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Copper underpotential deposition ͑UPD͒ on a conductive hydrous ruthenium oxide (RuO x H y ) surface was studied by progressive cyclic voltammetry and X-ray photoelectron spectroscopy ͑XPS͒. Cu UPD on an electrochemically prepared RuO x H y surface started at 0.15 V in a 2 mM CuSO 4 solution and reached a coverage plateau of ca. 0.9 monolayer ͑ML͒ beyond Ϫ0.05 V ͑vs. Ag/AgCl͒. XPS data confirmed that Cu deposits underpotentially on RuO x H y surface. The anodic polarization potential determines the chemical states and affects the Cu UPD/bulk deposition of RuO x H y electrode. We observed close to a 55% increase of underpotential shift for Cu UPD on RuO x H y ͑ca. 170 mV͒ in comparison to Ru surface ͑ca. 110 mV͒. The results suggest that interfacial binding of the first ML of Cu on RuO x H y is stronger than Ru by 12 kJ mol Ϫ1 . Possible applications of Cu UPD to Ru-based plateable seedless Cu diffusion barrier are discussed.Ruthenium oxide (RuO 2 ) exhibits distinct physical and chemical properties and is an important material for a wide range of technological applications. 1-3 RuO 2 has metal-like electronic conductivity ͑as high as 35 ⍀ cm͒ originating from partial filling of the 4d shells in its tetragonal rutile structure. 4 In electrochemistry, RuO 2 is used as a corrosion resistant, low overpotential electrode for Cl 2 and O 2 production in the chlor-alkali industry, and also as a charge storage electrode in ultracapacitors for energy storage application. 5,6 In heterogeneous catalysis, RuO 2 serves as a promising material for direct methanol fuel cell application, catalytic oxidation of methane to synthesis gas, and a robust catalyst for CO oxidation. [7][8][9] Owing to its excellent thermal and chemical stability, conductive RuO 2 also attracts wide interest in integrated circuit device applications, such as the oxygen-resistant contact electrode for the high density ferroelectric memory device, diffusion barrier for Al interconnects, and conductive wiring in integrated circuits. 10,11 Recently, there has been increasing interest in developing a seedless Cu diffusion barrier. 12 We and others have reported that Ru can function as a directly plateable Cu diffusion barrier for the next 65 and 45 nm node applications. 12 Ideal diffusion barriers should have good adhesion to both copper and interlayer dielectrics, in addition to affording a conductive Cu plating platform that allows for bottom-up Cu electrofill of high-aspect-ratio damascene microstructures. Our experimental results demonstrate that the interfacial electrochemistry between Cu and Ru plays a key role in the plateable barrier performance. Specifically, the observed Cu underpotential deposition ͑UPD͒ on Ru reflects the strong interfacial binding, i.e., strong adhesion, between Cu and Ru. Because Ru has a strong affinity for oxygen; in this work, we explore the interfacial electrochemistry between Cu and electrochemically oxidized Ru electrode substrate.Unlike UPD on a metal surface, the literature report of Cu UPD on a transition metal oxide surf...

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PurposeThis is a proof-of-principle study investigating the feasibility of using late gadolinium enhancement magnetic resonance imaging (LGE-MRI) to detect left atrium (LA) radiation damage.Methods and materialsLGE-MRI data were acquired for 7 patients with previous external beam radiation therapy (EBRT) histories. The enhancement in LA scar was delineated and fused to the computed tomography images used in dose calculation for radiation therapy. Dosimetric and normal tissue complication probability analyses were performed to investigate the relationship between LA scar enhancement and radiation doses.ResultsThe average LA scar volume for the subjects was 2.5 cm3 (range, 1.2-4.1 cm3; median, 2.6 cm3). The overall average of the mean dose to the LA scar was 25.9 Gy (range, 5.8-49.2 Gy). Linear relationships were found between the amount of radiation dose (mean dose) (R2 = 0.8514, P = .03) to the LA scar-enhanced volume. The ratio of the cardiac tissue change (LA scar/LA wall) also demonstrated a linear relationship with the level of radiation received by the cardiac tissue (R2 = 0.9787, P < .01). Last, the normal tissue complication probability analysis suggested a dose response function to the LA scar enhancement.ConclusionsWith LGE-MRI and 3-dimensional dose mapping on the treatment planning system, it is possible to define subclinical cardiac damage and distinguish intrinsic cardiac tissue change from radiation induced cardiac tissue damage. Imaging myocardial injury secondary to EBRT using MRI may be a useful modality to follow cardiac toxicity from EBRT and help identify individuals who are more susceptible to EBRT damage. LGE-MRI may provide essential information to identify early screening strategy for affected cancer survivors after EBRT treatment.