arXiv subjects

Lezli Matto

Publications and source records attributed to Lezli Matto.

12 recordsLinked to original sources

arXiv2026

Nonlinear Characterization of Thin-Film LiNbO3 Acoustic Filters

Compact, high-performance components in millimeter-wave (mmWave) communication systems demand new acoustic filter technology at increasingly higher frequencies. Among various promising mmWave platforms, first-order antisymmetric (A1) mode laterally excited bulk acoustic resonators (XBARs) in thin-film lithium niobate (LiNbO3) have perhaps the most impressive linear performance. Despite these advances, there are few reports of nonlinear characterization of LiNbO3 filters at mmWaves. Here, we address this gap by developing a new nonlinear methodology for high-frequency filters. The result is a methodology for performing power-dependent S-parameters and third-order intermodulation (IMD3) measurements. To test our methodology, we fabricated filters on transferred single-crystal LiNbO3 films on sapphire (Al2O3) and silicon (Si) substrates with amorphous silicon (aSi) sacrificial layer. At 21.8 GHz, the filters on Al2O3 demonstrated an insertion loss of 1.48 dB, a 3 dB fractional bandwidth (FBW) of 17.7%, and in-band third-order input intercept points (IIP3) of 50.8 dBm. At 21.6 GHz, the filters on silicon demonstrated an insertion loss of 2.47 dB, a 3 dB FBW of 18.6%, and in-band IIP3 of 46.5 dBm. The nonlinear results conclusively show that thermal stability and passband distortion improved on the Al2O3 substrate, confirming that substrate selection plays a pivotal role in mitigating nonlinearity in acoustic front-end modules.

eess.SP↗

arXiv2026

Bimorph Lithium Niobate Piezoelectric Micromachined Ultrasonic Transducers

Piezoelectric micromachined ultrasonic transducers (PMUTs) are widely utilized in applications that demand mechanical resilience, thermal stability, and compact form factors. Recent efforts have sought to demonstrate that single-crystal lithium niobate (LN) is a promising PMUT material platform, offering high electromechanical coupling (k2) and bidirectional performance. In addition, advances in LN film transfer technology have enabled high quality periodically poled piezoelectric films (P3F), facilitating a bimorph piezoelectric stack without intermediate electrodes. In this work, we showcase a bimorph PMUT incorporating a mechanically robust, 20 $μ$m thick P3F LN active layer. We establish the motivation for LN PMUTs through a material comparison, followed by extensive membrane geometry optimization and subsequent enhancement of the PMUT's k2. We demonstrate a 775 kHz flexural mode device with a quality factor (Q) of 200 and an extracted k2 of 6.4\%, yielding a high transmit efficiency of 65 nm/V with a mechanically robust active layer. We leverage the high performance to demonstrate extreme-temperature resilience, showcasing stable device operation up to 600 $^\circ$C and survival up to 900 $^\circ$C, highlighting LN's potential as a resilient PMUT platform.

cond-mat.mtrl-sci↗

arXiv2026

50 GHz Piezoelectric Acoustic Filter

This paper presents significant frequency scaling of acoustic filter technology to 50 GHz. This achievement is enabled by the P3F LiNbO3 multilayer stack, in which piezoelectric thin-films of alternating orientations are transferred in sequence, thereby allowing efficient exploitation of high-order modes with high quality factor (Q) and coupling coefficient (k2) in a thicker piezoelectric stack. The demonstrated filter is comprised of twelfth-order symmetric (S12) mode lateral-field-excited bulk acoustic wave resonators (XBARs), built on a 4-layer periodically poled piezoelectric (P3F) 128 Y-cut lithium niobate (LiNbO3) stack. The filter exhibits 3.3 dB insertion loss (IL) and a fractional bandwidth (FBW) of 2.9%. The miniature design, with a footprint of 0.36 mm2, makes it promising for future wireless front-end applications. These results represent the highest frequency acoustic filters reported to date, setting a new benchmark in piezoelectric filter technology. Upon further development, the platform could enable filters further into the FR2 range, essential for next-generation communication systems.

eess.SP↗

arXiv2026

62.6 GHz ScAlN Solidly Mounted Acoustic Resonators

We demonstrate a record-high 62.6 GHz solidly mounted acoustic resonator (SMR) incorporating a 67.6 nm scandium aluminum nitride (Sc0.3Al0.7N) piezoelectric layer on a 40 nm buried platinum (Pt) bottom electrode, positioned above an acoustic Bragg reflector composed of alternating SiO2 (28.2 nm) and Ta2O5 (24.3 nm) layers in 8.5 pairs. The Bragg reflector and piezoelectric stack above are designed to confine a third-order thickness-extensional (TE) bulk acoustic wave (BAW) mode, while efficiently transducing with thickness-field excitation. The fabricated SMR exhibits an extracted piezoelectric coupling coefficient (k2) of 0.8% and a maximum Bode quality factor (Q) of 51 at 63 GHz, representing the highest operating frequency reported for an SMR to date. These results establish a pathway toward mmWave SMR devices for filters and resonators in next-generation RF front ends.

