Picosecond Photoacoustic Metrology of SiO2 and LiNbO3 Layer Systems Used for High Frequency Surface-Acoustic-Wave Filters

Abstract

Many applications of thin films necessitate detailed information about their thicknesses and sound velocities. Here, we study SiO 2 /LiNbO 3 layer systems by picosecond photoacoustic metrology and measure the sound velocities of the respective layers and the film thickness of SiO 2 , which pose crucial information for the fabrication of surface-acoustic-wave filters for communication technology. Additionally, we utilize the birefringence and the accompanying change in the detection sensitivity of coherent acoustic phonons in the LiNbO 3 layer to infer information about the LiNbO 3 orientation and the layer interface.

Development and Application of SAW Filter

“…The SiO 2 /LiNbO 3 layer system was studied by picosecond photoacoustic metrology, and the sound velocity of each layer and the film thickness of SiO 2 were measured, which can be used for the manufacture of surface acoustic wave filters for communication technology. key information, using birefringence and concomitant changes in the detection sensitivity of coherent phonons in LiNbO 3 layers to infer information about LiNbO 3 orientation and layer interfaces, which can infer nanoscale film thickness ranges, as well as velocities, while film-dependent Many of the applications of the Picosecond Photoacoustic Metrology of Si require an understanding of the speed of sound and the thickness of the film [Picosecond Photoacoustic Metrology of Si [ 82 ]. At the same time filter integration will be the key to cost and scale.…”

Mechanical Properties of Nanoporous Metallic Ultrathin Films: A Paradigmatic Case

“…We pinpoint that a typical displacement involved in picosecond photoacoustic experiments is in the range of 1 to 10 pm (depending on the exploited pump pulse energy) for thicknesses in the order of 10 nm, thus resulting in a strain in the order of 10 −3 -10 −4 . Hence, in its various forms, photoacoustic nanometrology is emerging as the go-to technique for the inspection of thin-film [39,[49][50][51][52][53][54], ultrathin film [37,[39][40][41][42][43], and nanoparticle [55,56] mechanics, and the topic is in rapid and continuous evolution. Cross-feed from other topical areas has recently resulted in novel inspection protocols based on the photoacoustic effects.…”

“…An important point concerns the adhesion of the system to the substrate. Such information, which is hardly quantifiable with standard nano-indentation techniques or even by AFM, can be retrieved from the experimental film's breathing mode lifetime τ and quality factor Q [41,50,51] as a function of the film thickness (via the fitting Equation ( 3)) that are plotted in Figure 8c as full black and red circles, respectively. In general, attenuation is due both to radiative and intrinsic losses, the latter occurring within the film's bulk.…”

Picosecond ultrasonics with a free-running dual-comb laser

“…Picosecond ultrasonics is a technique, developed in the mid-1980s, in which ultrashort laser pulses are used to generate and detect acoustic waves with very short wavelength, typically in a nanometer range [1]. Established applications of the method include the determination of elastic parameters [2][3][4][5][6][7][8][9], acoustic damping properties [10][11][12][13][14][15], structural properties [16][17][18][19], interface adhesion and coupling [20][21][22][23] and imaging of embedded layers [24][25][26][27][28][29]. Ultrafast acoustic dynamics were studied in metals [6,21,[30][31][32][33][34][35], semiconductors [10,[36][37][38][39], dielectric materials [11,14,16,40] and polymers [41]…”

“…Established applications of the method include the determination of elastic parameters [2][3][4][5][6][7][8][9], acoustic damping properties [10][11][12][13][14][15], structural properties [16][17][18][19], interface adhesion and coupling [20][21][22][23] and imaging of embedded layers [24][25][26][27][28][29]. Ultrafast acoustic dynamics were studied in metals [6,21,[30][31][32][33][34][35], semiconductors [10,[36][37][38][39], dielectric materials [11,14,16,40] and polymers [41][42][43][44]. Recent developments have also shown the feasibility to ap...…”