Effect of Deep-Defects Excitation on Mechanical Energy Dissipation of Single-Crystal Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-11-12 |
| Journal | Physical Review Letters |
| Authors | Huanying Sun, Liwen Sang, Haihua Wu, Zilong Zhang, Tokuyuki Teraji |
| Institutions | Institute of Microelectronics, Tsinghua University |
| Citations | 22 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study investigates the intrinsic mechanical energy dissipation (Quality factor, Q) in Single-Crystal Diamond (SCD) mechanical resonators across a wide temperature range (Room Temperature up to 973 K). The findings are critical for optimizing diamond NEMS/MEMS devices for high-performance sensing and quantum applications.
- High Q Performance: SCD cantilevers maintained high Q factors, consistently greater than 10,000, across the entire temperature range, with a maximum Q factor observed near 200,000.
- Deep Defect Activation: Energy dissipation is governed by the thermal activation of deep mechanical defects (MD) at elevated temperatures, leading to two distinct local maxima in the Q factor near 400 K and 900 K.
- Defect Identification: The 400 K peak is attributed to Defect D1 (Boron-related impurities) with an activation energy of 0.31-0.33 eV. The 900 K peak is attributed to Defect D2 (Nitrogen-related impurities) with an activation energy of 0.91-0.92 eV.
- Intrinsic Low Loss: The deep-energy nature of the primary unintentional impurity (Nitrogen, D2) ensures that SCD maintains outstandingly low intrinsic energy dissipation at Room Temperature (RT) and above, unlike narrow-bandgap semiconductors where dopants are fully ionized at RT.
- Engineering Implication: Removing Boron impurities (D1) can substantially increase the RT quality factor of diamond mechanical resonators, confirming diamond as an ideal candidate for intrinsically high-Q devices.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Measurement Temperature Range | RT to 973 | K | Range for Q factor and resonance frequency analysis. |
| Maximum Observed Q Factor | ~200,000 | Dimensionless | Observed near 400 K (Sample DS1, Cantilever III-4). |
| Minimum Q Factor (Range) | >10,000 | Dimensionless | Maintained across the full temperature range (RT to 973 K). |
| Diamond Bandgap (UWBG) | 5.5 | eV | Ultra-wide bandgap characteristic. |
| Youngâs Modulus (E0) | 1100 | GPa | Used for theoretical fitting of resonance frequency. |
| Mass Density (rho) | 3.5 | g/cm3 | Used for theoretical fitting. |
| Defect D1 Activation Energy | 0.31 - 0.33 | eV | Associated with Boron acceptors; causes Q peak near 400 K. |
| Defect D2 Activation Energy | 0.91 - 0.92 | eV | Associated with Nitrogen impurities; causes Q peak near 900 K. |
| Cantilever Thickness (t) | 1.44 | ”m | Standard thickness for tested SCD cantilevers. |
| Measurement Vacuum Pressure | ~10-4 | Pa | High vacuum used to eliminate air damping. |
| Boron Doping Concentration (DS3) | 5 x 1018 | /cm3 | Concentration in the sample used for comparison (DS3). |
Key Methodologies
Section titled âKey MethodologiesâThe SCD cantilevers were fabricated and characterized using precise micro- and nano-electromechanical techniques:
- Fabrication Method: SCD cantilevers were created using a smart-cut method, resulting in an SCD-on-SCD structure.
- Defect Removal Annealing: Cantilevers were processed in an oxygen ambient at 773 K to remove ion-irradiated defects from the bottom layer.
- Surface Preparation: Before detailed measurements, the SCD cantilevers were annealed at 1000 K for 1 hour to exclude the effect of surface adsorbates on Q factors and resonance frequencies.
- Actuation: The out-of-plane resonance of the cantilevers was actuated by applying a radio-frequency signal to a probe placed adjacent to the structure.
- Detection: Resonance frequencies were measured using a laser Doppler vibrometer.
- Environmental Control: Measurements were conducted in a high vacuum environment (approximately 10-4 Pa) to ensure intrinsic mechanical dissipation was measured without air damping.
- Temperature Sweep: Temperature was controlled from RT up to 1000 K in 25 K steps using a Lake Shore Model 335 controller.
- Q Factor Determination: Q factors were calculated as Q = omega/Delta omega, where the measured resonance frequency spectra were fitted based on the Lorentzian line shape.
Commercial Applications
Section titled âCommercial ApplicationsâThe demonstrated high Q factors and thermal stability of SCD mechanical resonators, particularly due to the deep-defect nature of Nitrogen, enable several advanced engineering applications:
- Quantum Sensing and Control:
- Essential for coupling mechanical resonators with Nitrogen-Vacancy (NV) centers for ultra-sensitive quantum spin detection and quantum control systems.
- Ultra-sensitive MEMS/NEMS Sensors:
- Development of next-generation ultra-sensitive sensors for measuring mass, force, and single molecules, where low intrinsic energy dissipation is paramount for high resolution.
- High-Temperature Electronics and Sensors:
- Diamondâs ability to maintain high Q factors and mechanical stability up to 973 K makes it ideal for sensors and resonators operating in harsh, high-temperature environments (e.g., aerospace, industrial monitoring).
- High-Frequency Resonators:
- Supports the fabrication of diamond mechanical resonators capable of operating in the gigahertz range with high Q factors (reported up to 106).
- Material Science and Defect Engineering:
- The methodology provides a tool for controlling and optimizing the Q factor in other Ultra-Wide Bandgap (UWBG) semiconductors by engineering the concentration and activation energy of deep defects.
View Original Abstract
The ultrawide band gap of diamond distinguishes it from other semiconductors, in that all known defects have deep energy levels that are less active at room temperature. Here, we present the effect of deep defects on the mechanical energy dissipation of single-crystal diamond experimentally and theoretically up to 973 K. Energy dissipation is found to increase with temperature and exhibits local maxima due to the interaction between phonons and deep defects activated at specific temperatures. A two-level model with deep energies is proposed to explain well the energy dissipation at elevated temperatures. It is evident that the removal of boron impurities can substantially increase the quality factor of room-temperature diamond mechanical resonators. The deep energy nature of the defects bestows single-crystal diamond with outstanding low intrinsic energy dissipation in mechanical resonators at room temperature or above.