Syntheses, Modification And Properties Of Silicon Quantum Dots

New requirements and challenges on functional inorganic semiconductor materials are emerging with the high development of the energy and information technology, e.g., photovoltaic materials with high efficiency, high stability and environment friendly, new optoelectronic organic-inorganic hybrid materials compatible with the silicon based semiconductor technique. Silicon nanomaterial is such a promising candidate leading to breakthrough in the above areas. Powerful support for the silicon based functional material synthesis and device preparation comes from the advanced molecule synthesis and nanotechnology development in recent years. Aiming the national developing plan and orientation on energy and information industry, directed by the organic-inorganic complementary and coupling idea, to achieve the tailorable optoelectronic properties, this work will focus on to develop methods and technique to prepare silicon based hybrid materials tunable on size, nanostructure, doping and surface modification, to investigate the relationships between the silicon nano-structural and the optoelectronic properties. This research will provide abundant new possibilities for the optoelectronic devices using silicon based functional hybird materials.Under the direction of correlation theory, being oriented by function, a series of new optoelectronic materials have been developed through synthesis method, for the purpose of research. The details were shown as follows. Chapter1:We introduced the nanomaterials as starting point, described semiconductor quantum dots, the syntheses and applications of silicon quantum dots;Chapter2:Silicon quantum dot (Si QDs) is an important foundation for the research of functional modification. In this chapter, we explored the controllable syntheses Si QDs. High temperature hydrogen reduction method and annealing of SiOx powders were used to obtain Si QDs with different size. Moreover, the experiments also indicated that the temperature of reduction and HF etching time have impact on the size of Si QDs;Chapter3:In this chapter, we report the dual-emissive Si QDs, with the QDs surface modified by9-ethylanthracene. This hybrid nanomaterial dispersed well in nonpolar solvent such as mesitylene, exhibiting a dual-emission spectrum with the peaks centered at431and824nm, corresponding to the ligands and Si QDs related fluorescence, respectively. It is a general strategy for preparing dual-emission Si QDs with the wavelengths tunable either by the size of Si nanocrystals or by the molecules. This type of dual-emissive hybrid nanomaterials exhibit possible application potentials as active materials for visible to near infrared light emitting devices or bio-imaging;Chapter4:Si QDs is one of the most important semiconductor nanomaterials showing application potentials in opto-electronics and biology; besides, cadmium sulfide (CdS) as a typical â…¡-â…¥ semiconductor material is widely adopted and investigated in structural semiconductor nano materials, for example, CdS based core/shell structured QDs of CdSe/CdS, CdTe/CdS, PbS/CdS and InP/CdS etc. Here we report the synthesis and characterization of quasi-monodispersed colloidal core/shell Si/CdS NCs with a Si QD core and controllable CdS shell thickness. The bandgaps of Si and CdS are of the staggered structure-both the valence and conduction bands of CdS lower than of the Si-for their heterojunction, known as the type-II heterojunction. Accordingly, Si/CdS NCs are type-II NCs. Type-II NCs are expected to have many novel properties because of the band structure induced spatial separation of carriers. In this work, the spectroscopic and electronic properties of Si/CdS NCs were investigated. Tunable properties were exhibited with varying the thickness of the CdS shell.