The quantum spin Hall effect (QSHE), a hallmark of topological insulators, enables dissipationless, spin-polarized edge transport and has been predicted in various two-dimensional materials. However, challenges such as limited scalability, low-temperature operation, and the lack of robust electronic transport have hindered practical implementations. Here, we demonstrate the QSHE in an InAs/GaInSb/InAs trilayer quantum well structure operating at elevated temperatures. This platform meets key criteria for device integration, including scalability, reproducibility, and tunability via electric field. When the Fermi level is positioned within the energy gap, we observe quantized resistance values independent of device length and in both local and nonlocal measurement configurations, confirming the QSHE. Helical edge transport remains stable up to T = 60 kelvin, with further potential for higher-temperature operation. Our findings establish the InAs/GaInSb system as a promising candidate for integration into next-generation devices harnessing topological functionalities, advancing the development of topological electronics.

Among the different methods to grow graphene on silicon carbide (SiC), the chemical vapor deposition (CVD) in a hydrogen atmosphere has several interesting features arising from the use of this gas. Despite its versatility and its ability to grow graphene with a quality allowing applications in electrical metrology, this synthesis method remains largely understudied. This work is specifically dedicated to this growth technique in conditions leading to the epitaxy of graphene on a buffer layer. We first show that hydrogen has several effects during the cooling down, possibly leading to hydrogen intercalation beneath graphene, or even to graphene etching. Then, we use a specific cooling under argon, allowing the suppression of hydrogen effects, to follow the successive phases of the graphene formation, from the nucleation of islands and ribbons to their coalescence on SiC. Finally, we demonstrate that graphene growth is, in our growth conditions, self-limited to a unique monolayer.

There is a growing interest in the recent years toward developing wide gap semiconductor nanostructures, and a lot of efforts have been dedicated to ZnO. In order to design core shell structures, a larger bandgap material is needed, which would ideally be similarly environment friendly. ZnS is an interesting possibility and although some efforts were devoted to it in the literature, its properties are not yet fully understood and precisely measured. In this work, we make a thorough analysis of high quality ZnS epilayers, in order to precisely determine the basic optical properties related to excitons and impurities in ZnS. We have made the first precise quantitative determination of residual strain using high-resolution x-ray diffraction. This allows us to demonstrate that, as it was hypothesized in most previous works, thermoelastic strain originating from the layer-substrate expansion coefficient mismatch is responsible for shifts and splitting of exciton photoluminescence lines. The identification of the bound excitons’ optical transitions is analyzed through their temperature/power dependence, in order to precisely assess their exact nature. Combined with the careful determination of donor and acceptor ionization energies in our ZnS sample, we discard the possibility of sodium as the main residual acceptor, as it has often been proposed in the literature.