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Olsson, Roy H.

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

18 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Sub-quarter micrometer periodically poled Al 0.68 Sc 0.32 N for ultra-wideband photonics and acoustic devices

In this study, we demonstrate the ability of polarity inversion of sputtered aluminum scandium nitride thin films through post-fabrication processes with domain widths as small as 220 nm at a periodicity of 440 nm. An approach using photo- and electron-beam lithography to generate sub-quarter micrometer feature size with adjustable duty cycle through a lift-off process is presented. Here, the film with a coercive field $E_c^+$ of 5.35 MV/cm was exercised first with a 1 kHz triangular double bipolar wave and ultimately poled with a 0.5 kHz double monopolar wave using a Radiant Precision Premier II tester. The metal polar (M-polar) and nitrogen polar (N-polar) domains were identified and characterized through potassium hydroxide wet etching as well as piezoresponse force microscopy (PFM). Well-distinguished boundaries between the oppositely polarized domain regions were confirmed through the phase diagram of the PFM results. The relationship between the electrode width, poling voltage, and domain growth was experimentally studied and statistically analyzed, where 7.96 nm/V domain width broadening vs escalating poling voltage was observed. This method produces extremely high domain spatial resolution in III-nitride materials via poling and is transferable to a CMOS-compatible photolithography process. The spatial resolution of the periodically poled Al 0.68 Sc 0.32 N is suitable for second-harmonic generation of deep ultraviolet through quasi-phase-matching and RF MEMS operating in the X-Band spectrum.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Aluminum scandium nitride films for piezoelectric transduction into silicon at gigahertz frequencies

Recent advances in the growth of aluminum scandium nitride films on silicon suggest that this material platform could be applied for quantum electromechanical applications. Here, we model, fabricate, and characterize microwave frequency silicon phononic delay lines with transducers formed in an adjacent aluminum scandium nitride layer to evaluate aluminum scandium nitride films, at 32% scandium, on silicon interdigital transducers for piezoelectric transduction into suspended silicon membranes. We achieve an electromechanical coupling coefficient of 2.7% for the extensional symmetric-like Lamb mode supported in the suspended material stack and show how this coupling coefficient could be increased to at least 8.5%, which would further boost transduction efficiency and reduce the device footprint. The one-sided transduction efficiency, which quantifies the efficiency at which the source of microwave photons is converted to microwave phonons in the silicon membrane, is 10% at 5 GHz at room temperature and, as we discuss, there is a path to increase this toward near-unity efficiency based on a combination of modified device design and operation at cryogenic temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Ferroelectric behavior of sputter deposited Al 0.72 Sc 0.28 N approaching 5 nm thickness

Ferroelectric Al 1-x Sc x N has raised much interest in recent years due to its unique ferroelectric properties and complementary metal oxide semiconductor back-end-of-line compatible processing temperatures. Potential applications in embedded nonvolatile memory, however, require ferroelectric materials to switch at relatively low voltages. One approach to achieving a lower switching voltage is to significantly reduce the Al 1-x Sc x N thickness. In this work, ferroelectric behavior in 5-27 nm films of sputter deposited Al 0.72 Sc 0.28 N has been studied. We find that the 10 kHz normalized coercive field increases from 4.4 to 7.3 MV/cm when reducing the film thickness from 27.1 to 5.4 nm, while over the same thickness range, the characteristic breakdown field of a 12.5 μm radius capacitor increases from 8.3 to 12.1 MV/cm. In conclusion, the 5.4 nm film demonstrates ferroelectric switching at 5.5 V when excited with a 500 ns pulse and a switching speed of 60 ns.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2021

Neural interface methods and apparatus to provide artificial sensory capabilities to a subject

Embodiments of neural interfaces according to the present invention comprise sensor modules for sensing environmental attributes beyond the natural sensory capability of a subject, and communicating the attributes wirelessly to an external (ex-vivo) portable module attached to the subject. The ex-vivo module encodes and communicates the attributes via a transcutaneous inductively coupled link to an internal (in-vivo) module implanted within the subject. The in-vivo module converts the attribute information into electrical neural stimuli that are delivered to a peripheral nerve bundle within the subject, via an implanted electrode. Methods and apparatus according to the invention incorporate implantable batteries to power the in-vivo module allowing for transcutaneous bidirectional communication of low voltage (e.g. on the order of 5 volts) encoded signals as stimuli commands and neural responses, in a robust, low-error rate, communication channel with minimal effects to the subjects' skin.

