Effect of quantum confinement on electronic and dielectric properties of niobium dichalcogenides NbX₂ (X = S, Se, Te)

详细信息    查看全文

• 作者：Ashok Kumar ; ^{ashok.1777@yahoo.com} ; P.K. Ahluwalia ^{pk_ahluwalia7@yahoo.com}
• 关键词：Transition metal compounds ; Electronic band structure ; Dielectric response ; Electron energy loss spectra
• 刊名：Journal of Alloys and Compounds
• 出版年：2013
• 出版时间：15 February, 2013
• 年：2013
• 卷：550
• 期：Complete
• 页码：283-291
• 全文大小：1418 K

文摘

We have performed first principle pseudopotential and numerical pseudoatomic orbitals basis set based calculations to study the influence of slab thickness on the electronic and dielectric properties of niobium dichalcogenides (S, Se, Te). We have taken bulk, mono, bi, quadri and six-layer setup for this study. The importance of semicore states in Nb pseudopotential has been investigated. Electronic band structures of studied materials show splitting of the bands of the order of 0.7 eV at ¦£ point due to interlayer interactions for all the materials under consideration. Electron energy loss spectra (EELS) for in-plane polarization shows 0.65 eV (6.5 eV), 0.75 eV (7.5 eV) and 0.55 eV (6.9 eV) red shift in energy of ¦Ð(¦Ð + ¦Ò) plasmons peaks respectively for NbS₂, NbSe₂ and NbTe₂ by reducing the slab thickness from bulk to monolayer, while for out-of-plane polarization, approximately ¡Ö6.3 eV red shift in ¦Ð + ¦Ò plasmons peak has been found for all the studied materials on reducing the number of layers from bulk to monolayer. Interband transitions energies are found to remain same irrespective of the quantum confinement effect for all the dichalcogenides of Nb with an additional interband transition at 3.2 eV for NbTe₂.