Compared to traditional perovskite ferroelectric materials, HfO₂ has emerged as a prominent research focus due to its ability to retain significant ferroelectricity at the nanoscale. However, systematic studies on its performance in thicker films remain limited, leaving the intrinsic relationship between thickness variation and ferroelectric properties poorly understood. In this work, we successfully fabricated doped HfO₂-based ferroelectric thin films with thicknesses spanning tens to hundreds of nanometers. All these films exhibit robust ferroelectric characteristics, and their ferroelectric properties demonstrate a non-monotonic evolution with increasing thickness. Macroscopic electrical measurements and mesoscale domain switching analysis confirmed that the ferroelectric properties of Ce:HfO₂ films first diminish and then recover with the increase of film thickness. By further characterizing the evolution of microscopic structures, we elucidate the thickness effects on the grain size distribution and domain structure evolution. This framework clarifies the physical mechanism underlying the thickness-dependent ferroelectric behavior. Our findings provide critical experimental evidence for developing large-scale HfO₂-based ferroelectric devices and lay a theoretical foundation for optimizing thick-film ferroelectric materials for practical applications.

Flexible and transparent hafnium oxide-based ferroelectric films are attracting widespread attention because of the increasing demand for wearable electronic devices. However, the ultra-low voltage operation with robust and stable ferroelectricity, which is a prerequisite for portable device applications, has not been realized simultaneously. Here, we report flexible Hf_0.5Zr_0.5O₂ ferroelectric films with a saturation voltage of only 1.3/3 V and remanent polarization (2P_r) of 38/60 µC·cm². Negligible wake-up effect and superior stability resistance to compressive/tensile stress and high temperature up to 150 °C are also demonstrated. The polarization switching dynamics under bending are investigated based on the switching current measurement, suggesting that the intrinsic switching speeds keep almost constant at different bending radii. In addition, there is a negative correlation between the activation field and the compressive or tensile stress, which is due to the lowered energy barrier induced by the in-plane strain applied to the [111]-oriented hexagonal cell. Our work sheds light on the application of flexible, stable, and HfO₂-based ferroelectric thin films with ultra-low consumption.

Ferroelectric materials are ideal for self-powered sensors in Internet of Things (IoT) and high-precision detection systems due to their excellent polarization properties. Compatibility with miniaturization, high-density systems, and complementary metal oxide semiconductor (CMOS) processes is crucial for their widespread adoption. HfO₂-based ferroelectric films show potential in self-powered pyroelectric sensors as their thinness enables effective temperature and light detection. However, the disordered ferroelectric domain distribution limits their pyroelectric performance and hampers the development of highly integrated self-powered pyroelectric devices. This report investigates the temperature and light detection capabilities of Ce-doped HfO₂ ferroelectric films, which exhibit as-grown spontaneous polarization in the downward direction, making them a promising option for self-powered pyroelectric sensors. The findings provide robust evidence that the introduction of a temperature gradient significantly enhances pyroelectricity. In addition, their applications in the detection of hot/cold wind and breathing have been proved. Notably, the 30 nm thick Ce-doped HfO₂ ferroelectric film has a high pyroelectric coefficient of about 894.7 μC·m⁻²·K⁻¹ and enables high-precision detection of changes in temperature of 0.1 K. This study highlights the potential application of HfO₂-based ferroelectric films in self-powered sensors with temperature and light detection capabilities, making them a promising candidate for future IoT-based systems and high-precision detection systems.

Electronic devices that are transparent and flexible have a wide range of applications in the domains of vital sign parameter monitoring, health management, and so on. Ferroelectric memory is a revolutionary nonvolatile memory that is ideal for data storage and processing in transparent flexible electronic systems. In this study, Ce-doped hafnium oxide ferroelectric thin film is manufactured on mica substrate by the chemical solution deposition with transparent indium tin oxide (ITO) thin films as the bottom electrodes. The transmittance of mica/ITO/Hf_0.85Ce_0.15O₂ thin film is over 80%. The 2P_r of the transparent flexible Hf_0.85Ce_0.15O₂ ferroelectric thin film is increased by about 22.4% and the E_c is reduced by 26.7% compared with those of Hf_0.85Ce_0.15O₂ ferroelectric thin film grown on p+-Si substrate. The transparent flexible Hf_0.85Ce_0.15O₂ ferroelectric thin film can remain keeping good quality when being bent under ±2.5 mm bending radius. Additionally, degradation of polarization, retention, and endurance performance was not obvious even at a bending radius of 5.0 mm after 10⁴ bending cycles. This research provides a new strategy and an important experimental basis for the development and implementation of transparent flexible ferroelectric memories.