Effect of Oxide Defect Structure on the Electrical Properties of ZrO<sub>2</sub>

Kumar, Arun; Rajdev, Dilip; Douglass, D. L.

doi:10.1111/j.1151-2916.1972.tb11336.x

Cited by 75 publications

(42 citation statements)

References 16 publications

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“…For this material, we present in Fig. 1(a) [48,49] and oxide off-stoichiometry [50] of MZrO 2 exhibit a slope of −1=6 with log 10 P O 2 at low values of P O 2 and at temperatures as high as 1200 K. The forgone conclusion based on these experiments is that the −1=6 slope at low P O 2 is due to the equilibrium established between free electrons and V •• O . Our theoretical predictions are in accordance with this conclusion.…”

Section: Resultsmentioning

confidence: 84%

“…On the other hand, a slope of 1=4 is found in the electrical conductivity measurements of Ref. [49], and this is attributed to the compensation between holes and singly charged interstitial oxygen O 0 i . The discrepancy in the experimental findings could be, in part, due to the differences among the impurities within the samples.…”

Section: Resultsmentioning

confidence: 99%

“…Electron transport is expected to be slowest in the oxygen-rich part of the oxide [48,49], corresponding also to the oxide surface where the reduction of protons takes place. Electron transport is quantified by the electronic conductivity σ, and in an insulator σ is proportional to the concentration of electrons in the conduction band, n c .…”

Section: E Kinetic Factors: Proton Reduction and Hydrogen Diffusionmentioning

confidence: 99%

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Doping in the Valley of Hydrogen Solubility: A Route to Designing Hydrogen-Resistant Zirconium Alloys

2016

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Hydrogen pickup and embrittlement pose a challenging safety limit for structural alloys used in a wide range of infrastructure applications, including zirconium alloys in nuclear reactors. Previous experimental observations guide the empirical design of hydrogen-resistant zirconium alloys, but the underlying mechanisms remain undecipherable. Here, we assess two critical prongs of hydrogen pickup through the ZrO 2 passive film that serves as a surface barrier of zirconium alloys; the solubility of hydrogen in it-a detrimental process-and the ease of H 2 gas evolution from its surface-a desirable process. By combining statistical thermodynamics and density-functional-theory calculations, we show that hydrogen solubility in ZrO 2 exhibits a valley shape as a function of the chemical potential of electrons, μ e . Here, μ e , which is tunable by doping, serves as a physical descriptor of hydrogen resistance based on the electronic structure of ZrO 2 . For designing zirconium alloys resistant against hydrogen pickup, we target either a dopant that thermodynamically minimizes the solubility of hydrogen in ZrO 2 at the bottom of this valley (such as Cr) or a dopant that maximizes μ e and kinetically accelerates proton reduction and H 2 evolution at the surface of ZrO 2 (such as Nb, Ta, Mo, W, or P). Maximizing μ e also promotes the predomination of a less-mobile form of hydrogen defect, which can reduce the flux of hydrogen uptake. The analysis presented here for the case of ZrO 2 passive film on Zr alloys serves as a broadly applicable and physically informed framework to uncover doping strategies to mitigate hydrogen embrittlement also in other alloys, such as austenitic steels or nickel alloys, which absorb hydrogen through their surface oxide films.

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Section: Resultsmentioning

confidence: 84%

Section: Resultsmentioning

confidence: 99%

Section: E Kinetic Factors: Proton Reduction and Hydrogen Diffusionmentioning

confidence: 99%

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Doping in the Valley of Hydrogen Solubility: A Route to Designing Hydrogen-Resistant Zirconium Alloys

2016

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“…[2] Pure HfO 2 , however, becomes crystalline at temperatures lower than 500°C, [3] resulting in problems of leakage current and oxygen diffusion through the grain boundary. [4,5] Also, after rapid thermal annealing (RTA) at high temperatures, an interfacial layer between HfO 2 and the Si substrate was formed. [6] For high-k gate dielectrics, an amorphous structure is always preferred, because polycrystalline film can introduce a high leakage path along grain boundaries with non-uniformities in the dielectric constant, and an increase in surface roughness.…”

Section: Introductionmentioning

confidence: 99%

Cyclic Atomic Layer Deposition of Hafnium Aluminate Thin Films Using Tetrakis(diethylamido)hafnium, Trimethyl Aluminum, and Water

