Determination of the material properties of microstructures by laser based ultrasound

Bulk-wave and guided-wave photoacoustic evaluation of the mechanical properties of aluminum/silicon nitride double-layer thin films

“…The experimentally determined Young's moduli of silicon nitride films range from about 220 to 280 GPa. These values are much smaller than crystalline bulk silicon nitride (320 GPa) and they are in good agreement with literature reported Young's modulus of LPCVD fabricated silicon nitride [5,11,17], such as 280 GPa in Ref. [11].…”

“…Thermal and elastic excitations of thin films irradiated by ultra-short laser pulses have been studied extensively with a view to obtaining the physical properties of ultrathin films [13,17,18,21]. It has been noted that femtosecond laser pulses generally induce thermal non-equilibrium states between the electrons and the metal lattice [13].…”

“…A strong pump beam is used for photoacoustic generation, and a time-delayed weaker probe beam is used to obtain a series of snapshots of the transient optical reflectance change, typically using lock-in detection schemes. Such femtosecond pump-probe techniques have been widely applied to measure the transient thermal and acoustic phenomena of various types of materials, such as metals, semiconductors, nano-particles and thin films with sub-micron thickness [13][14][15][16][17][18]. Different models have been developed for femtosecond ultrafast laser heating to theoretically analyze femtosecond transient experiments on solid materials [19][20][21].…”

A continuum model with microstructures for wave propagation in ultra-thin films

“…According to this study, higher frequency waves were needed for thinner films. Recently, high-frequency (THz) mechanical bulk waves were employed to determine material properties or thicknesses of thin membranes in nanometer scale Profunser et al, 2004). In the studies above, the material properties were derived from the measured phase velocity using the conventional continuum model.…”

Double-transducer structure for picosecond ultrasound generation

“…Measurements of miscellaneous material properties such as sound velocity, 1-5 film thickness, 4,5 phonon attenuation 6,7 and dispersion, 8,9 electron transport, 10 interface bonding, 11,12 vibration of microstructure, 13,14 mechanical property of microstructure, 15 etc., have been demonstrated for thin films of submicrometer thickness. Picosecond ultrasonic techniques measure the optical transient reflectance change ͓⌬R͑t͔͒ induced by acoustic waves through a pump and probe detection scheme.…”