Kinetics of II-VI and III-V colloidal semiconductor nanocrystal growth: "Focusing" of size distributions
Kinetics of II-VI and III-V colloidal semiconductor nanocrystal growth: "Focusing" of size distributions
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DOI：
10.1021/ja9805425
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发表时间：
1998-06-03
影响因子：
15
通讯作者：
Alivisatos, AP
中科院分区：
文献类型：
--
作者：
Peng, XG;Wickham, J;Alivisatos, AP
在过去的几年里，开发可靠和可重复的方法来生产大量均匀尺寸的无机纳米晶体一直是材料化学研究的主要目标。以半导体为例，最成功的制备方法是从分子前体在溶液中生长。用这种方法制备了II-VI (CdS, CdSe) 5-7和III-V (InP, InAs) 8-16纳米晶体，得到了高结晶性和可加工的纳米颗粒。在这些类型的制剂中，以前采用了两种广泛的策略来制备窄尺寸分布。在第一种情况下，允许纳米颗粒在中等温度（180-300℃）下长时间成核和生长，5产生大范围的尺寸。然后可以对这种广泛的分布进行排序。第二种方法是通过在较高温度（350℃）下快速注入诱导成核，然后在生长阶段降低温度，使成核与生长分离，从而产生一种尺寸的颗粒。不幸的是，这种方法严重依赖于初始成核和生长的精确动力学，在iii - v中是不可能的。在微米级的胶体体系中，Reiss从理论上证明，通过考虑扩散面积与尺寸的关系，扩散限制生长可以导致尺寸分布随时间的缩小。只要晶体足够小，吉布斯-汤姆逊效应显著，那么晶体生长的动力学也会受到表面能随尺寸变化的强烈影响。在本文中，我们证明了这些效应确实影响了II-VI和III-V纳米晶体生长的动力学。在CdSe和InAs的情况下，众所周知，带边发光能量强烈依赖于尺寸，我们使用这一性质来评估生长过程的时间演化。纳米晶体的发光能量随尺寸的变化是先前通过透射电子校准的
The development of reliable and reproducible methods for producing large amounts of uniformly sized inorganic nanocrystals has been a major goal in materials chemistry research over the last several years. In the case of semiconductors, the most successful preparations involve growth in solution from molecular precursors. 1-4 Both II-VI (CdS, CdSe) 5-7 and III-V (InP, InAs) 8-16 nanocrystals have been prepared using such methods, yielding highly crystalline and processable nanoparticles. Two broad strategies have been employed previously for preparing narrow size distributions in these types of preparations. In the first case, nucleation and growth of nanoparticles are allowed to take place over an extended period of time at a moderate temperature (180-300 C), 5 yielding a wide range of sizes. This broad distribution can then be sorted. 6 The second approach involves separation of nucleation from growth by injecting rapidly at higher temperature (350 C) to induce nucleation and then reducing the temperature during the growth phase, 7 yielding particles of one size. Unfortunately, this approach depends critically on the precise kinetics of the initial nucleation and growth and has not been possible in the III-Vs. In micron-sized colloidal systems, Reiss demonstrated theoretically that diffusion-limited growth can lead to narrowing of size distributions with time by considering the diffusion area vs size. 17 The kinetics of crystal growth will also be influenced strongly by the variation of the surface energy with size, provided the crystallites are small enough that the Gibbs-Thomson effect is significant. 18-20 In this paper we demonstrate that these effects do indeed influence the kinetics of II-VI and III-V nanocrystal growth.In the cases of CdSe and InAs, the band edge luminescence energy is well-known to depend strongly on the size, and we use this property to assess the time evolution of the growth process. The variation of the luminescence energy of the nanocrystals versus size was calibrated previously by transmission electron