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In this paper, Bi2212 superconducting thin films were prepared with metal acetate as salt source and a mixture of acetic acid and N,N-dimethylformamide (DMF) as solvent. The volatilization process of the solvent was regulated by changing the ratio of the mixed solvent, which in turn achieved the regulation of the surface morphology and crystallinity of the Bi2212 superconducting films. The mechanism of the mixed solvents on the crystallinity and surface quality of Bi2212 superconducting films was systematically investigated. The results showed that the Bi2212 superconducting films were all (00 l) epitaxial growth. The grain size of Bi2212 increased continuously with the increase of the proportion of acetic acid in the solvents. The grain size of the largest grain size was 43.8 nm when the proportion of acetic acid was 80 %. However, the high proportion of acetic acid in the mixed solvents reduced the surface quality of Bi2212 thin films. The minimum surface roughness was 15.0 nm at 40 % acetic acid. All the samples exhibited good superconducting properties. This work provides a research basis for the systematic preparation of multicomponent oxide thin films. [ABSTRACT FROM AUTHOR]

Bose metals are metals made of Cooper pairs, which form at very low temperatures in superconducting films and Josephson junction arrays as an intermediate phase between superconductivity and superinsulation. We predicted the existence of this 2D metallic phase of bosons in the mid 1990s, showing that they arise due to topological quantum effects. The observation of Bose metals in perfectly regular Josephson junction arrays fully confirms our prediction and rules out alternative models based on disorder. Here, we review the basic mechanism leading to Bose metals. The key points are that the relevant vortices in granular superconductors are core-less, mobile XY vortices which can tunnel through the system due to quantum phase slips, that there is no charge-phase commutation relation preventing such vortices from being simultaneously out of condensate with charges, and that out-of-condensate charges and vortices are subject to topological mutual statistics interactions, a quantum effect that dominates at low temperatures. These repulsive mutual statistics interactions are sufficient to increase the energy of the Cooper pairs and lift them out of condensate. The result is a topological ground state in which charge conduction along edges and vortex movement across them organize themselves so as to generate the observed metallic saturation at low temperatures. This state is known today as a bosonic topological insulator. [ABSTRACT FROM AUTHOR]

The utilization of Bi-based superconductors in magnetic field environments is limited due to their anisotropic structure and lack of efficient magnetic flux pinning sites. Therefore, to enhance the performance of Bi-based superconductors in a magnetic field, this study presents the preparation of Bi2212 high-temperature superconducting thin films with varying NiO doping levels on SrTiO 3 (STO) single crystal substrates with different concentrations of NiO seed layers via the self-assembly method. Additionally, phase purity, crystal structure, surface morphology, and transport properties were thoroughly analyzed. According to the results, the NiO seed layers prepared on the STO substrates presented epitaxial growth characteristics, with the NiO second phase in the Bi2212 matrix growing epitaxially along the seed layers. As NiO doping slightly broadens the phase formation temperature range of Bi2212 superconducting thin films, the self-assembly method can be utilized to prepare NiO nanorods with epitaxial growth in Bi2212 thin films. Notably, the self-assembled NiO-doped Bi2212 thin film demonstrated higher critical current carrying capacity, with its J c reaching 6.28 × 104 A/cm2 at 10 K in self-field. This provides a technical reference for improving the performance of high-temperature superconducting thin films under a high magnetic field. [ABSTRACT FROM AUTHOR]

Geometrically confined superconductors often experience a breakdown in the quantization of magnetic flux owing to the incomplete screening of the supercurrent against field penetration. In this study, we report that magnetic field confinement occurs regardless of the dimensionality of the system, even extending to 1D linear potential systems. By using a vector-field magnetic force microscope, we successfully create a vortex‒antivortex pair connected by a 1D unquantized magnetic flux in ultrathin superconducting films. Through an investigation of the manipulation and thermal behavior of the vortex pair, we uncover a long-range interaction mediated by the unquantized magnetic flux. These findings suggest a universal phenomenon of unquantized magnetic flux formation, independent of the geometry of the system. Our results present an experimental route for investigating the impact of confinement on superconducting properties and order parameters in unconventional superconductors characterized by extremely low dimensionality. We demonstrate a 1D linear potential system in superconducting films by creating vortex-antivortex pairs linked by either quantized or unquantized magnetic flux. Our study of vortex pair manipulation and thermal behavior reveals a 1D force mediated by unquantized magnetic flux. This discovery suggests a universal mechanism for forming 1D force systems, offering a new paradigm in the physics of 1D forces. [ABSTRACT FROM AUTHOR]

