Combining Ultrafast Calorimetry and Electron Microscopy: Reversible Phase Transformations in SeTeAs Alloys

Abstract

Reversible amorphous–crystalline phase transitions are studied using complementary ultrafast differential scanning calorimetry and transmission electron microscopy techniques, which together allow a wealth of thermal and structural properties to be determined. The SeTe(As) system is investigated because these chalcogenide based materials have favorable properties as a phase-change memory material and in optical systems. Using calorimetry, we find that the addition of 10 at. % As to SeTe alloys strongly increases their glass forming ability, increasing both glass transition and crystallization temperatures while reducing critical quench rate. Ex situ investigation of SexTe90–xAs10 using electron microscopy and elemental mapping reveals a two-phase lamellar segregation mechanism, where a trigonal SeTe-phase and an amorphous As-rich phase are formed. These findings demonstrate the power of combining thermal and structural analysis techniques.

Study of Glass Formation and Crystallization Kinetics in a 2D Metal Halide Perovskite Using Ultrafast Calorimetry

“…The foremost requirement for a hybrid MHP to enable glass formation and reversible glass-crystal switching is for the hybrid to have a T m lower than its degradation temperature (typically, T d ≈ 200 °C), , which ensures a relatively stable working regime for the vitrification and devitrification processes. From within the limited set of two-dimensional (2D) MHP systems available to date with T m < 200 °C, we selected a representative member from this family with chemical formula [1-methyl-hexylammonium] 2 PbI 4 (abbreviated as 1-MeHa 2 PbI 4 ), which has one of the lowest reported T m values of ∼164 °C. ,, Melt processing of 1-MeHa 2 PbI 4 into films and monoliths generally leads to a crystalline phase, as demonstrated in our previous reports. , Due to a high propensity toward crystallization and facile reordering kinetics for the 1-MeHa 2 PbI 4 melt, crystallization cannot be averted when cooled at rates supported by conventional calorimeters (up to 50 °C/min). , On the other hand, ultrafast (“flash”) calorimetry (heating/cooling rates >1000 °C/s) has previously been used to study glass formation and cold crystallization phenomenon in metals, , organics, polymers, and chalcogenides. − Recently, we used flash-DSC to explore the kinetic control of solid–solid polymorphic structural transitions in an MHP …”

Promotion of Processability in a p-Type Thin-Film Transistor Using a Se–Te Alloying Channel Layer

“…The Se–Te system is a well-known solid-solution system, exhibiting a tunable E g ranging from 0.35 to 1.80 eV without undergoing any structural transitions (Figure S1). , In addition, this alloying composition influences the crystallization temperature, ,− making it a fundamental solution for achieving a suitable E g and a moderate crystallization temperature within the conventional process window.…”