Ultra-low Dissipation Research Articles

Porous polyimide composite films containing mesoporous hollow silica nanospheres with ultralow dielectric constant and dissipation loss

Porous polyimide hybrid films with ultralow dielectric constant and dissipation loss were synthesized during chemical imidization and rapid evaporation of polymer solutions. Polyimide (PI) of bis(4-aminophenyl)-1,4-diisopropylbenzene (BISP) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) were synthesized in N-methylpyrrolidinone (NMP) to yield the corresponding poly(amic acid)s (PAA)s, which were then chemically imidized. To reduce the dielectric properties of the porous PI films, amine-functionalized, surface-modified hollow silica nanoparticles (AHNS) with various sizes from 100 nm to 1 μm, prepared via sol-gel process, were added with PAA at 3, 5, or 10 % weight content, followed by chemical imidization to produce the porous PI/AHNS films. To avoid the high-volume shrinkage of wet gels and maintain the high porosity of the PI with low polarizability, AHNS nanoparticles were added to the porous structure of the PI xerogels as a physical crosslinker. The polyimide hybrid film with 10 nm AHNS nanoparticles at 10 % weight content showed a dielectric constant of 1.151 and a dissipation rate of 0.001 at a frequency of 10 GHz.

Epoxy composite films of superior dielectric properties promoted by active ester hardeners for applications in electronic packaging

Epoxy composites with ultralow dielectric dissipation factors (Df) are highly desired in advanced electronic packaging architectures to cater for high-frequency signal transmission. However, Df of epoxy systems traditionally cured by amine, anhydride or phenolic resin is too high due to the generated high-polarization groups like hydroxyl moieties. Using active esters as curing agents is an effective strategy to reduce polarization of cured epoxy by replacing hydroxyl moieties with ester groups. Herein, diallyl-based active ester hardeners (DAAE) are synthesized via one-step esterification reaction with a high yield of > 90 %. When DAAE is used to cure epoxy films containing SiO2 fillers, the cured epoxy composite films (DAAE-ECFs) demonstrate low dielectric constant (Dk, ∼3.0) and low Df (∼0.005) above 5 GHz at 25 ℃. Importantly, whether immersed in room-temperature water for 24 h or in boiling water for 1 h, DAAE-ECFs absorb < 0.6 wt% water with stable Dk and slightly increased Df (<0.0085). Moreover, DAAE-ECFs show excellent thermal stability (Td5% >365 ℃), dimensional stability (CTE of ∼ 30 ppm ℃-1 below 80 ℃), high storage modulus (∼10 GPa at 30 ℃). The appealing dielectric, thermal and mechanical properties imply that DAAE-ECFs could serve as promising candidates for electronic packaging materials in high-frequency signal transmission.

Scalable polyolefin-based all-organic dielectrics with superior high-temperature capacitive energy storage performance

Polymer dielectrics capable of efficient and stable operation at elevated temperatures (>150 °C) are urgently needed to meet the stringent requirements of capacitive energy storage in harsh environments. However, the current leading commercially available polymer dielectric, biaxially oriented polypropylene (BOPP), can only sustain continuous operation at temperatures below 85 °C due to its limited thermal stability and significant increase in electrical conduction at high temperatures. Here, we present an all-organic polymer composite comprising nonpolar polyolefin and organic semiconductor that demonstrates superior dielectric and capacitive energy storage performance at 150 °C. Notably, the dielectric properties of the polymer composite remain stable across a broad temperature range, exhibiting an ultralow dissipation factor at elevated temperatures. Benefiting from the deep trap energy levels introduced by the organic semiconductor, the composite film achieves one order of magnitude reduction in electrical conductivity. As a result, the composite film attains discharged energy densities of 7.1 J/cm3 and 5.5 J/cm3 with a charge-discharge efficiency of 90 % at 25 °C and 150 °C, respectively. Furthermore, the composite film maintains stable capacitive performance over extended charge-discharge cycles (50,000 cycles) in harsh environments (500 MV/m and 150 °C), along with excellent breakdown self-healing capability. These remarkable performances, coupled with the potential for large-scale production using commercially available raw materials, highlight the practically viability of the composite film for high-temperature capacitive energy storage applications.

Poly(ester imide)s with Low Linear Coefficients of Thermal Expansion and Low Water Uptake (VII): A Strategy to Achieve Ultra-Low Dissipation Factors at 10 GHz.

