摘要
高功率脉冲磁控溅射(HiPIMS)技术在其放电过程中,由于阴极高负电压对离子的吸引,发生离子回吸现象,严重限制薄膜快速生长。为改善离子回吸问题,采用同步脉冲偏压方式,研究其对HiPIMS石墨靶沉积类金刚石(DLC)薄膜结构与性能的影响。通过调控同步脉冲偏压的幅值与滞后时间,采用脉冲偏压同步HiPIMS的技术制备DLC薄膜。采用示波器对HiPIMS电源放电波形进行实时监控,同时利用Langmuir探针系统研究沉积过程中的等离子体特征。通过SEM、SPM、XPS和Raman等测试薄膜的表面形貌和微观结构,并利用纳米压痕仪、残余应力仪以及划痕仪,对比研究制备的DLC薄膜力学性能、应力和膜基结合力。结果发现:当同步脉冲偏压由-100 V增加至-900 V时,DLC薄膜的沉积速率和表面粗糙度均先增后减,在-500 V时沉积速率最大为352 nm/h,表面粗糙度最低达0.61±0.04 nm;sp^(3)含量从47%降低至34.8%,导致硬度从48.6 GPa下降至35.1 GPa,残余压应力相应由-3.39 GPa下降至-1.9 GPa。增加同步脉冲偏压滞后时间从0到40μs,DLC薄膜沉积速率单调增加,表面粗糙度变化不大,sp^(3)含量从38.3%略微增加至40.2%,但残余压应力和硬度增幅显著,分别由-1.92 GPa增加至-3.05 GPa和从37.7 GPa上升至45.4 GPa。增加同步脉冲偏压幅值能够提高沉积离子密度,减少靶表面的回吸和打弧,有利于表面光滑和高沉积速率,但偏压幅值过大会引起基体区的反溅射,降低薄膜表面质量和沉积速率,但因sp^(3)含量随偏压增加而减小,残余应力和硬度也随之下降。延长同步脉冲偏压的滞后时间,可获得高离子密度,同时提高薄膜沉积速率与sp^(3)含量,残余应力和硬度均相应上升。利用HiPIMS复合同步脉冲偏压大小和滞后时间调控,是实现高性能碳基薄膜设计制备的新思路。
During the discharge process in HiPIMS technology,the attraction of ions by the highly negative voltage of the cathode causes ion reabsorption,which significantly limits the rapid growth of thin films.To address this issue,a synchronous pulsed-bias method was employed to study its effects on the structure and properties of DLC films deposited on HiPIMS graphite targets.By adjusting the amplitude and hysteresis time of the synchronous pulsed-bias,DLC thin films were prepared using the HiPIMS technique.First,the discharge waveform and plasma characteristics during the HiPIMS process were monitored in situ using a combined oscilloscope and Langmuir probe system.The surface morphology and microstructure of the DLC films were comprehensively analyzed using scanning electron microscopy,X-ray photoelectron spectroscopy,atomic force microscopy,and Raman spectroscopy.The mechanical properties of the films were evaluated using a nanoindenter,scratch tester,and residual stress tester.The results demonstrated a strong dependence of the structure and mechanical properties of the DLC film on the applied amplitude and delay time of the synchronous pulsed-bias during deposition.Specifically,as the amplitude of the synchronous pulsed-bias increased from-100 to-900 V,the deposition rate of DLC films first increased and then decreased,reaching a maximum of 350 nm/h at a bias of-500 V,accompanied by the lowest surface roughness of approximately 0.61±0.04 nm.Meanwhile,the C-sp^(3)content decreased from 52.8%to 42.9%,resulting in a reduction of compressive residual stress from-3.39 to-1.9 GPa and a corresponding decrease in hardness from 48.6 to 35.1 GPa.In contrast,increasing the delay time of the synchronous pulsed-bias led to a monotonic rise in the deposition rate for DLC growth without significantly altering surface roughness.Although the C-sp^(3)content exhibited a slight increase from 45.2%to 46.7%,residual stress increased from-1.92 to-3.05 GPa,and hardness improved from 37.7 to 45.4 GPa.Analysis of plasma characteristics revealed that,at a fixed delay time of 40μs,increasing the amplitude of the synchronous pulsed-bias enhanced the acceleration effect of the substrate-front sheath potential on deposition ions.This caused the substrate-front sheath region to attract more ions from the plasma,directing them to the growing surface area and to participate in film growth reactions.A decrease in peak current on the target surface further indicated enhanced diffusion of target surface ions into the plasma,effectively reducing ion reabsorption at the target surface.This suppression of ion reabsorption mitigated target surface arcing,thereby improving both the surface quality and deposition rate of the film.However,excessive amplitude(above-500 V)caused back sputtering in the substrate region,reducing the deposition rate and surface quality of the film.Additionally,increasing the amplitude of the synchronous pulsed-bias resulted in higher ion energy,leading to intensified high-energy particle bombardment.This induced a thermal peak effect,promoting the transformation of sp^(3)hybridized bonds into sp2 hybridized bonds,thereby releasing stress and reducing the hardness,elastic modulus,and adhesion strength of the film.At a fixed amplitude of-500 V,increasing the delay time of the synchronous pulsed-bias enhanced the number of incident ions,which improved ion flux in the substrate region and increased film thickness.Simultaneously,higher incident-ion energy led to an increase in the sp^(3)content and residual stress of the film.Given the strong dependence of mechanical properties on carbon atomic bonding,the introduction of a synchronous pulsed-bias during the HiPIMS process is a promising strategy for developing amorphous carbon-based films with tailored performance.
作者
李琪刚
陈仁德
李昊
王振玉
郭鹏
崔丽
王梁
汪爱英
LI Qigang;CHEN Rende;LI Hao;WANG Zhenyu;GUO Peng;CUI Li;WANG Liang;WANG Aiying(College of Mechanical Engineering,Zhejiang University of Technology,Hangzhou 310023,China;Key Laboratory of Advanced Marine Materials,Ningbo Institute of Materials Technology and Engineering,Chinese Academy of Sciences,Ningbo 315201,China)
出处
《中国表面工程》
北大核心
2025年第2期233-244,共12页
China Surface Engineering
基金
国家重点研发计划(2022YFB3706205)
国家自然科学基金(52025014,U20A20296)
宁波市科技创新重大专项(2022Z054,2024Z134)。
关键词
磁控溅射
同步脉冲偏压
DLC薄膜
微结构
magnetron sputtering
synchronized pulsed-bias
diamond-like carbon film
microstructure
