arXiv subjects

Roy H. Olsson III

Publications and source records attributed to Roy H. Olsson III.

At least 19 recordsLinked to original sources

arXiv2026

Towards a monolithic platform for coupling superconducting circuits to low-loss microwave phonons in AlScN on 4H-SiC

Hybrid superconducting-phonon quantum processing is promising for cavity QED, measurement-based quantum computing, and other quantum applications. Relative to microwave photons at the same frequency, phonons can provide ultra-compact footprints, extremely low losses, and greater connectivity. Phonons can also couple strongly to superconducting circuits through the piezoelectric effect. However, this promise rests on scalable platforms that achieve these benefits without degrading superconducting circuit performance. This motivates a monolithic platform combining low phononic loss, strong electromechanical coupling, and superconducting-circuit compatibility without requiring suspended phononics. Here, we characterize a monolithic quantum acoustic platform combining aluminum superconducting circuits on exposed silicon carbide (SiC) with piezoelectric aluminum scandium nitride (AlScN) on SiC for integrated phononics. This architecture is enabled by selective removal of AlScN from selected chip regions, allowing aluminum superconducting microwave resonators to be fabricated directly on the SiC while preserving adjacent AlScN-on-SiC regions for phonon transduction. The resulting Al-on-SiC resonators exhibit a coherent lifetime of 2.9 μs, demonstrating compatibility with aluminum superconducting quantum devices. In parallel, cryogenic surface acoustic delay-line measurements on the retained AlScN-on-SiC regions show low phononic propagation loss at 4.05 GHz, corresponding to an estimated phonon lifetime of 7.6 μs. Together with a previously demonstrated electromechanical coupling coefficient of about 4.3% and a theoretical upper bound of 8%, these results establish Al-on-SiC/AlScN-on-SiC as a promising monolithic platform for integrating superconducting microwave circuits with piezoelectric phononic components for quantum acoustic networking and hybrid quantum systems.

quant-ph↗

arXiv2026

Dispersion Engineered Frequency Tunable Delay Platform based on Magnetostatic Surface Waves

Reconfigurable radio-frequency front ends in modern radar and wireless systems require delay elements that simultaneously offer low-loss, low noise, compact form factor, and wideband frequency agility. However, electromagnetic, acoustic, photonic, and active-circuit delay technologies each fail to deliver this combination. Here we report a microwave delay platform based on magnetostatic surface waves (MSSWs) in microfabricated 18 $μ$m yttrium iron garnet (YIG) waveguides, in which co-engineering the spin wave dispersion with the radiation impedance of meander-line transducers grants pitch-controlled access to distinct dispersive or near-constant group-delay regimes. Tuned continuously from 6 to 19.6 GHz under magnetic bias, the delay lines deliver group delays of 3.3 to 42.8 ns at insertion losses of 2.5 to 10.1 dB and nonreciprocal isolation of 24 to 39 dB, all measured directly into 50 $Ω$ without external impedance matching. Length-resolved characterization yields unit-time propagation losses of 56 to 109 dB/$μ$s and propagation Q-factors that rise monotonically from 3002 to 4893 across the operating range, exceeding state-of-the-art fixed frequency acoustic delay lines at every benchmarked frequency. These results establish microfabricated YIG as a versatile, low-loss microwave platform for next-generation reconfigurable RF signal processing.

physics.app-ph↗

arXiv2026

19 GHz Single-Ended-to-Balanced Modified Ladder-Lattice Filters Realized Using Periodically Polarized AlScN BAW Resonators

We present a single-ended to balanced modified ladder-lattice filter topology, realized with periodically polarized piezoelectric (P3F) AlScN resonators, for single-ended to differential filtering applications. This filter topology eliminates the need for baluns or other passive components and can interface, for instance, directly between differential antennas and single-ended power and low noise amplifiers. Two filter designs operating at 19 GHz were implemented. The first design exhibited a minimum insertion loss of 1.3 dB, a 6.26% fractional 3-dB bandwidth, an average out-of-band rejection of 30 dB and occupied a 348 um x 476 um footprint, while the second higher-selectivity filter achieved 1.58 dB of minimum insertion loss, 5.11% fractional 3-dB bandwidth, 33 dB of average out-of-band rejection, and occupied a 392 um x 476 um footprint - Making them highly competitive for wireless communications filters. The working principle of the modified ladder-lattice topology is discussed, the design of the filters are presented, and the linearity of the filters is explored through intermodulation and power handling measurements.

