Novel Heterostructured Ge Nanowires Based on Polytype Transformation

We report on a strain-induced phase transformation in Ge nanowires under external shear stresses. The resulted polytype heterostructure may have great potential for photonics and thermoelectric applications. ⟨111⟩-oriented Ge nanowires with standard diamond structure (3C) undergo a phase transformation toward the hexagonal diamond phase referred as the 2H-allotrope. The phase transformation occurs heterogeneously on shear bands along the length of the nanowire. The structure meets the common phenomenological criteria of a martensitic phase transformation. This point is discussed to initiate an on going debate on the transformation mechanisms. The process results in unprecedented quasiperiodic heterostructures 3C/2H along the Ge nanowire. The thermal stability of those 2H domains is also studied under annealing up to 650 °C by in situ TEM

Wafer-Scale Performance Mapping of Magnetron-Sputtered Ternary Vanadium Tungsten Nitride for Microsupercapacitors

To power Internet-of-Things applications, new materials are currently being investigated as efficient electrodes for microsupercapacitors. In recent years, multicationic materials were demonstrated to be an attractive new class of materials for electrodes. In this study, we deposited vanadium tungsten nitride by cosputtering. Our film shows excellent electrochemical performance, a capacitance of 700 F·cm–3, and no loss in capacitance retention after 5000 cycles. In addition, the properties of the film were investigated in many aspects using advanced characterization and mapping techniques. Our approach opens new perspectives and provides a powerful characterization tool for electrochemical materials