We have successfully synthesized Sr2MnO3F, a new layered perovskite oxyfluoride with a n = 1 Ruddlesden-Popper-type structure using a high-pressure, high-temperature method. Structural refinements against synchrotron X-ray diffraction data collected from manganese oxyfluoride demonstrated that it crystallizes in a tetragonal cell with the space group I4/mmm, in which the Mn cation is located at the octahedral center position. This is in stark contrast to the related oxyhalides that have square-pyramidal coordination such as Sr2MO3X (M = Fe, Co, Ni; X = F, Cl) and Sr2MnO3Cl. There was no evidence of O/F site order, but close inspection of the anion environment centered at the Mn cation on the basis of bond-valence-sum calculation suggested preferential occupation of the apical sites by the F ion with one oxide ion in a random manner. Magnetic susceptibility and heat capacity measurements revealed an antiferromagnetic ordering at 133 K (=TN), which is much higher than that of the chloride analogue with corrugated MnO2 planes (TN = 80 K).

The excitonic effect in semiconductors is sensitive to dopants. Origins of dopant-induced large variation in the exciton binding energy (E(b)) is not well understood and has never been systematically studied. We choose ZnO as a typical high-E(b) material, which is very promising in low-threshold lasing. To the best of our knowledge, its shortest wavelength electroluminescence lasing was realized by ZnO/BeZnO multiple quantum wells (MQWs). However, this exciting result is shadowed by a controversial E(b) enhancement claimed. In this Letter, we reveal that the claimed E(b) is sensible if we take Be-induced E(b) variation into account. Detailed first-principle investigation of the interaction between dopant atoms and the lattice shows that the enhancement mainly comes from the long-distance perturbation of doped Be atoms rather than the local effect of doping atoms. This is a joint work of experiment and calculation, which from the angle of methology paves the way for understanding and predicting the E(b) variation induced by doping.

Strong coupling between the Si photocathode and a low-cost cocatalyst is of great significance for enhancing the photoelectrochemical hydrogen evolution. Here, a facile method is proposed to in situ assemble amorphous MoS x (a-MoS x) thinfilm onto a single crystal p-Si through a self-reduction mechanism to achieve strong coupling. In the process of self-reduction, the (MoS 4) 2− anion is reduced to form a-MoS x by the oxidation of H-Si to form SiO x , which is etched further to form H-Si again in the hydrofluoric aqueous solution. The cyclic formation of H-Si and SiO x plays a decisive role in the continuous deposition of a-MoS x and provides a unique way to synthesize metal sulfides. Such a-MoS x /p-Si photocathode exhibits an excellent activity, achieving the optimal onset potential of +0.31 V RHE and the current density of −28.2 mA cm −2 at 0 V RHE with a Faradaic efficiency close to 98%, respectively, outperforming the thermally exfoliated 2H-MoS 2 and 1T-MoS 2 cocatalysts on p-Si and comparable to the previous studies. The proposed method for uniform deposition at room temperature is simple to carry out and can be used for fabricating other Si-based photoelectrodes.

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