First-principles study on ferromagnetism in two-dimensional ZnO nanosheet

Structural, electronic and optical properties of metalloid element (B, Si, Ge, As, Sb, and Te) doped g-ZnO monolayer: A DFT study

Stable geometries, electronic structure, and optical properties of ZnO monolayer doped with metalloid element (M = B, Si, Ge, As, Sb, and Te) atom have been studied using density functional theory. It is found that among these elements Ge, As, and Sb can be effectively doped at Zn site in the ZnO monolayer with the formation energies ranging from -1.02 to -0.96 eV. Except B element, all the metalloid atoms prefer to protrude out of the plane of the ZnO monolayer. The nonmagnetic nature of the ZnO monolayer is retained with the doping of B, Si, Ge, As, and Sb atom, while Te atom induces the magnetism in ZnO monolayer (2 μB). While doping of Si, As, Sb, and Te in ZnO monolayer resulted in a red shift in the absorption spectra of doped ZnO monolayer and the blue shift is observed for B and Ge doped ZnO. The static dielectric constant for ZnO monolayer is 1.49. With the doping of these metalloid elements in ZnO monolayer, the dielectric constant can be tuned from 1.36 to 2.84. These results are potentially useful for optoelectronic applications and the development of optical nanostructures.

Improved sensing characteristics of methane over ZnO nano sheets upon implanting defects and foreign atoms substitution

Thanks to the growing interests of metal oxide sensors in environmental and industrial uses, this study presents the sensing mechanism of methane gas (CH₄) on recently synthesized two-dimensional form of ZnO, ZnO nano sheets (ZnO-NS). The adsorption energy of CH₄ on pristine ZnO-NS, calculated by means of van der Waals corrected first-principles calculations, is found to be insufficient restricting its application as an efficient nano sensor. However, the creation of (O/Zn) vacancies and the substitution of foreign dopants into ZnO-NS considerably intensify the binding energy of CH₄. Through a comprehensive energetic analysis, it is observed that among all the substituents, boron (B), sulphur (S) and gallium (Ga) improves the binding of CH₄ to 2.75, 6.1 and 7.5 times respectively than its values on pristine ZnO-NS. In addition to the CH₄ binding energies falling ideally between physisorption and chemisorption range, a prominent variation in the electronic properties before and after CH₄ exposure indicates the promise of substituted Zn-NS as a useful nano sensors.