eess.SP↗

arXiv2025

Thermal Endurance of Suspended Thin-Film Lithium Niobate up to 800 °C

The need for high-temperature piezoelectric microelectromechanical systems (MEMS) requires pushing piezoelectric platforms to their thermal limits. In harsh thermal environments, piezoelectric MEMS devices are expected to sustain severe damage because of material degradation and coefficient of thermal expansion (CTE) mismatches between the functional layers and the carrier wafer. This paper investigates the thermal endurance of the suspended thin-film lithium niobate (LN) platform by observing the structural integrity and performance of acoustic Lamb wave resonators after annealing rounds at increasing temperatures, with a focus on temperatures between 550 $^\circ$C and 800 $^\circ$C, with 50 $^\circ$C temperature increments. Fundamental symmetric (S0) mode acoustic resonators are fabricated on 600 nm stoichiometric LN (sLN) with 40 nm thick platinum top electrodes and a thin titanium adhesion layer. After each annealing round, changes in the devices' resonant frequency and quality factor (\emph{Q}) are quantitatively studied. The devices and material stack are further analyzed with resistivity structures, optical microscope images, and X-ray diffraction (XRD) measurements. The results provide valuable insights into the design and material selection necessary to optimize the suspended thin-film LN platform for high temperatures. Understanding the thermal limit of the platform enables its use for sensors, actuators, resonators, and potentially other thin-film LN microsystems, e.g, photonics, electro-optical, and acousto-optical systems in harsh thermal environments.

physics.app-ph↗

arXiv2025

An 11.7-GHz ScAlN FBAR Filter: Case Study on Scaling Limits and Challenges

This paper reports an 11.7 GHz compact 50 ohm ladder filter based on single layer Scandium Aluminum Nitride (ScAlN) film bulk acoustic resonators (FBARs) with platinum (Pt) electrodes, and uses it as a quantitative case study of the limits encountered when directly scaling to higher frequencies. The measured filter achieves a 3 dB fractional bandwidth (FBW) of 4.0% and an out of band rejection greater than 23.1 dB, with a minimum insertion loss (IL) of 6.8 dB. We analyze the origin of this performance through a quantitative framework: (1) a loss decomposition study, (2) frequency shift sensitivity that explains the discrepancy between simulated and measured center frequency, (3) FBW sensitivity to series shunt separation and port impedance, and (4) stress limited aperture that constrains device size. The results establish a realistic, fabricable baseline for directly scaled single layer ScAlN FBAR filters and outline materials, electrode, and stress management directions toward lower loss mmWave acoustic filters.

physics.app-ph↗

arXiv2025

Periodically Poled Piezoelectric Lithium Niobate Resonator for Piezoelectric Power Conversion

As the demand for compact and efficient power conversion systems increases, piezoelectric power converters have gained attention for their ability to replace bulky magnetic inductors with acoustic resonators, enabling higher power density and improved efficiency. Achieving optimal converter performance requires resonators with high quality factor ($Q$), strong electromechanical coupling ($k^2$), high power handling capability, and a spurious-free response. Lithium niobate (LN) has emerged as a promising material in this context due to its high figure of merit (FoM = $Q \cdot k^2$). While previous studies on single-layer LN resonators have demonstrated high FoM values, they typically operate at relatively low resonance frequencies ($f_s$). Recently, periodically poled piezoelectric film (P3F) structures, formed by stacking piezoelectric layers with alternating crystal orientations, have shown the potential to both scale up the operating frequency and enhance the FoM compared to single-layer counterparts in piezoelectric power conversion. This work presents the first P3F thickness-extensional (TE) LN resonator for power conversion, operating at 19.23 MHz, with a large \textit{$k^2$} of 29\% and a high \textit{Q} of 3187, achieving a state-of-the-art (\textit{ $f_s \cdot Q$}) product among piezoelectric power resonators. A high-power testing procedure is performed to systematically study the nonlinear behavior and power handling of P3F LN for power applications. With further optimization, P3F TE resonators have the potential to open up a new design space for high-power and high-frequency power conversion.

