Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “TUNNEL EFFECT”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Scanning Probe Microscopy in the Information Age

Scanning probe microscopy (SPM) has brought scientific exploration, visualization, and control to nanoscale. A plethora of measurement approaches and techniques devised around SPM enabled probing structure and functionalities crucial for virtually all areas of science. While high-resolution electron microscopy techniques preceded scanning probes, SPM effectively opened the door to probing the structure–property relationship on length scales spanning 100s of micrometers down to a single atom. As the complexity of the material systems and the scientific questions increased, so too did the SPM techniques. Substantial efforts have been dedicated toward the development of better instrumentation platforms, probes, and novel spectroscopic measurements; however, many opportunities related to data processing and acquisition in SPM are just being realized now. This chapter will describe the recent progress in data-driven SPM by giving a broad overview of the field, the foundation of the scanning tunneling microscope (STM) and the atomic force microscope (AFM), as well as a description behind the operating principles and dynamic modes. A comprehensive overview of the multi-frequency techniques, Band excitation, and general acquisition mode SPM is given, setting the context for the application of big data, machine learning, and artificial intelligence in the field of dynamic SPM.

Collins, Liam↗
DOE OSTI2023

Deterministic Current–Induced Perpendicular Switching in Epitaxial Co/Pt Layers without an External Field

Current–induced spin–orbit torques (SOTs) have emerged as a powerful tool to control magnetic elements and non–uniform magnetic textures such as domain walls and skyrmions. SOT–induced switching of perpendicular magnetization generally requires an external field to break the rotational symmetry of the spin–orbit effective fields responsible for the deterministic reversal. The proposed mechanisms to eliminate this requirement often rely on complex multilayer structures that necessitate laborious optimization in the material and spin transport properties, making them less attractive for applications. Herein, current–induced, external field–free switching of an epitaxial MgO/Pt/Co trilayer with an extremely large perpendicular anisotropy in excess of 3 Tesla is reported. It is found that switching occurs due to the interplay of strong SOTs, local anisotropy fluctuations, and the Dzyaloshinkii–Moriya interaction inherent to this epitaxial system. Finally, given that these layers constitute the base stack of a magnetic tunnel junction, this switching mechanism offers the most technologically viable path toward devices such as field–free SOT–based magnetic random–access memories.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Sputtered indium tin oxide as a recombination layer formed on the tunnel oxide/poly-Si passivating contact enabling the potential of efficient monolithic perovskite/Si tandem solar cells

We focus on utilizing sputtered indium tin oxide (ITO) as a recombination layer, having low junction damage to an n-type silicon solar cell with a front-side tunnel oxide passivating electron contact, thereby enabling the development of a high efficiency monolithic perovskite/Si tandem device. High transparency and low resistivity ITO films are deposited via low power DC magnetron sputtering at room temperature onto a front-side thin SiO x /n + poly-Si contact in a complete Cz n-Si cell with a back-side Al 2 O 3 /SiN x passivating boron-diffused p + -emitter on a random pyramid textured surface. We report the cell characteristics before and after ITO sputtering, and we find a cure at 250 °C in air is highly effective at mitigating any sputtering induced damage. Our ITO coated sample resulted in an implied open-circuit voltage (iV oc ) of 684.7 ± 11.3 mV with the total saturation current density of 49.2 ± 14.8 fA/cm 2 , an implied fill factor (iFF) of 81.9 ± 0.8%, and a contact resistivity in the range of 60 mΩ-cm 2 to 90 mΩ-cm 2 . After formation of a local Ag contact to the rear emitter and sputtered ITO film as the front-side contact without grid fingers, the pseudo-efficiency of 20.2 ± 0.5% was obtained with the V oc of 670.4 ± 7 mV and pseudo FF of 77.3 ± 1.3% under simulated one sun with the calculated short-circuit current density of 30.9 mA/cm 2 from the measured external quantum efficiency. Furthermore, our modelling result shows that efficiency exceeding 25% under one sun is practically achievable in perovskite/Si tandem configuration using the ITO recombination layer connecting a perovskite top cell and a poly-Si bottom cell.

