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Electrical conductivity in oxygen-deficient phases of transition metal oxides from first-principles calculations

Desjarlais, Michael P.; Thompson, Aidan P.; Brennecka, Geoffrey L.; Marinella, Matthew J.

Density-functional theory calculations, ab-initio molecular dynamics, and the Kubo-Greenwood formula are applied to predict electrical conductivity in Ta2Ox (0 x 5) as a function of composition, phase, and temperature, where additional focus is given to various oxidation states of the O monovacancy (VOn; n=0,1+,2+). Our calculations of DC conductivity at 300K agree well with experimental measurements taken on Ta2Ox thin films and bulk Ta2O5 powder-sintered pellets, although simulation accuracy can be improved for the most insulating, stoichiometric compositions. Our conductivity calculations and further interrogation of the O-deficient Ta2O5 electronic structure provide further theoretical basis to substantiate VO0 as a donor dopant in Ta2O5 and other metal oxides. Furthermore, this dopant-like behavior appears specific to neutral VO cases in both Ta2O5 and TiO2 and was not observed in other oxidation states. This suggests that reduction and oxidation reactions may effectively act as donor activation and deactivation mechanisms, respectively, for VO0 in transition metal oxides.

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TYPE SAND Report YEAR 2013
OSTIDOI

A CMOS Compatible, Forming Free TaOx ReRAM

ECS Transactions (Online)

Stevens, James E.; Mickel, Patrick R.; Hughart, David R.; Marinella, Matthew J.

Resistive random access memory (ReRAM) has become a promising candidate for next-generation high-performance non-volatile memory that operates by electrically tuning resistance states via modulating vacancy concentrations. Here, we demonstrate a wafer-scale process for resistive switching in tantalum oxide that is completely CMOS compatible. The resulting devices are forming-free and with greater than 1x105 cycle endurance.

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TYPE Journal Article YEAR 2013
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Results 251–275 of 342
Results 251–275 of 342