限域量子态调控研究

电子、激子和声子等量子态在固体中的行为早已被人们所熟知. 然而，当体系的尺寸只有纳米量级的时候，已有的固体理论常常不能适用，需要新的低维物理理论的建立. 我们系统研究了低维体系限域量子态（包括电子、激子和声子）的行为对环境、应力、压力及光的响应和性质的调控. 较早认识到低维体系之显著的表面-体积比对量子态性质调控之有效性，系统地揭示了低维体系的一系列由表面和应力决定的新颖性质，证明了低维体系的表面和应力效应同量子限域效应同等重要. 本文概况了如下五个方面的结果：（1）一种使用应力效应调控电子能带结构的方法和（2）一种使用表面效应调控电子能带结构的方法（这两个方法都可将低维体系能带从间接能隙调控至直接能隙能带结构）；（3）一种低维体系表面掺杂方法，该方法将在低维体系掺杂中取代传统方法；（4）量子点表面诱导的光致异构现象；（5）基于表面自催化半导体低维结构的形成机理. 希望我们的研究工作有助于促进低维体系在光电子、纳电子、环境、能源、生物和医学等领域的应用.

Control of confined quantum states

The behavior of quantum states such as electrons, excitons and phonons in solids has long been known. However, when the size of the system is at nanometer scale, existing solid theories often can not be applied, and the establishment of new low-dimensional physics theory is needed. As is well known, the discovery of quantum confinement and size effects in nanostructures presents challenges and opportunities for the development of new science and technology. Related to this, we carried out thorough researches on the property tuning of quantum confined states (including electrons, excitons, and phonons) due to environment changes and applications of stress, pressure and light. We demonstrated that the surface effects of semiconductor nanostructures are as important as quantum confinement and size effects. Recognizing the effectiveness of the remarkable regulation of the quantum properties of low-dimensional systems due to their large surface-to-volume ratio, we have systematically studied several novel properties of low-dimensional systems determined by surface and stress, proving that the surface and stress effects of low-dimensional systems are as important as quantum confinement effects. Specially, we proposed a method of using stress effects to tune electronic band structures, a method of using surface effects to tune electronic band structures, both of which can tune the energy band structures of low-dimensional systems from indirect energy gap to direct energy gap nature, and a surface doping method for low-dimensional systems, which is expect to replace the conventional volume doping method in low-dimensional systems. We also revealed the photoisomerization phenomenon induced by surface effects of quantum dots and uncovered the formation mechanism based on the surface self-catalysis of semiconductor low-dimensional structure. We expect that our researches have a significant impact on the development of low-dimensional science and technology, which will promote the important applications of low-dimensional systems in the areas of optoelectronics, nanoelectrons, environment, energy, biology and medicine.