Integrating state-of-the-art nanostructures into prediction models enhances our understanding of superconductivity properties. Using artificial intelligence techniques and modeling, the mathematical method leverages the unique characteristics of nanoparticles to improve resistance-temperature projections. This paper proposes a novel artificial intelligence (AI) approach for predicting the resistance-temperature aspects of nanomaterial-infused superconducting films. In this paper, we offer a novel AI method called Progressive Red Fox Optimized Adaptive Decision Tree (PRFO-ADT) to predict the super conductiveness of film coatings. A sufficient information pretreatment step that addresses issues like feature creation and normalizing is part of the study's technique. A diversified dataset is employed, including synthesis factors, nanomaterial properties, and resistance-temperature patterns of several superconducting films. Next, the gathered data undergo the preprocessing stage using a min-max normalization. Our proposed method opens the door to a sophisticated comprehension of the resistance-temperature landscapes of their superconductivity films by investigating several nanotechnologies and their different effects on the prediction algorithm. Compared to other existing approaches, PRFO-ADT is efficient and produces a lower rate of errors, with a total of 1.2 RMSE, 1.25 MSE, 1.1 MAPE, and 4.8s of computing time. [ABSTRACT FROM AUTHOR]

Superconducting films of α-Ta are promising candidates for the fabrication of advanced superconducting qubits. However, α-Ta films suffer from many growth-induced structural inadequacies that negatively affect their performance. We have therefore explored a new synthesis method for α-Ta films, which allows for the growth of these films with an unprecedented quality. Using this method, high quality α-Ta films are deposited at a comparably high substrate temperature of 1150 °C. They are single-phase α-Ta and have a single out-of-plane (110) orientation. They consist of grains ≥2 μm that have one of three possible in-plane orientations. As shown by scanning transmission electron microscopy and electron energy loss studies, the substrate–film interfaces are sharp with no observable intermixing. The obtained insights into the epitaxial growth of body-centered-cubic films on quasi-hexagonal substrates lay the basis for harnessing the high structural coherence of such films in various applications. [ABSTRACT FROM AUTHOR]

Thermoelectric effects refer to the voltage generation from temperature gradients in condensed matter. Although various power generators are made from them, all the known effects, such as Seebeck effect, require macroscopic temperature gradients; since the sign of the generated voltage is reversed by reversing the temperature gradient, the net voltage disappears when the temperature distribution fluctuates temporarily or spatially with a macroscopic temperature gradient of zero. It is impossible to utilize such temperature fluctuations in the conventional thermoelectric effects, a situation which limits their application. Here we report the observation of a second-order nonlinear thermoelectric effect; we develop a method to measure nonlinear thermoelectricity and observe that a superconducting MoGe film on Y3Fe5O12 generates a voltage proportional to the square of the applied temperature gradient. The nonlinear thermoelectric generation demonstrated here provides a way for making power generators that produce electric power from temperature fluctuations. A second-order nonlinear thermoelectric effect can be used for making power generators using temperature fluctuations. Here, the authors report that a MoGe film on Y3Fe5O12 generates a voltage proportional to the square of the temperature gradient. [ABSTRACT FROM AUTHOR]

Thin films of the superconductor YBa2Cu3O7−δ (YBCO) were modified by low-energy light-ion irradiation employing collimated or focused He+ beams, and the long-term stability of irradiation-induced defects was investigated. For films irradiated with collimated beams, the resistance was measured in situ during and after irradiation and analyzed using a phenomenological model. The formation and stability of irradiation-induced defects are highly influenced by temperature. Thermal annealing experiments conducted in an Ar atmosphere at various temperatures demonstrated a decrease in resistivity and allowed us to determine diffusion coefficients and the activation energy Δ E = (0.31 ± 0.03) eV for diffusive oxygen rearrangement within the YBCO unit cell basal plane. Additionally, thin YBCO films, nanostructured by focused He+-beam irradiation into vortex pinning arrays, displayed significant commensurability effects in magnetic fields. Despite the strong modulation of defect densities in these pinning arrays, oxygen diffusion during room-temperature annealing over almost six years did not compromise the signatures of vortex matching, which remained precisely at their magnetic fields predicted by the pattern geometry. Moreover, the critical current increased substantially within the entire magnetic field range after long-term storage in dry air. These findings underscore the potential of ion irradiation in tailoring the superconducting properties of thin YBCO films. [ABSTRACT FROM AUTHOR]

In the field of high-precision physical field detection, measurements based on magnetic signals are crucial due to their exceptional accuracy, sensitivity, and stability. Superconducting Quantum Interference Devices (SQUIDs), with their ultra-high sensitivity, have become key in detecting minute changes in magnetic flux. However, with increasing demands for higher precision, further enhancing device performance under quantum constraints remains a significant challenge. This study improved the precision of SQUID sensors by optimizing the geometry of microscale washers using the physical response of superconducting films under micromachining technologies and quantum constraints. Our research extensively examined the effects of square, octagonal, and circular washers on the magnetic field response, shielding currents, and inductance. Experimental results showed that, compared to traditional square washers, octagonal washers significantly enhanced sensor sensitivity and efficiency by minimizing edge magnetic flux and optimizing current distribution. Notably, all observed inductance values exceeded predictions based on traditional empirical formulas, with square washers showing the highest average relative error of 80.8%, while circular and octagonal washers had errors of 65.31% and 66.43%, respectively. This breakthrough not only lays a new theoretical foundation for the design of SQUID sensors but also provides robust evidence for enhancing magnetic field detection through microscale technological innovation. [ABSTRACT FROM AUTHOR]

