited under the condition of a bias voltage of 800 volts, and the deposition time was 1.5 hours.

Example 2

In the FTIR spectrum, the characteristic vibrational absorption peaks of methyl and methylene appear in the range of 2800 cm ^-1 to 3000 cm ^-1 , indicating that the obtained diamond-like carbon film contains hydrogen. X-ray photoelectron spectroscopy analysis found that the binding energy of the C1s film was significantly higher than that of the conventional diamond-like film, indicating that the sp ³ carbon content in the film was higher. The reciprocating friction test results show that the film has excellent tribological properties. In the air (relative humidity is 20%), when the contact stress is 2.89 GPa, the friction coefficient can be maintained at about 0.005.

Claims (2)

1. the preparation method of ultra-slippery nanocrystal-amorphous carbon thin film under atmospheric environment, it is characterized in that this preparation method comprises the following steps: 1) Put the pre-cleaned silicon wafer into acetone and ethanol for ultrasonic cleaning, and then transfer it to the base plate at the lower part of the vacuum chamber of the plasma-enhanced chemical vapor deposition equipment, and the base plate is connected to the negative bias power supply; 2) Vacuum until less than 1.0×10 ^-3 Pa; 3) Introduce argon gas, and perform plasma cleaning under the condition of DC bias voltage 500~800 V; 4) Introduce methane and nitrogen, and coat for 20-40 minutes at a DC bias of 780-820 V; inject methane and hydrogen, and coat for 90-120 minutes at a DC bias of 780-820 V; The flow ratio of the methane and nitrogen is 0.8:1.0~1.2:1.0; the flow ratio of the methane and hydrogen is 1:1.8~1:2.2. 2. The preparation method according to claim 1, characterized in that the power supply is a DC power supply.