Holes in germanium nanowires have emerged as a realistic platform for quantum computing based on spin qubit logic. On top of the large spin−orbit coupling that allows fast qubit operation, nanowire geometry and orientation can be tuned to cancel out charge noise and hyperfine interaction. Here, we demonstrate a scalable approach to synthesize and organize Ge nanowires on silicon (100)-oriented substrates. Germanium nanowire networks are obtained by selectively growing on nanopatterned slits in a metalorganic vapor phase epitaxy system. Low-temperature electronic transport measurements are performed on nanowire Hall bar devices revealing high hole doping of ∼10 18 cm −3 and mean free path of ∼10 nm. Quantum diffusive transport phenomena, universal conductance fluctuations, and weak antilocalization are revealed through magneto transport measurements yielding a coherence and a spin−orbit length of the order of 100 and 10 nm, respectively.
Barium zirconium sulfide (BaZrS3) is an earth-abundant and environmentally friendly chalcogenide perovskite with promising properties for various energy conversion applications. Recently, sulfurization of oxide precursors has been suggested as a viable solution for effective synthesis, especially from the perspective of circumventing the difficulty of handling alkali earth metals. In this work, we explore in detail the synthesis of BaZrS3 from Ba-Zr-O oxide precursor films sulfurized at temperatures ranging from 700 °C to 1000 °C. We propose a formation mechanism of BaZrS3 based on a two-step reaction involving an intermediate amorphization step of the BaZrO3 crystalline phase. We show how the diffusion of sulfur (S) species in the film is the rate-limiting step of this reaction. The processing temperature plays a key role in determining the total fraction of conversion from oxide to sulfide phase at a constant flow rate of the sulfur-containing H2S gas used as a reactant. Finally, we observe the formation of stoichiometric BaZrS3 (1:1:3), even under Zr-rich precursor conditions, with the formation of ZrO2 as a secondary phase. This marks BaZrS3 quite unique among the other types of chalcogenides, such as chalcopyrites and kesterites, which can instead accommodate quite a large range of non-stoichiometric compositions. This work opens up a pathway for further optimization of the BaZrS3 synthesis process, straightening the route towards future applications of this material.
Tuning light emission in bulk and quantum structures by strain constitutes a complementary method to engineer functional properties of semiconductors. Here, we demonstrate the tuning of light emission of GaAs nanowires and their quantum dots up to 115 meV by applying strain through an oxide envelope. We prove that the strain is highly anisotropic and clearly results in a component along the NW longitudinal axis, showing good agreement with the equations of uniaxial stress. We further demonstrate that the strain strongly depends on the oxide thickness, the oxide intrinsic strain, and the oxide microstructure. We also show that ensemble measurements are fully consistent with characterizations at the single-NW level, further elucidating the general character of the findings. This work provides the basic elements for strain-induced band gap engineering and opens new avenues in applications where a band-edge shift is necessary.
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