In this contribution, we study the oscillations of the electrical-potential in a mesoscopic superconducting thin film when an external current is applied. We analyze the resistivity and electrical-potential as a function of the applied current for several external applied magnetic field and size of the sample. Also, we have calculated the electrical-potential as a function of the characteristic time. To study this problem, we solve the well know generalized time dependent-Ginzburg-Landau equations using the link-variable method. We found that the critical current decreases when the external magnetic field increases and the size of the sample decreases. Furthermore, the oscillation frequency of the kinematic vortex, evidenced in the oscillations of the electrical potential, is highly dependent on the applied magnetic field. [ABSTRACT FROM AUTHOR]

We demonstrate ion irradiation by argon or gallium as a wafer-scale post-processing method to increase disorder in superconducting thin films. We study several widely used superconductors, both single-elements and compounds. We show that ion irradiation increases normal-state resistivity in all our films, which is expected to enable tuning their superconducting properties, for example, toward a higher kinetic inductance. We observe an increase in superconducting transition temperature for Al and MoSi and a decrease for Nb, NbN, and TiN. In MoSi, ion irradiation also improves the mixing of the two materials. We demonstrate the fabrication of an amorphous and homogeneous film of MoSi with uniform thickness, which is promising, for example, for superconducting nanowire single-photon detectors. [ABSTRACT FROM AUTHOR]

Transition-edge sensor (TES) microcalorimeters are advanced cryogenic detectors that use a superconducting film for particle or photon detection. We are establishing a new production line for TES detectors to serve as cryogenic anticoincidence (i.e., veto) devices. These detectors are made with a superconducting bilayer of titanium (Ti) and gold (Au) thin films deposited via electron beam evaporation in a high vacuum condition on a monocrystalline silicon substrate. In this work, we report on the development of such sensors, aiming to achieve stable sensing performance despite the effects of aging. For this purpose, patterned and non-patterned Ti/Au bilayer samples with varying geometries and thicknesses were fabricated using microfabrication technology. To characterize the detectors, we present and discuss initial results from repeated resistance–temperature (R–T) measurements over time, conducted on different samples, thereby augmenting existing literature data. Additionally, we present a discussion of the sensor's degradation over time due to aging effects and test a potential remedy based on an easy annealing procedure. In our opinion, this work establishes the groundwork for our new TES detector production line. [ABSTRACT FROM AUTHOR]

The document titled "Alex's Vision in Functional Quantum Matter" is a personal reflection on the life and work of Karl Alex Müller, a renowned scientist and co-discoverer of high-Tc superconductors. The author, Davor Pavuna, shares his experiences and interactions with Müller, highlighting Müller's visionary approach to obtaining desired functionality in complex quantum matter. The document also mentions the importance of well-characterized samples in research and the role of pseudogap in high-Tc oxides. Overall, the document provides insights into Müller's contributions to the field of condensed matter physics and his lasting legacy. [Extracted from the article]

Featured Application: This work concerns the study of the granular nature of an YBa2Cu3O7-x superconducting film, whose expertise can be useful in understanding the temperature and the DC and AC field application ranges of these materials with non-optimized fabrication properties, which are typically found in superconducting wires and power cables. The study of granularity in superconducting films by using AC susceptibility has a crucial role in the development of and improvement in the ReBCO-coated conductors, which are a constantly evolving reality in the modern power applications of superconductivity. Specifically, the study of the granularity is essential because the ReBCO superconducting wires and tapes are far from the regularity of a single crystal while they often present an inter- and intragranular contribution to the critical current density. On the other hand, the AC susceptibility is a key part of the characterization of a granular sample because this technique is very sensitive to the presence of granularity in the superconductors and, moreover, the study of its first harmonic allows for determining pivotal properties such as the pinning energy as well as the dissipation processes acting in the sample. The pinning energy values and the granularity of an YBCO thin film have been studied by means of AC susceptibility measurements as a function of the AC amplitude, temperature, and DC field. In particular, the first harmonic imaginary component of the AC susceptibility χ 1 ″ related to the dissipation processes of the sample has been studied. First, starting from the Brandt approach, the critical current density Jc and the pinning energy U of the sample have been extracted at 77 K by using the χ 1 ″ measurements as a function of the AC amplitude at different AC frequencies and DC fields. From these measurements, a first signal of granularity appears. In order to confirm it, the temperature dependence of the χ 1 ″ at different DC fields has been studied and a contribution deriving from the inter- and intragranular part of the sample has emerged. By taking the temperature corresponding to the crossover between the two contributions at the different DC fields, the intergranular and intragranular response has been separated. Successively, the temperature has been fixed to 77 K, together with an AC frequency equal to 1597.9 Hz, and the χ 1 ″ as a function of the DC field at different AC amplitudes has been analyzed showing a clear presence of granularity in all the curves. By drawing the contour plot of the χ 1 ″ with the DC and AC values, it was possible to determine the best parameters to put at 77 K in order to exploit the material for applications. [ABSTRACT FROM AUTHOR]