14 SOLAR ENERGY↗
DOE OSTI2021

Photon-Instanton Collider Implemented by a Superconducting Circuit

Instantons, spacetime-localized quantum field tunneling events, are ubiquitous in correlated condensed matter and high-energy systems. However, their direct observation through collisions with conventional particles has not been considered possible. We show how recent advances in circuit quantum electrodynamics, specifically, the realization of galvanic coupling of a transmon qubit to a high-impedance transmission line, allows the observation of inelastic collisions of single microwave photons with instantons (phase slips). We develop a formalism for calculating the photon-instanton cross section, which should be useful in other quantum field theoretical contexts. In particular, we show that the inelastic scattering probability can significantly exceed the effect of conventional Josephson quartic anharmonicity and reach order-unity values.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Programmable Cryogenic Memory in a Ge/GeSi Heterostructure

Programmable memory components that operate optimally at cryogenic temperatures are essential for cryogenic computing architectures that seek to implement computing-in-memory. In this work, we demonstrate highly programmable memory in a Ge/GeSi heterostructure field-effect transistor (HFET). To operate, the HFET is gated to introduce positive carriers within the Ge quantum well, creating a high-conductance state. We show that this device can be set to a low-conductance state by sweeping a negative bias on the device drain, and reset it to its high-conductance state by sweeping a more positive bias on the device gate, thereby creating memory. We then determine that the device can be programmed within a 103 range of conductances using either the SET or the RESET operation. We propose that memory is achieved through charge trapping as carriers tunnel out of the quantum well, and that altering the density and spatial distribution of carriers modulates the device conductance. This mechanism exhibits endurance over 1000 cycles at temperatures ≤ 25 K, suggesting that the carrier traps are located at the oxide-semiconductor interface. As a first demonstration of programmable conductance in a Ge/GeSi HFET, this work highlights the potential of group-IV HFETs to perform as analog cryogenic memory components.

cryogenic memory↗
DOE OSTI2021

Coupling between bulk thermal defects and surface segregation dynamics

Surface segregation is a phenomenon that depends on the delicate interplay between thermodynamic driving forces and kinetic obstacles, for which elevated temperature is often needed to enhance the atom mobility and reach equilibrium. Using the classic system of Cu 3 Au ( 100 ) under nonisothermal conditions, in this study, we show an adatom process underlying transient surface segregation dynamics through the temperature-change-driven creation and annihilation of thermal vacancies in the bulk and the resulting bulk-surface mass exchanges. This is demonstrated by monitoring the surface composition evolution of Cu 3 Au ( 100 ) with temperature changes between 250 and 500 ° C , showing that the increase in temperature decreases monotonically the surface Au concentration as a result of the transfer of more Cu than Au from the bulk to the surface to form Cu-rich clusters of adatoms. Such a bulk thermal defect effect is expected to be universal in inducing the disparity in the bulk-surface mass exchanges of dissimilar atoms in multicomponent materials because of the inherent differences in the vacancy formation energies of the constituent atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Microcanonical rates from ring-polymer molecular dynamics: Direct-shooting, stationary-phase, and maximum-entropy approaches

We address the calculation of microcanonical reaction rates for processes involving significant nuclear quantum effects using ring-polymer molecular dynamics (RPMD), both with and without electronically non-adiabatic transitions. After illustrating the shortcomings of the naive free-particle direct-shooting method, in which the temperature of the internal ring-polymer modes is set to the translational energy scale, we investigate alternative strategies based on the expression for the microcanonical rate in terms of the inverse Laplace transform of the thermal reaction rate. It is shown that simple application of the stationary-phase approximation (SPA) dramatically improves the performance of the microcanonical rates using RPMD, particularly in the low-energy region where tunneling dominates. Using the SPA as a Bayesian prior, numerically exact RPMD microcanonical rates are then obtained using maximum entropy inversion of the thermal reaction rates for both electronically adiabatic and non-adiabatic model systems. Finally, the direct-shooting method is revisited using the SPA-determined temperature for the internal ring-polymer modes, leading to a simple, direct-simulation method with improved accuracy in the tunneling regime. This work suggests a general strategy for the extraction of microcanonical dynamical quantities from RPMD (or other approximate thermal) simulations.

