Testing Ultra-thin Diamond-like Carbon Films

Evaluating ultra-thin films of a few nano-meters thickness is still a challenge for mechanical testing. The laser-acoustic technique was demonstrated to have the capability of measuring the Young’s modulus of diamond-like carbon (DLC) films with thickness of 3 nm deposited on silicon wafers.
Figure 1 shows an example for a laser-acoustic results obtained for a 3.1 nm thick DLC-films on silicon. The film was deposited by pulsed cathodic vacuum arc deposition. The measurement provides the dispersion curve as phase velocity depending on frequency. The effect of the 3.1 nm DLC film causes a distinct rise of the dispersion curve compared to the uncoated substrate. The Young’s modulus is deduced by fitting the theoretical curve. The fit yielded a Young’s modulus of 398 GPa.

ultra thin

Figure 1: Laser-acoustic measuring result for ultra-thin diamond-like carbon films deposited on silicon

For diamond-like carbon, Young’s modulus was shown to correlate with the sp³ fraction of the atomic bonds that also determines the hardness of this film material [1]. That is the reason why Young’s modulus correlates with hardness (H > E/10 [2]). The high film modulus proved the high quality of the ultra-thin diamond-like carbon film deposited by a new plasma source consisting of a high current pulsed vacuum arc evaporator combined with a sectioned filter unit [3].

[1] D. Schneider, C. F. Meyer, H. Mai, B. Schöneich, H. Ziegele, H. J. Scheibe, and Y. Lifshitz, Diamond and Related Materials 7(1998)973

[2] B . Schultrich, K . Kailer, P. Rödhammer, D. Schneider, H.J. Scheibe, Proceedings of the 14th International Plansee Seminar, Eds. G. Kneringer, R. Rödhammer and P. Wilhartitz, Plansee AG, Reutte (1997), Vol. 3, p. 210

[3] T. Schuelke, A. Anders, P. Siemroth, IEEE Transactions on Plasma Science 25 (1997) 660

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