Buerger, Stephen P.↗
DOE OSTI2021

Al 0.68 Sc 0.32 N Lamb wave resonators with electromechanical coupling coefficients near 10.28%

Aluminum scandium nitride (Al 1-x Sc x N/AlScN) (x = 0.32) Lamb wave resonators (LWR) have been fabricated and tested to demonstrate electromechanical coupling coefficients (k t 2 ) in excess of 10%. The resonators exhibited an average k t 2 and unloaded quality factor (Q u ) of 10.28% and 711, respectively, when calculated from the measured data. Applying the Butterworth Van-Dyke (BVD) model to the measured data enabled the extraction of the resonator's lumped element parameters to calculate the motional quality factor (Q m ), which neglects the contributions of the electrical traces. For the best measured resonator response, results from the BVD model showed a Q m of 1184 and a resulting figure-of-merit (FOM = K 2 ·Q m ) of 100. Comparing the response of similar AlScN and AlN resonators shows that the AlScN LWR has a significantly lower motional resistance (R m ), suggesting that AlScN has a strong potential for use in piezoelectric microelectromechanical oscillators.

42 ENGINEERING↗
DOE OSTI2020

Hybrid semiconductor-piezoacoustic radiofrequency device

An amplifying radiofrequency device includes a piezoelectric film and a semiconductor amplifier layer. The piezoelectric film is conformed as an acoustic waveguide. The piezoelectric film has a principal acoustic propagation direction parallel to the principal conduction direction of the amplifier layer. Interdigitated transducers are positioned on the piezoelectric film to respectively launch an acoustic wave in response to an input RF signal, and transduce the acoustic wave back to an output RF signal. There is a distance of less than the acoustic wavelength between the semiconductor amplifier layer and the piezoelectric film. The piezoelectric film has a thickness of less than the acoustic wavelength. According to a method for making such a device, a stack of III-V layers is epitaxially grown on a III-V substrate, wherein the stack comprises a first etch stop layer, a second etch stop layer, an amplifier layer, and a contact layer. The stack is bonded to a lithium niobate film. The III-V substrate is removed by etching down to the first etch stop layer. Deposition windows are opened by etching from the first etch stop layer down to the contact layer. Metal contact electrodes are deposited in the deposition windows.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Trimming method for microresonators and microresonators made thereby

A micromechanical resonator is disclosed. The resonator includes a resonant micromechanical element. A film of annealable material deposited on a facial surface of the element. In one instance, the resonance of the element can be adjusting by using a feedback loop to control annealing of the deposited film.

42 ENGINEERING↗
DOE OSTI2018

Microsystems-based method and apparatus for passive detection and processing of radio-frequency signals

A radio frequency (RF) receiver comprises a passive impedance transforming voltage amplifier and a resonant, latching micromechanical switch having a deflectable bridge, an RF actuation electrode receivingly connected to the amplifier, and a DC bias electrode positioned to latch the switch in a closed position by electrostatic attraction when energized by a suitable voltage. The bridge is configured with a mechanical mode of vibration that periodically urges the switch toward the closed position.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Method and apparatus of enhanced thermoelectric cooling and power conversion

Methods and apparatus for removing heat from an object for the purpose of cooling or for the purpose of generating electrical power are disclosed. In an embodiment, at least two field-effect transistors (FETs) are operated under inversion. While the FETs are being operated, heat is conducted from the object through body portions of said FETs to an element configured for dissipating the conducted heat.

