POSSIBLE TECHNIQUE FOR THE CHARACTERIZATION OF DIAMOND FILMS USING AN ULTRASONIC RESONANCE TECHNIQUE

Among the various chemical vapour deposition (CVD) processes employed for diamond film production, those based on a d.c. plasma jet offer the most promise in terms of high growth rate. An important requirement in such studies is the quick and reproducible characterization of deposited films, preferably in such a way that a clear indication can be obtained of how closely the film approaches the ideal of a pure and perfect diamond structure. Among the various characterization techniques sensitive to the quality of the film, measurement of the elastic constants is one of the most attractive. Unfortunately, accurate measurements of, for example, the in-plane Young's modulus is usually rather difficult to carry out by conventional static methods, since the films are very thin, typically much thinner than the substrate, to which they adhere strongly. This paper gives an outline of how a simple procedure based on an impulse excitation technique for the measurement of resonance frequency can be applied to a substrate, before and after the deposition of a thin, adherent film, so as to measure the Young modulus of the film with a reasonably high degree of accuracy. Data are presented for Ni on Cu to check the validity of the technique. Some preliminary data with respect to diamond thin films deposited by d.c. plasma jet CVD are also presented.