physics.app-ph↗

arXiv2025

Spatially tailored spin wave excitation for spurious-free, low-loss magnetostatic wave filters with ultra-wide frequency tunability

Yttrium iron garnet magnetostatic wave (MSW) radio frequency (RF) cavity filters are promising for sixth-generation (6G) communication systems due to their wide frequency tunability. However, the presence of severe spurious modes arising from the finite cavity dimensions severely degrades the filter performance. We present a half-cone transducer that spatially tailors spin wave excitation to selectively enhance the primary cavity modes comprising the MSW filter passband, while strongly suppressing the undesired spurious modes. Theoretical analysis, numerical simulations and experiments verify the effectiveness of the spatially tailored technique. We utilize the half-cone transducer to demonstrate a spurious-free, single-cavity half-cone MSW filter (HC-MSWF) with an insertion loss (IL) of 2.4-3.2 dB over a frequency tuning range of 6.3-16.8 GHz. Extending our study, we further demonstrate a spurious-free, dual-cavity HC-MSWF with an unprecedented tuning range of 21.7 GHz (9.8-31.5 GHz) while maintaining a low IL of 2.9-3.8 dB. This significant advance in performance will enable highly reconfigurable and robust 6G networks.

eess.SP↗

arXiv2025

Tuning Breakdown-to-Coercive Field Ratio in Ultra-Thin Al1-xScxN Films via Reactive Nitrogen Atmosphere

Al1-xScxN has attracted significant interest due to its large remnant polarization and low processing temperature when compared to other ferroelectric material systems. However, device dielectric failure before ferroelectric switching remains a critical limitation for AlScN-based memory devices. With the continuing trend toward device miniaturization, expanding the operating window is essential for next-generation memory development. In this work, we optimized the breakdown field (EBD) and coercive field (EC) in ultra-thin Al1-xScxN films by controlling defect density via adjustment of nitrogen gas flow during sputter deposition. The characteristic breakdown field, EBD, was evaluated using Weibull statistics, yielding optimal characteristic breakdown fields of 12.47 MV/cm (EBD+) and -12.63 MV/cm (EBD-) for samples deposited under 27.5 sccm N2 flow. The minimum EC was achieved at a nitrogen flow of 25 sccm and increased for higher gas flows, a trend that is opposite to previous reports in much thicker films. The highest EBD over EC ratio of 2.25 occurred at 27.5 sccm, effectively expanding the operational window. Using a combination of X-ray diffraction and photoluminescence spectroscopy to study changes in crystal orientation and defects, device performance can be tuned by controlling the point defect concentration in the ultra-thin film via adjusting the sputtering N2 process gas flow rate.

cond-mat.mtrl-sci↗

arXiv2025

Low-Field Ferroelectricity in 10 nm AlBScN Thin Films

Ferroelectric aluminum scandium nitride (Al1-xScxN, AlScN) offers CMOS-compatible integration but suffers from high coercive fields and leakage currents that hinder thickness scaling. Further reduction in thickness is essential for low-voltage embedded nonvolatile memory applications. Boron incorporation into AlScN (AlBScN) suppresses leakage current in films down to 40 nm, yet its ferroelectric characteristics in ultrathin films remains unexplored. This letter demonstrates robust ferroelectric switching in 10 nm sputtered AlBScN capacitors with a low coercive field and approximately two orders of magnitude lower leakage than AlScN. Notably, ferroelectric switching was observed at 2.2 MV/cm in capacitance-voltage measurements, and symmetric polarization reversal occurred near 4.6 MV/cm in positive-up-negative-down (PUND) measurements using 2 μs pulses. Moreover, Weibull analysis revealed a breakdown-to-coercive-field ratio (EBD/Ec) of ~2.2. These findings demonstrated AlBScN as a promising candidate for CMOS back-end-of-line (BEOL) compatible ferroelectric applications with improved energy consumption and reduced leakage current.

