Temperature Dependence of the Pyroelectric Coefficient of AlScN Thin Films

Abstract

The piezoelectric and pyroelectric properties of aluminum nitride (AlN) can be further enhanced by alloying AlN with scandium nitride (ScN). However, while the pyroelectric effect can strongly affect the performance of electroacoustic devices such as surface acoustic wave (SAW) resonators, the pyroelectric properties of aluminum scandium nitride (AlScN) and their thermal dependence are not well known. In this work, the crystallographic, microstructural, and pyroelectric properties of 900 nm thick pyroelectric Al 1Àx Sc x N thin films (x ¼ 0 to 0.3) are investigated. All films have wurtzitetype crystal structure and are highly c-axis oriented. The pyroelectric coefficient in the temperature range of 20-80 C is determined by measuring the generated current as a function of sinusoidal temperature excitation. The effective pyroelectric coefficient of AlScN increases by approximately 85% in the investigated composition range. Moreover, no temperature dependence of the effective pyroelectric coefficient is observed for all samples. The increase of the effective pyroelectric coefficient is explained qualitatively by considering the contribution of primary and secondary pyroelectric effect as well as the substrate clamping.

Miniaturized CO2 Gas Sensor Using 20% ScAlN-Based Pyroelectric Detector

“… 44 The pyroelectric coefficient of our 20% ScAlN pyroelectric detectors show ∼11.4 μC/m 2 K at room temperature, slightly higher than those reported in the literature of ∼20% Sc-doped AlN. 44 , 47 Kurz et al 44 reported a pyroelectric coefficient of ∼8 μC/m 2 K at room temperature for 22% Sc-doped AlN and Bette et al 47 reported pyroelectric coefficient ∼9.7 μC/m 2 K for 27% Sc-doped AlN.…”

“…If we consider the following equation 44 , 46 on effective pyroelectric coefficient (ρ eff ) where ρ prim = primary pyroelectric effect, e ij = piezoelectric stress coefficients in Voigt notation, α a and α c = anisotropic linear thermal expansion, d 31 = transversal piezoelectric strain coefficient, s 11 E and s 12 E = elastic compliance coefficient of ScAlN, and α S = linear thermal expansion of substrate; the increase in Sc substitution of Al will result in softening of elastic constants leading to a reduction in s 11 E and s 12 E , increase in piezoelectric stress coefficients ( e 31 and e 33 ), and piezoelectric strain ( d 31 ). The terms (2 e 31 α a + e 33 α c ) and will then increase, leading to increase in effective pyroelectric coefficient.…”

Co-sputtering of $$\hbox {Al}_{1-x}\hbox {Sc}_{x}\hbox {N}$$ thin films on Pt(111): a characterization by Raman and IR spectroscopies

“…Due to the intricate phase diagram of the AlScN alloy, where AlN is predominantly wurtzite on one end, whereas ScN is predominantly cubic on the other one, careful determination of the intermediate stages must be performed. At present, such samples are routinely studied by X-ray diffraction (XRD) [10,16,21], which mainly provides information on the phase composition, the orientation, and the size of AlScN grains. Yet, the success of this method is prone to large volumes of the crystallites probed, and thus, it is not suitable for very thin films or layers within the films.…”

Quantifying Intrinsic, Extrinsic, Dielectric, and Secondary Pyroelectric Responses in PbZr1–xTixO3 Thin Films

“…Due to the ac nature of the pyroelectric measurements, dc-leakage currents induced by applied dc biases do not contribute to the collected i p . The major advantage of this proposed methodology is that it allows researchers to extract extrinsic contributions without the need for free-standing geometries, intricate knowledge of piezoelectric/thermal properties, and/or monodomain-reference samples (something that may not be possible to achieve for all ferroelectric systems). ,− …”