ZnO nanorod bunches formation by Electrophoresis Deposition Technique: influence of the conductivity of the substrate

ESPÍNDOLA, OMAR; MARIN, OSCAR; REAL, SILVINA; COMEDI, DAVID; ZELAYA, MARÍA PRISCILA; TIRADO, MONICA

Tel Aviv

Simposio; ELKIN 2022: 14th International Symposium on Electrokinetics and Research Workshop of the Israel Science Foundation; 2022

Universidad de Tel Aviv, Israel

A novel and simple self-assembled direct formation of ZnO nanorod (NR) bunches on boron (p-type)-doped crystalline Si (100) substrates has been achieved by the EPD technique. All the nanostructures were formed from a colloidal dispersion of ZnO NPs in 2-propanol, at room temperature, and without the use of sacrificial templates or pre-deposited Au nanoclusters on Si substrates.ZnO nanoparticle (NPs) colloidal dispersions were prepared based on a modification of the precipitation method reported by Bahnemann et al. [1]. ZnO NPs sizes were estimated from the absorbance spectra of NPs colloidal dispersions and compared to measurements obtained by TEM, which yielded an average diameter of 5 nm with a narrow size distribution, between 4 and 7 nm.The morphology of ZnO NR bunches is affected by the p-type Si substrate whole conductivity (i.e., B dopant concentration). The nanorod diameters and lengths, as well as the bunch diameters, are larger for substrates with lower conductivity. A ZnO nanoporous film is obtained on non-conductive (nominally undoped) Si substrates without any one-dimensional formation. XRD patterns indicated that ZnO NRs were preferentially formed in (002) direction corresponding to c-axis orientation in the wurtzite structure. Photoluminescence (PL) spectra from NR bunches show a low UV excitonic emission peak and a broad visible emission peak. The light emission properties of nanostructures are strongly determined by the properties of NPs used for the EPD deposition and not by the nanostructure morphology. The incorporation of NaOH during ZnO NP synthesis is useful to complete reactions of all the available Zn2+ to form dispersions with a higher ZnO NPs concentration. Therefore, as virtually all the Zn is consumed, PL spectra do not exhibit Zn-type defects compared to previous work [2]. The easy obtaining of different morphologies of ZnO nanostructures depending on the Si substrate conductivity is desirable for their use as functional materials in technological devices. The results presented in this work expand the EPD technique applications to form nanorod nanostructures in a single step, representing a high technological potential for nanoscale device applications [3].[1]D.W. Bahnemann, C. Kormann, M.R. Hoffmann, Preparation and characterization of quantum size zinc oxide: a detailed spectroscopic study, J. Phys. Chem. 91 (14) (1987) 3789-3798. https://doi.org/10.1021/j100298a015.[2]C. Sandoval, O. Marin, S. Real, D. Comedi, M. Tirado, Electrophoretic deposition of ZnO nanostructures: Au nanoclusters on Si substrates induce self-assembled nanowire growth, Mat. Sci. Eng. B. 187 (2014) 21-25. https://doi.org/10.1016/j.mseb.2014.04.002.[3] S. Real, O. Espíndola, M. P. Zelaya, O. Marin, D. Comedi, M. Tirado, Single-step ZnO nanorod bunches formation on p-type Si-conductive substrates by electrophoretic deposition, Surfaces and Interfaces, 23, 100930 (2021). https://doi.org/10.1016/j.surfin.2021.100930