Abstract
Keywords SnO.sub.2 Nanocrystals; Thin films; p-Type conductivity; Homojunction; I--V Measurements; Quantum tunneling Highlights * Fe-doped SnO.sub.2 thin films were elaborated through a new simple sol-gel method. * HRTEM images reveals the high crystallinity of the obtained nanocrystals. * A conversion of conductivity type from n to p is shown with high Fe doping. * The tunneling current through SnO.sub.2:Fe/p-Si heterojunction increases with iron amount. * Fe-doped SnO.sub.2/non-doped SnO.sub.2 homojunction presents a good rectifying behavior. Nanocrystalline highly Fe-doped SnO.sub.2 thin films were prepared using a new simple sol-gel method with iron amounts of 5, 10, 15 and 20%. The obtained gel offers a long durability and high quality allowing to reach a sub-5 nm nanocrystalline size with a good crystallinity. The films were structurally characterized through X-ray diffraction (XRD) that confirms the formation of rutile SnO.sub.2. High Resolution Transmission Electron Microscopy (HRTEM) images reveals the good crystallinity of the nanoparticles. Raman spectroscopy shows that the SnO.sub.2 rutile structure is maintained even for high iron concentration. The variation of the PL intensity with Fe concentration reveals that iron influences the distribution of oxygen vacancies in tin oxide. The optical transmittance results indicate a redshift of the SnO.sub.2 band gap when iron concentration increases. The above optical results lead us to assume the presence of a compensation phenomenon between oxygen vacancies and introduced holes following Fe doping. From current-voltage measurements, an inversion of the conduction type from n to p is strongly predicted to follow the iron addition. Electrical characterizations of SnO.sub.2:Fe/p-Si and SnO.sub.2:Fe/n-Si heterojunctions seem to be in accordance with this deduction. The quantum tunneling mechanism is expected to be important at high Fe doping level, which was confirmed by current-voltage measurements at different temperatures. Both optical and electrical properties of the elaborated films present a particularity for the same iron concentration and adopt similar tendencies with Fe amount, which strongly correlate the experimental observations. In order to evaluate the applicability of the elaborated films, we proceed to the fabrication of the SnO.sub.2:Fe/SnO.sub.2 homojunction for which we note a good rectifying behavior. Author Affiliation: (a) Departement de Physique, Faculte des Sciences de Tunis, Universite de Tunis El Manar 2092, Tunisia (b) Laboratoire des Materiaux Avances et Phenomenes Quantiques, Departement de Physique, Faculte des Sciences de Tunis, Universite Tunis El-Manar, Tunis, Tunisia (c) UMET, UMR CNRS 8207, Universite Lille 1, 59655 Villeneuve d'Ascq Cedex, France (d) Institut d'electronique, de microelectronique et de nanotechnologie, UMR CNRS 8520, Universite Lille1, Cite scientifique, Avenue Poincare -- CS 60069, 59652 Villeneuve d'Ascq Cedex, France * Corresponding author. Article History: Received 20 June 2017; Revised 17 October 2017; Accepted 4 November 2017 Byline: Walid Ben Haj Othmen [walid1314@yahoo.fr] (a,*), Zied Ben Hamed (b), Brigitte Sieber (c), Ahmed Addad (c), Habib Elhouichet (a), Rabah Boukherroub (d)