Filtered Cathodic Arc Deposited Diamond-Like Carbon: Electron Spin Resonance (ESR) and Raman Spectroscopy
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hardness is the one of the important problem for FCVA ta-C deposition process [I]. In this work, ta-C films with variable stress 3.5-8.5 GPa and hardness -(45 + 55) GPa were deposited using various cathodic arc plasma conditions. Electron Spin Resonance, Spin Lattice Relaxation (SLR), Raman spectra, mechanical and electrical properties of the films were studied. The consistent theoretical description of concentration and temperature dependence of ESR line width was developed. The paramagnetic properties of hydrogenated DLHC films deposited using r.f. inductively coupled CH4 plasma source [2] were studied as well. The obtained results are compared with data for ta-C films. EXPERIMENT The ta-C films were deposited using FCVA system. The carbon plasma was filtered by 900 curved magnetic solenoid filter to remove neutral species and macroscopic particles. The baffle traps were placed inside the duct guide to minimize the macro-particle flow in the output of source. The standard Veeco Instruments, Inc. type vacuum chamber equipped with rotating, water-cooled substrate-holder fixture was used for mounting the cathodic arc source. The system base pressure prior to arc ignition was -3- 10' Torr. It was found that stress of deposited ta-C films depends on process pressure. The stress was varied from 8.5 GPa to 3.5 GPa by variation of process pressure in range (1÷ 9). 10.' Torr. 249
Mat. Res. Soc. Symp. Proc. Vol. 593 © 2000 Materials Research Society
ESR measurements were carried out on ta-C films 20 - 100 nm thick deposited on high resistive (>40 Ohm.cm) Si substrates. The typical sizes of samples was -10x5 mm2 . The goal of film-on-substrate ESR measurements was to derive information about internal film stress impact on ESR parameters. In some previous works [3-5] ESR was measured on DLC films separated from substrates. Therefore this information as well as information about possible anisotropy effects in thin film DLC samples were lost. ESR measurements were performed in X-band (microwave frequency v _ 9.4 GHz) at T = 1.75-300K. ESR spectrometer with 100 kHz modulation of magnetic field was used for measurements of g-factor, AHpp and N values. The superheterodine pulse spectrometer was applied for direct measurements of SLR time T1 and detection of continuous saturation curves at wide range of microwave power. Estimated accuracy of g-factor measuring was ± 110.- for samples with AHoP___ lOG and ±2-10.4 for AHPP - 20G. The absolute accuracy of spin density estimation was ±50% whereas the relative accuracy of N measurements for sample to sample
was ±20%. The internal stress in the films was determined using surface profilometer Dektak 8000 by measuring the radius of curvature of 3" Si substrates before and after the deposition and employing well known Stoney's equation. Nanoindentation method using Bercovich's tip was applied for hardness measurements of ta-C films (-100 nm) on silicon substrates. The electrical resistivity of the films was measured by putting the colloidal silver electrodes onto fresh, clean surface of
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