XPS and DFT study of pulsed Bi-implantation of bulk and thin-films of ZnO - the role of oxygen imperfections

TL;DR

This study investigates how pulsed bismuth ion implantation alters the atomic and electronic structures of bulk and thin-film ZnO, emphasizing the role of oxygen imperfections through XPS and DFT analysis.

Contribution

It provides new insights into Bi-embedding in ZnO and the effects of oxygen imperfections, challenging the notion of pure secondary phases forming after implantation.

Findings

Bi-impurities do not form pure Bi2O3 or Bi metallic secondary phases.

Large Bi cluster formation is unfavorable in ZnO hosts.

Oxygen 2s electronic states exhibit pleomorphism.

Abstract

An atomic and electronic structure of the bulk and thin-film morphologies of ZnO were modified using pulsed Bi-ion implantation (1x1017 cm-2 fluence, 70 min exposure under Bi-ion beam, EBi+ = 30 keV, pulsed ion-current density of not more than 0.8 mA/cm2 with a repetition rate of 12.5 Hz). The final samples were qualified by X-ray photoelectron core-level and valence band mapping spectroscopy applying ASTM materials science standard. The spectroscopy data obtained was discussed on the basis of DFT-models for Bi-embedding into ZnO host-matrices. It was established that in the case of direct Bi-impurities insertion into the employed ZnO-host for both studied morphologies neither the only "pure" Bi2O3-like phase nor the only "pure" Bi-metal will be preferable to appear as a secondary phase. An unfavorability of the large cluster agglomeration of Bi-impurities in ZnO-hosts has been shown and an oxygen 2s electronic states pleomorphizm was surely established.