Mapping the Energy Landscape from a Nanocrystal-Based Field Effect Transistor under Operation Using Nanobeam Photoemission Spectroscopy.

As the field of nanocrystal-based optoelectronics matures, more advanced techniques must be developed in order to reveal the electronic structure of nanocrystals, particularly with device-relevant conditions. So far, most of the efforts have been focused on optical spectroscopy, and electrochemistry where an absolute energy reference is required. Device optimization requires probing not only the pristine material but also the material in its actual environment (i.

Emerging oxidized and defective phases in low-dimensional CrCl.

Two-dimensional (2D) magnets such as chromium trihalides CrX (X = I, Br, Cl) represent a frontier for spintronics applications and, in particular, CrCl has attracted research interest due its relative stability under ambient conditions without rapid degradation, as opposed to CrI. Herein, mechanically exfoliated CrCl flakes are characterized at the atomic scale and the electronic structures of pristine, oxidized, and defective monolayer CrCl phases are investigated employing density functional theory (DFT) calculations, scanning tunneling spectroscopy (STS), core level X-ray photoemission spectroscopy (XPS), and valence band XPS and ultraviolet photoemission spectroscopy (UPS). As revealed by atomically resolved transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis, the CrCl flakes show spontaneous surface oxidation upon air exposure with an extrinsic long-range ordered oxidized O-CrCl structure and amorphous chromium oxide formation on the edges of the flakes.

Exciton-phonon coupling and power dependent room temperature photoluminescence of sulphur vacancy doped MoSvia controlled thermal annealing.

Via experiments performed by varying the doping level of single-layer mechanically exfoliated MoSvia post exfoliation thermal annealing in the 200-300 °C temperature range, we study the power dependent room temperature (RT) photoluminescence (PL), which is dominated by A type excitons. The PL spectral yields of the as-exfoliated and annealed samples show sub-linear behaviour as a function of the excitation laser power. The PL signal of the 200 °C annealed sample is dominated by the charged exciton (trion) related peak, while the PL signal of the 300 °C annealed sample is dominated by the neutral exciton related peak, and the PL spectral weight of excitons is tunable in this temperature range.