(Cu,C)Ba2Ca3Cu4Oy is a nontoxic cuprate superconducting material with a superconducting transition temperature of about 116 K. Recently, it was found that bulk samples of this material synthesized under high pressure hold the highest irreversibility line among all the superconductors, which is very promising for its application in the liquid nitrogen temperature field. In this work, high-temperature (Cu,C)Ba2Ca3Cu4Oy superconducting films with large irreversible fields were prepared on SrLaAlO4(00l) substrates by pulsed laser deposition. The substrate temperature during deposition proved to be the most important parameter determining the morphology and critical temperature of the superconductors, with 680 °C considered to be the optimum temperature. X-ray diffraction (XRD) results showed that the (Cu,C)Ba2Ca3Cu4Oy films prepared under optimal conditions exhibited epitaxial growth with the a-axis perpendicular to the film surface and the b- and c-axes parallel to the substrate, with no evidence of any other orientation. In addition, resistivity measurements showed that the onset transition temperature (Tconset) was approximately 116 K, the zero-resistance critical temperature (Tc0) was around 53 K, and the irreversible field (Hirr) was about 9 T at 37 K for (Cu,C)Ba2Ca3Cu4Oy films under optimal temperature. This is the first example of the successful growth of superconducting (Cu,C)Ba2Ca3Cu4Oy films on SrLaAlO4(00l) substrates. This will facilitate high-performance applications of (Cu,C)Ba2Ca3Cu4Oy superconducting materials in the liquid nitrogen temperature field. [ABSTRACT FROM AUTHOR]

Detection of structural and transport inhomogeneities in superconducting thin films using the standard four-probe method requires multiple measurements and may be inaccurate. A new approach to extract the information about the inhomogeneous transition into the superconducting state using van der Pauw technique is presented. The proposed method is applied to an electrochemically-reduced In-Sn-oxide (ITO) films known to be simultaneously transparent and superconducting. Relationship between the processing parameters and superconducting characteristics of the ITO films is considered, and prospects for using such samples in integrated photonic-superconducting chips for quantum-information processing are discussed. [ABSTRACT FROM AUTHOR]

The critical current in a superconductor (SC) determines the performance of many SC devices, including SC diodes which have attracted recent attention. Hitherto, studies of SC diodes are limited in the DC-field measurements, and their performance under a high-frequency current remains unexplored. Here, we conduct the first investigation on the interaction between the DC and terahertz (THz) current in a SC artificial superlattice. We found that the DC critical current is sensitively modified by THz pulse excitations in a nontrivial manner. In particular, at low-frequency THz excitations below the SC gap, the critical current becomes sensitive to the THz-field polarization direction. Furthermore, we observed anomalous behavior in which a supercurrent flows with an amplitude larger than the modified critical current. Assuming that vortex depinning determines the critical current, we show that the THz-current-driven vortex dynamics reproduce the observed behavior. While the delicate nonreciprocity in the critical current is obscured by the THz pulse excitations, the interplay between the DC and THz current causes a non-monotonic SC/normal-state switching with current amplitude, which can pave a pathway to developing SC devices with novel functionalities. The authors study the [Nb/V/Ta] superconducting artificial superlattice, known to support a superconducting diode effect, by pulsed THz spectroscopy and simultaneous transport. They found a non-monotonic switching between the superconducting and normal state, which can be explained if the THz-driven vortex depinning determines the critical current. [ABSTRACT FROM AUTHOR]

This study investigated the relationship between the superconducting properties, electrical properties, sputtering process parameters, and post-growth annealing of NbN films. Four series of NbN films were deposited by DC magnetron sputtering using different process parameters. With the assistance of a four-probe method, the superconducting performance presented first an increase and then a decreasing trend as the resistance of the prepared films increased, which could be attributed to the variation of the N/Nb ratio in the films. This correlation implied that it is very challenging to fabricate films with both high Tc and high resistance or high Tc and low resistance by adjusting the sputtering process parameters. In order to overcome these bottlenecks, a series of films were deposited on Si, GaN/Si, SiN/Si, AlN/Si, and AlN/sapphire substrates, and the film deposited on Si was annealed at 900 °C. Annealing reduced the stress of the films on the buffer layer and increased the grain size and crystallinity of the films, except for the films on the GaN/Si substrates. This resulted in a significant decrease in the resistivity of the film and a significant increase in the superconducting transition temperature. [ABSTRACT FROM AUTHOR]

