Research

Our Areas of Interest

Our Main Projects

Surface Acoustic Wave Delay Line

5G/6G+ Communications Device

Emerging 5G applications require acoustic resonators operating beyond 3 GHz to enable filters with wider bandwidths (driven by resonator electromechanical coupling, Keff^2), low loss (driven by high acoustic quality factor, Q) and high power handling. Existing approaches to acoustic RF resonators, with desired electromechanical coupling factor for wide bandwidth, do not easily scale to higher frequencies. Therefore, our group utilizes new piezo materials, such as AlScN, for the implementation of bulk acoustic wave resonators (BAW), surface acoustic wave resonators (SAW), and lamb wave resonators (LWR). Previous studies have shown that by doping AlN with Sc atoms, the piezoelectric coefficients of AlScN can reach a value five times larger than that of AlN.  This dramatic enhancement of the piezoelectric properties and our group's capability of fabricating low stress gradient and ultra-smooth AlScN piezoelectric films enable us the ability to achieve high electromechanical coupling factor and quality factor for our resonators. Our research further facilitates the development of radio frequency filters and signal processors with wide bandwidth and low insertion loss.

Contacts: Zichen Tang, Xingyu Du, Anne-Marie Zaccarin, Rossiny Beaucejour, Adzo Fiagbenu, Dr. Paria Gharavi, and Dr. Izhar

Collaborators: Sandia National Laboratories, Akoustis Technologies, and Professor Firooz Aflatouni.

Our publications related to this topic:
  • Z. Tang, G. Esteves, and R. H. Olsson III, “Sub-quarter micrometer periodically poled Al0.68Sc0.32N for ultra-wideband photonics and acoustic devices,” Journal of Applied Physics, vol. 134, no. 11, p. 114101, Sep. 2023.
  • L. Hackett et al., “Aluminum scandium nitride films for piezoelectric transduction into silicon at gigahertz frequencies,” Applied Physics Letters, vol. 123, no. 7, p. 073502, Aug. 2023.
  • Izhar et al., "A K-Band Bulk Acoustic Wave Resonator Using Periodically Poled Al0.72Sc0.28N," in IEEE Electron Device Letters, vol. 44, no. 7, pp. 1196-1199, July 2023.
  • R. Beaucejour, M. D’Agati, K. Kalyan, and R. H. Olsson III, "Compensation of the Stress Gradient in Physical Vapor Deposited Al1− xScxN Films for Microelectromechanical Systems with Low Out-of-Plane Bending," Micromachines, vol. 13, no. 8, p. 1169, 2022.
  • R. Beaucejour, V. Roebisch, A. Kochhar, C. G. Moe, M. D. Hodge, and R. H. Olsson, "Controlling Residual Stress and Suppression of Anomalous Grains in Aluminum Scandium Nitride Films Grown Directly on Silicon," Journal of Microelectromechanical Systems, 2022.
  • X. Du, Z. Tang, C. Leblanc, D. Jariwala, and R. H. Olsson, "High-Performance SAW Resonators at 3 GHz Using AlScN on a 4H-SiC Substrate," in 2022 Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS), 2022: IEEE, pp. 1-2.
  • Z. Tang, G. Esteves, J. Zheng, and R. H. Olsson, "Vertical and Lateral Etch Survey of Ferroelectric AlN/Al1− xScxN in Aqueous KOH Solutions," Micromachines, vol. 13, no. 7, p. 1066, 2022.
  • G. Esteves et al., "Al0.68Sc0.32N Lamb wave resonators with electromechanical coupling coefficients near 10.28%," Applied Physics Letters, vol. 118, no. 17, p. 171902, 2021.
  • Y. Song et al., "Thermal Conductivity of Aluminum Scandium Nitride for 5G Mobile Applications and Beyond," ACS Applied Materials & Interfaces, vol. 13, no. 16, pp. 19031-19041, 2021/04/28 2021
  • C. R. Kagan, D. P. Arnold, M. G. Allen, and R. H. Olsson, "IoT4Ag: MEMS-Enabled Distributed Sensing, Communications, And Information Systems for The Internet Of Things For Precision Agriculture," in 2021 IEEE 34th International Conference on Micro Electro Mechanical Systems (MEMS), 2021, pp. 350-353.
  • C. Moe et al., "Highly Doped AlScN 3.5 GHz XBAW Resonators with 16% k2eff for 5G RF Filter Applications," in 2020 IEEE International Ultrasonics Symposium (IUS), 2020, pp. 1-4.
  • Z. Tang, M. D. Agati, and R. H. Olsson, "High Coupling Coefficient Resonance Mode in Al<inf>0.68</inf>Sc<inf>0.32</inf>N Surface Acoustic Wave Resonator with AlN Buffer Layer on a Silicon Substrate," in 2020 Joint Conference of the IEEE International Frequency Control Symposium and International Symposium on Applications of Ferroelectrics (IFCS-ISAF), 2020, pp. 1-3.

