SEMINAIRE LMGP - 31.05.2022 - Alexandre DIEULESAINT

“ Oxygen plasma treatment to engineer defect complexes in ZnO nanowires grown by chemical bath deposition”


Alexandre DIEULESAINT
PhD student,
LMGP, Univ. Grenoble Alpes, CNRS, Grenoble INP

Chemical Bath Deposition of ZnO nanowires (NWs) [1] is a low-cost and low temperature hydrothermal growth process of particular interest. It enables homogeneous and oriented growth of vertically aligned ZnO NWs from a polycrystalline ZnO seed layer deposited on a wide range of substrates. During the growth of NWs, the chemical bath reactants introduce crystal defects caused by the presence of numerous impurities such as carbon, nitrogen, and hydrogen [2]. These defects and their related complexes consequently impact the NW properties. On the one hand, interstitial hydrogen in bond-centered sites (H_BC) and 3-hydrogen paired zinc vacancy (V_Zn-3H) are examples of such defect complexes that operate as shallow donors with low formation energies [3] and govern the electrical behavior of ZnO NWs. On the other hand, the zinc vacancy paired with nitrogen and hydrogen (V_Zn-N_O-H) defect complex that also has a low formation energy behaves as a deep acceptor and acts as a compensating defect. Raman and cathodoluminescence spectroscopy revealed that thermal annealing under an oxygen atmosphere allows control of the concentration and nature of these defect complexes [4]. The increase of annealing temperature induces a series of associative and dissociative processes that affects the concentration of defect complexes under an oxidizing atmosphere.

The use of oxygen plasma is a different way of tuning the formation and concentration of these defects since it directly impacts their nature and the related electrical properties of ZnO NWs [5-6]. Although some plasma process parameters have been shown to play a significant role on the properties of ZnO NWs, data on local plasma parameters such as ion energy and ion flux near the interaction site is lacking. In this work, we measure those parameters using a retarding field energy analyzer (RFEA) and a Langmuir probe to report their impact on hydrogen-related defects and oxygen vacancies (V_O) using Raman spectroscopy and X-ray photoelectron spectroscopy .

[1] L. Vayssieres et al. J. Phys. Chem. B. 105 (17), 3350–3352 (2001).

[2] C. Van De Walle. Phys. Rev. Lett. 85 (5), 1012–1015 (2000).

[3] J. Villafuerte et al. J. Phys. Chem. C, 124 (30), 16652–16662 (2020).

[4] J. Villafuerte et al. Phys. Rev. Mater. 5 (5), 1–15 (2021).

[5] H. Jiang et al. R. Soc. Chem. 51 (8), 28928 (2018).

[6] D. Park et al. Korean J. Met. Mater. 59 (3), 209–216. (2021)