Reducing two-level systems dissipations in 3D superconducting niobium resonators by atomic layer deposition and high temperature heat treatment
Y. KalboussiBaptiste DelatteSarra BiraKassiogé DembéléXiaoyan LiF. MiserqueNathalie BrunMichael WallsJean‐Luc MauriceDiana DragoéJocelyne LeroyDavid LonguevergneA. GentilsS. Jublot-LeclercG.A. JullienFabien ÉozénouMatthieu BaudrierLuc MauriceThomas Proslier
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Superconducting qubits have arisen as a leading technology platform for quantum computing, which is on the verge of revolutionizing the world's calculation capacities. Nonetheless, the fabrication of computationally reliable qubit circuits requires increasing the quantum coherence lifetimes, which are predominantly limited by the dissipations of two-level system defects present in the thin superconducting film and the adjacent dielectric regions. In this paper, we demonstrate the reduction of two-level system losses in three-dimensional superconducting radio frequency niobium resonators by atomic layer deposition of a 10 nm aluminum oxide Al2O3 thin films, followed by a high vacuum heat treatment at 650 °C for few hours. By probing the effect of several heat treatments on Al2O3-coated niobium samples by x-ray photoelectron spectroscopy plus scanning and conventional high resolution transmission electron microscopy coupled with electron energy loss spectroscopy and energy dispersive spectroscopy, we witness a dissolution of niobium native oxides and the modification of the Al2O3-Nb interface, which correlates with the enhancement of the quality factor at low fields of two 1.3 GHz niobium cavities coated with 10 nm of Al2O3.The authors create a titrimetric method of determining niobium in the presence of tantalum. The proposed method permits the determination of niobium in various objects: niobium(V) oxide, technical niobium hydroxide, and columbite concentrate, at various ratios of niobium and tantalum. The data obtained are cited in tables and it can be seen that at the selected ratios of niobium and tantalum in the sample, niobium is virtually entirely determined. Tantalum(IV), vanadium(V), molybdenum(VI), and tungsten(VI) interfere with the determination of niobium.
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) accordingly. The low melting point of copper prevent s the us e of suc h atreatment in the case of niobium coated copper cavities (Nb/Cu). In orde r to overcom e thisproblem, niobium coated niobium cavities (Nb/Nb) have been produced with the ai m tostudy the evolution of the superconducting properties of the niobium film with increasingfiring temperatures. In preparation for such a study, a number of preliminary step s havebeen taken and are reported in the present note. They include:· the development of a firing procedure using titanium as solid state getter material,complemented with a Nb box to avoid Ti contamination of the Nb film,· its use on bulk niobium cavities and the study o f the resulting modificatio n of their RFsuperconducting properties,· the production of Nb/Nb cavities and the study of thei r RF superconductin g propertiesprior to firing,· studies performed on heat treated Nb/Nb samples, providing information on theevolution of the grain size with increasing firing temperature.The study uses single cell resonators, operated at 1.5 GHz in the fundamental TM
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The subnanoscale spatial distribution of La in La-incorporated HfO2 thin films grown by atomic layer deposition (ALD) is characterized using angle resolved X-ray photoelectron spectroscopy (AR-XPS) and ellipsometry. The (La 3d)/(O 1s) photoelectron intensity ratios and film void fractions are acquired by conducting AR-XPS at small take off angles and processing the ellipsometry data through the effective medium approximation model. The existence of a HfLaxOy−HfO2−HfLaxOy structure is confirmed by AR-XPS. The ellipsometry data reveal an abrupt decrease of film void fraction after two HfO2 growth cycles. More than two and less than three ALD HfO2 layers interact with one ALD layer of La2O3 in such a way that the first two ALD HfO2 layers mismatch with La2O3 and form a HfO2−La2O3 mixture with a different structure compared to films with a third ALD HfO2 layer that completes the formation of a continuous HfO2 surface. At least four ALD HfO2 layers are required for La free HfO2 interval layers to exist in the film. This AR-XPS-ellipsometry method is potentially applicable to characterizing other amorphous ALD grown systems containing incorporated elements with subnanoscale variations.
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This chapter contains sections titled: Nb Facts about Niobium Discovery Native Peoples Hunting Minerals A Discovery in the Museum One Element or Two? A New Name Question The Element Niobium The Niobium and Vanadium Discoveries – Great Similarities Niobium and Tantalum Minerals Industrial Niobium Manufacture Separation of Niobium and Tantalum Manufacture of Niobium Metal and Ferroniobium Uses of Niobium Niobium in Life
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Electronic excitations of Nb and Nb-O solid solutions are examined by electron-energy-loss spectroscopy using 250-keV electrons. Distinct differences are observed between Nb and Nb-O. It is found that oxygen in niobium changes the interband transitions and dampens the plasmon excitations.
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