Facile solution routes for the syntheses of GeTe nanocrystals

Abstract

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.