Solution-based synthetic routes are attractive strategies for synthesizing GeTe materials, because they have the potential to impart morphology control on the crystallites and permit liquid-based processing of films and patterned structures. Two liquid phase reaction systems for GeTe nanoparticles (NPs) have been studied using GeCl2·dioxane and trioctylphosphine-tellurium (TOP-Te) in oleylamine (OLA) as solvent and reducing agent and using GeCl2·dioxane and (Et3Si)2Te in trioctylphosphine oxide (TOPO) without the use of any reducing agent. The morphology of the GeTe powders had a strong dependence on the Te source and reaction medium. The SEM image of NPs obtained by the reaction of GeCl2·dioxane and (Et3Si)2Te reveals that with an increase in reaction time (2, 10, 15 and 30 min), the size of the NPs increases and their shape becomes uniform. However, it is interesting to observe that after 30 min, the morphology of the nanoparticles was maintained even after longer reaction times i.e., the duration of heating had no pronounced influence on the size and morphology of the nanocrystals after a particular period of time. Reaction with TOP-Te leads to the formation of irregular GeTe nanocrystals through the so called Ostwald-ripening process. However, with (Et3Si)2Te as Te source, a ligand exchange reaction mechanism has been proposed leading to the formation of well-dispersed GeTe nanoparticles of uniform shape.
基于溶液的合成路线是合成 GeTe 材料的诱人策略,因为它们有可能对晶体进行形态控制,并允许对薄膜和图案结构进行液基加工。以
油胺(O
LA)中的 GeCl2-
二氧六环和
三辛基膦-
碲(TOP-Te)为溶剂和还原剂,以及在不使用任何还原剂的情况下,以
三辛基氧化膦(TOPO)中的 GeCl2-
二氧六环和 (Et3Si)2Te 为溶剂和还原剂,研究了 GeTe 纳米粒子(NPs)的两种液相反应体系。GeTe 粉末的形态与 Te 源和反应介质有很大关系。由 GeCl2-
二氧六环和 (Et3Si)2Te 反应得到的 NPs 的扫描电镜图像显示,随着反应时间(2、10、15 和 30 分钟)的增加,NPs 的尺寸增大,形状变得均匀。然而,值得注意的是,在 30 分钟后,即使反应时间更长,纳米粒子的形态仍能保持不变,也就是说,在特定时间段后,加热时间的长短对纳米晶体的大小和形态没有明显影响。与 TOP-Te 反应会通过所谓的 Ostwald-ripening 过程形成不规则的 GeTe 纳米晶体。然而,以 (Et3Si)2Te 作为 Te 源,
配体交换反应机制被提出,从而形成了分散良好、形状均匀的 GeTe 纳米粒子。