A superconductor-insulator transition (SIT) in two dimensions is a prototypical quantum phase transition (QPT) with a clear quantum critical point (QCP) at zero temperature (T = 0). The SIT is induced by a field B and observed in disordered thin films. In some of weakly disordered or crystalline thin films, however, an anomalous metallic (AM) ground state emerges over a wide B range between the superconducting and insulating phases. It remains a fundamental open question how the QPT picture of the SIT is modified when the AM state appears. Here we present measurements of the Nernst effect N, which has great sensitivity to the fluctuations of the superconducting order parameter. From a thorough contour map of N in the B-T plane, we found a thermal-to-quantum crossover line of the superconducting fluctuations, a so-called ghost-temperature line associated with the QPT, as well as a ghost-field line associated with a thermal transition. The QCP is identified as a T = 0 intercept of the ghost-temperature line inside the AM state, which verifies that the AM state is a broadened critical state of the SIT. The authors present Nernst measurements on a 2D film of amorphous MoxGe1−x, which shows a magnetic-field-induced superconductor-metal-insulator transition. The intermediate metal phase is known as the "anomalous metal" (AM) state. The authors conclude that the AM state originates from broadening of the superconductor-insulator transition. [ABSTRACT FROM AUTHOR]

Vanadium nitride (VN) is a transition-metal nitride with remarkable properties that have prompted extensive experimental and theoretical investigations in recent years. However, there is a current paucity of experimental research investigating the temperature-dependent electronic structure of single-crystalline VN. In this study, high-quality VN(111) films were successfully synthesized on α -Al 2 O 3 (0001) substrates using magnetron sputtering. The crystal and electronic structures of the VN films were characterized by a combination of high-resolution X-ray diffraction, low-energy electron diffraction, resonant soft X-ray absorption spectroscopy, and ultraviolet photoelectron spectroscopy. The electrical transport measurements indicate that the superconducting critical temperature of the VN films is around 8.1 K. Intriguingly, the temperature-dependent photoelectron spectroscopy measurements demonstrate a weak temperature dependence in the electronic structure of the VN films, which is significant for understanding the ground state of VN compounds. [ABSTRACT FROM AUTHOR]

Superconductivity transition temperature (T c) marks the inception of a macroscopic quantum phase-coherent paired state in fermionic systems. For 2D superconductivity, the paired electrons condense into a coherent superfluid state at T c, which is usually lower than the pairing temperature, between which intrinsic physics including Berezinskii–Kosterlitz–Thouless transition and pseudogap state are hotly debated. In the case of monolayer FeSe superconducting films on SrTiO3(001), although the pairing temperature (T p) is revealed to be 65–83 K by using spectroscopy characterization, the measured zero-resistance temperature (⁠|${{T}}_{{\rm c}}^0$|⁠) is limited to 20 K. Here, we report significantly enhanced superconductivity in monolayer FeSe films by δ-doping of Eu or Al on SrTiO3(001) surface, in which |${{T}}_{{\rm c}}^0$| is enhanced by 12 K with a narrowed transition width Δ T c ∼ 8 K, compared with non-doped samples. Using scanning tunneling microscopy/spectroscopy measurements, we demonstrate lowered work function of the δ-doped SrTiO3(001) surface and enlarged superconducting gaps in the monolayer FeSe with improved morphology/electronic homogeneity. Our work provides a practical route to enhance 2D superconductivity by using interface engineering. [ABSTRACT FROM AUTHOR]

The presence of amorphous oxide layers can significantly affect the coherent time of superconducting qubits due to their high dielectric loss. Typically, the surface oxides of superconductor films exhibit lossy and unstable behavior when exposed to air. To increase the coherence time, it is essential for qubits to have stable and low dielectric loss oxides, either as barrier or passivation layers. In this study, we highlight the robust and stable nature of an amorphous tantalum oxide layer formed on α-Ta (110) film by employing chemical and structural analyses. Such kind of oxide layer forms in a self-limiting process on the surface of α-Ta (110) film in piranha solution, yielding stable thickness and steady chemical composition. Quarter-wavelength coplanar waveguide resonators are made to study the loss of this oxide. One resonator has a Qi of 3.0 × 106 in the single photon region. The Qi of most devices are higher than 2.0 × 106. Moreover, most of them are still over 1 × 106 even after exposed to air for months. Based on these findings, we propose an all-tantalum superconducting qubit utilizing such oxide as passivation layers, which possess low dielectric loss and improved stability. [ABSTRACT FROM AUTHOR]

A system of two equations based on one of the classical electricity laws was used to determine the sizes and temperatures of ohmic areas formed under action of overcritical nanosecond electrical pulses. Calculations were performed at five points for three experimentally obtained voltage–current (V-I) dependences for samples with the same geometry but different critical current density values. The system included two additional conditions to satisfy the known descriptive model of transition from superconducting (SC) to a normal (N) state—S-N switching—and to obtain physically acceptable solutions over the entire current range of V-I dependence. The solution for each point takes the form of a function, since the initial temperature increase of the primary channel across the film is entered as a parameter. Two modes of concentrated energy release in the channel were disclosed. Their random appearance leads to an unexpected degradation of the sample. As such, the obtained results correspond to the situations occurring during the experiments. The validity of applying additional conditions to the system is discussed. In the discussion, it is also explained at which moments the moving S-N border acquires the velocity of the order of ~106 m/s, comparable to the Fermi velocity. Consideration to describe the moving unstable S-N border as being constantly in a state of Richtmyer–Meshkov instability is presented. [ABSTRACT FROM AUTHOR]

