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Eur. Phys. J. Appl. Phys.
Volume 94, Number 3, June 2021
Article Number 30402
Number of page(s) 6
Section Nanomaterials and Nanotechnologies
Published online 21 June 2021

© EDP Sciences, 2021

1 Introduction

TiO2 and ZnO nanostructures are inexpensive, environmentally friendly and used for optoelectronic, photocatalytic, photonic and solar technologies [1]. The mixture of ZnO and TiO2 exist three forms crystallize: ZnTiO3 (Zn-TiO2), Zn2TiO4 (2ZnO-TiO2) and Zn2Ti3°8 (2Zn-3TiO2). Crystalline ceramics mainly perovskite-type oxides of ATiO3 type, such as ZnTiO3, SrTiO3, MgTiO3, ect., have attracted wide-spread attention in different frontier areas of research due to their outstanding potential in electronics [2], semiconductor [3], in electrodes of solid oxide fuels cell (SOFC) [4], gas sensors [5], memory devices [6], magnetic materials [7], photocatalysis and catalysis [8,9]. Pure perovskite ZnTiO3 is an attractive materiel and have excellent for various applications such as paints, thermistors, microwave dielectrics, dielectric resonators, catalysts, etc. [1015]. Various techniques have been used for the deposition of ZnTiO3, like sol-gel, electrode position, magnetron sputtering, etc. Among the different synthesis methods, the sol-gel one is the best for several advantages, such as producing good quality nano-crystalline films, low processing temperature, possibility of films deposition of both small as well as large areas and complicated forms on various substrates and also, and most important, it is cost effective. Several studies investigated the structural and morphological of ZnTiO3 film on glass and silicon substrates.

In the recent years, porous silicon is used as substrate for various applications such as solar cells, optoelectronics, biological sensors, and medical applications [16,17]. The high surface/volume ratio of PS renders it favorable as a possible matrix for a variety of nanoparticles.

Several researchers have studied the properties of TiO2 and ZnO on porous silicon [18].

The aim of this paper, we perform a systematic study on PS/ZnTiO3 heterostructure for photocatalysis application. For this propose we study the effect of ZnTiO3 thickness variation on the grain sizes. For less than 4 layers ZnTiO3 diffuse inside the pore silicon. We have found that the optimum number of layers which permits grain distribution on the sample surface varies between 4 and 8.

The crystalline phases and structure of the samples was investigated by X-ray diffraction (XRD), the morphology, using scanning electron microscopy (SEM), the surface topology by Atomic Force Microscopy (AFM).

2 Experimental

2.1 Preparation of solution & deposition of the thin films

Polished monocrystalline P-type silicon (boron −doped silicon) with an orientation of (100), thickness of 270 μm and resistivity of 0.8–2.00 Ω cm.

Porous silicon (PS) was elaborated by electrochemical anodization in solution containing HF: C2H5OH with a volume ratio of 1:1 (Fig. 1).

The current density (J = 10 mA/cm2) is used for time 5 min. The porous silicon was then cleaned with ethanol and dried with nitrogen gas.

ZnTiO3 films were prepared using the following procedure.

Zinc acetate dihydrate [Zn (CH3COO) 2 · 2H2O] (99.0%), citric acid monohydrate and Titanium (IV) n-butoxide Ti [O (CH2)3CH3]4 (99%) as precursor materials and ethanol as solvent. The solution A of Titanium (IV) n-butoxide was added drop wise in absolute ethanol maintained under magnetic stirring for 2 h, being observed the formation of a yellow color solution. Likewise, solution B was prepared by using of [Zn (CH3COO)2 · 2H2O] and citric acid as precursor, which were dissolved in ethanol under magnetic stirring for 2 h. The final solution (solution A, solution B) was mixed slowly with some drops of ethyleneglycol and HCl, being stirred overnight at 60 °C. The resultant ZnTiO3 was filtered using Whatman filterpaper.

The one layer of ZnTiO3 was deposited on porous silicon substrates by spin coating at 3000 rpm for 30 s. After deposition, all the films were dried at low temperature reaching 120 °C at 10 min. Then, they are subjected to heat treatment at 800 °C for 2 h in air.

thumbnail Fig. 1

SEM image and of photograph porous silicon. (a) SEM image of porous silicon (PS). (b) Image of porous silicon.

2.2 Characterization

Various analysis techniques were used to characterize the prepared samples. The different phases nature and crystalline structures were determined using a X-ray diffractometer (BRUKER D8 advance model, at room temperature), with CuKα radiation (λ = 1.5418 Å) in the 2θ range from 20° to 70°.

The surface topology, including RMS (Root Mean Square) roughness and roughness average (Ra) of ZnTiO3 films, were analyzed by using atomic force microscopy (AFM). The morphology and size of ZnTiO3films was analyzed by a scanning electron microscopy (SEM, FEI Vrios 460).

3 Results and discussion

3.1 Structural analysis

Figure 2 displays the X-ray diffraction patterns of zinc titanates ZnTiO3 films with different numbers of layers deposited on porous silicon substrates annealed at 800 °C for 2 h. As the annealing temperature was 800 °C, XRD spectra of PS/ZnTiO3 layers presented four diffraction peaks at 30°, 33.12°, 35.23° and 54.62° that corresponding to (220), (104), (311) and (116) peaks of hexagonal phase was observed, which could be matched with JCPDS file number (card No.00-014-0033). The intensities of the (104) peak was higher than other peaks of ZnTiO3 films.

The crystallite size of these samples was calculated along the (104) orientation of hexagonal ZnTiO3 phase using the Scherrer's formula [19].