cond-mat.mtrl-sci↗

arXiv2025

A Wideband Tunable, Nonreciprocal Bandpass Filter Using Magnetostatic Surface Waves with Zero Static Power Consumption

Modern wireless systems demand compact, power-efficient RF front-end components that support wideband tunability and nonreciprocity. We present a new class of miniature bandpass filter that achieves both continuously tunable frequency operation (4-17.7 GHz) and high nonreciprocity (>25 dB), all within a compact size of 1.07 cm3. The filter employs a microfabricated 18 micrometer thick Yttrium Iron Garnet waveguide with meander-line aluminum transducers, enabling low-loss unidirectional propagation via magnetostatic surface waves. Leveraging a benzocyclobutene planarization fabrication process, this study enables a dispersion profile unique to thick YIG films, resulting in enhanced filter skirt performance with minimal spurious modes. Frequency tuning is enabled by a zero-static-power magnetic bias circuit using transient current pulses, eliminating continuous power consumption. The filter demonstrates low insertion loss (3-5 dB), high out-of-band rejection (>30 dB), narrow bandwidth (100-200 MHz), robust power handling (>10.4 dBm), and high linearity (IIP3 > 26 dBm).

physics.app-ph↗

arXiv2025

Coercive Field Reduction in Ultra-thin Al1-XScXN via Interfacial Engineering with a Scandium Electrode

Aluminum scandium nitride (AlScN) ferroelectrics are promising for next-generation non-volatile memory applications due to high remnant polarization compared with Pb(ZrxTi1-x)O3 and doped-HfO2 material systems, as well as their fast switching and scalability to nanometer thicknesses. As AlScN films are thinned to 10 nm thickness, coercive field has been shown to substantially increase, which hinders low voltage operation. We demonstrate that interfacial engineering through bottom electrode selection and strain management reduces this coercive field increase with scaling and improves ferroelectric performance. Here, we demonstrate robust ferroelectricity in ultra-thin AlScN capacitors deposited on a Sc bottom electrode under both alternating current and direct current conditions. The coercive field is reduced by over 20 percent compared to capacitors with an Al bottom electrode. Furthermore, the difference in dynamic switching behavior over a decade of frequency was evaluated by applying the KAI model. At frequencies lower than 16.7 kHz, the capacitors with Sc and Al bottom electrodes exhibit comparable KAI exponents of 0.030 and 0.028, indicating similar switching kinetics. However, at higher frequencies, the capacitor with an Al bottom electrode shows a significantly higher exponent of 0.063, indicating a stronger frequency dependence, whereas the capacitor with a Sc bottom electrode maintains a stable exponent of 0.030, suggesting a lower frequency dependence during faster switching scenarios. The Scanning Electron Nanobeam Diffraction technique was selected to measure the strain difference in AlScN thin films grown on templates with different lattice mismatch, providing a correlation between lattice mismatch, film strain and switching behavior in ultra-thin film systems.

cond-mat.mtrl-sci↗

arXiv2025

A 5.9 GHz Sezawa SAW Acoustic Delay Line Based on Al0.6Sc0.4N-on-Sapphire with Propagation Q-factor > 3,000

