半导体纳米结构的发光性质及其机理doc.docVIP

半导体发光的分类： 1）光致发光，2）电致发光，3）阴极射线发光，4）X射线及高能例子发光，5）化学发光以及6）生物发光等。其共同点就是用不同的能量激发半导体，让其发光，也就是把不同形式的能量转换为光能。 PL定义： Luminescence is one of the most important methods to reveal the energy structure and surface states of semiconductor nanoparticles and has been studied extensively. Whenever a semiconductor is irradiated, electrons and holes are created. If electronhole pairs recombine immediately and emit a photon that is known as fluorescence and if the electrons and holes created do not recombine rapidly, but are trapped in some metastable states separately, they need energy to be released from the traps and recombine to give luminescence. If they spontaneously recombine after some time, it is called photoluminescence (PL). It is reported that the fluorescence process in semiconductor nanoparticles is very complex, and most nanoparticles exhibit broad and Stokes shifted luminescence arising from the deep traps of the surface states. Only clusters with good surface passivation may show high band-edge emission. 5,267,338,339 If the detrapping process is caused by heating or thermostimulation, the luminescence is called thermoluminescence (TL), and the energy corresponding to the glow peak is equal to the trap depth. The TL process is different from the PL not sufficiently high to excite the electrons from their ground states to their excited states. Only the carriers ionized from the surface states or defect sites are involved in the TL process; that is, the thermoluminescence has arisen from the surface states. Thermoluminescence is a good way to detect the recombination emission caused by the thermal detrapping of carriers. It is well known that the UV emission peaks originate from the recombination of free excitons through an exciton-exciton collision process corresponding to near-band-edge (NBE) emission The room-temperature photoluminescence (PL) using a Nd: yttrium-aluminum-garnet laser with a wavelength of 325 nm and a 6 ns pulse width as the excitation source a