Artificially engineered nanostrain in FeSexTe1-x superconductor thin films for supercurrent enhancement

Abstract

Although nanoscale deformation, such as nanostrain in iron chalcogenide FST) thin films, has attracted attention owing to the enhancement of general superconducting properties, including critical current density (Jc) and critical transition temperature, its formation has proven to be an extremely challenging and complex process thus far. Herein, we successfully fabricated an epitaxial FST thin film with uniformly distributed nanostrain by injection of a trace amount of CeO2 inside FST matrix using sequential pulsed laser deposition.Using transmission electron microscopy and geometrical phase analysis, we verified that a trace amount of CeO2 injection forms nanoscale fine defects with a nanostrained region, which has a tensile strain (ε ≅0.02) along the c-axis of the FST matrix. The nanostrained FST thin film achieves a remarkable Jc of 3.5 MA/cm 2 for a self-field at 6 K and a highly enhanced Jc under the entire magnetic field with respect to a pristine FST thin film.Technology,

Evolution of Superconducting Properties in Fe1.1Se0.8Te0.2 Films Before and After Structure Avalanche

“…Since the discovery of superconductivity in LaFeAsO in 2008, iron-based superconductors (IBS) have attracted widespread attention due to their unique properties compared with both traditional low-temperature and high- T c cuprate superconductors. − Among all the IBS, FeSeTe, known as the “11”-family IBS, has the advantages of simple structure, nontoxicity (without As), high current-carrying density, and low anisotropy, making it have great potential for high-field applications. − The critical transition temperature ( T c ) of a bulk FeSeTe superconductor is relatively low compared with the other family of IBS. It has been found, from the FeSe x Te 1– x phase diagram, that the optimal doping is observed at x = 0.5 with the maximum T c of 15 K .…”

Make Selenium Reactive Again: Activating Elemental Selenium for Synthesis of Metal Selenides Ranging from Nanocrystals to Large Single Crystals

“…Selenium has been a point of focus in materials research over the past few decades, owing to its high photoconductivity and use for the synthesis of a wealth of chemicals. − Particularly interesting are metal selenides, which find applications in thermoelectrics, semiconductor quantum dots, photovoltaics, magnetic semiconductors, and superconductors. − The ubiquitous applications of selenide materials prompt the need to develop facile, simple, and nontoxic means of synthesis. The conventional syntheses of transition metal selenides usually involve solid-state reactions of elements and precursors, chemical vapor deposition, and gas phase reactions. , These reactions require high temperatures, which are energy intensive and may restrict the control of products.…”

“…Trialkylphosphine selenides have also been used as precursors to synthesize high-quality transition metal selenide nanocrystals. − It has been demonstrated that the phosphine route may be suitable for materials where surface passivation is required to minimize surface recombination sites; − however, for materials with applications in photovoltaics and sensors, the presence of bulky surface-bound organic species may impede device performance. , Furthermore, the reaction of Se with alkyl phosphines such as trioctylphosphine (TOP) and tributylphosphine (TBP) results in unstable and hazardous products, which are difficult to control even under inert atmospheres. − This led to the adoption of phosphine-free precursors, which are formed by dissolving Se in high-boiling-point solvents such as oleylamine, octadecene, olive oil, and paraffin. − It has been demonstrated that these phosphine-free selenium precursors are more reactive toward particle growth when compared to their phosphine counterparts. , Unfortunately, this strategy is usually associated with the formation of H 2 Se, which acts as a major deactivation pathway during precursor formation and also poses health concerns . Another strategy involves the use of selenourea and elemental Se under a reductive atmosphere (NaBH 4 , hydrazine, concentrated NaOH/KOH), alkyl thiol reduction, and reaction of SeO 2 in coordinative solvents. ,,− Most of the aforementioned reducing agents are unstable in air, and their mechanisms of action are complicated .…”

Aqueous Synthesis, Doping, and Processing of n-Type Ag2Se for High Thermoelectric Performance at Near-Room-Temperature

“…Transition-metal chalcogenides display astounding properties ranging from electronic, thermal, optical properties to novel forms of superconductivity and magnetism. − Among various prominent transition-metal chalcogenides, silver-based ones are comparatively less well-explored in the literature. Among them, silver selenide (Ag 2 Se) is an n-type chalcogenide with a phase transition at atmospheric pressure from semiconducting orthorhombic to superionic cubic where Ag + becomes mobile within a rigid lattice of Se.…”