Tao, Xuecheng↗
DOE OSTI2025

Observation of Orbital-Selective Dual Modulations in an Anisotropic Antiferromagnetic Kagome Metal TbTi 3 ⁢Bi 4

Orbital selectivity is pivotal in dictating the phase diagrams of multiorbital systems, with prominent examples including the orbital-selective Mott phase and superconductivity. The intercalation of anisotropic layers represents an effective method for enhancing orbital selectivity and thereby shaping the low-energy physics of multiorbital systems. Despite its potential, related experimental studies, especially those elucidating the correlation between orbital selectivity and magnetism, remain limited. In this work, we systematically examine the interplay between orbital selectivity and magnetism in the newly discovered anisotropic kagome TbTi 3 ⁢Bi 4 single crystal, and report the coexistence of orbital-selective dual-band modulations (𝑞 1 ∼ 1/3⁢𝑎*, 𝑞 2 ∼ 0.28⁢𝑏*) within the antiferromagnetic (AFM) state. By combining soft x-ray and vacuum ultraviolet angle-resolved photoemission spectroscopy measurements, neutron powder diffraction, scanning tunneling microscopy, and density-functional-theory calculations, we identify these dual-band reconstructions as manifestations of the AFM order driven by a (approximately 1/3, 0.28, 0) nesting instability of the intercalated Tb 5⁢𝑑 𝑥⁢𝑧 orbitals. These orbital-selective modulations induce unusual momentum-dependent band folding and lead to the emergence of Dirac cones only at the $\bar{M}$ 1 point, signaling a topological phase transition in the AFM state. Importantly, the discovery of orbital-selective (approximately 1/3, 0.28, 0) AFM order offers crucial insights into the mechanism underlying the fractional magnetization plateau in this kagome AFM metal. Our findings not only underscore the essential role of both conducting and localized electrons in determining the magnetic orders of Ln⁢Ti 3 ⁢Bi 4 (Ln = lanthanide) kagome metals but also offer a pathway for manipulating magnetism through selective control of anisotropic electronic structures.

Zhang, Renjie [Shanghai Jiao Tong University (Chin↗
DOE OSTI2025

Probing the Effects of the First Atomic Layer on the Dynamic Behavior of Sub-2 nm MgO/Al 2 O 3 Memristors

As electronic devices continue to scale down from the current sub-5 nm range, atomic-scale control of defects becomes increasingly crucial to suppressing their impact on the physical properties of the devices. Memristors present an excellent example as a nonlinear and dynamic device with high speed and endurance required for electronic applications ranging from neuromorphic computing to nonvolatile memories. Herein we investigate the impact of atomic defects in sub-2 nm thick MgO/Al 2 O 3 atomic layer stack (ALS) memristors that use an M1 (switching layer)/M2 (oxygen vacancy reservoir layer) bilayer structure grown using in vacuo atomic layer deposition (iALD). Intriguingly, we revealed a direct correlation of the atomic defects in the M2 layer with the memristor dynamic behavior using a combined analysis of in situ scanning tunneling spectroscopy (iSTS) on the M2 layer and ex situ characterization on the memristors. Specifically, incomplete coverage of the 1st ALD atomic layer of M2 on the electrode yields defects at the M2/electrode interface. Despite the monotonic increase of ALD coverage, by almost three-fold from ~30% to >90%, at completion of the M2 layer of ~ 0.7 nm in thickness, the impact of the defects on the M2/electrode interface has been found detrimental to both memristor switching speed and endurance. Guided by atomistic simulation, we addressed the issue of interface defects via tuning of the Al surface hydroxylation to increase the first atomic layer ALD coverage to ~75%, leading to improved memristor switching speed and endurance by several orders of magnitude. In conclusion, these findings shed light on the correlation between the atomic defects and the dynamic behavior of sub-2 nm memristors and the importance of minimizing the atomic defects in memristors for future electronic applications.

