Enhanced pyroelectric response at morphotropic and field-induced phase transitions in ferroelectric hafnium oxide thin films

Abstract

The hafnium oxide material class is characterized by the coexistence of several polymorphs between which phase transitions are induced by means of composition and external electric fields. Pyroelectric materials, which convert heat into electrical energy, exhibit the largest response at such morphotropic or field-induced phase transitions. The hafnium oxide material system is of special interest for pyroelectric applications since it allows for scalable and semiconductor-compatible fabrication. Here, we report large pyroelectric coefficients at the morphotropic transition from the ferroelectric orthorhombic to the centrosymmetric tetragonal phase. The electric field-induced transition between these two phases in doped HfO2 is found to yield large pyroelectric coefficients of up to −142 µCm−2 K−1, a value that is 20 times larger compared to AlN.

Influence of Si-Doping on 45 nm Thick Ferroelectric ZrO2 Films

“…Moreover, thicker ZrO 2 ferroelectric films may have advantages in certain applications, such as piezoelectric sensors and actuators. 21,22 According to previous investigations, factors such as biaxial in-plane stress, 15,23,24 grain and crystallite size, 24 and doping 13,25,26 are hypothesized to influence ferroelectricity in ZrO 2 thin films. However, these factors have been researched independently, and there is still a lack of studies on their interactions.…”

“…These recent developments will likely act as a catalyst for more in-depth studies of ZrO 2 to understand better the scope and physical mechanisms of ferroelectricity in fluorite-structured materials. Moreover, thicker ZrO 2 ferroelectric films may have advantages in certain applications, such as piezoelectric sensors and actuators. , …”

Influence of the Ozone Dose Time during Atomic Layer Deposition on the Ferroelectric and Pyroelectric Properties of 45 nm-Thick ZrO2 Films

“…In general, after 10 3 cycles with the application of an electric field of 2.4 MV•cm −1 , a fairly linear relationship between p and ε r •ε 0 •P r is shown with an R-square value of 0.91, and the Curie constant (C c = ε r •ε 0 •P r /p) is calculated to be 5.1 ± 0.9•10 −7 K•C•m −1 •V −1 , which is consistent with the reported values in ferroelectric Si-doped HfO 2 thin films. 28,41,42 In addition, the figures of merit of the pyroelectric properties are shown in Table S1.…”

Characteristics of Low‐Energy Phases of Hafnia and Zirconia from Density Functional Theory Calculations

“…HfO 2 and ZrO 2 with their metastable but polar and ferroelectric phase are materials that possess excellent properties for microelectronic and technical applications, [ 1 ] which range from dense nonvolatile memories [ 2,3 ] over thin‐film piezoelectric transducers [ 4 ] to thin‐film pyroelectric devices. [ 5 ] The polymorphism of the phases in HfO 2 and ZrO 2 is still surprising as new relevant phases have been found only recently by simulations, [ 6–8 ] and some experimental findings are still not consistent with the conventionally considered phases, [ 9 ] which are the monoclinic ground‐state m ‐phase ( P2 1 /c , no.…”