Abstract

Porous films of metals and metal oxides exhibit larger surface areas and higher reactivities than those of dense films. Therefore, they have gained growing attention as potential materials for use in various applications. This study reports the use of a modified direct current magnetron sputtering method to form porous Zn-ZnO composite films, wherein a subsequent wet post-oxidation process is employed to fabricate pure porous ZnO films. The porous Zn-ZnO composite films were initially formed in clusters, and evaluation of their resulting properties allowed the optimal conditions to be determined. An oxygen ratio of 0.3% in the argon gas flow resulted in the best porosity, while a process pressure of 14 mTorr was optimal. Following deposition, porous ZnO films were obtained through rapid thermal annealing in the presence of water vapor, and the properties and porosities of the obtained films were analyzed. An oxidation temperature of 500 °C was optimal, with an oxidation time of 5 min giving a pure ZnO film with 26% porosity. Due to the fact that the films produced using this method are highly reliable, they could be employed in applications that require large specific surface areas, such as sensors, supercapacitors, and batteries.

Highlights

  • Fabrication of Highly Porous and Keywords: zinc oxide; porous film; post-oxidation; direct current (DC) magnetron sputtering; oxidation mechanism

  • The ZnO nanoparticles used for the preparation of pure porous ZnO films are commonly obtained through wet methods, such as hydrothermal, ball milling, sol–gel, and co-precipitation methods [18,19,20,21]

  • The experiment was performed at a process pressure range of 7–20 mTorr, and the substrates were deposited for 60 min at 150 W

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Summary

Introduction

Fabrication of Highly Porous and Keywords: zinc oxide; porous film; post-oxidation; DC magnetron sputtering; oxidation mechanism. Porous zinc oxide films are known to possess excellent semiconductor properties with wide band gaps (i.e., ~3.37 eV), thereby rendering them suitable for application in gas sensors. Porous zinc oxide films are n-type semiconductor materials and, are suitable for use in solar cells [13], photocatalysts [14], varistors, and electrodes. They are relatively inexpensive and are easy to fabricate in various forms, such as nanorods, nanoflakes, and nanofibers [15,16,17]. Dry fabrication methods can be considered, including the gas evaporation/condensation, aerosol [22], and sputtering routes [23]. The sputtering method is Academic Editor: Jordi Sort

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