El-Kady, Fathy Ihab↗
DOE OSTI2018

Lamb Wave Focusing Transducer for Efficient Coupling to Wavelength-Scale Structures in Thin Piezoelectric Films

This study describes the theoretical and experimental investigation of interdigitated transducers (IDTs) capable of producing focused acoustical beams in thin film piezo-electric materials. A mathematical formalism describing focused acoustical beams, Lamb beams, is presented and related to their optical counterparts in two- and three-dimensions. A novel Fourier domain transducer design methodology was developed and utilized to produce near diffraction limited focused beams with in a thin film AlN membrane. The properties of the acoustic beam formed by the transducer were studied by means of Doppler vibrometry implemented with a scanning confocal balanced homodyne interferometer. Fourier domain modal analysis confirmed that 85% of the acoustical power was delivered to the targeted focused beam which was constituted from the lowest order symmetric mode, while 2% was delivered unintentionally to the beam formed from the anti-symmetric mode, and the remaining power was isotropically scattered. The transmission properties of the acoustic beams as they interact with devices with wavelength scale features were also studied, demonstrating minimal insertion loss for devices in which a subwavelength, pinhole apertures was included.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Methods for suppressing spurious modes in microresonators

The present invention relates to methods for suppressing spurious modes in microresonators. In particular embodiments, such spurious modes can be reduced by providing one or more structural components that effectively reduce the acoustic velocity in the transducer domain. Additional methods and microresonators are described herein.

Branch, Darren W.↗
DOE OSTI2018

Attenuation of spurious responses in electromechanical filters

A spur cancelling, electromechanical filter includes a first resonator having a first resonant frequency and one or more first spurious responses, and it also includes, electrically connected to the first resonator, a second resonator having a second resonant frequency and one or more second spurious responses. The first and second resonant frequencies are approximately identical, but the first resonator is physically non-identical to the second resonator. The difference between the resonators makes the respective spurious responses different. This allows for filters constructed from a cascade of these resonators to exhibit reduced spurious responses.

42 ENGINEERING↗
DOE OSTI2018

Second harmonic generation in resonant optical structures

An optical second-harmonic generator (or spontaneous parametric down-converter) includes a microresonator formed of a nonlinear optical medium. The microresonator supports at least two modes that can be phase matched at different frequencies so that light can be converted between them: A first resonant mode having substantially radial polarization and a second resonant mode having substantially vertical polarization. The first and second modes have the same radial order. The thickness of the nonlinear medium is less than one-half the pump wavelength within the medium.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Thermally-isolated silicon-based integrated circuits and related methods

Thermally isolated devices may be formed by performing a series of etches on a silicon-based substrate. As a result of the series of etches, silicon material may be removed from underneath a region of an integrated circuit (IC). The removal of the silicon material from underneath the IC forms a gap between remaining substrate and the integrated circuit, though the integrated circuit remains connected to the substrate via a support bar arrangement that suspends the integrated circuit over the substrate. The creation of this gap functions to release the device from the substrate and create a thermally-isolated integrated circuit.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Single crystal micromechanical resonator

A single crystal micromechanical resonator includes a suspended plate of lithium niobate or lithium tantalate. The suspended plate and a support structure are formed from a single crystal.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Single crystal micromechanical resonator and fabrication methods thereof

The present invention relates to a single crystal micromechanical resonator. In particular, the resonator includes a lithium niobate or lithium tantalate suspended plate. Also provided are improved microfabrication methods of making resonators, which does not rely on complicated wafer bonding, layer fracturing, and mechanical polishing steps. Rather, the methods allow the resonator and its components to be formed from a single crystal.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Methods for dry etching semiconductor devices

The present invention provides methods for etching semiconductor devices, such aluminum nitride resonators. The methods herein allow for devices having improved etch profiles, such that nearly vertical sidewalls can be obtained. In some examples, the method employs a dry etch step with a primary etchant gas that omits BCl.sub.3, a common additive.

36 MATERIALS SCIENCE↗