In this study, a series of ester-linked tetracarboxylic dianhydrides (TCDAs) with 2,6-naphthalene-containing longitudinally extended structures consisting of different numbers of aromatic rings (NAr = 6-8) was synthesized to obtain novel modified polyimides, poly(ester imide)s (PEsIs). These TCDAs were fully compatible with the conventional manufacturing processes of conventional polyimide (PI) systems. As an example, the PEsI film obtained from the ester-linked TCDA (NAr = 8) and an ester-linked diamine achieved unprecedented outstanding dielectric properties without the support of fluorinated monomers, specifically an ultra-low dissipation factor (tan δ) of 0.00128 at a frequency of 10 GHz (50% RH and 23 °C), in addition to an extremely high glass transition temperature (Tg) of 365 °C, extremely low linear coefficient of thermal expansion (CTE) of 6.8 ppm K-1, suppressed water uptake (0.24%), requisite film ductility, and a low haze. Consequently, certain PEsI films developed in this study are promising candidates for heat-resistant dielectric substrates for use in 5G-compatible high-speed flexible printed circuit boards (FPCs). The chemical and physical factors denominating tan δ are also discussed.

Design of deeply cooled ultra-low dissipation amplifier and measuring cell for quantum measurements with a microwave single-photon counter

The requirements and details of designing a measuring cell and low-back-action deeply-cooled amplifier for quantum measurements at 10 mK are discussed. This equipment is a part of a microwave single-photon counter based on a superconducting flux qubit. The high-electron mobility transistors (HEMTs) in the amplifier operate in unsaturated microcurrent regime and dissipate only 1 μW of dc power per transistor. Simulated amplifier gain is 15 dB at 450 MHz with a high-impedance (≈ 5 kΩ) signal source and standard 50-Ω output.

High-Q Trampoline Resonators from Strained Crystalline InGaP for Integrated Free-Space Optomechanics.

Nanomechanical resonators realized from tensile-strained materials reach ultralow mechanical dissipation in the kHz to MHz frequency range. Tensile-strained crystalline materials that are compatible with epitaxial growth of heterostructures would thereby at the same time allow realizing monolithic free-space optomechanical devices, which benefit from stability, ultrasmall mode volumes, and scalability. In our work, we demonstrate nanomechanical string and trampoline resonators made from tensile-strained InGaP, which is a crystalline material that is epitaxially grown on an AlGaAs heterostructure. We characterize the mechanical properties of suspended InGaP nanostrings, such as anisotropic stress, yield strength, and intrinsic quality factor. We find that the latter degrades over time. We reach mechanical quality factors surpassing 107 at room temperature with a Q·f product as high as 7 × 1011Hz with trampoline-shaped resonators. The trampoline is patterned with a photonic crystal to engineer its out-of-plane reflectivity, desired for efficient signal transduction of mechanical motion to light.

Unraveling electronic fluctuation in passivation hypothesis for ultralow friction in diamond

Passivation hypothesis has been widely applied to interpret the outstanding tribological properties of diamond, where the ultralow friction is often attributed to the static charge repulsion between the passivated sliding surfaces. However, the action of the dynamic charge of the contact in the sliding process is still open. Here, the mechanism of passivation hypothesis is disassembled by the electronic fluctuation in the ultralow friction sliding. Typical frictional systems of diamond contact surfaces, ranging from different crystallographic structures and interfacial passivated groups, are studied by using density-functional theory (DFT) calculations. The charge density evolution along the sliding pathway is investigated to track the frictional energy dissipation in the mutual sliding between the passivated surfaces. It finds that the shallow energy corrugation synchronously varies with the charge redistribution during the slip, giving a linear dependence of ultralow friction on the electronic fluctuation acting within the sliding interfaces. The proportionality coefficient, which indicates the response of charge density in the ultralow dissipation, gives intrinsic quantity of the friction systems and is mainly determined by both the passivation groups and the lattice parameters of the sliding surfaces. Therefore, we demonstrate the dynamic fluctuation of charge density along the sliding direction underlies the mechanism of passivation hypothesis. An electronic fluctuation model is proposed to interpret the passivation hypothesis for guiding the design of superlubric diamond-like carbon (DLC). This is in contrast with the paradigm that the super-low friction is determined by the static charge repulsion.

