Superconducting radio‐frequency (SRF) resonators are critical components for particle accelerator applications, such as free‐electron lasers, and for emerging technologies in quantum computing. Developing advanced materials and their deposition processes to produce RF superconductors that yield nΩ surface resistances is a key metric for the wider adoption of SRF technology. Here, ZrNb(CO) RF superconducting films with high critical temperatures (
The study of the high critical temperature (
- NSF-PAR ID:
- 10303659
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Materials Research Express
- Volume:
- 7
- Issue:
- 7
- ISSN:
- 2053-1591
- Page Range / eLocation ID:
- Article No. 076001
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract T c) achieved for the first time under ambient pressure are reported. The attainment of aT cnear the theoretical limit for this material without applied pressure is promising for its use in practical applications. A range ofT c, likely arising from Zr doping variation, may allow a tunable superconducting coherence length that lowers the sensitivity to material defects when an ultra‐low surface resistance is required. The ZrNb(CO) films are synthesized using a low‐temperature (100 – 200 °C) electrochemical recipe combined with thermal annealing. The phase transformation as a function of annealing temperature and time is optimized by the evaporated Zr‐Nb diffusion couples. Through phase control, one avoids hexagonal Zr phases that are equilibrium‐stable but degradeT c. X‐ray and electron diffraction combined with photoelectron spectroscopy reveal a system containing cubic β‐ZrNb mixed with rocksalt NbC and low‐dielectric‐loss ZrO2. Proof‐of‐concept RF performance of ZrNb(CO) on an SRF sample test system is demonstrated. BCS resistance trends lower than reference Nb, while quench fields occur at approximately 35 mT. The results demonstrate the potential of ZrNb(CO) thin films for particle accelerators and other SRF applications. -
more » « less
Abstract The Zintl compound TlInTe2is an intriguing material because of its outstanding thermoelectric properties at ambient pressure. Interestingly, it has recently been found that TlInTe2exhibits a V-shape dependence of the superconducting critical temperature (
T c) under increasing pressure, which has been linked to the reversed behavior of the Raman active Agphonon mode and anharmonic effects. In this study, we have performed first-principles calculations of the electron-phonon interactions and the superconducting properties of TlInTe2in order to understand this unusual pressure-induced response. In contrast to experiment, we find a dome-shaped pressure-induced dependence ofT c with a maximum value of 0.23 K at 18 GPa, significantly lower than the experimental results. Electron doping has the potential to adjust theT cto fall within the experimental range, but it necessitates considerably high levels of doping. Furthermore, our analysis of the phonon spectra and phonon lifetimes, including anharmonic effects, show that anharmonicity is unlikely to influence the superconducting properties of TlInTe2. It remains an open question whether there is indeed an unusual V-shapeT cdependence with pressure or whether the phonon-mediated theory of superconductivity used here breaks down in this system. -
more » « less
Abstract Kagome materials are of topical interest for their diverse quantum properties linked with correlated magnetism and topology. Here, we report anomalous hydrostatic pressure (
p ) effect on ErMn6Sn6through isobaric and isothermal-isobaric magnetization measurements. Magnetic field (H ) suppresses antiferromagneticT Nwhile simultaneously enhancing the ferrimagneticT Cby exhibiting dual metamagnetic transitions, arising from the triple-spiral-nature of Er and Mn spins. Counter-intuitively, pressure enhances bothT CandT Nwith a growth rate of 74.4 K GPa−1and 14.4 K GPa−1respectively. Pressure unifies the dual metamagnetic transitions as illustrated throughp-H phase diagrams at 140 and 200 K. Temperature-field-pressure (T-H ,T-p ) phase diagrams illustrate distinct field- and pressure-induced critical points at (T cr= 246 K,H cr= 23.3 kOe) and (T cr= 435.8 K,p cr= 4.74 GPa) respectively. An unusual increase of magnetic entropy by pressure aroundT crand a putative pressure-induced tricritical point pave a unique way of tuning the magnetic properties of kagome magnets through simultaneous application ofH andp . -
more » « less
Wafer-scale synthesis of p-type TMD films is critical for its commercialization in next-generation electro/optoelectronics. In this work, wafer-scale intrinsic n-type WS2films and in situ Nb-doped p-type WS2films were synthesized through atomic layer deposition (ALD) on 8-inch
α -Al2O3/Si wafers, 2-inch sapphire, and 1 cm2GaN substrate pieces. The Nb doping concentration was precisely controlled by altering cycle number of Nb precursor and activated by postannealing. WS2n-FETs and Nb-doped p-FETs with different Nb concentrations have been fabricated using CMOS-compatible processes. X-ray photoelectron spectroscopy, Raman spectroscopy, and Hall measurements confirmed the effective substitutional doping with Nb. The on/off ratio and electron mobility of WS2n-FET are as high as 105and 6.85 cm2 V-1 s-1, respectively. In WS2p-FET with 15-cycle Nb doping, the on/off ratio and hole mobility are 10 and 0.016 cm2 V-1 s-1, respectively. The p-n structure based on n- and p- type WS2films was proved with a 104rectifying ratio. The realization of controllablein situ Nb-doped WS2films paved a way for fabricating wafer-scale complementary WS2FETs. -
more » « less
Abstract In order to better understand the design rules of epoxy–phenol thermosets we will report on the chemistry and (thermo)mechanical properties of cured epoxy–phenol thermoset films.
Ortho‐ ,meta‐ andpara‐ isomers of dihydroxybenzene (DHB) were reacted with the diglycidyl ether of bisphenol A (DGEBA) in the presence of an acid catalyst or triphenylphosphine (PPh3). The glass transition temperatures (T g) of the cross‐linked films decreases in the order ofmeta ‐ (T g = 115°C) >ortho‐ (T g = 102°C) >para‐ DHB (T g = 96°C) as measured by differential scanning calorimetry. Uniaxial tensile testing of cross‐linked films showed excellent stress–strain behavior. The average ultimate strength values ranged from 65 to 82 MPa and the average values of the strain‐at‐break ranged from 4.8% to 6.9% at 25°C for all cross‐linked films. When a PPh3was used, the network properties were profoundly different. The base catalyzed thermoset of DGEBA andmeta ‐DHB shows aT gof 85°C, which is 30°C lower than theT gof the acid‐catalyzed analog. Tensile films appear to be more ductile, as they exhibit a strain‐at‐break of 20%. The results of this study confirm that simple dihydroxybenzene hardeners can be used to prepare cross‐linked films with excellent thermomechanical properties.