Measured Hysteresis Loop of the 20 nm thick AlScN

Low Energy Memory Device

Ferroelectric based non-volatile memory has demonstrated advantageous features including low write energy, fast switching speed, and long endurance. However, for ferroelectric random access memory (FeRAM), the bit density is limited primarily by the remanent polarization (Pr) because the sense charge is the product of the Pr times the ferroelectric (FE) capacitor area. The bit density of a ferroelectric field-effect transistor (FeFET) is generally determined by the coercive field (Ec), with higher coercive field leading to thinner FE layers that can be patterned into smaller features while maintaining a wide memory window. Our group researches a newly found ferroelectric material, AlScN for the next generation of ferroelectric memory. We synthesize high quality sub-20 nm AlScN thin films, and thus enable ferroelectric memory with a low write voltage, a large remanent polarization, and a significant breakdown field to coercive field ratio. Moreover, the AlScN dielectric is able to be deposited on to a variety of substrates at temperatures below 350 °C, making the fabrication process compatible with back end of the line CMOS integration.


Contacts: Jeffrey Zheng, Adzo Fiagbenu, Yinuo Zhang, and Dr. Paria Gharavi.

Collaborators: Professor Deep Jariwala and Professor Eric Stach.

Our publications related to this topic:
  • Y. He et al., “Metal-ferroelectric AlScN-semiconductor memory devices on SiC wafers,” Applied Physics Letters, vol. 123, no. 12, p. 122901, Sep. 2023.
  • J. X. Zheng et al., “Ferroelectric behavior of sputter deposited Al0.72Sc0.28N approaching 5 nm thickness,” Applied Physics Letters, vol. 122, no. 22, p. 222901, Jun. 2023.
  • K.-H. Kim et al., "Scalable CMOS-BEOL compatible AlScN/2D Channel FE-FETs," arXiv preprint arXiv:2201.02153, 2022.
  • X. Liu et al., "Reconfigurable Compute-In-Memory on Field-Programmable Ferroelectric Diodes," arXiv preprint arXiv:2202.05259, 2022.
  • P. Musavigharavi, R. Beaucejour, R. H. Olsson, and E. A. Stach, "Strain-Engineering of Aluminum Scandium Nitride Films Grown Directly on Silicon by Utilizing a Gradient Seed Layer: Application of 4D-STEM Technique," Microscopy and Microanalysis, vol. 28, no. S1, pp. 444-445, 2022.
  • J. X. Zheng et al., "Electrical breakdown strength enhancement in aluminum scandium nitride through a compositionally modulated periodic multilayer structure," Journal of Applied Physics, vol. 130, no. 14, p. 144101, 2021.
  • P. Musavigharavi et al., "Strain Engineering in Aluminum Scandium Nitride Thin Film using Four-dimensional Scanning Transmission Electron Microscopy (4D-STEM) Technique," Microscopy and Microanalysis, vol. 27, no. S1, pp. 2204-2205, 2021.
  • P. Musavigharavi et al., "Nanoscale Structural and Chemical Properties of Ferroelectric Aluminum Scandium Nitride Thin Films," The Journal of Physical Chemistry C, vol. 125, no. 26, pp. 14394-14400, 2021/07/08 2021.
  • X. Liu et al., "Aluminum scandium nitride-based metal–ferroelectric–metal diode memory devices with high on/off ratios," Applied Physics Letters, vol. 118, no. 20, p. 202901, 2021/05/17 2021.
  • D. Wang et al., "Sub-Microsecond Polarization Switching in (Al,Sc)N Ferroelectric Capacitors Grown on Complementary Metal–Oxide–Semiconductor-Compatible Aluminum Electrodes," physica status solidi (RRL) – Rapid Research Letters, vol. 15, no. 5, p. 2000575, 2021.
  • X. Liu et al., "Post-CMOS Compatible Aluminum Scandium Nitride/2D Channel Ferroelectric Field-Effect-Transistor Memory," Nano Letters, vol. 21, no. 9, pp. 3753-3761, 2021/05/12 2021.
  • D. Wang et al., "Ferroelectric Switching in Sub-20 nm Aluminum Scandium Nitride Thin Films," IEEE Electron Device Letters, vol. 41, no. 12, pp. 1774-1777, 2020.
  • D. Wang et al., "Ferroelectric C-Axis Textured Aluminum Scandium Nitride Thin Films of 100 nm Thickness," in 2020 Joint Conference of the IEEE International Frequency Control Symposium and International Symposium on Applications of Ferroelectrics (IFCS-ISAF), 2020, pp. 1-4.