Suppressing mechanical dissipation of diamagnetically levitated oscillator via engineering conductive geometry

Diamagnetically levitated oscillators of millimeter and submillimeter size are emerging ultrasensitive sensors for gravitylike force and acceleration measurements. However, improving the levitation capability while keeping mechanical dissipation low remains an open challenge. Here, we propose and experimentally demonstrate an engineering conductive geometry scheme to efficiently reduce the mechanical dissipation of a diamagnetically levitated oscillator made of pyrolytic graphite. We show that with a specially designed conductive geometry, the eddy current damping is reduced, and the reduction factor increases as the engraving pattern being denser. Under high vacuum and room temperature, eddy current damping is the dominant contribution to mechanical dissipation, and we reduce it by a factor of 50 in the experiment. Our work opens up a new way to achieve diamagnetically levitated oscillator with ultralow mechanical dissipation and strong levitation capability, a candidate platform for studying a broad range of fundamental physics.

Design and implementation reversible multiplexer using quantum-dot cellular automata approach

Rapid progress in the field of nanotechnology includes using quantum dot-cellular automata (QCA) as a replacement for conventional transistor-based complementary metal oxide semiconductor (CMOS) circuits in the construction of nano-circuits. Due to ultra low thermal dissipation, rapid clocking, and extremely high density, the QCA is a rapidly growing field in the nanotechnological field to inhibit the field effect transistor (FET)-based circuit. This paper discusses and evaluates two multiplexer (MUX) architectures: an innovative and effective 4×1 MUX structure and an 8×1 MUX structures using QCA technology. The suggested architectural designs are constructed using the Fredkin and controlled-NOT (CNOT) gates. These constructions were designed to simulate using tool QCA designer 2.0.3. The 591 and 1,615 cells would be used by the 4×1 and 8×1 QCA MUX architectures, respectively. The simulation results demonstrate that, when compared to the previous QCA MUX structures, the suggested QCA MUX designs have the best clock latency performance and use of different gate types.

Investigation of the structure–dielectric relationship of polyimides with ultralow dielectric constant and dissipation factors using density functional theory

Polyimides (PIs) possessing both low dielectric constant (Dk) and dissipation factor (Df) remain an intriguing study for the ever-increasing demand for the high frequency transmission of signals. In this study, the relationship between the chemical structures and the dielectric properties of PIs were comprehensively investigated. 35 kinds of PIs with different types of functional groups such as ester, fluorine and ether were prepared via the polyaddition and the subsequent thermal imidization. Their chemical structures and physical properties including the mechanical and dielectric properties were systematically studied. We found that the additive group contribution method failed to provide an effective correlation on the PIs with low Dk and Df values, and it is incapable of distinguishing geometry isomers of PIs. Herein, by utilizing the density functional theory simulation, we successfully remedied those issues. The Dk and Df values of PIs provided strong correlations with volumetric polarizability and volumetric dipole moment. The results elaborated the effect of the interchain behavior to the Dk values and the impact of the chain rigidity on the Df values of PIs. Combining with the molar volume derived from the film density, and a correction factor expressing the polymer rigidity, we eventually established a confident correlation of Dk and Df values with the structure parameters of PIs, respectively. In the meantime, this study interprets the guidelines for the design on PIs molecular structure which sheds light on the development of the insulating materials at high frequencies.

Hierarchical tensile structures with ultralow mechanical dissipation

Structural hierarchy is found in myriad biological systems and has improved man-made structures ranging from the Eiffel tower to optical cavities. In mechanical resonators whose rigidity is provided by static tension, structural hierarchy can reduce the dissipation of the fundamental mode to ultralow levels due to an unconventional form of soft clamping. Here, we apply hierarchical design to silicon nitride nanomechanical resonators and realize binary tree-shaped resonators with room temperature quality factors as high as 7.8 × 108 at 107 kHz frequency (1.1 × 109 at T = 6 K). The resonators’ thermal-noise-limited force sensitivities reach 740 zN/Hz1/2 at room temperature and 90 zN/Hz1/2 at 6 K, surpassing state-of-the-art cantilevers currently used for force microscopy. Moreover, we demonstrate hierarchically structured, ultralow dissipation membranes suitable for interferometric position measurements in Fabry-Pérot cavities. Hierarchical nanomechanical resonators open new avenues in force sensing, signal transduction and quantum optomechanics, where low dissipation is paramount and operation with the fundamental mode is often advantageous.

