ZnTe semiconductor nanoparticles: A chemical approach of the mechanochemical synthesis

To have a better understanding on how ZnTe semiconductor nanoparticles were obtained by high-energy milling under composition, pressure and temperature vial conditions reached during milling, a molar Zn-Te-O ternary representation was disclosed. Through this approach, all the bulk and surface chemical transitions were revealed as: i) stable, ii) stoichiometric and iii) metastable or non-stoichiometric reaction products in the Zn-Te-O molar system. Surface studies (via X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy) and bulk analyses (X-ray diffraction and secondary ion mass spectrometry) were carried out to find out the mechanism of formation of the ZnTe semiconductor nanoparticles. The results showed that the as-milled ZnTe nanoparticles were polycrystalline - with a slight presence of amorphous phases - and chemically homogeneous (according to elemental chemical mapping of Zn K-line and Te L-line). Thus, the way in which the oxygen chemical potential was decreased from Zn2Te3O8 to ZnTe nanoparticles was proposed. Consequently, predicted transitions in the ternary molar representation were consistent with experimental results. A blue shift of the ZnTe nanoparticles (at 10 h milling time) was observed by optical measurements. It implied an enhancement in its direct band gap, attributed to the presence of nanoparticles and coarse particles with both, embedded quantum dots and nanoparticles.