In this report, nanoparticles (NPs) of zinc oxide (ZnO) were synthesized through auto-combustion route and annealed in air at different temperatures: 200, 400, 600 and 800 °C. The single phase nature has been confirmed via X-ray diffraction (XRD) and selected area electron diffraction (SAED) analysis. The average of crystallite sizes increased progressively as the thermal annealing increase and ranging between 13.8 and 39.7 nm. Raman spectra resembled to that of hexagonal ZnO wurtzite structure, the narrowing in E_2H (438 cm^-1) Raman phonon mode in sequence with further annealing indicates improvement in the crystallinity and reduction in the local atomic defects of oxygen vacancy (Vo²⁺). The defects create energy deep bands within the band gap region and diminish the UV emission efficiency that has been assessed through photoluminescence (PL) spectroscopic. The donor band of oxygen vacancy (Vo²⁺) was ∼1$\sim 1$ eV above valence band (VB), whereas the acceptor band of zinc vacancy (V_Zn^2-) was at ∼$\sim$ 0.85 eV above the VB. The ZnO NPs that was annealed at lowest temperature of 200 °C exhibited different behavior trend in which the UV-PL band was diminished clearly, blue shifted to lower wave length and appeared as small plateau at the range of 380-270 nm corresponding to high band gap energy (3.8-4.6 eV), which is indicative to low crystal quality and presence of clusters. We used density function theory (DFT) calculation for computing the HOMO-LUMO band gap of supposed clusters Zn_nO_n (n=2, 3, 5, 10). The high band gap energy of the simulated clusters was agreed with that of ZnO NPs annealed at 200 °C that gives indirect evidence on the formation of clusters.

在此报告中，通过自动燃烧途径合成了氧化锌（ZnO）的纳米颗粒（NPs），并在空气中在200、400、600和800°C的不同温度下进行了退火。单相性质已通过X射线衍射（XRD）和选定区域电子衍射（SAED）分析得到确认。随着热退火的增加，微晶尺寸的平均值逐渐增加，范围在13.8至39.7 nm之间。拉曼光谱类似于六角形的ZnO纤锌矿结构，随着进一步退火，E _2H（438 cm ^-1）拉曼声子模式逐渐变窄，表明结晶度提高，氧空位（Vo ²⁺）。缺陷会在带隙区域内产生能量深带，并降低通过光致发光（PL）光谱评估的UV发射效率。供体的氧空位（Vo ²⁺）为〜1$〜\mathrm{1个}$eV高于价带（VB），而锌空位的受体带（V _Zn ^2-）在〜$〜$比VB高0.85 eV。在最低200°C的温度下退火的ZnO NPs表现出不同的行为趋势，其中UV-PL谱带明显减弱，蓝色移至较低波长，并在380-270 nm范围内表现为小平台，对应于高带隙能量（3.8-4.6 eV），表明晶体质量低和存在团簇。我们使用密度函数理论（DFT）计算来计算假定簇Zn _n O _n（n = 2，3，5，10）的HOMO-LUMO带隙。模拟团簇的高带隙能与在200°C退火的ZnO NPs的能带隙能一致，从而间接证明了团簇的形成。