Atomic Layer Deposition↗
DOE OSTI2022

Switching the conductance of a single molecule: Lessons from molecular junctions

The concept of using single molecules as functional building blocks in electronic circuitry represents the ultimate device miniaturization and has garnered tremendous attention from physics, chemistry, and engineering. Recent advances in single-molecule junction techniques have enabled direct investigation of charge transport in a quasi-one-dimensional conduction channel composed of an individual molecule. Furthermore, one of the main research focuses over the past decade has been to understand the conductance switching effect of single molecules as it is essential for developing molecular-scale optoelectronics, computing, and sensing applications. In this perspective, we highlight the established physical and chemical mechanisms for single-molecule conductance switching behavior and examine the associated stimuli in single-molecule junction systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Autonomous quantum absorption refrigerators

Here, we propose a quantum absorption refrigerator using the quantum physics of resonant tunneling through quantum dots. The cold and hot reservoirs are fermionic leads, tunnel coupled via quantum dots to a central fermionic cavity, and we propose configurations in which the heat absorbed from the (very hot) central cavity is used as a resource to selectively transfer heat from the cold reservoir on the left to the hot reservoir on the right. Heat transport in the device is particle-hole symmetric; we find two regimes of cooling as a function of the dot energies—symmetric with respect to the Fermi energy of the reservoirs—and we associate them with heat transfer by electrons above the Fermi level and holes below the Fermi level. We also discuss optimizing the cooling effect by fine-tuning the energy of the dots as well as their linewidth and characterize regimes where the transport is thermodynamically reversible such that the Carnot coefficient of performance is achieved with zero cooling power delivered.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

An alcove at the acetyl-CoA synthase nickel active site is required for productive substrate CO binding and anaerobic carbon fixation

One of the seven natural CO 2 fixation pathways, the anaerobic Wood-Ljungdahl pathway (WLP) is unique in generating CO as a metabolic intermediate, operating through organometallic intermediates, and in conserving (versus utilizing) net ATP. The key enzyme in the WLP is acetyl-CoA synthase (ACS), which uses an active site [2Ni-4Fe-4S] cluster (A-cluster), a CO tunnel, and an organometallic (Ni-CO, Ni-methyl, and Ni-acetyl) reaction sequence to generate acetyl-CoA. Here, we reveal that an alcove, which interfaces the tunnel and the A-cluster, is essential for CO 2 fixation and autotrophic growth by the WLP. In vitro spectroscopy, kinetics, binding, and in vivo growth experiments reveal that a Phe229A substitution at one wall of the alcove decreases CO affinity thirty-fold and abolishes autotrophic growth; however, a F229W substitution enhances CO binding 80-fold. Our results indicate that the structure of the alcove is exquisitely tuned to concentrate CO near the A-cluster; protect ACS from CO loss during catalysis, provide a haven for inhibitory CO, and stabilize the tetrahedral coordination at the Nip site where CO binds. The directing, concentrating, and protective effects of the alcove explain the inability of F209A to grow autotrophically. The alcove also could help explain current controversies over whether ACS binds CO and methyl through a random or ordered mechanism. Our work redefines what we historically refer to as the metallocenter "active site". The alcove is so crucial for enzymatic function that we propose it is part of the active site. The community should now look for such alcoves in all "gas handling" metalloenzymes.

bacterial metabolism↗
DOE OSTI2024

Singular Hall Response from a Correlated Ferromagnetic Flat Nodal‐Line Semimetal

Abstract Topological quantum phases are largely understood in weakly correlated systems, which have identified various quantum phenomena, such as the spin Hall effect, protected transport of helical fermions, and topological superconductivity. Robust ferromagnetic order in correlated topological materials particularly attracts attention, as it can provide a versatile platform for novel quantum devices. Here, a singular Hall response arising from a unique band structure of flat topological nodal lines in combination with electron correlation in a van der Waals ferromagnetic semimetal, Fe 3 GaTe 2 , with a high Curie temperature ofT c = 347 K is reported. High anomalous Hall conductivity violating the conventional scaling, resistivity upturn at low temperature, and a large Sommerfeld coefficient are observed in Fe 3 GaTe 2 , which implies heavy fermion features in this ferromagnetic topological material. The scanning tunneling microscopy, circular dichroism in angle‐resolved photoemission spectroscopy, and theoretical calculations support the original electronic features of the material. Thus, low‐dimensional Fe 3 GaTe 2 with electronic correlation, topology, and room‐temperature ferromagnetic order appears to be a promising candidate for robust quantum devices.