In this work, we demonstrate a high-performance surface acoustic wave (SAW) delay line based on a Scandium alloyed aluminum nitride (AlScN)-on-sapphire platform operating at 5.9 GHz with an exceptionally high acoustic propagation Q-factor. An 800 nm AlScN thin film with 40% scandium alloying concentration was deposited on a thick sapphire substrate to achieve strong acoustic energy confinement and large electromechanical coupling effect, thereby minimizing the insertion loss (IL) and propagation loss (PL) of the acoustic delay line (ADL). The proposed ADL was designed to operate in the Sezawa mode using a Single-Phase Unidirectional Transducer (SPUDT) electrode configuration for better unidirectionality. The fabricated ADLs with different delay lengths, after conjugate matching, exhibited delay times spanning 13 to 214 ns and IL ranging from 7.6 to 18.3 dB. The extracted PL reached as low as 9.2 dB/mm at 5.9 GHz, with a group velocity (v_g) of around 5,779 m/s. Based on these results, the proposed ADLs exhibit a high acoustic propagation Q-factor of 3,044. These findings highlight the potential of AlScN-on-sapphire platforms for high operational frequency, low-loss SAW ADL devices in advanced RF applications.

physics.app-ph↗

arXiv2025

Kilobyte-Scale, Selector-Free, Temperature-Hard AlScN Ferroelectric Diode Crossbar Arrays

We report the fabrication and characterization of kilobyte-scale, selector-free, ferroelectric (FE) diode crossbar memory arrays based on aluminum scandium nitride (AlScN). Utilizing a fully CMOS back-end-of-line (BEOL) compatible process, we fabricated 2-kilobyte (128 $\times$ 128) arrays with device diameters down to 5 $μ$m, achieving memory densities up to 2500 bits/mm$^2$. Large-scale electrical characterization across 1000 randomly selected devices reveals a yield rate of 95.2%, a tight switching voltage distribution with a coefficient of variation (CV) of 0.003, and consistent on/off ratios of around 10 with a CV of 0.27. We demonstrate selector-free read and program operations of the array, enabled by the high nonlinearity, rectification, and uniform switching behavior of the FE diodes. Furthermore, we verified consistent ferroelectric switching during array operation at temperatures up to 600 $^\circ$C. Our results highlight the potential of AlScN FE diode arrays for energy-efficient, high-density memory applications and lay the groundwork for future integration in compute-near-memory, high-temperature memory, and analog compute-in-memory systems.

cond-mat.mes-hall↗

arXiv2025

Leakage Suppression Across Temperature in Al1-xScxN Thin Film Ferroelectric Capacitors through Boron Incorporation

This paper presents high-temperature ferroelectric characterization of 40~nm Al$_{1-x-y}$B$_x$Sc$_y$N (AlBScN) thin film capacitors grown by co-sputtering Al$_{0.89}$B$_{0.11}$ and Sc targets onto Pt(111)/Ti(002)/Si(100) substrates. Structural analysis confirmed a c-axis-oriented wurtzite structure with a low surface roughness of 1.37~nm. Ferroelectric switching, characterized by positive-up-negative-down (PUND) measurements up to 600~$^\circ$C, exhibited a linear decrease in coercive fields from 6.2~MV/cm at room temperature to 4.2~MV/cm at 600~$^\circ$C, while remanent polarization remained stable with temperature. Direct current I-V measurements highlight a significant suppression of leakage currents, over two orders of magnitude lower compared to AlScN capacitors fabricated under similar conditions. These results position AlBScN thin films as strong candidates for ferroelectric applications in extreme environments.

cond-mat.mtrl-sci↗

arXiv2025

Write Cycling Endurance Exceeding 1010 in Sub-50 nm Ferroelectric AlScN

Wurtzite ferroelectrics, particularly aluminum scandium nitride (AlScN), have emerged as a promising materials platform for nonvolatile memories, offering high polarization values exceeding 100 uC/cm2. However, their high coercive fields (>3 MV/cm) have limited cycling endurance to ~107 cycles in previous reports. Here, we demonstrate unprecedented control of polarization switching in AlScN, achieving write cycling endurance exceeding 1010 cycles a thousand fold improvement over previous wurtzite ferroelectric benchmarks. Through precise voltage modulation in 45 nm thick Al0.64Sc0.36N capacitors, we show that while complete polarization reversal (2Pr ~ 200 uC/cm2) sustains ~108 cycles, partial switching extends endurance beyond 1010 cycles while maintaining a substantial polarization (>30 uC/cm2 for 2Pr). This exceptional endurance, combined with breakdown fields approaching 10 MV/cm in optimized 10 um diameter devices, represents the highest reported values for any wurtzite ferroelectric. Our findings establish a new paradigm for reliability in nitride ferroelectrics, demonstrating that controlled partial polarization and size scaling enables both high endurance and energy efficient operation.

