Investigating the electronic properties of silicon nanosheets by first-principles calculations

• Published in: Journal of molecular modeling Vol. 18; no. 5; pp. 2147 - 2152
• Main Authors: Chigo Anota, Ernesto, Bautista Hernández, Alejandro, Castro, Miguel, Hernández Cocoletzi, Gregorio
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.05.2012
• Subjects: Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Computer Appl. in Life Sciences; Computer Applications in Chemistry; Electronics; Electrons; Graphite - chemistry; Molecular Medicine; Nanostructures - chemistry; Original Paper; Quantum Theory; Silicon - chemistry; Theoretical and Computational Chemistry; Thermodynamics; Vibration; H; Silicon; Isocoronene; Cluster C; DFT theory
• ISSN: 1610-2940; 0948-5023
• DOI: 10.1007/s00894-011-1235-9

Using first-principles total energy calculations within the density functional theory (DFT), we investigated the electronic and structural properties of graphene-like silicon sheets. Our studies were performed using the LSDA (PWC) and GGS (PBE) approaches. Two configurations were explored: one corresponding to a defect-free layer (h-Si), and the other to a layer with defects (d-Si), both of which were in the armchair geometry. These sheets contained clusters of the C n H m type. We also investigated the effects of doping with group IV-A elements. Structural stability was studied by only considering positive vibration frequencies. Results showed that both h-Si and d-Si present a corrugated structure with concavity. h-Si sheets were found to be ionic (D.M. = 0.33 Debye) with an energy gap (HOMO–LUMO) of 0.77 eV in the LSDA theory and 0.76 eV in the GGS approach, while d-Si sheets were observed to be covalent (D.M. = 2.78 D), and exhibited semimetallic electronic behavior (HOMO–LUMO gap = 0.32 eV within the LSDA theory and 0.33 eV within the GGS approach). d-Si sheets doped with one carbon or one germanium preserved the polarity of the undoped d-Si sheets, as well as their semimetallic electronic behavior. However, when the sheets were doped with two C or two Ge atoms, or with one of each atom (to give Si 52 CGeH 18 ), they retained the semimetallic behavior, but they changed from having ionic character to covalent character.