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A study on polarization switching processes in ferroelectric thin films investigated polarization switching as a function of stepwise increasing dc bias voltage using atomic force microscopy in tandem with a lock-in amplifier. It was found that there exist preferential sites for each polarization direction. The damping of piezoelectric response occurred at the point of domain reversal. The forward and sideways domain growth models were used to interpret the results.

Ferroelectricity in HfO2 thin films can be utilized for fast, power‐efficient, and highly scalable non‐volatile memories. However, the required wake‐up process for inducing ferroelectricity/ achieving higher polarization is one of the major hurdles that hinder HfO2‐based thin films from developing reliable electronic devices. The wake‐up effect is believed to originate from i) phase transformation from non‐ferroelectric to ferroelectric, ii) movement of defect entities (mainly oxygen vacancy defects) near the film‐electrode interface, and iii) heterogeneity of the electrode interfaces. In the present study, an experimental strategy is designed to overcome these sources of the wake‐up process. A multi‐step deposition and annealing process is carried out to induce wake‐up‐free ferroelectricity in Yttrium doped HfO2 (Y:HfO2) thin film directly grown on Si‐substrate. Furnace annealing is utilized instead of the standard rapid thermal annealing process to reduce the oxygen deficiencies and stimulate the direct growth of the polar Y:HfO2. The oxygen‐vacancy‐related defects are found to be the dominating source of wake‐up effect in Y‐doped HfO2 films. The step‐wise deposition and annealing in the oxygen atmosphere facilitate direct growth of the polar phase, reduce the oxygen vacancies, and induce wake‐up‐free ferroelectricity in Y:HfO2. [ABSTRACT FROM AUTHOR]

Chromium aluminum oxide was chosen as a new candidate for use as an attenuated phase-shifting mask (Att-PSM) material. The compositions of films were correlated with optical properties. With the measured and the fitted data, we simulated the transmittance and the phase shift using the matrix method. Consequently, we acquired optimum parameters for Att-PSM's, such as Al/Cr = 1.9-2.5 and d = 120 nm at a 193-nm wavelength, Al/Cr = 1.0-1.7 and d = 128 nm at a 248-nm wavelength, and Al/Cr = 0-0.1 and d = 170 nm at a 365-nm wavelength. This simulation was verified by transmittance measurement.

To acquire the required resolution for 248- and 193-nm lithography, a study of attenuated phase-shifting mask (Att-PSM) technology is in progress. We performed a simulation study using a matrix method to calculate relative transmittance and the amount of phase shift of light through the PSM. However, we found that the average film composition changed with deposition time. Accordingly, optical constants were found to be a strong function of film thickness. Therefore we rearranged the relationship between deposition parameters (e.g., deposition time or gas flow rate ratio) and optical constants (e.g., refractive index and extinction coefficient) to extract the empirical formula for the optical constants with respect to film composition. To verify our simulation study, we fabricated a phase shifter based on our simulation result, which was found to have a transmittance of 8.3% and a phase shift of 179.5 [degrees]. Consequently, we obtained a reliable optimum condition for the deep-ultraviolet Att-PSM. Key words: Phase-shifting mask, attenuated type, chromium-fluoride.

Hafnium zirconium oxide (HZO) has been studied intensively due to its potential application to memory and logic devices based on its outstanding dielectric and ferroelectric properties. Because many process factors can significantly impact the properties of HZO thin film, an optimized process or post‐treatment is necessary to ensure its performance. Herein, the effect of hydrogen on HZO thin film can make the film degraded. Analysis of the polarization–voltage hysteresis loops and I–V measurements indicate a leaky behavior in the film. To address this issue, post‐oxygen‐plasma treatment is performed on the film, which results in the decrease in hydrogen ions inside the film and consequently reduces the leakage current density. This finding can provide new insight into the effect of hydrogen incorporation for HZO thin films and methodology to remove leaky components inside ferroelectric films using O2 plasma treatment. [ABSTRACT FROM AUTHOR]

In this study, the pseudo wastewater containing Zn, Fe, Cu ions was clean-up by a combination of physical adsorption onto activated carbon medium and phytoaccumulation using Acrostichum aureum Linn. plants. The adsorption capability of the activated carbon for the Fe, Cu, and Zn ions was 3.05, 3.72, and 2.85 mg·g − 1, respectively, at the saturation. The phytoaccumulation performance was proved by analyzing the individual residual ash collected after pyrolysis up to 1000 °C of the leaf, stem, and root of the plants. Thermal analyses of thermogravimetry data showed that the weight of the residual ash of the phytoremediated leaf, stem, and root of the plants was 37.0, 19.0, and 65.7 wt.%, respectively. Energy-dispersive X − ray spectroscopy determined the amount of Fe element in the residual ash of phytoremediated root is 7.05 wt.%, while that of the initial root is 1.18 wt.%. Conclusively, it can be proved that combining physical and biological processes is feasible to treat wastewater containing metal ions. [ABSTRACT FROM AUTHOR]