cond-mat.mtrl-sci↗

arXiv2025

Low-voltage Ferroelectric Field-Effect Transistors with Ultrathin Aluminum Scandium Nitride and 2D channels

The continued evolution of CMOS technology demands materials and architectures that emphasize low power consumption, particularly for computations involving large scale data processing and multivariable optimization. Ferroelectric materials offer promising solutions through enabling dual-purpose memory units capable of performing both storage and logic operations. In this study, we demonstrate ferroelectric field effect transistors (FeFETs) with MoS2 monolayer channels fabricated on ultrathin 5 nm and 10 nm ferroelectric Aluminum Scandium Nitride (AlScN) films. By decreasing the thickness of the ferroelectric film, we achieve significantly reduced gate voltages (<3V) required to switch the conductance of the devices, enabling operation at low voltages compatible with advanced CMOS. We observe a characteristic crossover in hysteresis behavior that varies with film thickness, channel fabrication method, and environmental conditions. Through systematic investigation of multiple parameters including channel fabrication methods, dimensional scaling, and environmental effects, we provide pathways to improve device performance. While our devices demonstrate clear ferroelectric switching behavior, further optimization is required to enhance the ON/OFF ratio at zero gate voltage while continuing to reduce the coercive field of these ultrathin films.

physics.app-ph↗

arXiv2025

Observation of giant remnant polarization in ultrathin AlScN at cryogenic temperatures

The discovery of wurtzite ferroelectrics opens new frontiers in polar materials, yet their behavior at cryogenic temperatures remains unexplored. Here, we reveal unprecedented ferroelectric properties in ultrathin (10 nm) Al$_{0.68}$Sc$_{0.32}$N (AlScN) at cryogenic temperatures where the properties are fundamentally distinct from those of conventional oxide ferroelectrics. At 12 K, we demonstrate a giant remnant polarization exceeding 250 $μ$C/cm$^2$ -- more than twice that of any known ferroelectric -- driven by an enhanced c/a ratio in the wurtzite structure. Our devices sustain remarkably high electric fields (~13 MV/cm) while maintaining reliable switching, achieving over 104 polarization reversal cycles at 12 K. Critically, this breakdown field strength approaches that of passive dielectric materials while maintaining ferroelectric functionality. The extraordinary polarization enhancement and high-field stability at cryogenic temperatures contrasts sharply with oxide ferroelectrics, establishing wurtzite ferroelectrics as a distinct class of polar materials with implications spanning fundamental physics to cryogenic non-volatile memory and quantum technologies.

cond-mat.mtrl-sci↗

arXiv2025

Al0.68Sc0.32N/SiC based metal-ferroelectric-semiconductor capacitors operating up to 1000 °C

Ferroelectric (Fe) materials-based devices show great promise for non-volatile memory applications, yet few demonstrate reliable operation at elevated temperatures. In this work, we demonstrate Ni/Al0.68Sc0.32N/4H-SiC metal-ferroelectric-semiconductor capacitors for high-temperature non-volatile memory applications. Our 30-nm thick ferroelectric Al0.68Sc0.32N film grown on SiC exhibits stable and robust ferroelectric switching up to 1000°C. The coercive field decreases linearly from -6.4/+11.9 MV cm-1 at room temperature to -3.1/+7.8 MV cm-1 at 800°C, further reducing to -2.5 MV cm-1 at 1000°C. At 600°C, the devices achieve remarkable reliability with ~2000 endurance cycles and over at least 100 hours of retention with negligible polarization loss. At 800°C, the devices retain data for at least 10,000 seconds and exceed 400 write cycles. Our results further highlight the potential for ferroelectric AlScN thin-films particularly when paired with SiC semiconductor substrates for high-temperature non-volatile memory.

