Large voltage-induced coercivity change in Pt/Co/CoO/amorphous TiOx structure and heavy metal insertion effect

There is urgent need for spintronics materials exhibiting a large voltage modulation effect to fulfill the great demand for high-speed, low-power-consumption information processing systems. Fcc-Co (111)-based systems are a promising option for research on the voltage effect, on account of their large perpendicular magnetic anisotropy (PMA) and high degree of freedom in structure. Aiming to observe a large voltage effect in a fcc-Co (111)-based system at room temperature, we investigated the voltage-induced coercivity (Hc) change of perpendicularly magnetized Pt/heavy metal/Co/CoO/amorphous TiOx structures. The thin CoO layer in the structure was the result of the surface oxidation of Co. We observed a large voltage-induced Hc change of 20.2 mT by applying 2 V (0.32 V/nm) to a sample without heavy metal insertion, and an Hc change of 15.4 mT by applying 1.8 V (0.29 V/nm) to an Ir-inserted sample. The relative thick Co thickness, Co surface oxidation, and large dielectric constant of TiOx layer could be related to the large voltage-induced Hc change. Furthermore, we demonstrated the separate adjustment of Hc and a voltage-induced Hc change by utilizing both upper and lower interfaces of Co.

Large Voltage-Induced Coercivity Change in Pt/Co/CoO/Amorphous TiOx Structure and Heavy Metal Insertion Effect

There is urgent need for spintronics materials exhibiting a large voltage modulation effect to fulfill the great demand for high-speed, low-power-consumption information processing systems. Fcc-Co (111)-based systems are a promising option for research on the voltage effect, on account of their large perpendicular magnetic anisotropy (PMA) and high degree of freedom in structure. Aiming to observe a large voltage effect in a fcc-Co (111)-based system at room temperature, we investigated the voltage-induced coercivity (Hc) change of a perpendicularly magnetized Pt/heavy metal/Co/CoO/amorphous TiOx structure. The thin CoO layer in the structure was the result of the surface oxidation of Co. We observed a large voltage-induced Hc change of 20.2 mT by applying 2 V (0.32 V/nm) to a sample without heavy metal insertion, and an Hc change of 15.4 mT by applying 1.8 V (0.29 V/nm) to an Ir-inserted sample. The relative thick Co thickness, Co surface oxidation, and large dielectric constant of TiOx layer could be related to the large voltage-induced Hc change. Furthermore, we demonstrated the separate adjustment of Hc and a voltage-induced Hc change by utilizing both upper and lower interfaces of Co.

Robust ferroelectricity enhancement of PZT thin films by a homogeneous seed layer

With its excellent ferroelectric properties such as large dielectric constant and large remanent polarization, PZT thin films are extensively used in micro-sensors and other devices. In this study, the sol-gel process was used to fabricate Pb(Zr0.52Ti0.48)O3 thin films with Pb(ZrxTi1−x)O3 seed islands. The experimental consequences demonstrate that all the Pb(Zr0.52Ti0.48)O3 thin films with Pb(ZrxTi1−x)O3 seeds show pure perovskite phase with no other impurity phases, and the electrical properties of Pb(Zr0.52Ti0.48)O3 thin films modified by Pb(ZrxTi1−x)O3 seed islands with different Zr/Ti ratios are improved, such as remanent polarization increased, dielectric properties increased, coercive electric field decreased, leakage current density decreased, etc. In particular, the electrical properties of the Pb(Zr0.52Ti0.48)O3 thin films with Pb(ZrxTi1−x)O3 seed islands are the most optimal when the x is 0.52. This paper provides a new technique for optimizing the electrical properties of PZT thin films, which is of great significance for breaking through the bottleneck of the development of ferroelectric memory.

