Toward 40 GHz excitation of diamond-based HBAR

Abstract

We have obtained an excitation of longitudinal bulk acoustic waves in a diamond-based High overtone Bulk Acoustic Resonator (HBAR) at microwave and enhanced frequency bands as EHF up to 40 GHz. As an effective piezoelectric transducer, an aluminum-scandium nitride film is employed. The frequency response of acoustic overtones excited in the HBARs with a different aperture in the 1.0 up to 40 GHz range is measured. Some peculiarities of HBAR's frequency response concerned with the thin film piezoelectric transducer are studied. It is established that the maximal magnitude of the quality factor varies near the value of about 10 000 within all the frequency bands investigated. The approximately frequency-independent Q-factor behavior can explain in terms the Landau–Rumer approximation describing the acoustic attenuation in a diamond. An estimation of the HBAR's quality parameter as Q × f ≈ 4 × 1014 Hz at 40 GHz is obtained. In our opinion, that value exceeds all known data among the given devices. The results obtained will be helpful in the development of microwave and EHF acoustic resonators as well as highly sensitive acoustic sensors. The development of the EHF band opens up the possibility of obtaining acoustic waves of submicrometer and nanometer scales (in various media) and implementing acoustic studies of micro- and nanoobjects.

Peculiarities of the Acoustic Wave Propagation in Diamond-Based Multilayer Piezoelectric Structures as “Me1/(Al,Sc)N/Me2/(100) Diamond/Me3” and “Me1/AlN/Me2/(100) Diamond/Me3” under Metal Thin-Film Deposition

“…Electronics 2022, 11, x FOR PEER REVIEW 3 of 11 tenuation in diamond [17]. The L-BAW excitation of the diamond-based HBAR in the extremely high frequency band up to 40 GHz was published in [18]. A quality factor of ~10,000 at 40 GHz was obtained.…”

“…Piezoelectric films of aluminum nitride AlN and aluminum-scandium nitride (Al,Sc)N were used in the thin-film piezoelectric transducers (TFPT) as Me1/AlN/Me2 or Me1/(Al,Sc)N/Me2 to excite the longitudinal bulk acoustic wave (L-BAW). However, the application of aluminum-scandium nitride leads to more effective electromechanical excitation of L-BAW as an HBAR operational mode even in the extremely high-frequency band [18]. Figure 1 represents an example of such a sensory element based on the MPS "Pt/(Al,Sc)N/Pt/(001) diamond" (Sc content 15%).…”

“…After that, the shift of the overtone's resonant frequency and quality factors were measured. The process of the frequency response measurement of HBAR by the E5071C Agilent network analyzer was described in detail in [18]. The operational checkpoint frequencies were selected for every sensor separately, and the overtones with the highest quality factor or highest impedance response were prioritized.…”

“…It is shown that the diamond-based HBAR's quality factor of about 12,500 at ~20 GHz remained at such a high value only owing to Landau-Rumer's mechanism of microwave acoustic attenuation in diamond [17]. The L-BAW excitation of the diamond-based HBAR in the extremely high frequency band up to 40 GHz was published in [18]. A quality factor of ~10,000 at 40 GHz was obtained.…”

X–Ka Band Epitaxial ScAlN/AlN/NbN/SiC High-Overtone Bulk Acoustic Resonators

“…The high frequency and power handling requirements for applications such as millimeter wave radar and 5G FR2 require novel strategies. Composite or overtone resonators, including high overtone mode bulk acoustic resonators (HBARs) are a promising solution [2], [3], [4], [5], [6]. HBARs are thin film metal/piezoelectric/metal transducers on a thicker substrate (Fig.…”