Dielectric sensing by charging energy modulation in a nano-granular metal

Abstract

Several sensing concepts using nanostructures prepared by focused electron beam induced deposition have been developed over the last years. Following work on highly miniaturized Hall sensors for magnetic sensing with soft magnetic Co, strain and force sensing based on nano-granular platinum-carbon structures (Pt(C)) was introduced. Very recently the capability of nano-granular Pt(C) structures to detect the presence of adsorbate water layers by conductance modulations was demonstrated. For magnetic and strain sensing the underlying physical mechanisms of the sensing effect have been analyzed in detail and are now quite well understood. This is not the case for the adsorbate layer induced conductance modulation effect. Here we provide a theoretical framework that allows for a semi-quantitative understanding of the observed water-sensing effect. We show how the near-interface renormalization of the Coulomb charging energy in the nano-granular metal caused by the dielectric screening of the polarizable adsorbate layer leads to a conductance modulation. The model can account for the conductance modulation observed in the water adsorbate experiments and can also be applied to understand similar effects caused by nearinterface dielectric anomalies of ferroelectric thin films on top of nano-granular Pt(C). Our findings provide a pathway towards optimized nano-granular layer structures suitable for a wide range of dielectric or local potential sensing applications.

Focused electron beam induced deposition meets materials science

“…These comprise amorphous and polycrystalline superconductors [5,6,7], magnetic materials [8], alloys and intermetallic compounds [9,10,11,12,13,14,15], multilayer structures [15,16] and metamaterials in which suitable materials combinations result in a desired functionality [17,8]. The latter approach, in particular, has opened a new pathway to the realization of different sensor applications [18,19,20,21,22].…”

Single‐Electron Effects for Probing Local Electrical Polarization Changes and Charge Hopping

“…In particular, the temperature‐driven ferroelectric phase transition in the quasi one‐dimensional charge transfer salt tetrathiafulvalene‐chloranil (TTF‐QCl 4 , in short) was shown to cause strong conductance changes in the granular metal layer of thin film Pt(C)/TTF‐QCl 4 heterostructures in which Pt(C) is a granular metal consisting of Pt nanoparticles embedded in an amorphous carbon matrix . The conductance modulation in the Pt(C) layer was theoretically reproduced in a mean‐field like approach taking charging energy renormalization effects in the granular metal layer into account that are caused by the strong increase of the dielectric constant at the ferroelectric transition of the TTF‐QCl 4 layer …”

“…[9] The conductance modulation in the Pt(C) layer was theoretically reproduced in a mean-field like approach taking charging energy renormalization effects in the granular metal layer into account that are caused by the strong increase of the dielectric constant at the ferroelectric transition of the TTF-QCl 4 layer. [10] Here, we build on our recent work on conductance modulations in granular metals caused by dielectric changes in their immediate neighborhood and aim to develop a more general framework for the use of ordered or disordered nanoisland arrays for dielectric sensing. This approach is particularly suited for small-size nano-island arrays.…”

Microscopic theory of the Coulomb based exchange coupling in magnetic tunnel junctions

“…Figure 8 shows the temperature dependence of IEC, H ex , with TTF-CA FE as an insulating layer. The FE Curie point of TTF-CA is = T 56 C K [41,42]. Using data of [41,42] we find the temperature dependence of TTF-CA dielectric constant.…”

“…The FE Curie point of TTF-CA is = T 56 C K [41,42]. Using data of [41,42] we find the temperature dependence of TTF-CA dielectric constant. Experimental data are fitted well with the following dependence of dielectric constant on temperature insulating layer.…”