Chemistry↗
DOE OSTI2025

Mn(II)-induced phase transformation of Mn(IV) oxide in seawater

Manganese (Mn) oxides are key components of oceanic and lacustrine Mn nodules and influence metal cycling through oxidation and adsorption processes. Layered Mn oxides (LMOs) are the most common minerals in these nodules and the immediate products of microbially mediated Mn(II) oxidation by O 2 . LMOs can transform into tunneled Mn oxides (TMOs), Mn oxyhydroxides (MnOOH), or Mn(II,III) phase (Mn 3 O 4 ). LMOs often concur with Mn(II) in the environment and the adsorption and oxidation of Mn(II) by LMOs can greatly promote the transformation of LMOs to those phases. However, the Mn(II)-promoted transformation of LMOs in seawater—rich in various cations (300 mM Na + , 10 mM K + , 50 mM Ca 2+ , and 10 mM Mg 2+ ) remains poorly understood. We examined the transformation of δ-MnO 2 in artificial seawater (pH 8.2) under anoxic conditions with the Mn(II)/MnO 2 ratio (r) ranging from 0.08 to 3.83. To assess the effect of ionic strength (IS), parallel experiments were conducted in a mixed 530 mM NaCl and 10 mM KCl solution (having seawater ionic strength but without Ca 2+ and Mg 2+ ) and in 100 mM NaCl solution as a control. At low r (0.08), δ-MnO 2 transformed into triclinic birnessite and a 4 × 4 TMO in 100 mM NaCl solution, which, however, was suppressed in seawater due to strong interactions of Ca 2+ /Mg 2+ with δ-MnO 2 . In the mixed 530 mM NaCl and 10 mM KCl solution (the same ionic strength as of seawater), the transformation occurred extensively but the products had lower crystallinity compared to in 100 mM NaCl solution. At the high Mn(II)/MnO 2 ratios (0.5 ≤ r ≤ 3.83), δ-MnO 2 transformed extensively into MnOOH phases and hausmannite (Mn 3 O 4 ) in 100 mM NaCl solution. The seawater suppressed the transformation, but the suppression became weaker with increasing Mn(II)/MnO 2 ratio. For example, the transformation was completely suppressed at r = 0.5 but essentially negligible at r = 3.83. The suppression at these high Mn(II)/MnO 2 ratios was mainly ascribed to the influence of Ca 2+ and Mg 2+ rather than of the high IS, and the weaker suppression at the higher Mn(II)/MnO 2 ratio suggests stronger competition of Mn(II) with Ca 2+ /Mg 2+ for interacting with δ-MnO 2 . Moreover, the composition and crystallinity of the transformation products (i.e., the relative abundance of MnOOH (α, β, and γ) and Mn 3 O 4 ) were influenced by both the high ionic strength and the presence of Ca 2+ and Mg 2+ . Therefore, even though Ca 2+ and Mg 2+ concentrations are much lower than Na + in seawater, their impacts on the transformation are dominant. Our study explains why MnOOH phases, hausmannite, and TMOs are less common than LMOs in oceanic environments, partially because seawater chemistry suppresses their formation. LMOs are the most reactive for metal adsorption and oxidation among all Mn oxides. Thus, the high stability of LMOs in an oceanic environment confers the high impacts of Mn oxides on metal cycling in the ocean.

Divalent manganese↗
DOE OSTI2020

Circular quantum dots in twisted bilayer graphene

Within a tight-binding approach, we investigate the effect of twisting angle on the energy levels of circular bilayer graphene (BLG) quantum dots (QDs) in both the absence and presence of a perpendicular magnetic field. The QDs are defined by an infinite-mass potential, so that the specific edge effects are not present. In the absence of magnetic field (or when the magnetic length is larger than the moiré length), we show that the low-energy states in twisted BLG QDs are completely affected by the formation of moiré patterns, with a strong localization at AA-stacked regions. When magnetic field increases, the energy gap of an untwisted BLG QD closes with the edge states, localized at the boundaries between the AA- and AB-stacked spots in a twisted BLG QD. In this work, our observation of the spatial localization of the electrons in twisted BLG QDs can be experimentally probed by low-bias scanning tunneling microscopy measurements.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Realizing gapped surface states in the magnetic topological insulator Mn Bi 2 - x Sb x Te 4