cond-mat.mtrl-sci↗

arXiv2024

Reconfigurable SWCNT ferroelectric field-effect transistor arrays

Reconfigurable devices have garnered significant attention for alleviating the scaling requirements of conventional CMOS technology, as they require fewer components to construct circuits with similar function. Prior works required continuous voltage application for programming gate terminal(s) in addition to the primary gate terminal, which undermines the advantages of reconfigurable devices in realizing compact and power-efficient integrated circuits. Here, we realize reconfigurable devices based on a single-gate field-effect transistor (FET) architecture by integrating semiconducting channels consisting of a monolayer film of highly aligned SWCNTs with a ferroelectric AlScN gate dielectric, all compatible with CMOS back-end-of-line (BEOL) processing. We demonstrated these SWCNT ferroelectric FETs (FeFETs) in a centimeter-scale array (~1 cm^2) comprising ~735 devices, with high spatial uniformity in device characteristics across the array. The devices exhibited ambipolar transfer characteristics with high on-state currents and current on/off ratios exceeding 10^5, demonstrating an excellent balance between electron and hole conduction (~270 μA/μm at a drain voltage of 3 V. When functioning as a non-volatile memory, the SWCNT FeFETs demonstrated large memory windows of 0.26 V/nm and 0.08 V/nm in the hole and electron conduction regions, respectively, combined with excellent retention behavior for up to 10^4 s. Repeated reconfiguration between p-FET and n-FET modes was also enabled by switching the spontaneous polarization in AlScN and operating the transistor within a voltage range below the coercive voltage. We revealed through circuit simulations that reconfigurable SWCNT transistors can realize ternary content-addressable memory (TCAM) with far fewer devices compared to circuits based on silicon CMOS technology or based on resistive non-volatile devices.

cond-mat.mtrl-sci↗

arXiv2024

Reconfigurable Compute-In-Memory on Field-Programmable Ferroelectric Diodes

The deluge of sensors and data generating devices has driven a paradigm shift in modern computing from arithmetic-logic centric to data-centric processing. Data-centric processing require innovations at device level to enable novel compute-in-memory (CIM) operations. A key challenge in construction of CIM architectures is the conflicting trade-off between the performance and their flexibility for various essential data operations. Here, we present a transistor-free CIM architecture that permits storage, search and neural network operations on sub-50nm thick Aluminum Scandium Nitride ferroelectric diodes (FeDs). Our circuit designs and devices can be directly integrated on top of Silicon microprocessors in a scalable process. By leveraging the field-programmability, non-volatility and non-linearity of FeDs, search operations are demonstrated with a cell footprint < 0.12 um2 when projected onto 45-nm node technology. We further demonstrate neural network operations with 4-bit operation using FeDs. Our results highlight FeDs as candidates for efficient and multifunctional CIM platforms.

physics.app-ph↗

arXiv2024

Materials for High Temperature Digital Electronics

Silicon microelectronics, consisting of complementary metal oxide semiconductor (CMOS) technology, have changed nearly all aspects of human life from communication to transportation, entertainment, and healthcare. Despite the widespread and mainstream use, current silicon-based devices suffer significant reliability issues at temperatures exceeding 125 C. The emergent technological frontiers of space exploration, geothermal energy harvesting, nuclear energy, unmanned avionic systems, and autonomous driving will rely on control systems, sensors, and communication devices which operate at temperatures as high as 500 C and beyond. At these extreme temperatures, active (heat exchanger, phase change cooling) or passive (fins and thermal interface materials) cooling strategies add significant mass and complication which is often infeasible. Thus, new material solutions beyond conventional silicon CMOS devices are necessary for high temperature, resilient electronic systems. Accomplishing this will require a united effort to explore development, integration, and ultimately manufacturing of non-silicon-based logic and memory technologies, non-traditional metals for interconnects, and ceramic packaging technology.

cond-mat.mtrl-sci↗