By means of the full-potential linearized augmented plane-wave method (FP-LAPW), the electronic structures and optical properties of Sn15FeO32 with electron-injection are studied. The results show that Fe-doped SnO2 materials are all direct transition semiconductors. The Fermi level goes into conduction band gradually and the band gap decreases with the increase of electron injection. The peaks of optical properties, such as the imaginary part of dielectric function and absorption spectra, change greatly at low energy. The absorption spectra exhibit blue shift, and the optical absorption edge increases, which are consistent with the change of the band gaps.
The diluted magnetic semiconductors (DMS) have attracted a lot of experimental and theoretical attention [
As a wide band-gap semiconductor, doped SnO2 play a promising role in short-wavelength LED, gas sensor, and laser diode due to its large band gap (3.6 eV) and high exciton binding energy (130 meV) at the room temperature [
The first-principle calculations are performed using FP-LAPW as implemented in WIEN2k code [
All calculation models are constructed with 2 × 2 × 2 supercell of SnO2, which contains 16 Sn atoms and 32 O atoms. In current work, only substitutional doping of Fe with Sn atoms is considered. Then, electron injection into Sn15FeO32 is taken with electron concentrations of
The calculated total DOS of the Sn15FeO32 supercell is shown in Figure
(Color online) The total DOS of the Sn15FeO32 supercell. The blue lines represent total DOS and the red lines represent Fe total DOS, respectively. (a)
The total and partial DOS of Sn15FeO32 supercell with electron-injection concentration
(Color online) Total DOS plots and partial DOS plots of the Sn15FeO32 supercell with electron-injection (1)
The band structure of Sn15FeO32 supercell is shown in Figure
Band structures for supercell: Sn15FeO32. (a)
Band structures for supercell: Sn15FeO32. (a)
It is well known that the interaction of a photon with the electrons can be described according to time-dependent perturbations of the ground-state electronic states, and the optical transitions between occupied and unoccupied states are caused by the electric field of the photon. More importantly, solid dielectric function reflects the information between energy band structure and optical spectral lines and can characterize the physical properties of materials. The formula of dielectric function is defined by
The real part
Figure
The imaginary part of dielectric function
Figure
Absorption spectra of Sn15FeO32 with electron-injection.
In summary, the band structure, the total and partial DOS, and the optical properties of Sn15FeO32 with electron injection have been investigated by the FP-LAPW method. With the increase of the injected electrons, the conduction band moves to valence band gradually. The SnO2 material shows half-metallic properties when the injected electron is less than 1.0. There exists strong coupling interaction between Fe atom and O atom. For the optical properties (the imaginary part of dielectric function, absorption, and reflection), we found that the peaks changed greatly at low energy, the blue shift occurred, and the optical absorption edge increased.
The authors declare that there is no conflict of interests regarding the publication of this paper.
This work was supported by the National Natural Science Foundation of China (Grant nos. 61172028 and 61076088) and the Natural Science Foundation of Shandong Province (Grant no. ZR2010EL017).