Demonstration of TiO2 Based Ultra High-k (k = 30) Metal-Insulator–Semiconductor Capacitor and Its Electrical Properties

In this paper, we investigated TiO2 as gate dielectric to achieve the large dielectric constant. The ultra high-k value over 30 was obtained by Capacitance–Voltage measurement of Al/Ti/TiO2/Si Metal-Insulator–Semiconductor (MIS) capacitor. Among as deposited, rapid thermal annealing (RTA) at 750 °C and 1000 °C, the RTA at 750 °C showed the lowest gate leakage current. It implies that TiO2 has optimum RTA temperature having the lowest leakage current. When TiO2 is annealed at 750 °C, the phase of TiO2 changes to anatase and interfacial layer between TiOx and Si was formed. While TiO2 is annealed at 1000 °C, the phase of TiO2 changes to rutile and diffusion of silicon atoms was clearly observed and it causes the silicide formation. Based on measurement data, we proposed the energy band diagram of Al/TiO2/Si MIS capacitors. This diagram shows that the energy band gap of RTA at 750 °C is expanded while that of RTA at 1000 °C is contracted. In addition, TiO2 with RTA at 550 °C was tested to confirm leakage current and it shows lower leakage current than RTA at 750 °C as we expected. This result confirmed that optimum RTA temperature of TiO2 would exist under 750 °C.

Study on the synthesis and application of BaTiO3 nanospheres

In the present study, BaTiO3 nanospheres with a uniform particle size of around 100 nm were prepared by a hydrothermal route using Ba(OH)2.8H2O and TiO2 nanoparticles. Experimental results revealed that the main influencing factors for the formation of BaTiO3 nanospheres were molar Ba/Ti ratio (R Ba/Ti), hydrothermal temperature, and time. Highly-dispersed BaTiO3 nanospheres (100 nm) were obtained under the optimum hydrothermal conditions at temperature = 200°C, time = 12 h, and R Ba/Ti = 1.5. Under these optimum conditions, BaTiO3 ceramics were synthesized from the as-prepared BaTiO3 nanospheres, and their structural, microstructural, and electrical properties were investigated. The BaTiO3 ceramics exhibited a high dielectric constant of 7300 at a Curie temperature of 125 °C, great density (ρ), 5.83 g cm–3; large dielectric constant at room temperature er = 3586 and tan d = 0.03, high remanant polarization P r = 10.6 μC cm–2, low coercive field E c = 4.5 kVcm–1.

Influence of Alumina Dopant and Environment on the Electrical Properties of Calcium Copper Titanate Ceramics

Calcium copper titanate (CaCu3Ti4O12; CCTO) ceramics are useful as capacitor dielectrics for many applications. In this study the effect of doping with alumina and testing atmospheres in air and dry N2 on the stability and reproducibility of electrical and dielectric properties of CCTO-xAl2O3 system, where x = 0, 0.5, and 4 wt.% as a function of temperature are investigated. Solid-state synthesis route is used to fabricate the pure and doped CCTO samples sintered at 1080 °C and 1100 °C for 5 h in air. Stable and reproducible dielectric properties are obtained only by switching the measuring atmosphere from air to dry N2. Increased space charge accumulation at the grain boundaries leading to large dielectric constant (ε′) and tan δ are measured in air. Much lower tan δ values of 0.021–0.020 are obtained with a large ε′ (8,815–11,090) at low frequencies (500–800 Hz) in N2 at 23 °C for 0.5 wt.% alumina in both samples sintered at 1080 °C and 1100 °C. These results clearly demonstrate that testing environment can dominate the dielectric properties of pure and alumina-doped CCTO at low frequencies unless measured in dry nitrogen atmosphere to achieve intrinsic behavior useful for applications as capacitors.

Simple furan-based polymers featuring self-healing function enable efficient eco-friendly organic solar cells with high stability

Herein, two simple furan-based polymers PFO3 and PFO4 grafting oligoethylene glycol (OEG) side chains are developed. PFO3 and PFO4 feature high hole mobility, large dielectric constant and good solubility. Compared...

High-temperature All-organic Energy Storage Dielectric with Performance of Self-adjusting Electric Field Distribution

As a key component of dielectric capacitor, the dielectric material directly determines the performance of capacitor. P(olyvinylidene fluoride) (PVDF) has received extensive attention for its large dielectric constant. However, PVDF...