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In this paper, a method based on density functional theory is used to replace varying numbers of sulfur atoms with carbon atoms in the original monolayer ZrS₂ system, resulting in a new doped system. The theory is based on the First Principle. The photovoltaic properties of the new carbon-atom doping systems have been calculated and investigated. The pristine system and the carbon-atom doped systems were structurally optimized using the automatic optimization method. It was found that the stability of the structure decreases as the number of carbon atoms increases. Pristine monolayer 1T-ZrS₂ is an indirect bandgap material. The results show that after doping carbon atoms in monolayer 1T-ZrS₂, the p-type conductivity of the system increases and exhibits metallicity. The density of states analysis shows that the conduction band consists mainly of S-3p, Zr-4d, Zr-4p, Zr-5s and C-2p orbitals, while the valence band consists mainly of S-3p, S-3s, Zr-4d, C-2p and C-2s orbitals. It is concluded that strong hybridization between Zr-d and S-p orbitals is exhibited by both the pristine and doped systems. The analysis of the optical properties shows that the peak absorption coefficient and reflectivity peaks are blue-shifted in the doped system, and these peaks are lower than in the pristine system. The peaks of the real and imaginary parts of the dielectric function are also blue shifted. With the increase of doping concentration, the system’s energy loss decreases, indicating that proper doping can effectively reduce the system’s energy loss. The above studies provide theoretical support for applying ZrS₂ in nano-optoelectronics.

The CaCuO₂ with infinite-layer structure (IL CaCuO₂) was synthesized under high-pressure. The p-type doped infinite layer compounds Ca_1-xNa_xCuO₂ with the different carriers concentration (x=0.05, 0.1) were also prepared from high temperature and high-pressure technique. The lattice parameter a decreases with increasing Na content x in the p-type doped Ca_1-xNa_xCuO₂, suggesting that the hole like carriers enter into the CuO₂ plane, and Na is successfully doped into the infinite-layer CaCuO₂. This was confirmed by the systematic evolution of resistance with increasing the doping level. However, no superconductivity was observed in the samples.

This paper investigates the properties of ZnSe nanocrystals doped with single N, P or As atoms (for p-type doping) or single F, Cl or Br atoms (for n-type doping). The crystals are simulated using the local density functional method. Structures doped with an N or Cl atom remained symmetrical, but some distortion appeared with the other dopants. We found that N is the most efficient acceptor impurity for p-type doping, while Cl is the most suitable impurity for n-type doping. In the case of heavy p-type doping, complex defects such as N_Se–Zn–V_Se and N_Se–Zn_int easily form in the structure. We found that N_Se–Zn–V_Se produces a deep acceptor level in the bandgap, while N_Se–Zn_int produces a compensating donor level in p-type doping. The latter is the main reason for that p-type ZnSe is difficult to achieve. This study is useful to researchers investigating p- and n-type doping as well as device manufacturers.