Kim¹,

Rhee²

2006

Chemical Vapor Deposition

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Hafnium aluminate thin films were deposited at 225°C by cyclic atomic layer deposition (ALD) of hafnia and alumina with Hf(N(C 2 H 5 ) 2 ) 4 (tetrakis(diethylamido)hafnium: TDEAH), Al(CH 3 ) 3 (trimethyl aluminum: TMA), and H 2 O. The multi-component thin films were formed by switching between the alumina and hafnia deposition cycles, and the chemical composition of the film was controlled by adjusting the number of cycles of each oxide. The surface of the film was very smooth and the formation of an interfacial layer was suppressed. The crystallization temperature of the film became higher as the Al incorporation in the film was increased. The hafnium aluminate thin film with the composition Hf 0.68 Al 0.32 O x showed a dielectric constant of 13.94 and leakage current of 4.3 × 10 -7 A cm -2 at 1 MV cm -1 . At this composition, the formation of an interfacial layer was minimal after rapid thermal annealing (RTA).

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“…[4±7] Unfortunately these materials are either thermodynamically unstable on silicon (e.g., tantalum and titanium oxides), or the interface can be oxidized due to ionic conductivity (as in the case of zirconium and hafnium oxides). [8,9] Thus, after a thermal annealing step, all of them can form an interface layer of silicon dioxide, metal silicide, or metal silicate, decreasing the performance of a potential device. A possible solution is to directly deposit a metal silicate based on zircon (ZrSiO 4 ), i.e., an alloy of zirconium dioxide and silicon dioxide (Zr 1±x Si x O 2 ).…”

Section: Introductionmentioning

confidence: 99%

New Single-Source Precursors for the MOCVD of High-κ Dielectric Zirconium Silicates to Replace SiO2 in Semiconducting Devices

Zürcher¹,

Morstein

Spencer³

et al. 2002

Chem. Vap. Deposition

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Two new single-source zirconium silicate precursors Zr(acac) 2 (OSiMe 3 ) 2 A, and Zr(acac) 2 (OSi t BuMe 2 ) 2 B, have been synthesized. The stability and vapor pressure of the two compounds were investigated. They have been used to deposit films of Zr 1±x Si x O 2 by metal±organic (MO)CVD in the temperature range 400±700 C. Zirconium silicate films with very low carbon contamination and silicon content, x, in the range 0.05±0.25 have been obtained. The two precursors differ, by a factor of two, in activation energy for the MOCVD of films (63 kJ mol ±1 for A, and 145 kJ mol ±1 for B), and differential scanning calorimetry (DSC) shows they have quite different decomposition temperatures. The film composition was determined by X-ray photoelectron spectroscopy (XPS) and the crystallinity of the layers was studied by X-ray diffraction (XRD). Preliminary electrical characterizations of the zirconium silicate films were conducted on MOS capacitors with Al as gate electrodes. The experiments exhibit the generation of negative charges in the layers during the measurements, shown by a large hysteresis in the CV curves and a shift of the IV curves from the first to the following measurements. Low leakage current densities in the lower voltage regime are observed.

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Effect of Oxide Defect Structure on the Electrical Properties of ZrO₂

Cited by 75 publications

References 16 publications

Doping in the Valley of Hydrogen Solubility: A Route to Designing Hydrogen-Resistant Zirconium Alloys

Doping in the Valley of Hydrogen Solubility: A Route to Designing Hydrogen-Resistant Zirconium Alloys

Cyclic Atomic Layer Deposition of Hafnium Aluminate Thin Films Using Tetrakis(diethylamido)hafnium, Trimethyl Aluminum, and Water

New Single-Source Precursors for the MOCVD of High-κ Dielectric Zirconium Silicates to Replace SiO2 in Semiconducting Devices

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Effect of Oxide Defect Structure on the Electrical Properties of ZrO2

Cited by 75 publications

References 16 publications

Doping in the Valley of Hydrogen Solubility: A Route to Designing Hydrogen-Resistant Zirconium Alloys

Doping in the Valley of Hydrogen Solubility: A Route to Designing Hydrogen-Resistant Zirconium Alloys

Cyclic Atomic Layer Deposition of Hafnium Aluminate Thin Films Using Tetrakis(diethylamido)hafnium, Trimethyl Aluminum, and Water

New Single-Source Precursors for the MOCVD of High-κ Dielectric Zirconium Silicates to Replace SiO2 in Semiconducting Devices

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Effect of Oxide Defect Structure on the Electrical Properties of ZrO₂