Resonant Multiferroics MEMS Device

Wearable & Implantable Multiferroics

The human body produces magnetic fields anywhere an electric current is present, including the heart, brain, nerves, and muscles. Multiferroic materials provide a unique way to sense these tiny magnetic fields, providing high sensitivity, lower power, and small size. In these heterostructures, a magnetostrictive material strains in response to magnetic field, which is coupled to the piezoelectric material, producing output charge in response to the magnetically induced strain. In our group,  AlScN is employed in resonant multiferroics structures along with a variety of magnetostrictive materials. Our studies have greatly enhanced the quality factor and the electromechanical coupling of resonant multiferroic structures.  Additionally, similar multiferroic devices can be used for implantable or wearable wireless power transfer, where an external magnetic field can provide the power necessary for the sensors and circuits to operate in biomedical IoT applications. In addition, we explore novel, low power circuit interfaces for the  multiferroic devices.


Contacts: Michael D’Agati, Sydney Sofronici, Yujia Huo

Collaborators: Professor Mark Allen and US Navy Research Laboratories.

Our publications related to this topic:
  • T. Mion et al., “High Isolation, Double-Clamped, Magnetoelectric Microelectromechanical Resonator Magnetometer,” Sensors, vol. 23, no. 20, Art. no. 20, Jan. 2023.
  • Y. Huo, S. Sofronici, M. J. D’Agati and R. H. Olsson, "Low Power Circuit Interfaces for Strain Modulated Multiferroic Biomagnetic Sensors," in IEEE Open Journal of the Solid-State Circuits Society, vol. 3, pp. 214-222, 2023.
  • Y. Huo, S. Sofronici, et al., "Low Noise, Strain Modulated, Multiferroic Magnetic Field Sensor Systems," in IEEE Sensors Journal, vol. 23, no. 13, pp. 14025-14040, 1 July1, 2023.
  • M. D’Agati et al., "High-Q Factor Multiferroic Resonant MEMS Low Frequency Magnetic Field Sensors," in 2022 Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS), 2022: IEEE, pp. 1-3.
  • M. D'Agati et al., (2022). High-Q Factor, Multiferroic Resonant Magnetic Field Sensors and Limits on Strain Modulated Sensing Performance [Manuscript submitted for publication]. Department of Electrical and Systems Engineering, University of Pennsylvania.

Passive Subsurface Soil Sensor Schematic

IoT for Agriculture

Precision agriculture systems enabled by internet of things (IoT) technologies, through high spatial resolution monitoring of field conditions, can facilitate more efficient deployment of agriculture resources. Such systems require sensors that can provide information about the condition of the soil, including moisture and nutrient levels. Sensors that are biodegradable and inexpensive are key to enabling scalable IoT systems for agriculture. Our group is focused on developing passive wireless subsurface soil sensors. High-performance resonators are critical in passive capacitive sensors. The maximal frequency shift of the system is directly proportional to the electromechanical coupling coefficient of the LWR, while sensor sensitivity (or minimum detectable frequency shift) improves with quality factor. We use AlScN to design and implement such lamb-wave resonators (LWR). Our research also focuses on antenna and sensor designs compatible with biodegradable materials and low-cost high-throughput fabrication technologies. The implementation of time-domain gating-based interrogation of the sensor nodes is also under investigation.

Contacts: Anne-Marie Zaccarin

Collaborators: The Internet of Things for Precision Agriculture ,an NSF Engineering Research Center

Our publications related to this topic:
  • A.-M. Zaccarin, G. M. Iyer, R. H. Olsson and K. T. Turner, "Fabrication and Characterization of Soil Moisture Sensors on a Biodegradable, Cellulose-Based Substrate," in IEEE Sensors Journal, doi: 10.1109/JSEN.2023.3299430.
  • A.-M. Zaccarin, G. M. Iyer, A. Kochhar, R. Vetury, K. T. Turner and R. H. Olsson, "High Performance Lamb Wave Resonator Operating in the 900 MHz ISM Band for Wireless Sensing Applications," 2023 IEEE/MTT-S International Microwave Symposium - IMS 2023, San Diego, CA, USA, 2023, pp. 1168-1171
  • G. M. Iyer, A. -M. Zaccarin, R. H. Olsson and K. T. Turner, "Fabrication and Characterization of Cellulose-Based Materials for Biodegradable Soil Moisture Sensors," 2022 IEEE Sensors, Dallas, TX, USA, 2022, pp. 1-4
  • C. R. Kagan, D. P. Arnold, M. G. Allen, and R. H. Olsson, "IoT4Ag: MEMS-Enabled Distributed Sensing, Communications, And Information Systems for The Internet Of Things For Precision Agriculture," in 2021 IEEE 34th International Conference on Micro Electro Mechanical Systems (MEMS), 2021, pp. 350-353.