Cotunneling current affected by spin-polarized wire molecules in networked gold nanoparticles

Abstract

As a bottom-up approach toward spintronics, a network structure of gold nanoparticles connected with spin-polarized wire molecules has been studied. A spinless network is prepared as a reference system. The network of gold nanoparticles with an average diameter of 4 nm form granules ͑average diameter of 100 nm͒, which in turn, connect themselves with each other to bridge 2 m-gap gold electrodes. Since the charging energy of a 4-nm gold nanoparticle amounts to 160 meV, it works as a Coulomb island and the conduction through the network is dominated by Coulomb blockade effect at room temperature. Thermal-activation-type conduction is found in a temperature range of 300 K-30 K, below which cotunneling is suggested to dominate. Important findings reported here are as follows: ͑1͒ The cotunneling occurs at elevated temperatures as high as T = 30 K due to the small size of gold nanoparticles: Nonlinear characteristics featured by I-V 3 are found, suggesting that the number of tunnel junctions relevant to the cotunneling is two. ͑2͒ The cotunneling current is substantially smaller in spin-polarized network than in spinless network, suggesting that spin-flip scattering caused by localized spins on wire molecules suppresses cotunneling process: The interpretation is supported by negative magnetoresistance observed in spin-polarized networks.

Superperiodic conductance in a molecularly wired double-dot system self-assembled in a nanogap electrode

“…6 is quite reasonable. Although the cotunneling conduction in a highly ordered domain of the hybrids was studied extensively, 14,21,22 that in the network composed of a limited number of hybrids has scarcely been studied. Our result clearly shows that cotunneling occurred in the double-dot system of hybrids, based on the observation of I SD − V D curves, Coulomb diamond, and the SEM image of the device.…”

Designing organic spin filters in the coherent tunneling regime

“…To understand the spin filtering properties that are due to single molecules, it makes sense to examine them in a variety of environments and to identify unique properties by comparison. Experimentally, organic radical bridges have been studied using conductance measurements on gold nanoparticle arrays, where radicals bridge the nanoparticles, 12 and in electron donor-bridge-acceptor complexes. 13,14 For the latter, it has been found that radical bridges may influence the charge recombination dynamics of the charge separated state, and that these dynamics depend on the spin state of the chargeseparated system.…”

Electron Cotunneling Transport in Gold Nanocrystal Arrays

“…We show now that an analysis of the electric field dependence of I(V) curves at low temperature allows to establish the signature of cotunneling transport in the array. In previous works on gold NC arrays [2,[14][15][16], the nonequilibrium transport properties have been analyzed in the context of Middleton and Wingreen (MW) model [27] of percolating currents. One essential parameter of this model is the screening length λ/r = C 0 /C G , where C G = 4πεε 0 r 2 /d is the capacitive coupling of the NC with the gate electrode.…”