Re-Oxidation of ZnO Clusters Grown on HOPG

Carlos Morales,Javier Méndez,Pilar Prieto,Leonardo Soriano,Adolfo del Campo

doi:10.3390/coatings10040401

Carlos Morales, Javier Méndez + Show 3 more

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https://doi.org/10.3390/coatings10040401

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Abstract

This article studies the chemical interaction between ZnO and highly oriented pyrolytic graphite for as grown and thermally treated samples. In-situ X-ray photoelectron spectroscopy and ex-situ Raman spectroscopy confirm that graphite is affected by these processes, becoming oxidized and defective only in the presence of ZnO clusters that become recrystallized upon thermal re-oxidation processes performed at 400 °C. By comparing these results with other identical experiments performed with ZnO clusters grown on graphene and even with CoO clusters grown on graphite, the present results show how the interaction of the ZnO clusters with graphitic substrates depend on two factors—firstly, the mode of growth and corresponding morphology, and secondly, the reactivity of the graphitic substrates, either graphene or graphite. The results presented here will help us understand the fundamental interactions in ZnO/graphitic heterostructures and to define their operating limits.

Highlights

The main purpose of the present article is to study the chemical interactions between as grownZnO and highly oriented pyrolytic graphite (HOPG) before and after a set of thermal treatments.ZnO has been deeply studied in the last few decades due to its important optoelectronic properties, its wide band gap at room temperature (~3.3 eV) and large exciton binding energy (~60 meV) [1,2,3]
By means of X-ray photoelectron and Raman spectroscopies, the effects of depositing ZnO on HOPG at room temperature and its interactions after the equivalent re-oxidation thermal treatments that lead to nanopatterning in the case of CoO
ZnO grown on HOPG follows a Volmer–Weber mode of growth characterized by two different regimens [15]

Summary

Introduction

ZnO has been deeply studied in the last few decades due to its important optoelectronic properties, its wide band gap at room temperature (~3.3 eV) and large exciton binding energy (~60 meV) [1,2,3]. These characteristics make ZnO an excellent low-cost candidate substitute for indium tin oxide (ITO) as a transparent conducting oxide in many applications [4,5]. ZnO-graphene structures find applications in multiple fields, such as in high-performance supercapacitors [9], environmental decontamination by photocatalysis [10,11], sensors [12], and solar cells [13]

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