Application of Thin Piezoelectric Films in Diamond-Based Acoustoelectronic Devices

Abstract

The theory of external loading influence on acoustic parameters of piezoelectric fivelayered structure as "Al/(001) AlN/Mo/(001) diamond/Me" has been developed. Oscillations in diamond-based high-overtone bulk acoustic resonators (HBARs) have been investigated in terms of 3D FEM simulation. Peculiarities of technology of aluminum-scandium nitride (ASN) films have been discussed. Composition Al 0.8 Sc 0.2 N was obtained to create the diamond-based HBAR and SAW resonator. Application of ASN films has resulted in a drastic increasing an electromechanical coupling up to 2.5 times in comparison with aluminum nitride. Development of ASN technology in a way of producing a number of compositions with the better piezoelectric properties has a clear prospective. SAW resonator based on "Al IDT/(001) AlN/(001) diamond" structure has been investigated in the band 400-1500 MHz. The highest-quality factor Q ≈ 1050 was observed for the Sezawa mode at 1412 MHz. Method of measuring HBAR's parameters within 4-400 K at 0.5-5 GHz has been developed. Results on temperature dependence of diamond's Qfactor at relatively low frequencies were quite different in comparison with the ones at the frequencies up to 5 GHz. Difference could be explained in terms of changing mechanism of acoustic attenuation from Akhiezer's type to the Landau-Rumer's one at higher frequencies in diamond.

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

“…The basis is that the frequency response of an HBAR is closely concerned with the TFPT frequency dependence, where the minimal and maximal Q values should be observed in the vicinity of the points where the conditions 𝑑 𝑛 λ 4 or 𝑑 𝑚 λ 2 are fulfilled, respectively. Here, d is the TFPT thickness, λ is the wavelength in piezoelectric material, and n = 1, 3, …; m = 1, 2, … For more detail, see [20]. An example of a mentioned dependence is presented in Figure 5e.…”

“…Recently, we obtained a Patent RF dedicated to the diamond-based microwave acoustic mass sensor [19]. Earlier, by means of diamond-based HBAR as a sensor, the deposition of thin and ultrathin metal films such as Mo, Al,Sc, and Pt was experimentally studied [20][21][22]. A new useful approach for analyzing the wave propagation in piezoelectric nano-size plates under special boundary conditions was proposed in [23].…”

Microwave Diamond-Based HBAR as a Highly Sensitive Sensor for Multiple Applications: Acoustic Attenuation in the Mo Film

“…It is important to highlight that the aluminum-scandium nitride Al 1-x Sc x N (ASN) piezoelectric film was provided with L-type acoustic wave excitation in a frequency band up to 40 GHz [15]. Earlier, diamond-based HBAR sensors using the "Me1/(Al,Sc)N/Me2/(100) diamond/Me3" and "Me1/AlN/Me2/(100) diamond/Me3" structures were applied to study the thin and ultrathin metal films such as Mo, Al, Sc, and Pt [17][18][19][20]. The thickness sensitivity under the Pt deposition was estimated as ±0.5 nm.…”