In this study, we present a novel approach to localized superconductivity induction in BaFe2As2 films via targeted implantation of cobalt (Co) ions. Primarily, our study focuses on the systematic distribution of Co ions and the subsequent evolution of superconducting properties in Co-ion-implanted BaFe2As2 films. Our observations show that Co-ion distribution in the films is congruent with the results of analytical methodologies employed in the semiconductor industry, as confirmed via transmission electron microscopy imaging. The temperature-dependent resistivity curves reveal the concurrent presence of superconducting and non-superconducting regions. Moreover, the superconducting domain demonstrates the typical diamagnetic behavior intrinsic in superconductors. Importantly, Co-ion concentrations of ∼1020 cm−3 can be achieved by finely tuning the beam energy and ion dose. This concentration is instrumental in establishing an effective superconducting percolation pathway within the films. [ABSTRACT FROM AUTHOR]

This paper utilizes the TFA-MOD (Trifluoroacetate Metal-Organic Decomposition) method to prepare YB 2 C 3 O 7-δ (YBCO) superconducting films on a LaMnO 3 metal substrate. Using a self-made process curve, we investigate the nucleation and growth orientation of crystals at various temperatures under specific oxygen partial pressures (P O2). We successfully obtain an oxygen partial pressure-temperature phase diagram at a fixed time. This diagram provides critical insight into the trends that guide our regulation of parameters to ultimately achieve a relatively pure a -axis oriented YBCO film. Temperature and nucleation rate are important parameters that influence crystal nucleation orientation. The key conditions for producing a -axis-oriented YBCO films include low temperature, high Δ μ , and extended crystallization time. [ABSTRACT FROM AUTHOR]

We have successfully synthesized a series of Bi-doped BaFe2As2 high-quality single crystals for the first time. X-ray diffraction (XRD) patterns show an expansion of lattice parameter c with Bi doping, indicating a negative pressure effect. By investigating the resistivity, a Fermi liquid (FL) to non-Fermi liquid (NFL) crossover is observed from normal state to antiferromagnetic order state, accompanied by three superconducting transitions labeled as SC I, SC II and SC III, which are supposed to be induced by three superconducting realms with various Bi concentrations. Thus, we propose that the NFL behavior is closely related to the presence of superconductivity. The magnetic susceptibility measurements further speculate that the SC I and SC III phases should exhibit filamentary superconductivity while the SC II exhibits a possible bulk superconductivity of TC~7 K. [ABSTRACT FROM AUTHOR]

We fabricated high-quality c-axis-oriented epitaxial YBa2Cu3O7−x films with 15% of the yttrium atoms replaced by terbium (YTBCO) and studied their electrical properties. The Tb substitution reduced the charge carrier density, resulting in increased resistivity and decreased critical current density compared to pure YBa2Cu3O7−x films. The electrical properties of the YTBCO films showed an in-plane anisotropy in both the superconducting and normal states that, together with the XRD data, provided evidence for, at least, a partially twin-free film. Unexpectedly, the resistive transition of the bridges also demonstrated the in-plane anisotropy that could be explained within the framework of Tinkham's model of resistive transition and the Berezinskii–Kosterlitz–Thouless (BKT) model, depending on the sample parameters. Measurements of the differential resistance in the temperature range of the resistive transition confirmed the occurrence of the BKT transition in the YTBCO bridges. Therefore, we consider the YTBCO films to be a promising platform for both the fabrication of devices with high kinetic inductance and fundamental research on the BKT transition in cuprate superconductors. [ABSTRACT FROM AUTHOR]

The ability to realistically simulate the electronic structure of superconducting materials is important to understand and predict various properties emerging in both the superconducting topological and spintronics realms. We introduce a tight-binding implementation of the Bogoliubov–de Gennes method, parameterized from density functional theory, which we utilize to explore the bulk and thin films of Nb, known to host a significant superconducting gap. The latter is useful for various applications such as the exploration of trivial and topological in-gap states. Here, we focus on the simulation's aspects of superconductivity and study the impact of temperature, Cooper-pair coupling and dimensionality on the value of the superconducting pairing interactions and gaps. [ABSTRACT FROM AUTHOR]

We study the local interaction of the gravitational field with a superfluid condensate. To this end, we exploit the Ginzburg–Landau formalism with generalized Maxwell fields. The analysis shows that a slight local alteration of the gravitational field in a thin superconducting film can be achieved by laser pulses with particular characteristics. [ABSTRACT FROM AUTHOR]

