Obodo K O, Gebreyesus G, Ouma C N M, Obodo J T, Ezeonu S O, Rai D P, Bouhafs B
HySA Infrastructure Centre of Competence, Faculty of Engineering, North-West University, South Africa (NWU) 2531 South Africa
Department of Physics, School of Physical and Mathematical Sciences, College of Basic and Applied Sciences, University of Ghana Ghana
RSC Adv. 2020 Apr 23;10(27):15670-15676. doi: 10.1039/d0ra02464c. eCollection 2020 Apr 21.
Two dimensional HfS is a material with potential applications in the field of photo-catalysis and advanced solid state devices. Density functional theory with the Hubbard parameter (DFT+) calculations were carried out to investigate the structural, electronic and optical properties of lanthanide dopant atoms (LN = La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) in the HfS mono-layer. The calculated electronic band gap for a pristine HfS mono-layer is 1.30 eV with a non-magnetic ground state. The dopant substitutional energies under both Hf-rich and S-rich conditions were evaluated, with the S-rich condition for the dopant atoms being negative. This implies that the incorporation of these LN dopant atoms in the HfS is feasible and experimental realization possible. The introduction of LN dopant atoms in the HfS mono-layer resulted in a significant change of the material properties. We found that the presence of LN dopant atoms in the HfS mono-layer significantly alters its electronic ground states by introducing defect states as well as changes in the overall density of states profile resulting in a metallic ground state for the doped mono-layers. The doped mono-layers are all magnetic with the exception of La and Lu dopant atoms. We found that LN dopant atoms in the HfS mono-layer influence the absorption and reflectivity spectra with the introduction of states in the lower frequency range (<1.30 eV). Furthermore, we showed that the applicability of doped HfS mono-layers as photo-catalysts is very different compared with the pristine HfS mono-layer.
二维HfS是一种在光催化和先进固态器件领域具有潜在应用的材料。采用含哈伯德参数的密度泛函理论（DFT+）计算，研究了镧系掺杂原子（LN = La、Ce、Pr、Nd、Pm、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb和Lu）在HfS单层中的结构、电子和光学性质。计算得到的原始HfS单层的电子带隙为1.30 eV，基态为非磁性。评估了富Hf和富S条件下的掺杂替代能，发现富S条件下掺杂原子的替代能为负。这意味着在HfS中掺入这些LN掺杂原子是可行的，并且有可能通过实验实现。在HfS单层中引入LN掺杂原子导致材料性质发生显著变化。我们发现，HfS单层中LN掺杂原子的存在通过引入缺陷态以及改变态密度分布的整体情况，显著改变了其电子基态，导致掺杂单层的基态为金属态。除了La和Lu掺杂原子外，掺杂单层均具有磁性。我们发现，HfS单层中的LN掺杂原子通过在较低频率范围（<1.30 eV）引入态来影响吸收和反射光谱。此外，我们表明，与原始HfS单层相比，掺杂HfS单层作为光催化剂的适用性有很大不同。
