The importance of catalysis is obvious and unquestionable, especially bearing in mind that about 90% of all commercially produced chemical products involve catalysts at some step of their manufacture ......
Ferroelectric materials feature a switchable spontaneous electric polarization and can enable low‐power logic and nonvolatile memories. These applications require reliable and precise control of ...ferroelectric domains and domain walls in ferroelectric thin films. Mechanical manipulation is a promising route to engineer ferroelectric domains, but it has proved ineffective when going beyond a critical thickness. Here, multi‐step 90° switching polarization reversal processes in (111)‐oriented PbZr0.2Ti0.8O3 thin films by applying mechanical forces along the direction parallel to the domain bands are reported. By probing the interrelationships between the relevant order parameters, coupled lattice distortion and piezoelectricity is revealed to facilitate domain switching from downward to upward in PbZr0.2Ti0.8O3, a mechanism that is supported by the evolution of domains and electrical performances at different temperatures and under varying pressures, respectively. The multi‐step domain reversal processes render PbZr0.2Ti0.8O3 thin films an excellent candidate for multilevel data storage. The study's results have implications for the manipulation of polarization switching in ferroelectrics and open an avenue to domain reversal driven by mechanical loads for the development of next‐generation ferroelectric devices.
This study demonstrates that the nano‐twinned ferroelectric domains can be manipulated in a mechanical way. The domain switching from downward to upward is realized by applying the tip force parallel to the domain bands. Our findings open an avenue to the engineering of ferroelectrics for multilevel information storage.
The HfO
2
-based ferroelectric field effect transistor (FeFET) with a metal/ferroelectric/insulator/semiconductor (MFIS) gate stack is currently being considered as a possible candidate for ...high-density and fast write speed non-volatile memory. Although the retention performance of the HfO
2
-based FeFET with a MFIS gate stack could satisfy the requirements for practical applications, its memory window (MW) and reliability with respect to endurance should be further improved. This work investigates the advantage of employing ZrO
2
seed layers on the MW, retention, and endurance of the Hf
0.5
Zr
0.5
O
2
(HZO)-based FeFETs with MFIS gate stacks, by using fast voltage pulse measurements. It is found that the HZO-based FeFET with a ZrO
2
seed layer shows a larger initial and 10-year extrapolated MW, as well as improved endurance performance compared with the HZO-based FeFET without the ZrO
2
seed layer. The results indicate that employing of a direct crystalline high-k/Si gate stack would further improve the MW and reliability of the HfO
2
-based FeFETs.
To improve the safety performance of lithium-ion batteries, the research of composite separator with high temperature resistance is one of the strategies. Herein, a poly(vinylidene ...fluoride-hexafluoropropylene)/cellulose/carboxylic titanium dioxide (PVDF-HFP/cellulose/C-TiO
2
) composite separator is prepared by the phase inverse method. The composite separator has higher porosity (63.65%) and electrolyte uptake (210.3%) than PP separator, exhibiting good heat resistance that can keep its shape and size under 160 °C for 0.5 h. Additionally, it has a superior ionic conductivity of 1.24–1.49 mS cm
−1
and a lower charge transfer impedance at a room temperature, which brings about better cycle and rate performance. Promisingly, the cell assembled with the PVDF-HFP/cellulose/C-TiO
2
composite separator has a high electrochemical working window and a high current charge of ability, and can undergo 10 charge-discharge cycles normally under 120 °C. The PVDF-HFP/cellulose/C-TiO
2
composite separator has promising potentials for high current and voltage charging, which can improve the safety performance of the lithium-ion battery.
To improve the thermal shrinkage and ionic conductivity of the separator for lithium-ion batteries, adding carboxylic titanium dioxide nanofiber materials into the matrix is proposed as an effective ...strategy. In this regard, a poly(vinylidene fluoride-hexafluoro propylene)/dibutyl phthalate/carboxylic titanium dioxide (PVDF-HFP/DBP/C-TiO2) composite separator is prepared with the phase inversion method. When the content of TiO2 nanofibers reaches 5%, the electrochemical performance of the battery and ion conductivity of the separator are optimal. The PVDF-HFP/DBP/C-TiO2 (5%) composite separator shows about 55.5% of porosity and 277.9% of electrolyte uptake. The PVDF-HFP/DBP/C-TiO2 (5%) composite separator has a superior ionic conductivity of 1.26 × 10 −3 S cm−1 and lower interface impedance at room temperature, which brings about better cycle and rate performance. In addition, the cell assembled with a PVDF-HFP/DBP/C-TiO2 separator can be charged or discharged normally and has an outstanding discharge capacity of about 150 mAh g−1 at 110 °C. The battery assembled with the PVDF-HFP/DBP/C-TiO2 composite separator exhibits excellent electrochemical performance under high and room temperature environments.
