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The IoT era necessitated the need for hardware-based security devices due to their strong resistance to hacking compared to software-based systems, which are limited by CPU usage and performance. Hardware-based systems are more unpredictable due to their unique and non-discernible external properties. This research focused on developing a security device based on lead-free metal oxide CaTiO 3 perovskite material with irregular electrical characteristics, known as physical unclonable functions. These irregularities were created by increasing the number of grain boundaries on the device surface through high-temperature annealing, resulting in greater adsorbed oxygen. The outcome was a highly random and unique security key using irregular electrical characteristics with 49.53% uniformity and a 46.55% inter-Hamming distance. • A lead-free CaTiO 3 perovskite material leads to physically unclonable functions. • The irregularities produced by the formation of grain boundaries and oxygen vacancies. • A CaTiO 3 film was investigated by AFM, SEM, XRD, UV–vis, FT-IR, and XPS. • Security keys were achieved with a 49.53% uniformity and a 46.55% inter-HD. [ABSTRACT FROM AUTHOR]

GaN has become an important material in the optoelectronics due to its suitable band gap and excellent physical and chemical properties, however, the grown substrates limit device geometry owing to their poor electrical and thermal conductivity. Herein, horizonal and vertical GaN ultraviolet photodetectors (UV PDs) were fabricated using the freestanding GaN membranes obtained by an epitaxial lift-off technique. The photoresponse behaviors in the fabricated PDs were then optimized by the piezo-phototronic effect. Owing to the synergistic effect of spontaneous polarization and asymmetric electrodes, the vertical UV PD exhibits unique self-powered characteristics with the light on/off of 3.3 × 103 and the responsivity (R) of 114 mA/W at the bias of 0 V. Optimized by the piezo-phototronic effect, the R increases to 168 mA/W at a tension strain of 0.25 %. In comparison, the R of horizontal UV PD decreases, regardless of the compression or tension. Physical mechanisms of the performances optimization in the vertical and horizontal UV PDs are proposed and analyzed. This study opens a pathway to fabricate GaN UV PDs with different device configurations and provides fundamental support for their performance modulation by the piezo-phototronic effect. • Horizonal and vertical GaN ultraviolet photodetectors (UV PDs) were fabricated using the freestanding GaN membranes. • The vertical UV PD exhibits unique self-powered characteristics with the light on/off of 3.3 × 103. • Optimized by the piezo-phototronic effect, the R of vertical PD was increased from 114 mA/W to 168 mA/W. • Physical mechanisms of the performances optimization in the vertical UV PDs is proposed and analyzed. [ABSTRACT FROM AUTHOR]

The commercialization of nanocrystalline metals and alloys is currently entering a renaissance period. Many of the processing and consolidation challenges that have haunted them are now more fully understood, opening the doors for stabilized nanocrystalline metals to be produced on a bulk scale. While challenges remain, the increased volume at which these materials are being supplied is for the first time allowing for investigations into more traditional methods of metal working, such as extruding, rolling, forming, and forging. Recently, the manufacturing science has been developed to allow nanocrystalline Cu-Ta alloys to progress to this point. This article therefore builds upon the last decade of evolutionary progression within the family of stabilized nanocrystalline Cu-Ta alloys by presenting some of the first findings related to scaled powder synthesis, production of billets, thin sheets, and foils. The mechanical performance and physical properties relevant to forming electrical contacts and pins including, tensile, J-integral fracture toughness, Charpy Impact, bi-axial tension, and conductivity are reported. This introductory investigation into forming such a novel material, provides evidence to these alloys potential at bridging the gap between being a scientific curiosity to that of a real engineering material. • The commercialization of nanocrystalline metals and alloys is currently entering a renaissance period. Many of the processing and consolidation challenges that have haunted them are now more fully understood, opening the doors for stabilized nanocrystalline metals to be produced on a bulk scale. While challenges remain, the increased volume at which these materials are being supplied, is for the first time allowing for investigations into more traditional methods of metal working, such as extruding, rolling, forming and forging. Recently, the manufacturing science has been developed to allow nanocrystalline Cu-Ta alloys, to progress to this point. This article therefore builds upon the last decade of progression within the family of stabilized nanocrystalline Cu-Ta alloys by presenting some of the first findings related to scaled powder synthesis, production of billets, thin sheets and foils. The mechanical performance and physical properties relevant to forming electrical contacts and pins including, tensile, J-integral fracture toughness, Charpy Impact, bi-axial tension, and conductivity are reported. This introductory investigation into forming such a novel material, provides evidence to these alloys potential at bridging the gap between being a scientific curiosity to that of a real engineering material. [ABSTRACT FROM AUTHOR]