At the present time, ultrahigh performance superconducting nanowire single-photon detectors are the key elements in a variety of devices from biological research to quantum communications and computing. Accurate tuning of superconducting material properties is a powerful resource for fabricating single-photon detectors with desired properties. Here, we report on the major theoretical relations between ultrathin niobium nitride (NbN) film properties and superconducting nanowire single-photon detector characteristics, as well as the dependence of ultrathin NbN film properties on reactive magnetron sputtering recipes. Based on this study, we formulate the exact requirements for ultrathin NbN films for ultrahigh performance superconducting nanowire single-photon detectors. Then, we experimentally studied the properties of ultrathin NbN films (morphology, crystalline structure, critical temperature, and sheet resistance) on silicon, sapphire, silicon dioxide, and silicon nitride substrates sputtered with various recipes. We demonstrate ultrathin NbN films (obtained with more than 100 films deposition) with a wide range of critical temperature from 2.5 to 12.1 K and sheet resistance from 285 to 2000 Ω/sq and report a sheet resistance evolution of more than 40% within two years. Finally, we found out that one should use ultrathin NbN films with a specific critical temperature near 9.5 K and a sheet resistance of about 350 Ω/sq for ultrahigh performance state-of-the-art superconducting nanowire single-photon detectors at 1550 nm wavelength. [ABSTRACT FROM AUTHOR]

Dynamical ordering from a disordered plastic flow to an anisotropically ordered smectic flow induced by a dc force has been studied in various many-particle systems, including vortices in type-II superconductors. However, it remains unclear whether the dynamical ordering is a true phase transition because of lack of suitable experimental methods. Here, we study the response of vortex flow to the transverse force using a cross-shaped amorphous Mo x Ge 1 - x film. From transverse current-voltage (force-velocity) characteristics under various longitudinal currents, we find a change of the transverse response in low voltage (velocity) regions from a nonlinear to linear behavior at a well-defined longitudinal current that marks the dynamical ordering transition. We also find the scaling collapse of the transverse current-voltage curves to a universal scaling function, providing evidence of the second-order transition for the dynamical ordering transition. [ABSTRACT FROM AUTHOR]

For mass production, a high deposition rate is necessary. A powerful approach is to deposit Fe(Se, Te) (FST) superconducting films at a high laser repetition rate by pulsed laser deposition. Hence, the FST films were grown on flexible metallic tapes using pulsed laser deposition at different laser repetition rates to explore the effect of laser repetition rate on the properties. It was found that as the laser repetition rate increases, the crystallinity and stoichiometry of FST films deteriorate, resulting in a degeneration in superconductivity. The critical temperature Tczero$T_{\mathrm{c}}^{{\mathrm{zero}}}$ of the FST film deposited at a high repetition rate of 120 Hz dropped to 12.89 K. Furthermore, high‐performance FST film was successfully deposited at 120 Hz by increasing the substrate temperature with Tczero$T_{\mathrm{c}}^{{\mathrm{zero}}}\ $= 16.96 K and Tconset$T_{\mathrm{c}}^{{\mathrm{onset}}}\ $= 18.32 K. The self‐field critical current density can reach 1.3 MA/cm2 at 4.2 K. The analysis of the pinning mechanism reveals that normal surface pinning centers play a dominant part in the FST film and are independent of the temperature. The collective pinning theory states that the FST film exhibits δl pinning. The results may offer valuable information for rapid deposition of FST‐coated conductors for industrial production. [ABSTRACT FROM AUTHOR]

Due to the great differences in electron pairing characteristics between the hole-type (p-type) high-temperature superconductor (HTS) and the electron-type (n-type) HTS, when the Cooper pairs enter from a p-type to an n-type HTS or an n-type to a p-type HTS, pairing adjustment or even the recombination of them will inevitably occur at the interface, and the superconducting current dominated by them will be bound to change. Therefore, it is possible to better understand the electron pairing mechanism of the HTS and develop new HTS junction devices by studying these changes. In this paper, p-/n-type YBa2Cu3O7−δ/Nd1.85Ce0.15CuO4 (YBCO/NCCO) heterostructures were prepared via pulsed laser deposition on (00l)-oriented single-crystal SrTiO3 substrates. X-ray diffraction measurements indicate that the NCCO films prepared on YBCO do not exhibit good c-axis epitaxial growth, while excellent c-axis epitaxial growth is obtained for YBCO/NCCO heterostructures with NCCO at the bottom. Due to the high-temperature oxygen atmosphere and the deoxygenation process, the superconducting electrical properties of the bilayer structure are seriously degraded, and it is not possible to obtain good superconducting electrical properties for both the upper and lower layers using the traditional preparation process based on an oxygen atmosphere. Subsequently, the effects of different growth atmospheres on the electrical properties of the YBCO superconductors were studied, and high-quality YBCO superconducting films could be grown in oxygen, nitrous oxide, and nitrogen atmospheres. However, the oxygen and nitrous oxide atmospheres degrade the superconducting electrical properties of the underlying NCCO layer, while the nitrogen atmosphere does not seem to affect it significantly. YBCO/NCCO superconducting bilayers with critical transition temperatures of 85 and 8 K for YBCO and NCCO, respectively, were finally prepared by growing NCCO in an oxygen atmosphere and YBCO in a nitrogen atmosphere using a low-temperature oxygenation process. The successful preparation of the p-/n-type HTS heterostructure will help further study on the HTS. [ABSTRACT FROM AUTHOR]

