Imaging of a patterned and buried molecular layer by coherent acoustic phonon spectroscopy

Hettich, Mike; Jacob, Karl I.; Ristow, Oliver; He, Chuan; Mayer, J.; Schubert, M.; Gusev, Vitalyi; Bruchhausen, A. E.; Dekorsy, Thomas

doi:10.1063/1.4767141

Cited by 14 publications

(5 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We obtain a readily usable analytic expression assuming that the gold mode frequency is only slightly influenced by the molecular layer. This assumption is corroborated by measurements on patterned APTES layer systems 15 where we observed negligible frequency shifts with or without APTES layer between the gold film and the substrate. The details regarding the theoretical calculations are given in the Theory section.…”

Section: Resultssupporting

confidence: 83%

Viscoelastic properties and efficient acoustic damping in confined polymer nano-layers at GHz frequencies

Hettich

Jacob

Ristow

et al. 2016

Sci Rep

Self Cite

View full text Add to dashboard Cite

We investigate the viscoelastic properties of confined molecular nano-layers by time resolved optical pump-probe measurements. Access to the elastic properties is provided by the damping time of acoustic eigenmodes of thin metal films deposited on the molecular nano-layers which show a strong dependence on the molecular layer thickness and on the acoustic eigen-mode frequencies. An analytical model including the viscoelastic properties of the molecular layer allows us to obtain the longitudinal sound velocity as well as the acoustic absorption coefficient of the layer. Our experiments and theoretical analysis indicate for the first time that the molecular nano-layers are much more viscous than elastic in the investigated frequency range from 50 to 120 GHz and thus show pronounced acoustic absorption. The longitudinal acoustic wavenumber has nearly equal real and imaginary parts, both increasing proportional to the square root of the frequency. Thus, both acoustic velocity and acoustic absorption are proportional to the square root of frequency and the propagation of compressional/dilatational acoustic waves in the investigated nano-layers is of the diffusional type, similar to the propagation of shear waves in viscous liquids and thermal waves in solids.

show abstract

Section: Resultssupporting

confidence: 83%

Viscoelastic properties and efficient acoustic damping in confined polymer nano-layers at GHz frequencies

Hettich

Jacob

Ristow

et al. 2016

Sci Rep

Self Cite

View full text Add to dashboard Cite

show abstract

“…Sub-nanometer thick interfacial layers separating thin films from the substrate can influence both the decay time of the thin film vibration [18] and propagation of the coherent acoustic pulses [19]. Later it was demonstrated thatthe quantitative evaluation of the thickness of broad interfacial layers [20][21][22][23][24] and the rigidity of thin interfacial bonds [2, 25-29] can be obtained. Here, we study interfacial adhesion as well as damping behaviorin two-layer Al/Si-membranes.…”

mentioning

confidence: 99%

Characterization of thin-film adhesion and phonon lifetimes in Al/Si membranes by picosecond ultrasonics

Großmann

Schubert

et al. 2017

New J. Phys.

Self Cite

View full text Add to dashboard Cite

We quantitatively study interfacial adhesion in a two-layer membrane system consisting of Al and Si with femtosecond time-resolved laser spectroscopy. High-frequency acoustic pulses in the sub-THz regime are utilized to characterize the membrane system. In order to explain the distinct features of the measured data, a spring model for the Al/Si interface is employed. We show that acoustic dissipation in this system needs to be included for accurate modeling of the interface adhesion over a broad frequency range. This modeling approach yields a spring constant of h = -17 Al Si -kg nm s 2 2 , an acoustic phonon lifetime of t = 68 Al ps at 240 GHz in polycrystalline Al and a frequency dependence of the lifetime in Si w µ -1 in thefrequency range from 50-800 GHz.Heat dissipation in Si is central to the operation of semiconductor devices [1-3]. This becomes even morechallengingdue to the miniaturization of all components as the contribution ofthe boundaries to phonon scattering becomes larger [4][5][6]. The question of understanding and controlling thermal phonons is of major interest [7][8][9]. Quantitative values forintrinsic phonon-phonon scattering processes and extrinsic scattering processes due to defects and surface/interface roughness are still under investigation [10][11][12]. While there exista wide variety of tools for the spatial mapping of temperature [13,14], there are not many temporal techniques for measuring nonequilibrium heat transport. One way is to look at coherent acoustic phonons at frequencies that contributeto the spectrum of thermal phonons [15]. Picosecond laser ultrasonics [16,17] is known to bea powerful tool for the characterization of the elastic properties of thin films. Sub-nanometer thick interfacial layers separating thin films from the substrate can influence both the decay time of the thin film vibration [18] and propagation of the coherent acoustic pulses [19]. Later it was demonstrated thatthe quantitative evaluation of the thickness of broad interfacial layers [20][21][22][23][24] and the rigidity of thin interfacial bonds [2, 25-29] can be obtained. Here, we study interfacial adhesion as well as damping behaviorin two-layer Al/Si-membranes. As a quantitative measure for the interface adhesion, the spring constant of a massless spring model is determined [25].The investigated system is a 13 nm thick Al film on top of a 350 nm thick Si membrane (see figure 1(a)). Details regarding the fabrication of the membrane are given in [27]. In [27], Al films with different thicknesses were fabricated by sputtering deposition on the membranes, which led tostrong adhesion between both layers. Here, in contrastto this approach, the Al film was thermally evaporated,resultingin reduced interface adhesion. The measurements were conducted with an 800 MHz Ti:sapphire pump-probe setup, utilizing the asynchronous optical sampling principle. Further details regarding the setup are given in [27,30]. We impulsively excite the Al film with an fs-laser pump pulse (30 mW power, 790 nm wave...

show abstract

“…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]…”

Section: Introductionmentioning

confidence: 99%

Picosecond ultrasonics with a free-running dual-comb laser

Pupeikis

Willenberg

Bart

et al. 2022

Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XXII

Self Cite

View full text Add to dashboard Cite

We present a free-running 80-MHz dual-comb polarization-multiplexed solid-state laser which delivers 1.8 W of average power with 110-fs pulse duration per comb. With a high-sensitivity pump-probe setup, we apply this free-running dual-comb laser to picosecond ultrasonic measurements. The ultrasonic signatures in a semiconductor multi-quantum-well structure originating from the quantum wells and superlattice regions are revealed and discussed. We further demonstrate ultrasonic measurements on a thin-film metalized sample and compare these measurements to ones obtained with a pair of locked femtosecond lasers. Our data show that a free-running dual-comb laser is well-suited for picosecond ultrasonic measurements and thus it offers a significant reduction in complexity and cost for this widely adopted non-destructive testing technique.

show abstract

Imaging of a patterned and buried molecular layer by coherent acoustic phonon spectroscopy

Cited by 14 publications

References 32 publications

Viscoelastic properties and efficient acoustic damping in confined polymer nano-layers at GHz frequencies

Viscoelastic properties and efficient acoustic damping in confined polymer nano-layers at GHz frequencies

Characterization of thin-film adhesion and phonon lifetimes in Al/Si membranes by picosecond ultrasonics

Picosecond ultrasonics with a free-running dual-comb laser

Contact Info

Product

Resources

About