Structure and properties of diamond-like carbon films prepared by intermediate frequency pulsed unbalanced magnetron sputtering technology

Diamond-like carbon (DLC) films were prepared on glass slides using intermediate frequency pulsed unbalanced magnetron sputtering technology, and the influence of deposition pressure on film thickness, microstructure, mechanical properties and optical properties was studied. The thickness test results show that the thickness of the DLC film increases with the deposition pressure. X-ray photoelectron spectroscopy test results show that when the deposition pressure increases from 0.18 Pa to 1.50 Pa, the sp3 hybrid carbon content in the DLC film decreases with the increase of the deposition pressure. The test results of nanoindentation and ellipsometer show that the nanohardness and refractive index of DLC film decrease with the increase of deposition pressure. The shallow injection model is used to analyze the influence of deposition pressure on film growth and bonding structure. The above results show that the deposition pressure has a great influence on the thickness of the DLC film, the content of sp3 hybrid carbon, and the mechanical and optical properties.

Diamond-like carbon (DLC) film is a metastable, amorphous, and amorphous carbon material containing a diamond structure (sp3 bond). The film has comprehensive properties similar to diamond film, such as high hardness and low friction. Coefficient, high thermal conductivity, low dielectric constant, wide band gap, high infrared transmittance, good chemical stability and biocompatibility, etc. Compared with diamond film, it has low deposition temperature, high cost performance, film surface It has the advantages of small roughness and easy preparation, so it has good application prospects in the fields of machinery, electronics, optics, medicine, and corrosion-resistant materials.

Since Aisenberg and Chabot first produced DLC films by ion beam deposition (IBD) at room temperature in 1971, a variety of methods have been developed to prepare DLC films, such as magnetron sputtering, ion beam assisted Deposition method, vacuum cathodic arc deposition method, pulsed laser deposition method, radio frequency glow discharge chemical vapor deposition method, electron cyclotron resonance chemical vapor deposition method, plasma assisted chemical vapor deposition method and other physical vapor deposition (PVD) and chemical vapor deposition ( CVD) method.

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Magnetron sputtering is one of the most commonly used methods for the preparation of DLC films. It has the remarkable characteristics of uniform film layer, good density, good process repeatability, high deposition rate, and low substrate temperature. The intermediate frequency pulse unbalanced magnetron sputtering technology developed in recent years combines the advantages of intermediate frequency pulse sputtering and unbalanced magnetron sputtering. It has become the recognized process of choice for preparing a variety of functional thin film materials including insulating materials. It has been widely used in laboratories and industry. In addition to the advantages of general magnetron sputtering deposition, the method can effectively eliminate arcing and target poisoning, effectively improve the structure, quality and properties of the film, and improve the adhesion between the film and the substrate.

The carbon atoms in the DLC film are combined by covalent bonds. The chemical bonds are mainly sp2 hybrid bonds and sp3 hybrid bonds. The content of these two directly affects the performance of the DLC film: the higher the content of sp3 hybrid bonds, The closer the properties of the film are to the diamond film, the more dense the film, the higher the hardness, the better the chemical resistance, the wide band gap, and the higher the resistivity. The deposition method and deposition parameters are different, and the content of the sp3 hybrid bond in the prepared DLC film is different, and the performance of the film will have a greater difference. In this paper, diamond-like carbon films were prepared by intermediate frequency pulsed magnetron sputtering technology, and the influence of deposition pressure on film thickness, chemical bond structure, mechanical properties and optical properties was studied.

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Using intermediate frequency pulse unbalanced magnetron sputtering technology, graphite (purity 99.99%) as the target, argon (purity 99.99%) as the sputtering gas, diamond-like carbon (DLC) film is deposited on the glass slide. Before the substrate is put into the vacuum chamber, it is first ultrasonically cleaned with acetone, absolute alcohol, and deionized water for 15 minutes, and then dried with an infrared lamp and placed in the vacuum chamber. A molecular pump is used to vacuum. After the vacuum degree reaches 5.0×10-4 Pa, argon gas is introduced to make the vacuum degree 2.0 Pa, and a pulse bias power supply is used to apply a negative bias voltage of 700V to the substrate for sputtering cleaning for 15 minutes (accounting for The air ratio is 80%) to further remove impurities and oily molecules adsorbed on the surface of the substrate, thereby greatly improving the interface state. During the film deposition process, the target-base distance is 90 mm, the medium frequency sputtering power supply power is 290 W, the frequency is 40 kHz, the duty cycle is 80%, the pulse bias power supply is fixed at 100V, the frequency is 40 kHz, and the duty cycle It is 80%, the substrate temperature is room temperature, and the deposition pressure is 0.18 Pa, 0.36 a, 0.72 Pa and 1.50 Pa, respectively.

The thickness of the prepared DLC film was measured with a Veeco Dektak 150 step meter. KRATOS-XSAM800 surface analysis system is used for X-ray photoelectron spectroscopy (XPS) analysis of samples, using 13 kV×19 mA Al Ka X-ray (1486.6 eV) source, and the vacuum degree of the analysis chamber is higher than 1×10-6 Pa . The nano-hardness test is completed on the MTS nano-indenter (xp type). During nano-indentation, 3 points are taken for each sample, and then the average value of the 3 points is taken as the average value of each sample Average nano hardness. The measurement of the optical constants of the film was carried out on the M-2000DI spectroscopic ellipsometer produced by J.A. Woollam Company in the United States, and the test wavelength range was 600-1700nm.

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Using argon as the auxiliary gas, diamond-like carbon films were prepared by intermediate frequency pulsed unbalanced magnetron sputtering technology, and the influence of deposition pressure on the microstructure and mechanical properties of DLC films was studied:

(1) The thickness of the DLC film increases with the increase of the deposition pressure.

(2) XPS test results show that when the deposition pressure increases from 0.18 to 1.50Pa, the sp3 hybrid bond content in the DLC film decreases with the increase of the deposition pressure. The influence of deposition pressure on the content of sp3 hybrid bonds in DLC films can be explained by the "shallow injection model".

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(3) Nanoindentation test results show that when the deposition pressure increases from 0.18 Pa to 1.50 Pa, the nano hardness and elastic recovery in the DLC film decrease with the increase of the deposition pressure.

(4) The ellipsometer test results show that at the same test wavelength, the refractive index of the DLC film decreases with the increase of the deposition pressure, which is related to the density of the film and the content of sp3 hybrid bonds.

Founded in 2015,Zunhua Baorui Titanium Equipment Co.,Ltd. is a manufacturer specializing in pvd vacuum ion coating equipment. The company’s products mainly include large plate coating machine, large tube collating machine, tool coating machine and LOW-E glass production line. Mr.Wang baijiang ,general manager of the company ,has been engaged in vacuum coating industry for more than 30 years. He continuously improve production technology, improve product performance and devote himself to provide customers with better product experience and higher production efficiency.