Hot excitons in CuCl and CuBr crystalline thin films grown by vacuum deposition
Hot excitons in CuCl and CuBr crystalline thin films grown by vacuum deposition
复制标题
真空沉积生长的 CuCl 和 CuBr 晶体薄膜中的热激子
DOI：
10.1103/physrevb.55.10099
复制
发表时间：
1997
影响因子：
3.7
通讯作者：
H. Nishimura
中科院分区：
文献类型：
--
作者：
M. Nakayama;A. Soumura;K. Hamasaki;H. Takeuchi;H. Nishimura
我们从热激子的角度报道了层厚为 3.5-100 nm 的 CuCl 和 CuBr 薄膜的发光特性。通过真空沉积在(0001)Al 2 O 3 基底上生长沿<111>晶轴优先取向的晶体薄膜。 CuCl 和 CuBr 薄膜中自由激子发光与束缚激子发光的相对强度随着膜厚度的减小而显着增加。所有薄膜中自由激子发光的激发光谱都清晰地表现出随 LO 声子能量周期的振荡结构。反映热激子弛豫过程的激发光谱的轮廓几乎不依赖于薄膜厚度。结果表明，自由激子辐射效率的提高是由于极化子瓶颈区弛豫末期的非平衡所致。此外，还发现CuBr薄膜中自由激子发光的能量对激发能与LO声子能量的周期和振幅具有振荡依赖性。这表明自由激子的强烈不平衡。
We report on the luminescence properties of CuCl and CuBr thin films with layer thickness of 3.5–100 nm from the viewpoint of hot excitons. Crystalline thin films preferentially oriented along the< 111> crystal axis were grown on (0001) Al 2 O 3 substrates by vacuum deposition. The relative intensity of the free-exciton luminescence to the bound-exciton one in the CuCl and CuBr thin films remarkably increases with a decrease in the film thickness. The excitation spectra of the free-exciton luminescence clearly exhibits oscillatory structures with the period of the LO-phonon energy in all of the thin films. The profiles of the excitation spectra, which reflect the relaxation processes of the hot excitons, hardly depend on the film thickness. It is concluded that the enhancement of the radiative efficiency of the free excitons results from nonequilibrium at the final stage of the relaxation in the polariton bottleneck region. Furthermore, it has been found that the energy of the free-exciton luminescence in the CuBr thin films has an oscillatory dependence on the excitation energy with the period and amplitude of the LO-phonon energy. This indicates the intense nonequilibrium of the free excitons.