Strained crystalline nanomechanical resonators with quality factors above 10 billion

In strained mechanical resonators, the concurrence of tensile stress and geometric nonlinearity dramatically reduces dissipation. This phenomenon, called dissipation dilution, is employed in mirror suspensions of gravitational-wave interferometers and at the nanoscale, where soft clamping and strain engineering have allowed extremely high quality factors. However, these techniques have so far been applied only to amorphous materials, specifically Si3N4. Crystalline materials exhibit substantially lower intrinsic damping at cryogenic temperatures. Applying dissipation dilution engineering to strained crystalline materials could, therefore, enable extremely low loss nanomechanical resonators, as they combine low internal friction, high intrinsic strain and high yield strength. This potential has not yet been fully exploited. Here we demonstrate that single-crystal strained silicon—a material developed for high-mobility transistors—can be used to realize mechanical resonators with ultralow dissipation. We fabricate strained silicon nanostrings with high aspect ratios supporting megahertz mechanical modes with quality factors exceeding 1010 at 7 K, a tenfold improvement over values reported in Si3N4. We estimate a thermal-noise-limited force sensitivity of (5 ± 2) × 10–20 N Hz–1/2 at 7 K—approaching that of carbon nanotubes—and a heating rate of only 60 quanta per second. The low mass and high quality factors of our nanomechanical resonators make them particularly promising for quantum sensing and transduction. Soft clamping reduces the dissipation of nanomechanical resonators, but this method has been limited to amorphous materials. When applied in crystalline silicon, it enables resonators with quality factors beyond ten billion.

Ultra-coherent nanomechanical resonators based on inverse design

Engineered micro- and nanomechanical resonators with ultra-low dissipation constitute a promising platform for various quantum technologies and foundational research. Traditionally, the improvement of the resonator’s performance through nanomechanical structural engineering has been driven by human intuition and insight. Such an approach is inefficient and leaves aside a plethora of unexplored mechanical designs that potentially achieve better performance. Here, we use a computer-aided inverse design approach known as topology optimization to structurally design mechanical resonators with optimized performance of the fundamental mechanical mode. Using the outcomes of this approach, we fabricate and characterize ultra-coherent nanomechanical resonators with, to the best of our knowledge, record-high Q ⋅ f products for their fundamental mode (where Q is the quality factor and f is the frequency). The proposed approach - which can also be used to improve phononic crystals and coupled-mode resonators - opens up a new paradigm for designing ultra-coherent micro- and nanomechanical resonators, enabling e.g. novel experiments in fundamental physics and extreme sensing.

Study of Thermal Conductivity in Two-dimensional Bi2Te3 from Micro- Raman Spectroscopy

Background: Topological insulator (TI), Bi2Te3 is a new class of quantum materials. Having ultralow dissipation surface states, TIs hold great promise toward different potential applications. Micro-Raman spectroscopy is a conventional and non-destructive technique, which has been widely used to characterize the structural and electronic properties of thermoelectric materials. Objective: The objective of this study is to review power dependent and temperature dependent Raman spectra of B2Te3 nanoflakes on SiO2/Si substrate to estimate the temperature coefficient and thermal conductivity of these flakes for possible application of this material in thermoelectrics. Methods: Bi2Te3 flakes of different thicknesses were mechanically exfoliated from high-quality bulk Bi2Te3 crystal using scotch tape on 300 nm SiO2/ Si substrates. The power dependent and temperature dependent Raman spectra were acquired with the help of HORIBA LabRAM confocal micro- Raman system in a backscattering geometry. Result: The observed power dependent and temperature dependent Raman spectra of Bi2Te3 nanoflakes follow the same trend as discussed in various pieces of literature. From temperature coefficient and power coefficient values, the in-plane thermal conductivity has been estimated, which is found to be in the order of 102 W/m-K. The enhancement in the thermal conductivity suggests that the underlying substrate significantly affects the heat dissipation of the Bi2Te3 flake based on the coupling strength with Bi2Te3. Conclusion: This work provides a good platform to understand the role of the substrate on the thermal conductivity of exfoliated Bi2Te3 nanoflakes and this study can be extended to other substrates.

Mechanical Dissipation Below 1μHz with a Cryogenic Diamagnetic Levitated Micro-Oscillator

Ultralow dissipation plays an important role in sensing applications and exploring macroscopic quantum phenomena using micro-and nano-mechanical systems. We report a diamagnetic-levitated micro-mechanical oscillator operating at a low temperature of 3K with measured dissipation as low as 0.59 $\mu$Hz and a quality factor as high as $2 \times 10^7$. To the best of our knowledge the achieved dissipation is the lowest in micro- and nano-mechanical systems to date, orders of magnitude improvement over the reported state-of-the-art systems based on different principles. The cryogenic diamagnetic-levitated oscillator described here is applicable to a wide range of mass, making it a good candidate for measuring both force and acceleration with ultra-high sensitivity. By virtue of the naturally existing strong magnetic gradient, this system has great potential in quantum spin mechanics study.