The interplay between magnetism and nontrivial topology in magnetic topological insulators (MTIs) is expected to give rise to exotic topological quantum phenomena like the quantum anomalous Hall effect and the topological axion states. A key to assessing these novel properties is to realize gapped topological surface sates. MnBi 2 Te 4 possesses nontrivial band topology with an intrinsic antiferromagnetic state. However, the highly electron-doped nature of the MnBi 2 Te 4 crystals obstructs the exhibition of the surface band gap. Here, we tailor the material through Sb substitution to reveal the gapped surface states in MnBi 2-x Sb x Te 4 . By shifting the Fermi level into the bulk band gap, we access the surface states and show a band gap of 50 meV at the Dirac point from quasiparticle interference measured by scanning tunneling microscopy (STM). Surface-dominant conduction is confirmed through transport spectroscopy measured by multiprobe STM below the Néel temperature. The surface band gap is robust against the out-of-plane magnetic field despite the promotion of field-induced ferromagnetism. Finally, the realization of bulk-insulating MTIs with the large exchange gap offers a promising platform for exploring emergent topological phenomena.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

UAE6 - Wind Tunnel Tests Data - UAE6 - Sequence V - Raw Data

Sequence V: Tip Plate (F) This test sequence used an upwind, rigid turbine with a 0° cone angle. The wind speed ranged from 5 m/s to 25 m/s, and the yaw angle was held at 0°. The blade pitch angle was 3°. The rotor rotated at 72 RPM. Blade pressure measurements were collected. The five-hole probes were removed and the plugs were installed. Plastic tape 0.03-mm-thick was used to smooth the interface between the plugs and the blade. The teeter dampers were replaced with rigid links, and these two channels were flagged as not applicable by setting the measured values in the data file to –99999.99 Nm. The teeter link load cell was pre-tensioned to 40,000 N. During post-processing, the probe channels were set to read -99999.99. The standard tip blocks were replaced with a tip plate to simulate the effect of an undeployed tip-mounted aerodynamic brake as shown in Appendix A. Note that the blade radius was not changed during post-processing so the pressure tap locations are at the same radial location, but the reference to 30% represents 30% of 5.029 m, not 4.943 m. Throughout this report, references to the blade span are made for the 5.029- m radius, not the 4.943-m radius.

17 WIND ENERGY↗
DOE OSTI2021

Growth, sintering, and chemical states of Co supported on reducible CeO 2 (111) thin films: The effects of the metal coverage and the nature of the support

The growth, sintering, and interaction of cobalt with ceria were studied under ultrahigh vacuum conditions by vapor-deposition of Co onto well-defined CeOx(111) (1.5 < x < 2) thin films grown on Ru(0001). Charge transfer from Co to ceria occurs upon deposition of Co on CeO 1.96 and partially reduced CeO 1.83 at 300 K. X-ray photoelectron spectroscopy studies show that Co is oxidized to Co 2+ species at the cost of the reduction of Ce 4+ to Ce 3+ , at a lesser extent on reduced ceria. Co 2+ is the predominant species on CeO 1.96 at low Co coverages (e.g., ≤0.20 ML). The ratio of metallic Co/Co 2+ increases with the increase in the Co coverage. However, both metallic Co and Co 2+ species are present on CeO 1.83 even at low Co coverages with metallic Co as the major species. Scanning tunneling microscopy results demonstrate that Co tends to wet the CeO 1.96 surface at very low Co coverages at room temperature forming one-atomic layer high structures of Co–O–Ce. The increase in the Co coverage can cause the particle growth into three-dimensional structures. The formation of slightly flatter Co particles was observed on reduced CeO 1.83 . In comparison with other transition metals including Ni, Rh, Pt, and Au, our studies demonstrate that Co on ceria exhibits a smaller particle size and higher thermal stability, likely arising from strong metal–support interactions. The formed particles upon Co deposition at 300 K are present on the ceria surface after heating to 1000 K. The Co–ceria interface can be tuned by varying the Co metal coverage, the annealing temperature, and the nature of the ceria surface.

36 MATERIALS SCIENCE↗