Fundamental Issues and Problems in the Realization of Memristors

TL;DR

This paper critically examines the physical and theoretical foundations of the HP memristor model, highlighting overlooked electrochemical factors and fundamental principles that challenge its validity as a genuine memristor.

Contribution

It provides a detailed critique of the HP memristor model, emphasizing overlooked electrochemical effects and fundamental energy principles that question its authenticity.

Findings

The HP model neglects diffusion currents at boundary regions.

The device may operate as a chemical capacitor, violating memristor properties.

The dynamical state equation conflicts with Landauer's principle.

Abstract

In 2008, researchers at the Hewlett-Packard (HP) laboratories claimed to have found an analytical physical model for a genuine memristor device [1]. The model is considered for a thin TiO_2 film containing a region which is highly self-doped with oxygen vacancies and a region which is less doped, i.e., a single-phase material with a built-in chemical inhomogeneity sandwiched between two platinum electrodes. On base of the proposed model, Strukov et al. [1] were able to obtain the characteristic dynamical state equation and current-voltage relation for a genuine memristor. However, some fundamental facts of electrochemistry have been overlooked by the authors while putting forward their model, namely the coupling of diffusion currents at the boundary between both regions. The device will operate for a certain time like a "chemical capacitor" until the chemical inhomogeneity is balanced out, thus violating the essential requirement on a genuine memristor, the so-called "no energy discharge property". Moreover, the dynamical state equation for the HP-memristor device must fail as this relation violates by itself Landauer's principle of the minimum energy costs for information processing. Maybe, such an approach might be upheld if one introduces an additional prerequisite by specifying the minimum amount of electric power input to the device which is required to continuously change internal, physical states of the considered system. However, we have reasonable doubts with regard to this.