Strain-Mediated Giant Magnetoelectric Coupling in a Crystalline Multiferroic Heterostructure.

Multiferroic heterostructures based on the strain-mediated mechanism present ultralow heat dissipation and large magnetoelectric coupling coefficient, two conditions that require endless improvement for the design of fast nonvolatile random access memories with reduced power consumption. This work shows that a structure consisting of a [Pb(Mg1/3Nb2/3)O3]0.7-[PbTiO3]0.3 (001) substrate on which a crystalline FeGa(001)/MgO(001) bilayer is deposited exhibits a giant magnetoelectric coupling coefficient of order 15 × 10–6 s m–1 at room temperature. That result is a 2-fold increment over the previous highest value. The spatial orientation of the magnetization vector in the epitaxial FeGa film is switched 90° with the application of electric field. The symmetry of the magnetic anisotropy is studied by the angular dependence of the remanent magnetization, demonstrating that poling the sample generates a switchable uniaxial magnetoelastic anisotropy in the film that overcomes the native low 4-fold magnetocrystalline anisotropy energy. Magnetic force microscopy shows that the switch of the easy axis activates the displacement of domain walls and the domain structures remain stable after that point. This result highlights the interest in single-crystalline structures including materials with large magnetoelastic coupling and small magnetocrystalline anisotropy for low-energy-consuming spintronic applications.

Strain-induced Megahertz Oscillation and Stable Velocity of an Antiferromagnetic Domain Wall

Manipulation of magnetic domain walls (DWs) in an antiferromagnet plays a fundamental role in developing antiferromagnetic (AFM) devices with small size and high velocity for information processing. On the other hand, in addition to the ultrahigh-frequency (THz) AFM magnetization precession, recent investigation shows that an antiferromagnet may also exhibit unique dynamical behaviors at a lower frequency (GHz) by an optical method. In this work, we predict the characteristic frequency of AFM magnetization dynamics can be further widened to MHz by triggering the oscillation of an AFM DW under a stress that is a sinusoidal function in a spatial coordinate. This low frequency is due to the mismatch of size between the spatial period of stress and DW width. Based on this low-frequency oscillation, DW can move at an almost constant velocity by shifting the phase of stress. The proposition in this work paves the way to develop AFM devices with small size and ultralow dissipation.

Precision Deep Reactive Ion Etching of Monocrystalline 4H-SiCOI for Bulk Acoustic Wave Resonators with Ultra-Low Dissipation

Integrated mechanical resonators with high quality factors (Q) made in high acoustic velocity materials are essential for a wide range of applications, including chemical sensors, timing resonators, and high-performance inertial sensors for navigation in GPS-occluded environments. While silicon is the most popular substrate for the implementation of microelectromechanical systems (MEMS) resonators, SiC exhibits an exceptionally small intrinsic phononic dissipation due to its low Akhiezer damping limit. This paper reports on the latest developments of precision deep reactive ion etching (DRIE) of monocrystalline 4H SiC-on-Insulator (SiCOI) substrates with the aim to fully take advantage of the exquisite mechanical properties of crystalline SiC. To wit, capacitive Lamé mode micromechanical resonators exhibit ƒ·Q products beyond 1 × 1014 Hz independent of crystalline orientation. The contribution of surface roughness to dissipation and practical considerations to etch mirror-polished trenches in SiCOI substrates are discussed, paving the way towards micromechanical monocrystalline SiC resonators with Qs beyond 100 Million.

Testing dissipative collapse models with a levitated micromagnet

We present experimental tests of dissipative extensions of spontaneous wave function collapse models based on a levitated micromagnet with ultralow dissipation. The spherical micromagnet, with radius $R=27$ $\mu$m, is levitated by Meissner effect in a lead trap at $4.2$ K and its motion is detected by a SQUID. We perform accurate ringdown measurements on the vertical translational mode with frequency $57$ Hz, and infer the residual damping at vanishing pressure $\gamma/2\pi<9$ $\mu$Hz. From this upper limit we derive improved bounds on the dissipative versions of the CSL (continuous spontaneous localization) and the DP (Di\'{o}si-Penrose) models with proper choices of the reference mass. In particular, dissipative models give rise to an intrinsic damping of an isolated system with the effect parameterized by a temperature constant; the dissipative CSL model with temperatures below 1 nK is ruled out, while the dissipative DP model is excluded for temperatures below $10^{-13}$ K. Furthermore, we present the first bounds on dissipative effects in a more recent model, which relates the wave function collapse to fluctuations of a generalized complex-valued spacetime metric.

