Effect of the Helium Background Gas Pressure on the Structural and Optoelectronic Properties of Pulsed-Laser-Deposited PbS Thin Films

Ameni Rebhi; Anouar Hajjaji; Joël Leblanc-Lavoie; Salma Aouida; Mounir Gaidi; Brahim Bessais; My Ali El Khakani

doi:10.3390/nano11051254

Effect of the Helium Background Gas Pressure on the Structural and Optoelectronic Properties of Pulsed-Laser-Deposited PbS Thin Films

Nanomaterials (Basel). 2021 May 11;11(5):1254. doi: 10.3390/nano11051254.

Authors

Ameni Rebhi^{1

2

3}, Anouar Hajjaji¹, Joël Leblanc-Lavoie², Salma Aouida¹, Mounir Gaidi^{1

4}, Brahim Bessais¹, My Ali El Khakani²

Affiliations

¹ Photovoltaic Laboratory, Research and Technology Centre of Energy (CRTEn), BP 95, 2050 Hammam-Lif, Tunisia.
² Centre Énergie Matériaux et Télécommunications (INRS-EMT), Institut National de la Recherche Scientifique (INRS), 1650 Boulevard Lionel Boulet, Varennes, QC J3X 1S2, Canada.
³ Faculty of Sciences, University of Tunis El Manar, 2092 Tunis, Tunisia.
⁴ Center of Advanced Research Materials, Research Institute of Sciences and Engineering, University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates.

Abstract

This work focuses on the dependence of the features of PbS films deposited by pulsed laser deposition (PLD) subsequent to the variation of the background pressure of helium (P_He). The morphology of the PLD-PbS films changes from a densely packed and almost featureless structure to a columnar and porous one as the He pressure increases. The average crystallite size related to the (111) preferred orientation increases up to 20 nm for P_He ≥ 300 mTorr. The (111) lattice parameter continuously decreases with increasing P_He values and stabilizes at P_He ≥ 300 mTorr. A downshift transition of the Raman peak of the main phonon (1LO) occurs from P_He = 300 mTorr. This transition would result from electron-LO-phonon interaction and from a lattice contraction. The optical bandgap of the films increases from 1.4 to 1.85 eV as P_He increases from 50 to 500 mTorr. The electrical resistivity of PLD-PbS is increased with P_He and reached its maximum value of 20 Ω·cm at P_He = 300 mTorr (400 times higher than 50 mTorr), which is probably due to the increasing porosity of the films. P_He = 300 mTorr is pointed out as a transitional pressure for the structural and optoelectronic properties of PLD-PbS films.

Keywords: PbS thin films; background pressure effect; bandgap; electrical resistivity; morphology; optoelectronic properties; pulsed laser deposition (PLD).