With the increased concerns on the toxicity of lead, the barium titanate (BT) has developed a vital lead-free ferroelectric material to replace lead-based one due to the extraordinary multi-functionality. However, to date the deep understanding on evolution mechanisms of multiple electro-related performances in single BT based ceramics is still limited, and the simultaneous enhancement or balanced development of comprehensive performance in BT ceramics face challenges. Here, a new lead-free ceramic system of Ba 0.9+ x Sr 0.1- x Ti 0.91 Sn 0.09 O 3 (BSTS, 0 ≤ x ≤ 0.1) was successfully prepared by the conventional solid-state reaction method, and the dopant tuned multi-functionality and underlying physical mechanism of performance evolutions were revealed in detail. The BSTS ceramics present R-O-T-C multiphase coexistence at a wider temperature range near room temperature, along with the structural features with flattened thermodynamic energy landscape and flexible polarization rotation. Accordingly, the enhanced piezoelectric coefficient (d 33 = 600 pC/N), large electrostrictive coefficient (Q 33 = 0.0405 m4/C2, E = 30 kV/cm), superior electrocaloric effect (Δ T = 0.77 K, E = 30 kV/cm) with a wider temperature span of 49 °C (Δ T > 0.5 K), and strong electrocaloric strength (Δ T /Δ E = 0.3857 K mm/kV, E = 5 kV/cm) are simultaneously attained under smaller electric field for BSTS ceramics. It exhibits a superior comprehensive performance than many reported BT based ceramics, which is suitable for more potential applications in the emerging fields of advanced functional devices, such as high precision displacement or strain actuators and zero-global-warming-potential refrigeration with larger capacity near room temperature. This work sheds insight into simultaneously optimizing different electro-related performances, and stimulates future studies on dopant tuned multi-functionality in BT based ceramics. • A new BT based material system with R-O-T-R multiphase boundary is designed. • Enhanced d 33 , large Q 33 , and high Δ T with a wider temperature span are simultaneously achieved. • The physical origin of enhanced performance is revealed. [ABSTRACT FROM AUTHOR]

• Undoped and copper-doped flake like ZnO nanopowders were synthesized using the hydrothermal synthesis method. • All samples have highly crystallized hexagonal wurtzite structure. • The effects of both doping and the dye adsorption time on the DSSC cell performance were investigated. • %0.1 Cu doped ZnO nanopowder dipped in N719 solution for only one hour showed the highest performance. In this study, the effects of two fabrication factors, the Cu doping and the dye adsorption time on the ZnO-DSSC, were systematically investigated. ZnO nanostructures were obtained by hydrothermal synthesis method at different Cu doping ratio (0%, 0.1%, 1%, 3%) and used as photoanode in DSSC. The effects of Cu incorporation to ZnO on the morphological, structural, and optical properties were examined. As a result of XRD analysis, it was determined that all samples have highly crystallized hexagonal wurtzite structure. The doping process has caused the formation of protruding surfaces in the ZnO nanostructure and increased the surface area, which has been observed using SEM images. X-ray photoelectron spectroscopy (XPS) study demonstrated Cu-O and Zn-O bonding in the synthesized flake-shaped Cu doped ZnO nanostructures, which confirmed the Zn substitution by the Cu-ions. The maximum cell efficiency of 2.03% was achieved in DSSC when photoanode was fabricated by using %0.1 Cu doped ZnO nanopowder dipped in N719 solution for only one hour. The efficiency of DSSC with Cu doped ZnO photoanode has improved by 20%, and the dye adsorption time has been decreased by three times, obviously. [ABSTRACT FROM AUTHOR]