Oxidation‐induced nanostructures on Cu{100}, Cu(Ag) and Ag/Cu{100} studied by photoelectron spectroscopy

The Journal of Chemical Physics

Hirsimäki

Lampimäki

et al. 2008

Self Cite

Surface oxidation of Cu(100) has been investigated by variable temperature scanning tunneling microscopy and quantitative x-ray photoelectron spectroscopy as a function of O2 pressure (8.0×10−7 and 3.7×10−2mbar) at 373K. Three distinct phases in the initial oxidation of Cu(100) have been observed: (1) the formation of the mixed oxygen chemisorption layer consisting of Cu(100)-c(2×2)-O and Cu(100)-(22×2)R45°-O domains, (2) the growth of well-ordered (22×2)R45°-O islands, and (3) the onset of subsurface oxide formation leading to the growth of disordered Cu2O. We demonstrate that the (22×2)R45°-O reconstruction is relatively inert in the low pressure regime. The nucleation and growth of well-ordered two-dimensional Cu–O islands between two (22×2)R45°-O domains is revealed by time-resolved scanning tunneling microscopy experiments up to 0.5 ML of oxygen. The formation of these islands and their nanostructure appear to be critical to the onset of further migration of oxygen atoms deeper into copper and subsequent Cu2O formation in the high pressure regime. The reactivity of each phase is correlated with the surface morphology and the role of the various island structures in the oxide growth is discussed.

Section: Resultsmentioning

confidence: 99%

Section: Experimental and Computational Methodsmentioning

confidence: 99%

Oxygen adsorption-induced nanostructures and island formation on Cu{100}: Bridging the gap between the formation of surface confined oxygen chemisorption layer and oxide formation

The Journal of Chemical Physics

Hirsimäki

Lampimäki

et al. 2008

Self Cite

“…39 We have previously investigated the nanoscale oxide formation on Ag/Cu͑100͒ surface alloy and polycrystalline Cu͑Ag͒ alloy by x-ray photoelectron spectroscopy ͑XPS͒, x-ray excited AES ͑XAES͒, and AES. 15,40 One of the main conclusions of these studies is that the oxygen adsorptioninduced segregation of Cu is operative on both silvercontaining samples leading to lower reactivity toward Cu surface oxidation. In this paper, we continue this investigation by combining in situ constant current topographic STM ͑CCT-STM͒ imaging and XPS/XAES/angle resolved XPS ͑ARXPS͒ methods to gain more detailed information on the surface segregation, oxidation kinetics, and especially local nanostructures forming on the Cu͑100͒ -c͑10ϫ 2͒-Ag surface at 373 K upon O 2 exposures.…”

Section: Introductionmentioning

confidence: 98%

“…While aluminum oxide ͑Al 2 O 3 ͒ forms uniform diffusion barrier resulting in a stable self-passivated surface, 6 copper oxides ͑Cu 2 O, CuO͒ grow nonuniformly as three-dimensional islands deeper into the bulk material. [7][8][9][10][11][12][13][14][15][16] Functionalization and passivation of a copper surface are typically governed by alloying or employing barrier layers. Self-encapsulation and passivation of copper damascene structure in interconnects are achieved, e.g., by a titanium nitride, 17,18 tantalum nitride, 19 or silver barrier layer.…”

Section: Introductionmentioning

confidence: 99%

Kinetic hindrance during the surface oxidation of Cu(100)–c(10×2)-Ag

The Journal of Chemical Physics

Lampimäki

Hirsimäki

et al. 2008

Self Cite

The influence of c(10x2)-Ag superstructure on the oxidation kinetics and oxygen adsorption-induced nanostructures on Cu(100) has been investigated as a function of O(2) exposure at 373 K by employing scanning tunneling microscopy and x-ray photoelectron spectroscopy. The oxygen adsorption-induced segregation of Cu through the Ag overlayer is found to trigger agglomeration of Ag and subsequent formation of ordered oval-shaped nanosize metallic Ag islands separated by Cu(100)-(2 radical2x radical2)R45 degrees -O surface phase. As oxygen exposure is further increased, all Ag is eventually covered by oxidized Cu. The presence of Ag delays the completion of the fully reconstructed (2 radical2x radical2)R45 degrees -O surface and the nucleation and growth of Cu(2)O islands by limiting Cu diffusion toward the surface. Once Cu(2)O grows into the bulk deeper than buried Ag, the oxidation kinetics follow that of the unalloyed clean Cu(100) surface. Similar kinds of Cu-O nanostructures are found on both clean Cu(100) and Cu(100)-c(10x2)-Ag surfaces. Details of the morphology of the Ag structures and kinetic control of the surface oxidation mechanism on Cu(100)-c(10x2)-Ag are discussed.

“…The XPS high-resolution spectra of C 1s, O 1s, Cu 2p and Cu LMM peaks were analysed. The analysis procedure of the Cu LMM transition is described elsewhere in more detail [16]. The inelastic electron energy-loss background thickness analysis was performed with QUASES software package [17], using reference spectra of experimentally obtained line shapes of metallic Cu, Cu 2 O and PET.…”

Section: Methodsmentioning

confidence: 99%

Effect of dielectric barrier on rectification, injection and transport properties of printed organic diodes

Lilja

Majumdar

J. Phys. D: Appl. Phys.

et al. 2011

To cite this version:K E Lilja, H S Majumdar, K Lahtonen, P Heljo, S Tuukkanen, et al.. Effect of dielectric barrier on rectification, injection and transport properties of printed organic diodes. Journal of Physics D: Applied Physics, IOP Publishing, 2011, 44 (29) Author to whom any correspondence should be addressed.Abstract. Rectification ratios of 10 5 were observed in printed organic copper/polytriarylamine (PTAA)/silver diodes with a thin insulating barrier layer at the copper/PTAA interface. To clarify the origin of the high rectification ratio in the diodes, the injection, transport and structure of the diodes with two different copper cathodes were examined using impedance spectroscopy and X-ray photoelectron spectroscopy (XPS). The impedance data confirm that the difference in diode performance arises from the copper/PTAA interface. The XPS measurements show that the copper surface in both diode structures is covered by a layer of Cu 2 O topped by an organic layer. The organic layer is thicker on one of the surfaces, which results in lower reverse currents and higher rectification ratios in the printed diodes. We suggest a model where a dipole at the dual insulating layer induces a shift in the semiconductor energy levels explaining the difference between the diodes with different cathodes.