**3. Atomic 2D graphene crystal**

Graphene is a crystalline two-dimensional layer of carbon with the thickness of one atom (**Figure 3**). A huge interest in this material appeared in 2004 after the joint publication of researchers from IMT RAS and Manchester University on the effect of an electric field in atomic-thin carbon films [11]. Six years later in 2010, Andrei Geim and Konstantin Novoselov were awarded the Nobel Prize in Physics for "pioneering experiments with 2D graphene material."

Graphene consists of two symmetric carbon sublattices that form the Dirac cone of the linear energy dispersion of the electrons, which are called Dirac fermions. The peculiarity of these particles is that they are massless and behave like photons. In consequence, graphene demonstrates magical properties. Graphene transparent (97.7%), resistant to an extremely high current density (one million times higher than that of copper), has the highest electron mobility of known materials (~10<sup>6</sup> cm2 B−1 s−1, three orders of magnitude higher than in silicon) and a very high thermal conductivity (K > 5 × 103 W/(m × K)), which is higher than that of a diamond. Graphene is a well stretchable (25%) material with a unique mechanical strength E > 10<sup>12</sup> Pa (six times higher than steel). In addition, graphene shows very good biocompatibility.

**3.2. The mechanism of resistive switching in graphene/graphene oxide**

**Figure 4.** Resistive switching of the Al/GO/Al structure, performed at 5 V [12].

conductivity in carbon nanomaterials by 50% [18]. Graphene oxide with a sp3

**3.3. Self-organization of memristors based on graphene/graphene oxide**

an important role. One sp3

**Figure 3.** The crystal lattice of graphene.

The mechanism of resistive switching in G/GO was studied in detail in a number of works [12–17] in which it was shown that the migration of oxygen-containing groups in GO plays

tion possessing low electrical conductivity was switched in an electric field locally in the sp<sup>2</sup> configuration of carbon (**Figure 6**), which led to high electrical conductivity. This process can be controlled both by adsorption/desorption of oxygen and by migration of oxygen-related groups.

The photocatalytic oxidation of graphene coated with a layer of 10–15 nm ZnO nanoparticles under ultraviolet (UV) irradiation conditions led to the formation of self-organized G/GO memristors with very high density (1012 cm−2) [16, 17]. **Figure 7** shows the scheme of photocatalytic oxidation of graphene with ZnO nanoparticles. A 2–3-layer graphene coated with

carbon-oxygen or carbon-hydroxyl bond on 106

sp2

Memristive Systems Based on Two-Dimensional Materials

http://dx.doi.org/10.5772/intechopen.78973

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bonds reduced

carbon configura-

#### **3.1. Memristor based on graphene/graphene oxide**

In 2010, researchers from IMT RAS and Dongguk University demonstrated a graphene/ graphene oxide (G/GO) memristor that switched at 0.7 V and 1 nA, with an on/off ratio of about 103 (**Figure 4**) [12, 13]. The electron beam-induced current method made it possible to reveal, with a high spatial resolution, the formation of randomly distributed current filaments (**Figure 5**) and to study the switching mechanism in this device like a synapse. The resistance of this device varied nonlinearly in the electric field, and the values of high and low resistance were nonvolatile.

**Figure 3.** The crystal lattice of graphene.

associative memory and the ability to learn deeply, the knowledge of which was laid down in the works of the Russian physiologist Ivan Pavlov, who received the Nobel Prize in Physiology in 1904. The study of digestion pushed him to the idea of conditioned reflexes. Such acquired reflexes arise under certain conditions and disappear when conditions are not observed.

Graphene is a crystalline two-dimensional layer of carbon with the thickness of one atom (**Figure 3**). A huge interest in this material appeared in 2004 after the joint publication of researchers from IMT RAS and Manchester University on the effect of an electric field in atomic-thin carbon films [11]. Six years later in 2010, Andrei Geim and Konstantin Novoselov were awarded the Nobel Prize in Physics for "pioneering experiments with 2D graphene

Graphene consists of two symmetric carbon sublattices that form the Dirac cone of the linear energy dispersion of the electrons, which are called Dirac fermions. The peculiarity of these particles is that they are massless and behave like photons. In consequence, graphene demonstrates magical properties. Graphene transparent (97.7%), resistant to an extremely high current density (one million times higher than that of copper), has the highest elec-

silicon) and a very high thermal conductivity (K > 5 × 103 W/(m × K)), which is higher than that of a diamond. Graphene is a well stretchable (25%) material with a unique mechanical strength E > 10<sup>12</sup> Pa (six times higher than steel). In addition, graphene shows very good

In 2010, researchers from IMT RAS and Dongguk University demonstrated a graphene/ graphene oxide (G/GO) memristor that switched at 0.7 V and 1 nA, with an on/off ratio of

reveal, with a high spatial resolution, the formation of randomly distributed current filaments (**Figure 5**) and to study the switching mechanism in this device like a synapse. The resistance of this device varied nonlinearly in the electric field, and the values of high and low resistance

(**Figure 4**) [12, 13]. The electron beam-induced current method made it possible to

B−1 s−1, three orders of magnitude higher than in

**3. Atomic 2D graphene crystal**

70 Advances in Memristor Neural Networks – Modeling and Applications

**Figure 2.** Neural network.

tron mobility of known materials (~10<sup>6</sup> cm2

**3.1. Memristor based on graphene/graphene oxide**

material."

biocompatibility.

were nonvolatile.

about 103

**Figure 4.** Resistive switching of the Al/GO/Al structure, performed at 5 V [12].
