Memristive and magnetoresistance effects of SnSe2

Abstract

Memristor and magnetoresistance (MR) are widely used in the field of information storage. In recent years, SnSe₂, as an information storage material with both memristor and MR effects, has received a lot of attention of the researchers. It is of great significance to further explore its electrical transport mechanism. In this paper, the high-purity bulk SnSe₂ samples are prepared by melting method together with spark plasma sintering. The <i>V</i>-<i>I</i> curves are measured under different temperatures and magnetic fields. The memristive and MR effect of SnSe₂ are systematically investigated. After the memristive characteristics are excluded from interfacial junction effect, phase transition and conductive wire channels, the memristive effect at different temperatures is attributed to the space charge limiting current effect under defect control. Under low electric field conditions, the internal carrier concentration of material is much higher than the injected carrier concentration and the <i>V</i>-<i>I</i> curve obeys ohmic conduction. When the voltage increases to the switching voltage <i>V</i>_on, the internal defects of the material are filled with the injected carriers as the transport time of the injected carrier is less than the dielectric relaxation time, and the <i>V</i>-<i>I</i> curves deviate from ohmic conductivity. When the voltage reaches the transition voltage <i>V</i>_TFL, the injected carrier increases exponentially, and the <i>V</i>-<i>I</i> curve presents negative differential phenomenon. Finally, the space charge inside the material will limit the further injection of external carriers, and the <i>V</i>-<i>I</i> curve follows the Child law. As the temperature decreases to 10 K, the memristive phenomenon weakens because a large number of defects for accepting the injected carriers are reduced due to the decrease of impurity ionization at low temperatures. At the same time, the sample exhibits a large negative MR at 10 K and 100 K. When impurity scattering predominates, the electrons will be subjected to multiple scattering by the impurities, resulting in localization of carriers. The negative MR effect is related to the inhibition of the carrier localization by the magnetic field. In our work, a large negative MR of about –37% at 0.6 T and 10 K are obtained, which is likely to originate from the disordered distribution of Se vacancy in the material. With the increase of temperature, the scattering mechanism gradually evolves from the impurity scattering into the lattice scattering, and the negative MR effect gradually develops into the positive MR effect.