HfZrO thin films are one of the most appealing HfO-based ferroelectric thin films, which have been researched extensively for their applications in ferroelectric memory devices. In this work, a 1 mol % La-doped HfZrO thin film was grown by plasma-assisted atomic layer deposition and annealed at temperatures of 450 and 500 °C to crystallize the film into the desired orthorhombic phase. Despite the use of a lower temperature than that used in previous reports, the film showed highly promising ferroelectric properties-a remnant polarization of ∼30 μC/cm and switching cycle endurance up to 4 × 10. The performance was much better than that of undoped HfZrO thin films, demonstrating the positive influence of La doping. Such improvements were mainly attributed to the decreased coercive field (by ∼30% compared to the undoped film), which allowed for the use of a lower applied field to drive the cycling tests while maintaining a high polarization value. La doping also decreased the leakage current by ∼3 orders of magnitude compared to the undoped film, which also contributed to the strongly improved endurance. Nonetheless, the La-doped film required a larger number of wake-up cycles (∼10 cycles) to reach a saturated remnant polarization value. This behavior might be explained by the increased generation of oxygen vacancies and slower migration of these vacancies from the interface to the bulk region. However, the maximum number of wake-up cycles was less than 0.01% of the total possible cycles, and therefore, initializing the film to the maximum performance state would not be a serious burden.

The crystalline structure and electrical response of La-doped HfO2-ZrO2 thin films of which processing temperature did not exceed 400 °C were examined, where the La-doping concentration was varied from zero to ≈2 mol. %. The film structure and associated properties were found to vary sensitively with the minute variation in the La-concentration, where the ferroelectric response at low La-concentration (<≈1 mol. %) gradually became antiferroelectric-like for La-concentration >≈1 mol. %, which was accompanied by a significant increase in dielectric permittivity. La-doping was found to be very effective in inhibiting the monoclinic phase formation and in decreasing the leakage current. Notably, the high coercive field, which was one of the most significant problems in this material system, could be decreased by ∼35% at the most promising La-concentration of 0.7 mol. %. As a result, a highly promising field cycling endurance up to 1011 cycles could be secured while maintaining a high remnant polarization value (≥25 μC/cm2). This is one of the best results in this field of the authors' knowledge.

We designed, fabricated, and tested for the first time a prototype of nuclear micropower battery with an overall active area about 15 cm 2 consisted in 130 single cells based on Schottky barrier diamond diodes. Diodes selection for the battery assembly was performed on the basis of I-V curves measurements at electron beam irradiation in SEM. A typical energy conversion efficiency of each cell was about 4-6%. To characterize a battery prototype performance, we carried out photovoltaic measurements using different radioisotopes. Under irradiation by 63 Ni source with activity of 5 mCi cm À2 , the output power density of 3 nW cm À2 was obtained. Due to large energy loss of the emitted b particles in source itself, the total battery efficiency was only 0.6%. However, with the longlived 63 Ni isotope, this already gives the battery specific energy of about 120 W Á hr/kg, comparable with the commercial chemical cells. During experiments with high activity 90 Sr-90 Y source, no degradation was observed after 1,400 h of the radiation exposure. The maximum output power density of 2.4 mW cm À2 was achieved using 238 Pu a source. The results display that synthetic diamond is a highly promising material for nuclear microbattery fabrication. A strategy to further cell optimization is also discussed.

The structural and ferroelectric properties of lightly La-doped (1 mol. %) HfO2 thin films grown by plasma-assisted atomic layer deposition were examined. An annealing temperature as low as 400 °C crystallized the film into the desired orthorhombic phase, which resulted in it displaying promising ferroelectric performance. The remanent polarization (Pr) increased with annealing temperature, but the performance enhancement seemed to saturate at 500 °C. A slight decrease in the dielectric constant, which was associated with the preferential formation of a polar orthorhombic phase at higher temperatures, was also observed. The long-term wake-up effect, i.e., a marked rise in the 2Pr value during field cycling, was demonstrated for films processed at all annealing temperatures. The presence of domain groups with opposite internal electric biases was found in the pristine state, while the internal bias distribution became more uniform during wake-up. The endurance of up to 4 × 108 switching cycles without marked fatigue using bipolar pulses with a duration of 600 ns, and an amplitude of ±3 MV/cm was demonstrated.

Fabrication of polyelectrolyte microcapsules and their use as carriers of drugs, fluorescent labels, and metal nanoparticles is a promising approach to designing theranostic agents. Semiconductor quantum dots (QDs) are characterized by extremely high brightness and photostability that make them attractive fluorescent labels for visualization of intracellular penetration and delivery of such microcapsules. Here, we describe an approach to design, fabricate, and characterize physico-chemical and functional properties of polyelectrolyte microcapsules encoded with water-solubilized and stabilized with three-functional polyethylene glycol derivatives core/shell QDs. Developed microcapsules were characterized by dynamic light scattering, electrophoretic mobility, scanning electronic microscopy, and fluorescence and confocal microscopy approaches, providing exact data on their size distribution, surface charge, morphological, and optical characteristics. The fluorescence lifetimes of the QD-encoded microcapsules were also measured, and their dependence on time after preparation of the microcapsules was evaluated. The optimal content of QDs used for encoding procedure providing the optimal fluorescence properties of the encoded microcapsules was determined. Finally, the intracellular microcapsule uptake by murine macrophages was demonstrated, thus confirming the possibility of efficient use of developed system for live cell imaging and visualization of microcapsule transportation and delivery within the living cells.Electronic supplementary materialThe online version of this article (10.1186/s11671-018-2447-z) contains supplementary material, which is available to authorized users.