Perovskite solar cells (PSCs) have been developed rapidly in recent years, representing the most promising candidates for photovoltaics. Regarding their application in spacecraft, it is essential to ...exploring the space radiation tolerance of PSCs. In this paper, the mechanism of performance degradation of ternary cation (methylammonium (MA), formamidinium (FA) and cesium (Cs)) lead trihalide perovskite planar heterojunction (PHJ) solar cells under gamma-ray radiation was analyzed layer by layer. The results demonstrate that PSCs experience obvious performance degradation under gamma-ray irradiation, especially undergoing apparent recession of short-circuit current density (Jsc) and accordingly power conversion efficiency (PCE). They are mainly attributed to the phase transition of perovskite films and the color appearance of the glass substrate induced by the irradiation, deteriorating the perovskite film absorbance and the substrate transmittance. These results serve as a strong necessity to improve the stability of PSCs for the future application in aerospace.
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•Perovskite solar cells experience obvious performance degradation under gamma-ray irradiation.•The perovskite films undergo a phase transition under gamma-ray irradiation.•The glass substrate exhibits the color appearance and decreased transmittance under gamma-ray irradiation.•It is strongly necessary to improve the stability of PSCs under gamma-ray irradiation for the application in aerospace.
HfO
2
thin films with different praseodymium doping contents (Pr:HfO
2
) were fabricated by chemical solution deposition (CSD) method at ambient conditions. The chemical bonding and the composition ...of Pr doped HfO
2
thin film were characterized by X-ray photoelectron spectroscopy (XPS), while the structural properties were investigated by glancing incidence X-ray diffraction (GIXRD) and high resolution transmission electron microscopy (HRTEM). It is found that the ferroelectric orthorhombic phase was induced in the HfO
2
based thin films by Pr doping. The combined results of
P–E
(polarization–electrical field) and
C–V
(capacitance–voltage) measurements demonstrated that the 5 mol% Pr doped HfO
2
film exhibited a distinct ferroelectricity, with a maximum remanent polarization (
P
r
) of 6.9 µC/cm
2
and a coercive field (
E
c
) of 1.2 MV/cm. Notably, the polarization did not show obvious degradation over 1 × 10
8
switching cycles, suggesting good endurance performance of the Pr doped HfO
2
thin film. These results indicate that Pr dopant could effectively induce ferroelectricity in HfO
2
thin films, thereby becoming a new member of dopants for HfO
2
based ferroelectrics.
The multilevel memory performances of ferroelectric field effect transistor (FeFET) with Hf 0.5 Zr 0.5 O 2 (HZO) ferroelectric thin film are investigated. First, similar retention characteristics are ...observed for intermediate and saturated polarization states of HZO ferroelectric thin film, which enables memories for multi-bit data storage. And then, 2-bit/cell operation of HZO-based FeFET is demonstrated utilizing two NAND architecture compatible write schemes of varying program pulse amplitude and width. Low cycle-to-cycle variability, long retention to extrapolation of 10 years at 85°C, and endurance of 500 cycles are achieved for the both schemes. Moreover, the mechanism for multilevel memory operations of the FeFET is illustrated based on the polarization switching dynamics of HZO ferroelectric thin film.
Plasmonic photocatalysts have been extensively studied for the past decade as a possible solution to energy crisis and environmental problems. Although various reports on plasmonic photocatalysts ...have been published, including synthesis methods, applications, and mechanism clarifications, the quantum yields of photochemical reactions are usually too low for commercialization. Accordingly, it has been proposed that preparation of plasmonic photocatalysts with efficient light harvesting and inhibition of charge carriers’ recombination might result in improvement of photocatalytic activity. Among various strategies, nano-architecture of plasmonic photocatalysts seems to be one of the best strategies, including the design of properties for both semiconductor and noble-metal-deposits, as well as the interactions between them. For example, faceted nanoparticles, nanotubes, aerogels, and super-nano structures of semiconductors have shown the improvement of photocatalytic activity and stability. Moreover, the selective deposition of noble metals on some parts of semiconductor nanostructures (e.g., specific facets, basal or lateral surfaces) results in an activity increase. Additionally, mono-, bi-, and ternary-metal-modifications have been proposed as the other ways of performance improvement. However, in some cases, the interactions between different noble metals might cause unwanted charge carriers’ recombination. Accordingly, this review discusses the recent strategies on the improvements of the photocatalytic performance of plasmonic photocatalysts.
HfO2-based ferroelectric field-effect transistors (FeFETs) are regarded as one of the most promising non-volatile memory technologies in the future. However, the charge trapping phenomenon during the ...program/erase operation is still a challenge. In this work, we comprehensively investigate the behaviors of semiconductor/insulator interface charge trapping in HfO2-based FeFETs. Through analyzing the effects of the spatial distribution of interface traps and the polarization switching speed, the coupling effects of semiconductor/insulator interface charge trapping and polarization switching are recognized. We also find that the band tail state traps have much less influence on the electrical characteristics of the FeFETs than the deep level state traps. Through engineering the devices with band tail state traps with concentrations as small as possible, the influences of charge trapping could be effectively suppressed. Moreover, the gate voltage (VG) scanning rate has a significant influence on the interface charge trapping process due to the time dependent change of ferroelectric polarization. The largest memory window could be obtained by carefully choosing the VG scanning rate of the FeFETs based on the polarization switching speed. This work represents a key step for realizing highly reliable HfO2-based FeFETs.
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