Stress Regulation And Laser Damage Characteristics Of Diamond-Like Carbon Films

Diamond-like carbon(DLC)films have many advantages similar to those of diamond films,such as high infrared transmittance,high resistivity,high hardness,small friction coefficient and high thermal conductivity,etc.It is an excellent infrared antireflection and protection material.It can be used in infrared windows of other precision optical instruments such as spacecraft.However,there are many defects in the preparation process of DLC films.When the thickness of the films increases,the stress will increase accordingly,which can easily make the films rupture and even fall off,which leads to the premature failure of DLC films in the process of application.This makes the DLC thin film with good infrared characteristics,because the stress is too large,its application field is limited.In order to solve the above problems,DLC thin films are deposited by RF magnetron sputtering device.The effects of RF power,gas flow and sputtering angle on the stress of DLC thin films are studied.The effects of different shapes and sizes of substrates on the stress of DLC thin films are analyzed.By changing the relevant process parameters,the stress of DLC thin films is regulated,and the optimum preparation parameters of DLC thin films with lower stress are obtained.The effects of stress on laser damage characteristics are also investigated.The main contents of the study are as follows:(1)The effect of process parameters on the stress of DLC film are studied.DLC films are deposited by RF magnetron sputtering,and different RF power(250 W,350 W,450 W),different argon flow(40sccm,60sccm,80sccm),different sputtering angles(30°,60°,90°)are used to study the effects of process parameters on the stress of DLC films.The results show that under the same substrate shape and size,when the RF power is 350W,the argon flow rate is 60 sccm and the sputtering angle is 90°,the stress of the film exhibits a minimum value.(2)The stress states of DLC thin films with different substrate shapes and sizes are investigated.In the same process parameters,when the shape and sizes of substrate are 10mm ×10mm,20mm × 20mm,30mm × 30mm,45mm × 10mm,40mm × 10mm,30mm × 10mm,the preparation and testing of the DLC films of different thicknesses are carried out.That is,when the substrate is 30 mm × 30 mm,the film stress is minimized;for a rectangular base Si sheet,the stress of the DLC film increases as the aspect ratio is increased,that is,the stress is the most when the substrate is 45 mm × 10 mm.(3)The causes and control mechanisms of stress are analyzed.When the thin films are prepared,if the atoms sputtered from the target are not successfully filled in the migration process by ion bombardment,there will be gaps on the substrate,which will reduce the density of the film surface and make the structure of the thin films loose.In this case,the film stress of the film is larger On the contrary,when the surface of the film is denser and there are fewer defects in the inner impurity,and the film stress is smaller.(4)The laser damage states of DLC thin films under different stress conditions are investigated.The laser damage test of DLC thin films with different stresses under different process parameters is carried out.The results show that the laser damage resistance of the films is better when the stress is small,and the laser damage resistance of the films is better than that of the thin films.Ion beam post-treatment can also improve the laser damage resistance of the films.Therefore,through the preparation and stress measurement of DLC thin films with different process parameters and substrate shapes and sizes are carried out.The causes of stress and the mechanisms of stress regulation are analyzed.The laser damage tests of DLC thin films under different stress conditions are also carried out.Finally,the DLC thin films with low stress are obtained.The results not only provide theoretical and experimental references for the preparation of DLC films with high performance and low stress,but also provide a basis for improving the laser damage characteristics of DLC thin films with infrared windows.