Summary: Experiments were conducted to study in vitro maturation of prepubertal goat oocytes and their developmental potential after chemical activation. In Experiment 1, cumulus–oocytes complexes collected from the ovaries of prepubertal goats slaughtered at a local abattoir were matured in vitro in TCM-199-based medium supplemented with 10 µg/ml luteinizing hormone (LH) (treatment 1) or 10 µg/ml LH + 0.1 mM l-cysteine (treatment 2). In Experiment 2, mature oocytes were activated with either 5 µM ionomycin or 7% ethanol. After 18 h, some oocytes were randomly fixed and stained to evaluate their chromatin status, while others were cultured in embryo culture medium to study their further development. In Experiment 3, oocytes activated with 5 µM ionomycin were cultured for 7 days in one of the four different culture media [Charles Rosenkrans medium (CR-1), TCM-199, potassium simplex optimization medium (KSOM) and synthetic oviductal fluid (SOF)] to study their developmental potential. The maturation rate in control, treatment 1, and treatment 2 media did not differ from each other (P > 0.05). However, the lowest degeneration of oocytes was observed in treatment 3 (P < 0.05) when compared with the other two groups. The proportion of activated oocytes was higher, while non-activated oocytes were lower in ionomycin group when compared with the group activated with ethanol (P < 0.05). The proportions of oocytes cleaved were 65.7, 56.8, 61.0 and 54.4% in CR-1, TCM-199, KSOM and SOF medium, respectively, with no significant difference. However, further development of cleaved oocytes was better in KSOM followed by SOF. [ABSTRACT FROM AUTHOR]

Multiferroic nanocomposites, consisting of branched, ferrimagnetic CoFe2O4 filaments and large protruding PbTiO3 particles embedded in a piezoelectric PbTiO3 matrix, have been fabricated by co-deposition using metalorganic chemical vapor deposition. Branched CoFe2O4 filaments reduce the CoFe2O4/PbTiO3 interfacial strain and induce a perpendicular magnetic anisotropy. Three-dimensional characterizations reveal that in addition to the c-domain, grains with a second orientation in PbTiO3 particles contribute to an additional four apparent variants of polarization. In contrast, the PbTiO3 matrix exhibits only c-domain polarization with a smaller magnitude. The smaller piezoresponse results from the constraints imposed by the branched CoFe2O4 filaments. Three-dimensional microstructure and property analysis provide a comprehensive insight on the structure-property relationship of multiferroic nanocomposites grown by metalorganic chemical vapor deposition. [ABSTRACT FROM AUTHOR]

A 17 nm thick PbTiO3 (PTO) films were fabricated via PbO gas phase reaction with TiO2 starting layer in a sputtering chamber. The influence of deposition temperature of TiO2 on the piezoelectric properties of PTO thin films was investigated. The remnant piezoresponse of PTO films nonlinearly increased as a function of TiO2 deposition temperature, which is correlated with the increase in average grain diameter of PTO film. As grain size increases, the restriction on remnant piezoresponse imposed by the grain boundary via coupling between local strain and polarization becomes less pronounced, which results in the increase in remnant piezoresponse. Furthermore, we found that the vertical shift in piezoresponse hysteresis loops is closely related to the residual stress state. A strong correlation between the negative vertical shift and the residual tensile stress reveals that residual stress on the resulting PTO film contributed to the asymmetric piezoelectric property. [ABSTRACT FROM AUTHOR]

We have studied the effect of local surface potential distribution on its relaxation in the polycrystalline ferroelectric thin films. A lower surface potential region, i.e., potential pit, is generated near a grain boundary. The deep potential pit has a faster relaxation than the area far away from the potential pit due to the acceleration of the screen charge draining near the grain boundary and the domains formed by applying higher voltage have a faster relaxation due to the larger gradient of screen charge distribution. In addition, the surface potential and its relaxation depend on the sign of applying voltage. The result shows that the surface potential distribution may influence significantly to the reliability of bit signal on the memory devices. [ABSTRACT FROM AUTHOR]

