Superconducting transition temperature versus thickness of Nb film on various substrates

Kodama, Junichi; Itoh, M.; Hirai, Heihachiro

doi:10.1063/1.332534

Cited by 47 publications

(35 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It seems to be in qualitative agreement with experimental results which indicate a minimal thickness of a film for the disapearance of superconductivity [Abreu et al (2004); Kodama et al (1983)]; also, the behavior of nanowires and nanograins have been studied [Shanenko et al (2006); Zgirski et al (2005)], searching for a limit on its size for the material while retaining its superconducting character.…”

Section: −Dsupporting

confidence: 67%

“…As one can see in Figure 2, in this case, the critical temperature increases monotonically from zero, again corresponding to a finite minimal film thickness, going asymptotically to the bulk transition temperature as L → ∞ [Abreu et al (2004)]. Such behavior has been experimentally found for a variety of transition-metal materials [Kodama et al (1983);Minhaj et al (1994);Pogrebnyakov et al (2003); Raffy et al (1983)]. Since in this section a first-order transition is explicitly assumed, it is tempting to infer that the transition described in the experiments of Strongin et al (1970) is first order.…”

Section: Wwwintechopencommentioning

confidence: 70%

See 1 more Smart Citation

Ginzburg–Landau Theory of Phase Transitions in Compactified Spaces

Linhares¹,

Malbouisson²,

Roditi³

2012

Advances in Quantum Field Theory

View full text Add to dashboard Cite

Section: −Dsupporting

confidence: 67%

Section: Wwwintechopencommentioning

confidence: 70%

Ginzburg–Landau Theory of Phase Transitions in Compactified Spaces

Linhares¹,

Malbouisson²,

Roditi³

2012

Advances in Quantum Field Theory

View full text Add to dashboard Cite

“…To see whether or not the degradation of superconductivity is simply related to the sample's disorder, we collect in one plot ( Figure 3) the data of transition temperature T c as a function of electronic mean free path (MFP) l from different groups [2][3][4][5][6][7] . The MFP is calculated by ρl = 3.72× 10 −6 Ω·cm 2 [8] .…”

Section: Discussionmentioning

confidence: 99%

Grain-size dependence of superconductivity in dc sputtered Nb films

Jin

Song

Dian-lin

2009

Sci. China Ser. G-Phys. Mech. Astron.

View full text Add to dashboard Cite

The superconducting transition temperature and grain size of dc sputtered Nb films are systematically investigated. The results show that the superconductivity is closely related to the grain size, rather than to the scattering strength of electrons or the surface layer proximity effect of the films. dc sputtering, superconductivity, Nb film, grain size effect, localization effect, proximity effect It almost becomes a common sense that the superconductivity of a thin film is progressively destroyed when the thickness of the film reduces to well below the coherence length, yet the underlying mechanism of the phenomenon is still a standing problem, in spite of the continuous experimental efforts on different systems [1] . In the present work, a series of dc sputtered high quality Nb films are investigated. The results show a close correlation between the superconducting transition and the grain size of the films.Nb films are easily contaminated by reactive gases, especially oxygen, during the depositing process. Two special measures are taken to ensure the high quality of the samples. First, the magnetron sputtering system is prevacuumed to better than 2×10 −7 Pa. Then the pump is switched off and a built-in Non-Evaporable Getter (NEG) 1) is activated. Thanks to the very low leakage of the system and the usefulness of NEG in selective absorption of oxygen, the system can be kept in a nearly "oxygen free" situation in the whole sputtering process. Secondly, a "static" Ar atmosphere is established for sputtering. In contrast to the usual way where a flowing gas is used, the present method is proved to be useful in avoiding contamination by flowing gas and getting a stable sputtering rate. Experiments and resultsAn Nb target with a purity of 99.999% is used. The film substrates are high-polished Si covered by a SiO 2 layer of about 500 nm. The substrates are precleaned in an ultrasonic cleaner by sequentially using acetone, alcohol and distilled water. Before sputtering, the substrates are further baked in-situ to 150℃ for about 7-8 h to degas the surfaces.Superconducting transition temperature, normal state resistivity and its temperature dependence, and XRD are measured for Nb films of thicknesses from 740 to 2.5 nm. The high quality of the samples is demonstrated by comparing their resistivities with MBE films [2] and sputtering samples in UHV base vacuum [3,4] (Figure 1). We see that the resistivities of all these samples can roughly be normalized to follow a single thickness dependence, except for the data of the e-beam films reported in ref. [5]. The superconducting transition width ΔT c gives the information of how the homogeneity of the film is. The results are plotted in Figure 2. In most cases, ΔT c of our samples are narrower than that of the MBE samples [2] .

show abstract

“…Superconducting properties of thin niobium films strongly depend on their thickness, purity and preparation conditions. 24,25,26,27,28,29 In order to compare our samples with those measured earlier, 24 termined T c of each film by the so called 90% criterion, i.e. the transition temperature was defined as the temperature where microwave absorption ∆(1/2Q) reaches 90% of its normal state value.…”

Section: Samplesmentioning

confidence: 99%

Microwave response of thin niobium films under perpendicular static magnetic fields

et al. 2006

View full text Add to dashboard Cite

The microwave response of high quality niobium films in a perpendicular static magnetic field has been investigated. The complex frequency shift was measured up to the upper critical fields. The data have been analyzed by the effective conductivity model for the type-II superconductors in the mixed state. This model is found to yield consistent results for the coherence lengths in high-κ superconducting samples, and can be used with HTSC even at temperatures much below Tc. It is shown that for samples with high values of depinning frequency, one should measure both components of the complex frequency shift in order to determine the flow resistivity.The thick Nb film (160 nm) has low resistivity at 10 K, comparable to the best single crystals, and low κ value. In contrast, the thinnest (10 nm) film has κ ≈ 9.5 and exhibits a high depinning frequency (≈ 20 GHz). The upper critical field determined from microwave measurements is related to the radius of nonoverlaping vortices, and appears to be larger than the one determined by the transition to the normal state.

show abstract

Superconducting transition temperature versus thickness of Nb film on various substrates

Cited by 47 publications

References 2 publications

Ginzburg–Landau Theory of Phase Transitions in Compactified Spaces

Ginzburg–Landau Theory of Phase Transitions in Compactified Spaces

Grain-size dependence of superconductivity in dc sputtered Nb films

Microwave response of thin niobium films under perpendicular static magnetic fields

Contact Info

Product

Resources

About