First-principles simulations on bulk Ta2O5 and Cu/Ta2O5/Pt heterojunction: Electronic structures and transport properties

Abstract

Electronic structures and transport properties of bulk Ta2O5 and Cu/Ta2O5/Pt heterojunction have been studied from first principles. Of the two room-temperature phases of bulk Ta2O5, β-, and δ-Ta2O5, our calculated results showed that the β phase has much narrower band gap than the δ-Ta2O5. For Cu/δ-Ta2O5/Pt heterojunction, the p-type Schottky barriers between the Cu (Pt) and Ta2O5 were estimated as 0.9–1.2 eV. Both the standard density-functional calculation and the nonequilibrium Green’s function showed that no conducting channels were formed from Cu to Pt through δ-Ta2O5.

Hidden Structural Order in OrthorhombicTa2O5

“…Figure 1 shows representative structural models for low-temperature Ta Table I shows the calculated lattice parameters and relative total energies of the structural models given in A, and c = 3.88Å. The calculated lattice parameters for the β and δ models are consistent with the experimentally determined values of the orthorhombic and hexagonal phases, respectively, as was found in previous theoretical works [15][16][17][18][19][20], and regarded as evidence that these models are correct. Our calculated total energies, however, show that both models are energetically unstable, with total energies of +1.27 and +0.91 eV/f.u., respectively, with respect to the amorphous structure.…”

“…The superstructure periodicity was shown to change when aliovalent cations, such as W or Li, were incorporated in small amounts to stabilize the phase [12,13]. The superstructures consist of a set of small-unit basic structures and invoked the concept of infinitely adaptive structures [14] for nonstoichiometric Ta 2 O 5−x thatwithin certain composition limits-every composition orders into a different superstructure.Extensive theoretical studies have been made with regards to the bulk properties, dielectric response, and oxygen vacancies (and their diffusion) of Ta 2 O 5 [15][16][17][18][19][20][21][22][23]. In these studies, the low-temperature Ta 2 O 5 phase was typically modeled by high-symmetry structural models, such as the orthorhombic β model [24], or the hexagonal δ model [15] (See Fig.…”

“…Extensive theoretical studies have been made with regards to the bulk properties, dielectric response, and oxygen vacancies (and their diffusion) of Ta 2 O 5 [15][16][17][18][19][20][21][22][23]. In these studies, the low-temperature Ta 2 O 5 phase was typically modeled by high-symmetry structural models, such as the orthorhombic β model [24], or the hexagonal δ model [15] (See Fig.…”

In situ observation of filamentary conducting channels in an asymmetric Ta2O5−x/TaO2−x bilayer structure

“…The simulation results using the first-principles method based on density functional theory [23][24][25] are shown in Fig. 1d.…”

Oxygen vacancy effects in HfO2-based resistive switching memory: First principle study

“…The atomic switch usually has an asymmetric structure where an insulator (HfO 2 , NiO, ZrO 2 , Ti 2 O 5 ,etc) [6][7][8][9][10][11] layer is sandwiched between an oxidiza-ble electrode (Ag or Cu) and an inert electrode (Pt or Au). 12,13 The polarities of the applied voltage in the SET (from high to low resistance states) and RESET (from low to high resistancestates) operations of the switch are opposite to each other. Among them, the Transition Metal Oxides (TMOs) are widely considered as the most promising materials, and the conduction filament mechanism in TMO is widely accepted by most people.…”