We report the dependence of the ferroelectric domain configuration and switching behavior on the shape (square versus round) of epitaxial BiFeO3 (BFO) nanostructures. We fabricated (001) oriented BFO(120 nm)/SrRuO3(SRO,125 nm) film layers on (001) SrTiO3 single crystals by rf magnetron sputter deposition, and patterned them to square (500×500 nm2) and round (502 nm in diameter) shaped nanostructures by focused ion-beam lithography. The surface morphology and the crystalline structure of the nanostructures were characterized by scanning electron microscopy and x-ray diffraction, respectively, while the domain configuration was investigated using piezoelectric force microscopy. We found that the square-shaped nanostructures exhibit a single variant domain configuration aligned along the [111] direction, whereas the round-shaped nanostructures exhibit seven variants of domain configuration along the [111], [111], [111], [111], [111], [111], and [111] directions. Moreover, local d33 piezoelectric coefficient measurements showed hysteresis loops with a strong displacement in the voltage axis (strong imprint) for the square-shaped nanostructures, while the round-shaped ones exhibited more symmetric loops. These findings have critical implications for the development of nanocapacitors for gigabyte to terabyte nonvolatile ferroelectric memories. [ABSTRACT FROM AUTHOR]

A Series of Hybrid Multifunctional Interfaces as Artificial SEI Layer for Realizing Dendrite Free, and Long-Life Sodium Metal Anodes (Adv. Funct. They facilitate rapid Na-ion transportation and notably inhibit the formation of sodium dendrites. Artificial SEI layer, dendrites, density functional theory, sodium metal anode, solid electrolyte interphase. [Extracted from the article]

An analysis of the current-voltage (I-V) characteristics of bridge-type Josephson junction of YBa2Cu3O(7-x) superconductor thin films microwave-irradiated at 77 K indicates that an enhancement of intensity of irradiation reduces current density and leads to constant voltage steps in the I-V curves. The constant voltage steps are not wide, due to a low value of normalized frequency. Subharmonic steps are not visible in the I-V characteristics of these thin films.

Pb(Zr[sub 0.52]Ti[sub 0.48])O[sub 3] (PZT) thin films were fabricated on Pt( 111)/TiO[sub x]/SiO[sub 2]/Si substrates at 375°C by radio frequency magnetron sputtering. A mixture of (110) and (100) orientations was found in all the PZT thin films. However, the in-plane grain size increased with an increase in film thickness, all films had smooth surfaces, and the root mean square roughness of the PZT films was in the range of 1-1.5 nm. As the film thickness increased, a decrease in residual stress and volume density of the PZT films was observed. PZT films become poorly crystallized with a decrease in film thickness. The magnitude of the maximum displacement from atomic force microscopy in local piezoresponse hysteresis mode increased from 187.25 ± 9.363 in 40 nm to 418.5 ± 20.925 in 152 nm. We suggest that the degradation in piezoelectric properties with a decrease in film thickness resulted from degradation of the crystallinity observed using transmission electron microscopy analysis, size effects derived from the grain size, and the residual stress evaluated using a laser reflectance method. [ABSTRACT FROM AUTHOR]

The contrast mechanisms of domain imaging experiments assisted by atomic force microscope (AFM) have been investigated by model experiments on nonpiezoelectric (silicon oxide) and piezoelectric [Pb(Zr,Ti)O[sub 3]] thin films. The first step was to identify the electrostatic charge effects between the tip, the cantilever, and the sample surface. The second step was to explore the tip-sample piezoelectric force interaction. The static deflection of the cantilever was measured as a function of dc bias voltage (V[sub dc]) applied to the bottom electrode (n-type Si wafers) for noncontact and contact modes. In addition, a small ac voltage (V[sub ac] sin ωt) was applied to the tip to measure the amplitude (A[sub ω]) and phase (Φ[sub ω]) of the first harmonic (ω) signal as a function of V[sub dc]. By changing from the noncontact to the contact mode, a repulsive contribution to the static deflection was found in addition to the attractive one and a 180° phase shift in Φ[sub ω] was observed. These results imply that in the contact mode the cantilever buckling is induced by the capacitive force between the cantilever and the sample surface. This interaction adds to the tip-sample piezoelectric interaction thereby overlapping the obtained tip vibration signal. Therefore, the antiparallel ferroelectric domain images obtained at zero dc bias voltage will show a variation in A[sub ω] but a negligible one in Φ[sub ω]. The capacitive force contribution to the tip vibration signal was further verified in piezoelectric hysteresis loop measurement assisted by the AFM. The observed vertical offset of the loops was explained by the contact potential difference between the cantilever and the bottom electrode. The shape of the curve could be explained by the capacitive force interaction combined with the tip-sample piezoelectric interaction. The experimental results obtained in this study support the interpretation of the ... [ABSTRACT FROM AUTHOR]