Tuning the Physical and Chemical Properties of 2D InSe with Interstitial Boron Doping: A First-Principles Study

InSe monolayer is a new two-dimensional (2D) material with unique geometric configuration. Its crystal structure has a large atom interval, significantly different from those of graphene and MoS₂, two typical 2D materials. This structural characteristic may facilitate interstitial doping, which is obviously impossible in graphene and MoS₂. In this work, first-principles calculations are employed to study the effects of interstitial doping of boron atoms on the electronic and magnetic properties of InSe monolayer. For comparison, substitutional doping is also studied with In replaced by boron. It is found that interstitial doping can induce spin-polarized state and nonzero local magnetic moments. In order to investigate the effects of doping contents on electronic structures and magnetism, three dopant concentrations (6.25%, 12.5%, 25%) are taken into account. For interstitial doping, with increasing the B contents, the local magnetic moments first emerge and then disappear, corresponding to the nonmonotonic doping-content dependence. For substitutional doping, no local magnetic moments are observed with any doping contents. These results show that B-doping-induced magnetism strongly depends on the doping methods and doping contents in the InSe monolayer. The reasons leading to the doping behaviors are discussed in detail. This work opens up an alternative way for tuning the physical and chemical properties of 2D InSe material, and would be helpful for future InSe-based spintronics devices

Synthesis, Structure, and Properties of the Layered Oxyselenide Ba₂CuO₂Cu₂Se₂

A new layered oxyselenide, Ba₂CuO₂Cu₂Se₂, was synthesized under high-pressure and high-temperature conditions and was characterized via structural, magnetic, and transport measurements. It crystallizes into space group <i>I</i>4/<i>mmm</i> and consists of a square lattice of [CuO₂] planes and antifluorite-type [Cu₂Se₂] layers, which are alternately stacked along the <i>c</i> axis. The lattice parameters are obtained as <i>a</i> = <i>b</i> = 4.0885 Å and <i>c</i> = 19.6887 Å. The Cu–O bond length is given by half of the lattice constant <i>a</i>, i.e., 2.0443 Å. Ba₂CuO₂Cu₂Se₂ is a semiconductor with a resistivity of ∼18 mΩ·cm at room temperature. No magnetic transition was found in the measured temperature range, and the Curie–Weiss temperature was obtained as −0.2 K, suggesting a very weak exchange interaction. The DFT+<i>U</i>_eff calculation demonstrates that the band gap is about 0.2 eV for the supposed antiferromagnetic order, and the density of state near the top of the valence band is mainly contributed from the Se 4p electrons