Structure And Properties Of Diamond-like Films Made By Medium Frequency Pulsed Nonequilibrium Magnetron Sputtering Technology

- Mar 28, 2019-

Structure and properties of diamond-like films made by Medium frequency pulsed nonequilibrium magnetron sputtering technology

 

 

Diamond-like (DLC) films were prepared by if pulsed non-equilibrium magnetron sputtering on glass slides, and the effects of deposition pressure on film thickness, microstructure, mechanical properties and optical properties were studied. Thickness test results show that DLC film thickness increases with the increase of deposition pressure. X-ray photoelectron spectroscopy test results show that when the deposition pressure increases from 0.18Pa to 1.50Pa, the content of sp3 hybrid carbon in DLC film decreases with the increase of deposition pressure. The results of nano indentation and ellipsometry test show that the nano hardness and refractive index of DLC film decrease with the increase of deposition pressure. The effects of deposition pressure on the growth and bonding structure of thin films were analyzed by shallow injection model. The above results show that the deposition pressure has a great influence on DLC film thickness, sp3 hybrid carbon content, mechanical and optical properties.

 

(diamond - like carbon DLC) thin film is key (sp3) containing diamond structure of metastable amorphous, amorphous carbon materials, the comprehensive performance of the membrane is similar to diamond film, such as high hardness, low friction coefficient, high heat conductivity and low dielectric constant, high broadband gap, infrared transmittance, good chemical stability and biocompatibility and so on, and compared with the diamond film deposition temperature low, high cost performance, the membrane surface roughness is small, the advantages of easy preparation, Therefore, it has a good application prospect in the fields of machinery, electronics, optics, medicine and corrosion resistant materials.

 

Since Aisenberg and Chabot first in 1971 by Ion beam deposition method at room temperature (Ion beam deposition IBD) after the preparation of the DLC film, have developed a variety of preparation methods of DLC film, such as magnetron sputtering, Ion beam assisted deposition, cathodic vacuum arc deposition, pulsed laser deposition, radio frequency glow discharge chemical vapor deposition method, electron cyclotron resonance chemical vapor deposition method, plasma assisted chemical vapor deposition method, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD) method.

 

Magnetron sputtering is one of the most commonly used methods to prepare DLC films, with remarkable characteristics such as uniform film layer, good density, good process repeatability, high deposition rate and low substrate temperature. The technology of if pulsed non-equilibrium magnetron sputtering developed in recent years, combining the advantages of if pulsed sputtering and non-equilibrium magnetron sputtering, has become the recognized preferred process for the preparation of a variety of functional thin films, including insulating materials, and has been widely used in the laboratory and industry. In addition to the advantages of general magnetron sputtering deposition, this method can effectively eliminate the phenomenon of arc discharge and target poisoning, effectively improve the structure, quality and properties of the film, and improve the adhesion between the film and the substrate.

 

DLC film combination in the form of covalent bond between the carbon atoms, chemical bonds are mainly sp2 and sp3 hybridized key hybrid key, the two levels of how much a direct impact on the performance of DLC film: the sp3 hybridization key content is higher, more close to the nature of the diamond film, characterized by membrane layer density, high hardness, good resistance to chemical corrosion, the band gap width and high resistivity. With different deposition methods and parameters, the content of sp3 hybrid bond in the prepared DLC film is different, and the film's performance will be greatly different. In this paper, diamond-like films were prepared by pulsed if magnetron sputtering. The effects of deposition pressure on film thickness, chemical bond structure, mechanical properties and optical properties were studied.

 

1. Experiment

 

Diamond-like (DLC) films were deposited on the glass slides using medium frequency pulsed non-equilibrium magnetron sputtering technology, with graphite (purity 99.99%) as the target material and argon (purity 99.99%) as the sputtering gas.Before the substrate is put into the vacuum chamber, it is first cleaned with acetone, anhydrous alcohol and deionized water respectively by ultrasound for 15min, and then dried with infrared lamp and placed in the vacuum chamber.Molecular pump was used for vacuum extraction. After the vacuum degree reached 5.0 10-4 Pa, argon was injected to change the vacuum degree to 2.0 Pa, and a pulse bias power supply was used to add negative bias 700V on the substrate for sputtering cleaning for 15min (duty ratio of 80%) to further remove impurities and oil molecules adsorbed on the surface of the substrate, thus greatly improving the interface state.In the film deposition process, the target-base distance was 90 mm, the power of if sputtering power supply was 290 W, the frequency was 40 kHz, and the duty cycle was 80%, the pulse bias power supply was fixed at 100V, the frequency was 40 kHz, the duty cycle was 80%, the substrate temperature was room temperature, and the deposition pressure was 0.18 Pa, 0.36 a, 0.72Pa, and 1.50 Pa, respectively.

 

Veeco Dektak 150 step instrument was used to measure the thickness of the prepared DLC film. The kratos-xsam800 surface analysis system is used for the analysis of the X-ray photoelectron spectroscopy (XPS) of the samples, using 13 kV 19 mA Al Ka X-ray (1486.6 eV) source, and the vacuum degree in the analysis room is higher than 1 10-6 Pa. The nano-hardness test was completed on the MTS nano-indentation instrument (xp type). During the nano-indentation, 3 points of each sample were taken for testing, and then the mean value of the nano-hardness of the 3 points was taken as the mean nano-hardness of each sample. The optical constants of the thin film were measured on the m-2000 di spectroscopic ellipsometer produced by J.A.W. ollam in the United States, with the wavelength range of 600-1700nm.

 

2. Conclusion

 

Diamond-like films were prepared with argon as an auxiliary gas and by means of intermediate frequency pulsed non-equilibrium magnetron sputtering technology. The influence of deposition pressure on the microstructure and mechanical properties of DLC films was studied:

 

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

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

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

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


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