(Invited) Nano-Precision Deep Reactive Ion Etching of Monocrystalline 4H-SiCOI for Bulk Acoustic Wave Resonators with Ultra-Low Dissipation

Introduction Micromechanical resonators with ultra-low energy dissipation are essential for a wide range of applications, including chemical sensors, and inertial sensors for navigation in GPS-occluded environments [1]. While ease of batch fabrication along with high-fidelity wafer-level processing have made monocrystalline silicon (Si) the preeminent substrate for seamlessly integrated microelectromechanical systems (MEMS), Si may not be suited to address the ever-growing demand for high-precision MEMS instruments robust to harsh environments. As the quest for low dissipation is plateauing with the direct observation of Si’s quantum limit, monocrystalline Silicon Carbide (SiC) is under active investigation for its promise of room-temperature mechanical Qs exceeding 100M at 6 MHz, owing to its extraordinary Akhiezer damping, which sits 30x below that of Si. Such high Qs are critical to demonstrate navigation-grade resonant gyroscopes with Angle Random Walk (ARW) near 0.00017°√hr, matching the performance of ring laser gyroscopes while being potentially vastly more portable and affordable. Ultra-low Dissipation SiC Resonators This paper reports on the implementation of capacitive SiC resonators with micron-scale transduction gaps, exhibiting fQ=1.25x1014 Hz, a 5-fold improvement over Si’s limits which has already been reported in [3]. These results are particularly interesting because SiC is more susceptible to thermoelastic damping (TED) than Si, by a factor near 5x. To break through the barrier set by material properties that grant an inferior Q TED limit, we have fabricated clamped-clamped beam [4], bulk acoustic wave (BAW) disk [5-6], and Lamé mode resonators [3] using high-density plasma etching of monocrystalline 4H-SiC-on-Insulator (SiCOI) fusion-bonded substrates in STS AOE. We have experimentally verified that these resonators have a decreasing susceptibility to TED in accordance with COMSOL simulations. While the volume-preserving Lamé mode is virtually TED-free in a tether-less square configuration, the unavoidable introduction of tethers and sidewall roughness due to the finite precision of deep reactive ion etching (DRIE) of SiC exacerbates TED. Method While the overarching fabrication details have been published elsewhere [3-6], the SiC DRIE optimization in STS AOE is presented here for the fist time. Plasma etching of SiC can be accompanied by the undesired formation of micropillars because the metallofluorinated NiCxFy compound accumulates on the sidewall and flakes off under various conditions. This issue is circumvented by tailoring the DRIE recipe to reduce the growth rate of the passivation layer. With that in mind, we typically flow an excess of Ar compared to SF6 to starve the trenches from F-based species that tend to polymerize with exposed C atoms. We optimize the coil and platen power to generate a self-bias DC voltage of nearly 280V and reduce the pressure to 8mTorr to prevent any sidewall damage due to the lack of passivation on the sidewall. Results and Conclusions Fig. 1 reveals that selecting bulk acoustic wave (BAW) mode resonators and operating deep in their adiabatic regime enables to the barrier set by TED in monocrystalline SiC, unlike for flexural resonator that operate near the Debye peak. However, surface TED can still limit Q if asperities form on the sidewall of the SiC BAW resonators; we prevent their formation by tailoring the DRIE recipe to limit the deposition of the NiCxFy passivation and by intermittently removing the passivation in wet etchants (Fig. 2). Moreover, removing the passivation enables to etch high-aspect-ratio trenches in SiCOI wafers with nanoscale smoothness (Fig. 3). By designing acoustically deaf SiC Lamé resonators [3], we reveal that SiCOI substrates can support ultra-low dissipation resonators, which fQ=1.25x10 14 Hz, 5x improvement over the limit of monocrystalline Si (Fig. 4). Through the development of nano-scale precision SiC DRIE, this paper opens the door to a myriad of high-performance chip-scale SiC instruments that can be deployed in harsh environments.