4.1.4 Transport Property of Pt/a-TaO x /Pt Resistive Switch
Next, we discuss the electron transport in the Pt/a-TaO x /Pt device [7]. To examine
this, we first constructed a Pt/a-TaO 2.5 /Pt structure (Fig. 18a): the a-TaO 2.5 with
16.5 Å thick was generated by melt-quenching method, and then the structural
optimization and MD simulation were carried out on the a-TaO 2.5 with including
the Pt layers. The transmission spectrum for the Pt/a-TaO 2.5 /Pt heterostructure
shown in Fig. 18b reveals the poor electron conductivity due to the insulating nature
of a-Ta 2 O 5 . On the other hand, in the case of the Pt/a-TaO 2.5-x /Pt structure, generation of discontinued Ta-rich regions between the two electrodes were detected by
visual inspection (note that the O-deficient models were generated by removing
oxygen atoms that were located near other oxygen atoms). As seen in Fig. 18b, small
amount of defect states appear around the Fermi level, which results in the increased
conduction (to ~0.03 in the unit of quantized conductance, 2e
2 /h) in this system
compared with the stoichiometric case. For the system with a continued CF (Pt/aTaO 2-x /Pt), the value of transmission is about 0.6. It is worth noting that the on/off
ratio of 20 in our calculation is comparable to that in a real device (~10) [4].
Fig. 18 (a) Structure of Pt/a-Ta 2 O 5 /Pt, (b) transmission spectra and (c) current-voltage curves of
the Pt/a-TaO x /Pt. Adapted from Ref. [7] with permission from The Royal Society of Chemistry
118
S. Watanabe and B. Xiao
Next, we discuss the electron transport in the Pt/a-TaO x /Pt device [7]. To examine
this, we first constructed a Pt/a-TaO 2.5 /Pt structure (Fig. 18a): the a-TaO 2.5 with
16.5 Å thick was generated by melt-quenching method, and then the structural
optimization and MD simulation were carried out on the a-TaO 2.5 with including
the Pt layers. The transmission spectrum for the Pt/a-TaO 2.5 /Pt heterostructure
shown in Fig. 18b reveals the poor electron conductivity due to the insulating nature
of a-Ta 2 O 5 . On the other hand, in the case of the Pt/a-TaO 2.5-x /Pt structure, generation of discontinued Ta-rich regions between the two electrodes were detected by
visual inspection (note that the O-deficient models were generated by removing
oxygen atoms that were located near other oxygen atoms). As seen in Fig. 18b, small
amount of defect states appear around the Fermi level, which results in the increased
conduction (to ~0.03 in the unit of quantized conductance, 2e
2 /h) in this system
compared with the stoichiometric case. For the system with a continued CF (Pt/aTaO 2-x /Pt), the value of transmission is about 0.6. It is worth noting that the on/off
ratio of 20 in our calculation is comparable to that in a real device (~10) [4].
Fig. 18 (a) Structure of Pt/a-Ta 2 O 5 /Pt, (b) transmission spectra and (c) current-voltage curves of
the Pt/a-TaO x /Pt. Adapted from Ref. [7] with permission from The Royal Society of Chemistry
118
S. Watanabe and B. Xiao