Lattice small polarons and magnetic interactions drive preferential nanocrystal growth in silicon doped hematite

• DOI: 10.48550/arxiv.1908.03377
• Publication Date: 2019-01-01
• Authors: Mattia Allieta; Marcello Marelli; Mauro Coduri; M. Stefan; Daniela Ghica; Giorgio Morello; F. Malara; Alberto Naldoni
• Keywords: Nanomaterials

Understanding the interplay between structural, chemical and physical properties of nanomaterials is crucial for designing new devices with enhanced performance. In this regards, doping metal oxides a general strategy to tune size, morphology, charge, lattice, orbital spin degrees freedoms has been shown affect photoelectrochemical water splitting, batteries, catalysis, magnetic applications optics. Here we report role lattice small polaron in driving morphological transition from nearly isotropic nanowire crystals Si doped hematite ($\alpha-Fe_2O_3$). Lattice formation well evidenced by increase hexagonal strain degree distortion $FeO_6$ showing hyperbolic trend increasing content. Local analysis via pair distribution function highlights an unreported crossover large polarons, which affects correlation length polaronic short average scales. Ferromagnetic double exchange interactions $Fe^{2+}/Fe^{3+}$ species found be force crossover, constraining chaining bonds along [110] crystallographic direction. This promotes reticular density Fe atoms basal plane only, boosts anisotropic growth nanocrystals more extended facets. Our results show that electronic drive preferential oxides, thus providing route design their functional properties.