Stabilization of p-type ZnO with ZnO2 as precursor – ZnO-typé-p

Within the framework of fundamental investigations carried out in collaboration between the Institut des Matériaux Jean Rouxel and the Institut des Sciences Chimiques de Rennes, the stabilization of a p-type zinc oxide material with the wurtzite structure has recently been achieved by ammonolysis at low temperature with zinc peroxide as precursor (see J. Am. Chem. Soc., 2012, 134, 464). The nature of the charge carriers was identified without ambiguity by photo-electrochemistry, complex impedance spectroscopy and pump-probe spectroscopy. At first glance, the stabilization of p-type carriers would result from a strong zinc non-stoichiometriy coupled with the coexistence of O2- entities, (O2)2- pairs and nitrides whose the exact chemical form remains to be determined (eg. N3-, NH2-, NH2-, ...). Surprisingly, the p-type conductivity remains stable for more than two and a half years at ambient conditions. This is a significant result considering the various controversies regarding the potential existence of such a material. Note that the stabilization of p-type derivative of ZnO could pave the way for the manufacturing of inorganic electronic components (diodes, transistors ...) based on n-ZnO/p-ZnO: N colorless homo-junctions that could gradually lead to the replacement of expensive gallium nitride in optoelectronics.
The objective of this project is to reproduce the synthesis of zinc oxide doped with nitrogen and to characterize it in detail to better understand the origin of the p-type conductivity, the high stability of the hole carriers, and the impact of defects on the electrical and optical properties. We then plan to deposit the material as a thin film with the aim of preparing a homo-junction n-ZnO/p-ZnO:N. Meanwhile, we will try to generate other p-type derivatives of ZnO:N. Formally, recent studies in the laboratory highlighted the possibility to stabilize zinc oxide severely deficient in cations (up to 20% Zn vacancies) using ZnO2 as precursor. These cationic vacancies can be partially or completely refilled by appropriate cations, thus opening the door for multiple substitutions to access p-type conductivity. Obviously, this cationic substitution could be accompanied by anionic substitution O / N.