physics.app-ph↗

arXiv2025

Acoustic resonators above 100 GHz

Piezoelectric resonators are a common building block for signal processing because of their miniature size, low insertion loss, and high quality factor. As consumer electronics push to millimeter waves frequencies, designers must increase the operating frequency of the resonator. The current state-of-the-art approach to increase the operating frequency is to decrease the thickness of the piezoelectric film to shorten the acoustic wavelength or to use higher order modes. Unfortunately, maintaining high crystal quality typically requires thicker piezoelectric layers. Thinner layers suffer from higher defect densities and increased surface damping, which degrade the electromechanical coupling and quality factor. While acoustic high order modes can also increase operating frequency, the electromechanical coupling rapidly decreases with increasing mode number. Here, we overcome these limitations by utilizing a piezoelectric stack of three layers of lithium niobate with alternating crystallographic orientations to preferentially support higher order modes and thereby enhance the electromechanical coupling without degrading the quality factor. Our approach improves the figure of merit of millimeter-wave acoustic resonators by roughly an order of magnitude greater compared to state-of-the-art piezoelectric resonators above 60 GHz. This concept of alternating crystallographic orientations facilitates a new path to develop millimeter wave resonators with high figures of merit, low insertion loss, and miniature footprints, enabling new applications in millimeter wave signal processing and computing.

physics.app-ph↗

arXiv2025

Thin-film scandium aluminum nitride bulk acoustic resonator with high Q of 208 and K2 of 9.5% at 12.5 GHz

This work describes sputtered scandium aluminum nitride (ScAlN) thin-film bulk acoustic resonators (FBAR) at 12.5 GHz with high electromechanical coupling (k2) of 9.5% and quality factor (Q) of 208, resulting in a figure of merit (FoM, Qk2) of 19.8. ScAlN resonators employ a stack of 90 nm thick 20% Sc doping ScAlN piezoelectric film on the floating bottom 38 nm thick platinum (Pt) electrode to achieve low losses and high coupling toward centimeter wave (cmWave) frequency band operation. Three fabricated and FBARs are reported, show promising prospects of ScAlN-Pt stack towards cmWave front-end filters.

physics.app-ph↗

arXiv2023

Transferred Thin Film Lithium Niobate as Millimeter Wave Acoustic Filter Platforms

This paper reports the first high-performance acoustic filters toward millimeter wave (mmWave) bands using transferred single-crystal thin film lithium niobate (LiNbO3). By transferring LiNbO3 on the top of silicon (Si) and sapphire (Al2O3) substrates with an intermediate amorphous Si (aSi) bonding and sacrificial layer, we demonstrate compact acoustic filters with record-breaking performance beyond 20 GHz. In the LN-aSi-Al2O3 platform, the third-order ladder filter exhibits low insertion loss (IL) of 1.62 dB and 3-dB fractional bandwidth (FBW) of 19.8% at 22.1 GHz, while in the LN-aSi-Si platform, the filter shows low IL of 2.38 dB and FBW of 18.2% at 23.5 GHz. Material analysis validates the great crystalline quality of the stacks. The high-resolution x-ray diffraction (HRXRD) shows full width half maximum (FWHM) of 53 arcsec for Al2O3 and 206 arcsec for Si, both remarkably low compared to piezoelectric thin films of similar thickness. The reported results bring the state-of-the-art (SoA) of compact acoustic filters to much higher frequencies, and highlight transferred LiNbO3 as promising platforms for mmWave filters in future wireless front ends.

eess.SP↗

arXiv2023

Thin-Film Lithium Niobate Acoustic Resonator with High Q of 237 and k2 of 5.1% at 50.74 GHz

This work reports a 50.74 GHz lithium niobate (LiNbO3) acoustic resonator with a high quality factor (Q) of 237 and an electromechanical coupling (k2) of 5.17% resulting in a figure of merit (FoM, Q x k2) of 12.2. The LiNbO3 resonator employs a novel bilayer periodically poled piezoelectric film (P3F) 128 Y-cut LiNbO3 on amorphous silicon (a-Si) on sapphire stack to achieve low losses and high coupling at millimeter wave (mm-wave). The device also shows a Q of 159, k2 of 65.06%, and FoM of 103.4 for the 16.99 GHz tone. This result shows promising prospects of P3F LiNbO3 towards mm-wave front-end filters.

eess.SP↗

arXiv2023

Thin-Film Lithium Niobate Acoustic Filter at 23.5 GHz with 2.38 dB IL and 18.2% FBW

This work reports an acoustic filter at 23.5 GHz with a low insertion loss (IL) of 2.38 dB and a 3-dB fractional bandwidth (FBW) of 18.2%, significantly surpassing the state-of-the-art. The device leverages electrically coupled acoustic resonators in 100 nm 128° Y-cut lithium niobate (LiNbO3) piezoelectric thin film, operating in the first-order antisymmetric (A1) mode. A new film stack, namely transferred thin-film LiNbO3 on silicon (Si) substrate with an intermediate amorphous silicon (a-Si) layer, facilitates the record-breaking performance at millimeter-wave (mmWave). The filter features a compact footprint of 0.56 mm2. In this letter, acoustic and EM consideration, along with material characterization with X-ray diffraction and verified with cross-sectional electron microscopy are reported. Upon further development, the reported filter platform can enable various front-end signal-processing functions at mmWave.

eess.SP↗