XRD pattern have been used to determine the crystallites size (D) of the films as a function of the number of layers. The average nanocrystallites size of PS/ZnTiO3 layers were estimated using the Scherrer's formula:where D is the average size of a crystallite, λ is the X-ray wavelength of CuKα radiation and equals to 0.154 nm), θ is the Bragg diffraction angle, β1/2 is the FWHM of the XRD peak appearing at the diffraction angle θ and k is a constant usually taken equal to 0.9.

Table 1 shows the average crystallites size (D) of PS/ZnTiO3 layers annealed at 800 °C for 2 h in air. The results indicate that the crystallite size of ZnTiO3 increased from 111 to 125 nm when the number of layers increases from 4 layers to 8 layers, which confirms the obtained values by AFM measurements. On the other hand, the change in the average crystallite size D of ZnTiO3 deposited on porous silicon may be due to the decrease of the pore size and the reaction between ZnTiO3 layers and the oxygen and the effect of temperature causes the agglomeration of the particle inside the pore induce a smaller grain size.

thumbnail Fig. 2

X-ray diffraction of ZnTiO3 thin films at various number layers deposition.

Table 1

The obtained results of the XRD for ZnTiO3 thin films at various number layers deposition.

3.2 Morphological analysis

3.2.1 AFM analysis

The surface morphology of ZnTiO3 thin films was analyzed using atomic force microscope. Figure 3 shows the typical three-dimensional AFM image of ZnTiO3 thin films prepared by spin coating on porous silicon substrates with different number layers deposition 4, 6 and 8 with annealing temperature 800 °C and a fixed annealing time of 2 h in air. AFM images show that all films are well faceted crystallites, uniform packed and small grain. Compared to PS/ZnTiO3 (4 layers) (218 nm roughness), 6 layers (266 nm roughness) and 8 layers (291 nm roughness), we observed that the surface roughness increases with increasing number layers deposition as shown in Table 2. These results agree with the previous results [20].

thumbnail Fig. 3

Three-dimensional AFM images of ZnTiO3 thin films with various layers. (a) 4 layers, (b) 6 layers, (c) 8 layers.

Table 2

Variation of roughness for ZnTiO3 at different layer deposition.

3.2.2. Scanning electron microscopy (SEM) analysis

SEM micrographs are shown in Figures 4a–4c revealing the nanostructure of the synthesized perovskite ZnTiO3 on porous silicon (PS) for various layers.

Figure 4a shows the porous silicon coated with four layers of perovskite ZnTiO3 and 4b shows PS covered with six layers of ZnTiO3. Two morphologies can be observed, the first Figure 4a correspond to irregular particles heterogeneous and is more dense and much bigger agglomerates of nanoparticles because the particles enter in the pore of silicon but the second Figure 4b, the morphologies changed, and the average grain size changed and increased from 81 to 119 nm. As can be observed in Figure 4c the PS coated with 8 layers, it exhibits a radical changed with (4a) and (4b). The change of the morphology may be due to increase of ZnTiO3 content because the number of layers increased, and the pore of silicon covered totally with the perovskite ZnTiO3. The zinc titanates nanoparticles possess semi-spherical morphology, and it is around 131 nm.

thumbnail Fig. 4

SEM image of ZnTiO3 with different numbers of layers (a) 4 layers, (b) 6 layers and (c) 8 layers.

4 Conclusion

In this work, we have investigated correlation between structural and morphological properties of multilayers perovskite ZnTiO3 coated porous silicon (PS). The structural and morphological properties of the films were studied as a function of the numbers of layers. The XRD patterns of ZnTiO3 present hexagonal phase at 800 °C and the average crystallite size increased with the number of layers. The surface roughness of the film measured from AFM agrees well with result extracted from XRD, the layers surface roughness (Rms), determined by AFM, increased with the number of layers. SEM images reveal that the ZnTiO3-4layers, ZnTiO3-6 layers and ZnTiO3-8 layers have mean particle size of about 81, 119.8 and 131 nm, respectively. These results are very interesting; it is opening the way for possible in the other applications.

Which means that these kinds of structures could be used for specific applications in electronics or in photocatalytic application.

Author contribution statement

Khadija Hammedi performed the measurements. Marouan Khalifa wrote the manuscript.

M. Consuelo Alvarez−Galvan and Hatem Ezzaouia conceived of the presented idea.

All authors commented on previous versions of the manuscript, read and approved the final manuscript.


This work was supported by the Ministry of Higher Education and Scientific Research, Tunisia.


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Cite this article as: Hammedi Khadija, Marouan Khalifa, M. Consuelo Alvarez-Galvan, Hatem Ezzaouia, Correlation between Structural and morphological properties of multilayer perovskite ZnTiO3 coated porous silicon, Eur. Phys. J. Appl. Phys. 94, 30402 (2021)

All Tables

Table 1

The obtained results of the XRD for ZnTiO3 thin films at various number layers deposition.

Table 2

Variation of roughness for ZnTiO3 at different layer deposition.

All Figures

thumbnail Fig. 1

SEM image and of photograph porous silicon. (a) SEM image of porous silicon (PS). (b) Image of porous silicon.

In the text
thumbnail Fig. 2

X-ray diffraction of ZnTiO3 thin films at various number layers deposition.

In the text
thumbnail Fig. 3

Three-dimensional AFM images of ZnTiO3 thin films with various layers. (a) 4 layers, (b) 6 layers, (c) 8 layers.

In the text
thumbnail Fig. 4

SEM image of ZnTiO3 with different numbers of layers (a) 4 layers, (b) 6 layers and (c) 8 layers.

In the text

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