Microstructural and optical properties of Sn4Sb6S13 nanocrystals deposited on PAA templates

https://doi.org/10.1016/j.materresbull.2020.110791Get rights and content

Highlights

  • The prepared Sn4Sb6S13 (TAS) thin film on PAA at different deposition temperatures results an evolution in the crystal sizes and shapes at the surface.

  • XRD and Raman patterns presented an increase in the peak intensity and a change in the peaks position toward higher energy indicating the crystalline quality enhancement.

  • The average R% spectra decreased significantly from 71.6% for the PAA layer to 59.9%, indicating the large absorbance of the deposited compound on PAA substrates.

  • The average reflectivity of TAS/PAA multilayered structure increases significantly from 59.9%–61.4% by increasing substrate temperature from 30 to 140 °C, owing to an improvement in the film crystallization.

  • The refractive index (n), extinction coefficient (k), the real and imaginary dielectric constants, as well as the thickness of TAS/PAA multilayers were estimated from the ellipsometric measurements.

Abstract

In this study, the Sn4Sb6S13 (TAS) nanocrystals were grown on the porous anodic alumina (PAA) templates through the vacuum thermal evaporation process at different deposition temperatures. The influence of deposition temperature on the microstructural and optical properties of TAS/PAA was investigated systematically. As the substrate temperature is increased, crystallite size increases while the strain and the dislocation density decrease. An improvement of the crystallinity is deduced from Raman spectra and X-Ray diffraction (XRD) patterns. The homogeneous distribution of TAS nanocrystals on PAA substrates was observed from surface morphology by using atomic force microscopy (AFM) and scanning electron microscope (SEM). The average reflectance of TAS/PAA films decreased significantly from 77 % to 60 % in the visible and near-infrared spectral regions, indicating the large absorbance of the deposited thin film. The optical parameters and thickness of TAS/PAA layers were estimated on the basis of spectroscopic ellipsometry measurements.

Introduction

In recent years, the ternary SnxSbySz compounds have attracted a lot of attention due to their excellent optical and electrical properties in different technological applications in various fields, including thermoelectric energy conversion [1], solar cells [[2], [3], [4]], and sensors [[5], [6], [7], [8]]. Moreover, tin antimony sulfur (TAS) Sn4Sb6S13 nanomaterial can offer novel opportunities for thermo-electronic and solar energy applications due to their cheaper cost, low toxicity and high absorbance [[9], [10], [11]].

Nowadays, the porous anodic alumina (PAA) layer with highly ordered pore arrangement structure and controlled pores diameters can be used as support for growing nanomaterials on which gas sensor and photovoltaic applications are based [[12], [13], [14], [15], [16], [17]]. PAA template has been used as a suitable substrate for depositing various nanomaterials and alloys with various sizes, shapes, and nature, such as Si nanocrystals (NCs) and nanowires (NWs), SnO2 nanotubes (NTs), Ti particles, Ni-Fe alloys, Cu and Ni nanowires (NWs), CdSe NRs, and LiCoO2 NRs [[18], [19], [20], [21], [22], [23], [24], [25], [26]]. The deposition of TAS nanocrystals on PAA template might be used in applications such as photocatalysis and solar energy technology. Due to the porous surface, the PAA substrate is able to accommodate more nanomaterials than planar surface substrates. The effect of the nanoporous alumina substrate on the growth of Sn4Sb6S13 nanocrystals and on their morphological and optical properties has not been studied yet. In this context, we study the effect of PAA template and the deposition temperature on the growth of the TAS compounds and their microstructural and optical properties. In this work, we report the PAA synthesis process by using electrochemical anodization. We also describe the growth of TAS nanocrystals on the PAA template by means of a vacuum thermal evaporation method. This research aims at studying the influences of the porous substrate and the deposition temperature on microstructural, morphological and optical properties of the TAS film. X-Ray diffraction (XRD) and Raman spectroscopy are used to supply information on the stresses, microstrain and crystalline quality of the TAS/PAA. The surface morphology of TAS films on PAA substrates is presented by using the scanning electron microscope (SEM) and atomic force microscopy (AFM). Energy dispersive X-ray (EDX) analysis is performed to determine the elemental compositions of PAA and TAS/PAA layers. UV–vis–NIR spectroscopy is used to measure the evolution of total reflectivity of the TAS film deposited on PAA substrate as a function of deposition temperature. In this study, we have performed ellipsometric measurements to determine the optical parameters (n and k), dielectric constants (εr and εi), and thickness of the TAS/PAA structures deposited at various temperatures.

