研究目的
To investigate the Ni doping effect on the structural, mechanical, electronic, and optical properties of ZnO thin films with nanometer scale using first-principles calculations based on density functional theory.
研究成果
Ni doping in ZnO thin films enhances elastic stiffness, reduces bandgap, increases electron effective mass, decreases dielectric constant and refractive index, causes a red shift in absorption peaks, and reduces reflectance in the UV-vis region. The structures are mechanically stable, and the findings align with available experimental data, supporting the use of Ni-doped ZnO in optoelectronic applications.
研究不足
The study is based on computational simulations using DFT, which may have approximations in exchange-correlation functionals affecting accuracy. The models assume ideal conditions at T=0 K and P=0 GPa, not accounting for temperature or pressure effects. Experimental validation is limited to comparisons with literature, and no new experimental data were generated. The focus is on nanometer-scale thin films, which may not fully represent bulk or other nanostructure behaviors.
1：Experimental Design and Method Selection:
The study used first-principles calculations based on density functional theory (DFT) as implemented in the DMol3 package. A 2×2×2 ZnO supercell (72-atoms) was constructed with host Zn atoms substituted by one or two Ni atoms. A ZnO (001) slab surface model was used with a vacuum of 10 ?. The Hamprecht–Cohen–Tozer–Handy (HCTH407) functional at the GGA level was chosen for property calculations after testing LDA and GGA functionals. A double numerical plus polarized (DNP) basis set was employed with a global orbital cutoff of 4.5 ?. Fermi smearing of 0.01 Hartree was used, and Brillouin zone integration was performed using the Monkhorst–Pack scheme with a 3×3×1 k-points grid. Self-consistent field (SCF) calculations had a convergence accuracy of 1×10^{-6} Ha, with no point group symmetry constraints.
2：5 ?. Fermi smearing of 01 Hartree was used, and Brillouin zone integration was performed using the Monkhorst–Pack scheme with a 3×3×1 k-points grid. Self-consistent field (SCF) calculations had a convergence accuracy of 1×10^{-6} Ha, with no point group symmetry constraints.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: The samples included undoped ZnO and Ni-doped ZnO thin films with 1.4 at.% and 2.8 at.% Ni concentrations. Data for comparison were sourced from available experimental and theoretical literature.
3：4 at.% and 8 at.% Ni concentrations. Data for comparison were sourced from available experimental and theoretical literature.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Computational software packages were used, including DMol3 for DFT calculations and VESTA for simulating X-ray diffraction spectra. No physical equipment was mentioned.
4：Experimental Procedures and Operational Workflow:
Structural optimization was performed to determine equilibrium lattice constants and bulk moduli. Elastic constants were calculated by applying homogeneous deformations and computing second derivatives of total energy. Band structures, density of states, electron effective masses, dielectric functions, absorption coefficients, refractive indices, extinction coefficients, reflectance, and energy loss functions were computed using the defined parameters.
5：Data Analysis Methods:
Results were analyzed by comparing calculated values with experimental and other theoretical data. Parabolic effective mass approximation was used for electron effective mass calculations. Kramers–Kronig relations were applied to derive real and imaginary parts of the dielectric function.
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