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1993
Journal Article
Title
Characterization of thin diamond-like carbon films by ultrasonic surface waves
Other Title
Charakterisierung dünner diamantähnlicher Kohlenstoffschichten mittels Ultraschall-Oberflächenwellen
Abstract
The method of ultrasonic surface waves is suitable to determine the elastic modulus of thin diamond-like carbon films deposited on silicon wafers (111) by the laser-induced vacuum arc deposition (Laser-Arc) if frequencies in the range up to 100 MHz are used. Surface wave pulses have been generated in the thermoelastic regime by an eximer-laser (XeCl/308nm). The ultrasonic signals influenced by the film structure have been detected with a piezoelectric transducer. The surface wave phase velocity depending on frequency has been measured with a Fourier transformation technique. To calculate the elastic modulus of the films the inverse problem of surface wave dispersion in coated materials has been solved. Carbon films with a thickness of 300 nm deposited at different substrate temperatures in the range between 60 degree C and 500 degree C are studied. Young's modulus values up to 230 GPa were obtained for substrate temperatures smaller then 150 degree C. The very small modulus for T small er then 150 degree C suggest a drastic decrease of sp3/sp2 bonding ratio in the amorphous DLC-structure. These results correlate to optical studies. High frequency surface waves have been demonstrated to be a sensitive indicator for evaluating the C-film structure depending on the deposition conditions.
Conference
Keyword(s)
Diamantschicht
diamond-film
DLC-film
DLC-film Abscheidung
DLC-film characterization
DLC-film Charakterisierung
DLC-film deposition
DLC-Schicht
E-Modul
e-modulus
elastische Konstante
Laser-Arc
laser-induced film deposition
laserinduzierte Schichtabscheidung
LPVD
Oberflächenwelle
PVD-Technik
PVD-technique
ultrasonic surface wave
Young's modulus