Strain‐Engineered Modulation on the Electronic Properties of Phosphorous‐Doped ZnO

Abstract

The modulation of strain on the electronic properties of ZnO:P is investigated by density functional theory calculations. The variation of formation energy (E(f)) and band structure with strains ranging from -0.1 to 0.1 are considered. Although both the conduction band minimum (CBM) and the valence band maximum of ZnO are antibonding states, the CBM is more sensitive to strain, reducing the band gap with an increase in strain. P-substituted O (PO) defects show poor p-type conductivity due to a smaller E(f) and lower lying acceptor levels as a consequence of lattice expansion. The E(f) of P-substituted Zn (PZn) defects decreases under tension, owing to the release of strong repulsive stress induced by excess electrons from PZn. The donor energy band of PZn broadens under tensile strain, which benefits n-type conductivity. For Zn vacancies (VZn) and PZn-2VZn complexes, the distances between the O atoms around VZn are so large that repulsive and attractive interactions become weak, which results in an easy release of the strain. We herein present for the first time that the E(f) values of VZn and PZn-2VZn complexes decrease under both tension and compression, or in the high-pressure rock-salt phase. Under a strain of 0.1 the PZn-2VZn complex shows the smallest E(f). Under -0.07 strain the wurtzite/rock-salt phase transition occurs and the direct band gap becomes an indirect one. The variation of band structures in the rock-salt phase is similar to that in the wurtzite phase. Consequently, the p-type conductivity of ZnO:P can be improved with an increase in solubility of PZn-2VZn or VZn defects.

How does the multiple constituent affect the carrier generation and charge transport in multicomponent TCOs of In–Zn–Sn oxide

“…61 This immediately implies that the binding energy E b needs to be larger than either of E for (A) and E for (B). As reported previously, wavefunctions of extra free electrons are so dispersed that it could produce a local repulsive stress in the lattice, 63,64 and thus the variation of the electronic environment limits the solubility of the Sn In defect. Therefore, it is evident that the Zn In -Sn In complex should be codoped into the In 2 O 3 supercell easier than the isolated Sn In or Zn In defect during the preparation process of IZTO materials.…”

“…For ITO materials, when the isolated Sn In defect forms, for the reason of Sn 4+ is a tetravalent ion with respect to the In 3+ ion, it would induce an extra free electron. As reported previously, wavefunctions of extra free electrons are so dispersed that it could produce a local repulsive stress in the lattice, 63,64 and thus the variation of the electronic environment limits the solubility of the Sn In defect. The electronic environment effect is also confirmed by the change of lattice parameters during the substitution process.…”

Magnetism tuned by the charge states of defects in bulk C-doped SnO2materials

“…However, the atomic size of an element is not constant as one might expect and is determined by both the intrinsic size (e.g., the covalent radius) and the electronic environment. 27,28 Thus, a dopant induced volume change arises as a result of two factors: the intrinsic size difference DV i and the electronic environment induced volume change DV e . Thus, the charge state of the defect is also a critical parameter used to determine the geometrical structure of a SnO 2 :C supercell.…”

Carbon induced magnetism of SnO2 surfaces

“…[38] This indicates the symmetry of the local structure is a critical factor to analyze magnetic moment. [16,42] Therefore, the similarities and differences between these (110), (100) and (101) SnO 2 surfaces are investigated by series of density functional theory (DFT) calculations. Considering the local symmetry variation and Jahn-Teller effect, it is found that magnetism emerges in all of the three surfaces, but the performance and the corresponding mechanism are distinct manifestly between them.…”