Charge Disproportionation and Voltage‐Induced Metal–Insulator Transitions Evidenced in β‐Pb_xV₂O₅ Nanowires

Abstract

The roster of materials exhibiting metal–insulator transitions with sharply discontinuous switching of electrical conductivity close to room temperature remains rather sparse, despite the fundamental interest in the electronic instabilities manifested in such materials and the plethora of potential technological applications ranging from frequency‐agile metamaterials to electrochromic coatings and Mott field‐effect transistors. Here, unprecedented, pronounced metal‐insulator transitions induced by application of a voltage are demonstrated for nanowires of a vanadium oxide bronze with intercalated divalent cations, β‐PbxV2O5 (x ≈ 0.33). The induction of the phase transition through application of an electric field at room temperature makes this system particularly attractive and viable for technological applications. A mechanistic basis for the phase transition is proposed based on charge disproportionation evidenced at room temperature in near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy measurements, ab initio density functional theory calculations of the band structure, and electrical transport data, suggesting that transformation to the metallic state is induced by melting of specific charge localization and ordering motifs extant in these materials.

Integrating β-Pb0.33V2O5 Nanowires with CdSe Quantum Dots: Toward Nanoscale Heterostructures with Tunable Interfacial Energetic Offsets for Charge Transfer

“…6,14 Figure S1 (Supporting Information) shows the crystal structure of β-Pb x V 2 O 5 where Pb 2+ cations reside within tunnels defined by a V 2 O 5 framework constituted from parallel chains of [VO 6 ] and [VO 5 ] polyhedra. Powder X-ray diffraction and X-ray absorption and emission spectroscopy characterization of the nanowires along with detailed verification of the stoichiometry have been published in previous work.…”

“…Powder X-ray diffraction and X-ray absorption and emission spectroscopy characterization of the nanowires along with detailed verification of the stoichiometry have been published in previous work. 6 The cations are highly ordered along the tunnel framework as indicated by the appearance of superlattice reflections in the powder diffraction patterns. 6 Linker-Assisted Assembly of CdSe QDs onto Nanowire Surfaces.…”

“…6 The cations are highly ordered along the tunnel framework as indicated by the appearance of superlattice reflections in the powder diffraction patterns. 6 Linker-Assisted Assembly of CdSe QDs onto Nanowire Surfaces. Water-dispersible Cys-CdSe and MP-CdSe QDs were synthesized for adsorption onto β-Pb x V 2 O 5 nanowires.…”

“…However, several of the reflections can be indexed to the wurtzite phase of CdSe (JCPDS # 08-0459), whereas others can be indexed to β-Pb 0.304 V 2 O 5 (JCPDS # 41-1426) as depicted in Figure 4D. 6 The lattice spacings of the β-Pb x V 2 O 5 nanowires deduced from the SAED pattern are not substantially altered upon SILAR deposition of the QDs, which is also consistent with Raman data discussed below. The EDS and SAED data depicted in Figure 4 thus provide unequivocal determination of the growth of CdSe QDs stabilized in the wurtzite phase on the nanowire surfaces.…”

“…Mixedvalence ternary vanadium oxide bronzes with a composition of M x V 2 O 5 , where M is a main-group or transition-metal cation and x describes the cation stoichiometry (variable with the specific cation and crystal structure), have been the subject of interest for many years owing to their various intriguing structural and electronic properties. 6,7 Recent attention has focused on the unusual low-dimensional charge transport pathways in these materials, which result from their highly anisotropic crystal structures and distinctive intercalant-dependent charge and spin-ordering motifs. 8−13 Specifically, electronic instabilities in these intrinsically anisotropic materials can be modulated to induce colossal metal−insulator transitions above room temperature and to stabilize superconducting states at high pressure.…”