Realization of a composite ferroelectric characterization test system using a modified constant current method and a modified virtual ground method.

A composite ferroelectric characterization test system constructed using a modified constant current method (CCM) and a modified virtual ground method (VGM) has been successfully designed and implemented. By sending instructions to the microcontroller through software, the system's test mode can be easily changed by arranging the switching status of six switching elements. When validating the system, a dual-channel precision source/measure unit B2912B was used to verify this design. There is also parasitic capacitance that cannot be ignored in this commercial machine. This parasitic capacitance affects the appearance of the entire hysteresis curve. However, the parasitic capacitance values also differ in various test current ranges. In addition, to confirm the data credibility of this composite ferroelectric test system, Keysight B1530A and Radiant Premier II were used to conduct cross-verification between different systems. The results obtained between different systems show good consistency. Furthermore, reproducible and recoverable imprint phenomena were found in this composite system during interactive validation using VGM and CCM methods. After designing different voltage profiles for verification, it was found that the root cause of this imprint phenomenon was the difference between the final polarization state of the previous test and the pre-initialized polarization state. This imprint phenomenon exists in traditional Pb(Zr, Ti)O3 (PZT) ferroelectric capacitors and Hf0.5Zr0.5O2-based ferroelectric capacitors. Fortunately, this imprint phenomenon is reversible. Moreover, this imprint phenomenon disappears through the design of the time-varying voltage profile on the ferroelectric capacitor of the CCM method.

Defect-Rich SnO2 Nanofiber as an Oxygen-Defect-Driven Photoenergy Shield against UV Light Cell Damage.

Usually, most studies focus on toxic gas and photosensors by using electrospinning and metal oxide polycrystalline SnO2 nanofibers (PNFs), while fewer studies discuss cell-material interactions and photoelectric effect. In this work, the controllable surface morphology and oxygen defect (VO) structure properties were provided to show the opportunity of metal oxide PNFs to convert photoenergy into bio-energy for bio-material applications. Using the photobiomodulation effect of defect-rich polycrystalline SnO2 nanofibers (PNFs) is the main idea to modulate the cell-material interactions, such as adhesion, growth direction, and reactive oxygen species (ROS) density. The VO structures, including out-of-plane oxygen defects (op-VO), bridge oxygen defects (b-VO), and in-plane oxygen defects (ip-VO), were studied using synchrotron analysis to investigate the electron transfer between the VO structures and conduction bands. These intragrain VO structures can be treated as generation-recombination centers, which can convert various photoenergies (365-520 nm) into different current levels that form distinct surface potential levels; this is referred to as the photoelectric effect. PNF conductivity was enhanced 53.6-fold by enlarging the grain size (410 nm2) by increasing the annealing temperature, which can improve the photoelectric effect. In vitro removal of reactive oxygen species (ROS) can be achieved by using the photoelectric effect of PNFs. Also, the viability and shape of human bone marrow mesenchymal stem cells (hMSCs-BM) were also influenced significantly by the photobiomodulation effect. The cell damage and survival rate can be prevented and enhanced by using PNFs; metal oxide nanofibers are no longer only environmental sensors but can also be a bio-material to convert the photoenergy into bio-energy for biomedical science applications.

Enhancement in the Detection Ability of Metal Oxide Sensors Using Defect-Rich Polycrystalline Nanofiber Devices.

The development of SnO2 and TiO2 polycrystalline nanofiber devices (PNFDs) has been widely researched as a method of protecting humans from household air pollution. PNFDs have three significant advantages. The nanofibers before the annealing process are polymer-rich materials, which can be used as particulate material (PM) filters. The multiporous nanofibers fabricated by the annealing process have numerous defects that can serve as generation-recombination centers for electron-hole pairs, enabling the PNFDs to serve as multiple-wavelength light (from 365 to 940 nm) detectors. Lastly, the numerous surface/interface defects can drastically enhance the toxic gas detection ability. The toxic gas detection range of PNFDs for CO(g) and NO(g) is from 400 to 50 ppm and 400 to 50 ppb, respectively. Quick response times and recovery properties are key parameters for commercial applications. The recovery time of NO(g) detection can be improved from 1 ks to 40 s and the PNFD operating temperature lowered to 50 °C. These results indicate that SnO2 and TiO2 PNFDs have good potential for commercialization and use as toxic gas and photon sensors in daily lives.