Chou Han-Sheng, Yang Kai-Di, Xiao Sheng-Hong, Patil Ranjit A, Lai Chien-Chih, Vincent Yeh Wang-Chi, Ho Ching-Hwa, Liou Yung, Ma Yuan-Ron
Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan.
Graduate Institute of Applied Science & Technology and Department of Electronic & Computer Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan.
Nanoscale. 2019 Jul 28;11(28):13385-13396. doi: 10.1039/c9nr05235f. Epub 2019 Jul 5.
The temperature-dependent effects on the ultraviolet (UV) photoluminescence (PL) enhancement, blueshift, thermal quenching, and chromaticity of the two-dimensional (2D) Zn nanosheets, 2D-hierarchical ZnO nanostructures, and 2D-hierarchical ZnO/Zn nanostructures are presented. In this study, 2D Zn nanosheets were synthesized using a hot-plate metal vapor deposition technique, after which 2D-hierarchical ZnO nanostructures and ZnO/Zn were prepared from the 2D Zn nanosheets by a simple thermal annealing method. The enhancement and blueshift of the UV PL emissions from the three nanostructures at low temperatures arose from three distinct PL mechanisms. For the ZnO nanostructures, the UV PL emission enhancements and blueshifts at low temperature were due to the conversion of the free excitons (FXs) to neutral-donor-bound-excitons (DXs). The ZnO/Zn nanostructures possessed the highest UV PL intensities among the three nanostructures, because the free electrons from the Zn portions across the metal-semiconductor heterojunctions greatly assisted in enhancing the PL emissions. The enhancement and thermal quenching were quantitatively analyzed with simple normalization methods. The results show that all three kinds of nanostructures are excellent candidates for use in UV light emitters.
本文展示了温度对二维（2D）锌纳米片、二维分级氧化锌纳米结构和二维分级氧化锌/锌纳米结构的紫外（UV）光致发光（PL）增强、蓝移、热猝灭和色度的影响。在本研究中，采用热板金属气相沉积技术合成了二维锌纳米片，之后通过简单的热退火方法由二维锌纳米片制备了二维分级氧化锌纳米结构和氧化锌/锌。三种纳米结构在低温下的紫外PL发射增强和蓝移源于三种不同的PL机制。对于氧化锌纳米结构，低温下的紫外PL发射增强和蓝移是由于自由激子（FXs）向中性施主束缚激子（DXs）的转变。氧化锌/锌纳米结构在三种纳米结构中具有最高的紫外PL强度，因为来自金属-半导体异质结处锌部分的自由电子极大地有助于增强PL发射。采用简单的归一化方法对增强和热猝灭进行了定量分析。结果表明，所有三种纳米结构都是用于紫外发光体的优秀候选材料。