Section snippets

Elaboration of the PAA templates

PAA films were synthesized on aluminum foils (Al purity > 99.999 %) by electrochemical anodization in a two-step process using 10% sulfuric acid solution under a constant voltage of 25 V for 45 min at 10 °C [18,27,28]. The initial PAA films obtained in the first step were completely removed from the Al substrate using an acid mixture solution (H2SO4: 28 %, H3PO4: 60 %, HNO3: 12 %). The second anodization step was performed under the same conditions as the first step in order to obtain PAA

SEM and EDX analysis

In Fig. 1(a), the top view SEM images of as-prepared PAA layer on aluminum foil are shown. The surface morphology of the PAA layer exhibits hexagonal pore arrays with high regularity and average pores diameter of about 30 nm. The SEM micrographs of the TAS films prepared on PAA substrate at various deposition temperatures (from 30 to 200 °C) are shown in Fig. 1(b–f). A partially smooth surface with the presence of some voids was observed for the TAS film deposited at 30 °C (Fig. 1(b)). As

Conclusion

TAS nanocrystals were successfully deposited on the PAA templates at various temperatures via the vacuum thermal evaporation method. Using SEM and AFM microscopes, we found that the PAA template pores were hexagonally arranged with an average pore size of 30 nm. The TAS thin films deposited on PAA at different temperatures caused an evolution in the crystal sizes and shapes, which exhibit an elongated TAS nanocolumn array with average diameter in the range of 17-19 nm. The XRD and Raman

Author statement

I hereby assure that the contents of this article are original and have neither been published elsewhere in any language fully or partly, nor under review for publication anywhere.

Declaration of Competing Interest

None.

Acknowledgements

The author is grateful to the Tunisian Ministry of Higher Education and Scientific Research for its financial support.

References (48)

  • M.Y. Versavel et al.

    Thin Solid Films

    (2007)
  • J. Gutwirth et al.

    Solids

    (2008)
  • A. Harizi et al.

    Mater. Sci. Semicond. Process.

    (2016)
  • A. Harizi et al.

    Mater. Res. Bulletin

    (2016)
  • I. Trabelsi et al.

    Thin Solid Films

    (2017)
  • S. Senthilkumaar et al.

    Superlattices Microstruct.

    (2012)
  • S. Wedekind et al.

    Surf. Sci.

    (2012)
  • S. Ma et al.

    Mater. Lett.

    (2013)
  • C. Gu et al.

    Sensors Actuators B Chem.

    (2013)
  • F. Laatar et al.

    J. Alloy. Comp.

    (2016)
  • T. David et al.

    Superlattices Microstruct.

    (2008)
  • S. Vasić et al.

    Mater. Charact.

    (2010)
  • A. Santibanez et al.

    Superlattices Microstruct.

    (2016)
  • S. Kumar et al.

    Superlattices Microstruct.

    (2011)
  • K.-H. Xue et al.

    Superlattices Microstruct.

    (2003)
  • F. Laatar et al.

    Superlattices Microstruct.

    (2015)
  • C.L. Liao et al.

    J. Alloy. Comp.

    (2006)
  • F. Laatar et al.

    J. Lumin. Appl.

    (2016)
  • G. Ali et al.

    Sung Oh Cho, Micron

    (2010)
  • L. Petit et al.

    Mater. Chem. Phys.

    (2006)
  • F. Laatar et al.

    Mater. Res. Bull.

    (2016)
  • M. Ghrib et al.

    Appl. Surf. Sci.

    (2012)
  • J. De Laet et al.

    Thin Solid Films

    (1993)
  • F. Laatar et al.

    J. Alloys and Comp.

    (2017)
  • Cited by (0)

    View full text