Low-dimensional systems: quantum size effects and electronic properties of semiconductor microcrystallites (zero-dimensional systems) and some quasi-two-dimensional systems

作者：Abraham D. Yoffe · 发表于：Advances In Physics · 年份：1993 · DOI：10.1080/00018739300101484 · 被引用次数：1214 · 研究领域：Quantum Dots Synthesis And Properties、Silicon Nanostructures and Photoluminescence、Semiconductor materials and devices

This review is concerned with quantum confinement effects in low-dimensional semiconductor systems. The emphasis is on the optical properties, including luminescence, of nanometre-sized microcrystallites, also referred to as zerodimensional systems. There is some discussion on certain of the two-dimensional systems, such as thin films and layer structures. The increase in energy of excitation peaks (blue shift) as the radius R of a microcrystallite is reduced is treated theoretically, and experimental data when they are available are used to assess the reliability of the different models that have been used. These experiments normally make use of microcrystallites dispersed in a large-bandgap matrix such as glass, rocksalt, polymers, zeolites or liquids. Exciton binding energies E b are larger than for bulk semiconductors, and oscillator strengths are higher for the microcrystallites. The regimes of direct interest are as follows. Firstly there is the so-called weak-confinement regime where R is greater than the bulk exciton Bohr radius a B. Experimentally, semiconductors such as CuCl with a B ≈ 7 Å, are suitable for study in this case. Secondly there is the moderate-confinement regime, where R ≈ a B, and a h < R < a h, a h and a e being the hole and electron Bohr radii respectively. Finally there is the strong-confinement regime, with R < a B, and R < a h, a e. For this case we are concerned with a ladder of discrete energy levels, as in molecular systems, rather than energy...