We report a milestone in achieving large-scale, ultrathin (~5 nm) superconducting NbN thin films on 300 mm Si wafers using a high-volume manufacturing (HVM) industrial physical vapor deposition (PVD) system. The NbN thin films possess remarkable structural uniformity and consistently high superconducting quality across the entire 300 mm Si wafer, by incorporating an AlN buffer layer. High-resolution X-ray diffraction and transmission electron microscopy analyses unveiled enhanced crystallinity of (111)-oriented δ-phase NbN with the AlN buffer layer. Notably, NbN films deposited on AlN-buffered Si substrates exhibited a significantly elevated superconducting critical temperature (~2 K higher for the 10 nm NbN) and a higher upper critical magnetic field or Hc2 (34.06 T boost in Hc2 for the 50 nm NbN) in comparison with those without AlN. These findings present a promising pathway for the integration of quantum-grade superconducting NbN films with the existing 300 mm CMOS Si platform for quantum information applications. [ABSTRACT FROM AUTHOR]

Microwave loss in superconducting TiN films is attributed to two-level systems in various interfaces arising in part from oxidation and microfabrication-induced damage. Atomic layer etching (ALE) is an emerging subtractive fabrication method which is capable of etching with angstrom-scale etch depth control and potentially less damage. However, while ALE processes for TiN have been reported, they either employ HF vapor, incurring practical complications, or the etch rate lacks the desired control. Furthermore, the superconducting characteristics of the etched films have not been characterized. Here, we report an isotropic plasma-thermal TiN ALE process consisting of sequential exposures to molecular oxygen and an SF 6 /H 2 plasma. For certain ratios of SF 6 :H 2 flow rates, we observe selective etching of TiO 2 over TiN, enabling self-limiting etching within a cycle. Etch rates were measured to vary from 1.1 Å/cycle at 150 ° C to 3.2 Å/cycle at 350 ° C using ex situ ellipsometry. We demonstrate that the superconducting critical temperature of the etched film does not decrease beyond that expected from the decrease in film thickness, highlighting the low-damage nature of the process. These findings have relevance for applications of TiN in microwave kinetic inductance detectors and superconducting qubits. [ABSTRACT FROM AUTHOR]

Magneto-transport characteristics of 2D and 3D superconducting layers, in particular, temperature and angular dependences of the upper critical field Hc2, are usually considered to be fundamentally different. In the work, using non-local resistance measurements at temperatures near the normal-to-superconducting transition, we probed an effective dimensionality of nm-thick NbN films. It was found that in relatively thick NbN layers, the thicknesses of which varied from 50 to 100 nm, the temperature effect on Hc2 certainly pointed to the three-dimensionality of the samples, while the angular dependence of Hc2 revealed behavior typical for 2D samples. The seeming contradiction is explained by an intriguing interplay of three length scales in the dimensionally confined superconducting films: the thickness, the Ginzburg–Landau coherence length, and the magnetic-field penetration depth. Our results provide new insights into the physics of superconducting films with an extremely large ratio of the London penetration depth to the Ginzburg–Landau coherence length exhibiting simultaneously 3D isotropic superconducting properties and the 2D transport regime. [ABSTRACT FROM AUTHOR]

The infinite-layer nickelates, isostructural to the high-Tc cuprate superconductors, have emerged as a promising platform to host unconventional superconductivity and stimulated growing interest in the condensed matter community. Despite considerable attention, the superconducting pairing symmetry of the nickelate superconductors, the fundamental characteristic of a superconducting state, is still under debate. Moreover, the strong electronic correlation in the nickelates may give rise to a rich phase diagram, where the underlying interplay between the superconductivity and other emerging quantum states with broken symmetry is awaiting exploration. Here, we study the angular dependence of the transport properties of the infinite-layer nickelate Nd0.8Sr0.2NiO2 superconducting films with Corbino-disk configuration. The azimuthal angular dependence of the magnetoresistance (R(φ)) manifests the rotational symmetry breaking from isotropy to four-fold (C4) anisotropy with increasing magnetic field, revealing a symmetry-breaking phase transition. Approaching the low-temperature and large-magnetic-field regime, an additional two-fold (C2) symmetric component in the R(φ) curves and an anomalous upturn of the temperature-dependent critical field are observed simultaneously, suggesting the emergence of an exotic electronic phase. Our work uncovers the evolution of the quantum states with different rotational symmetries in nickelate superconductors and provides deep insight into their global phase diagram. The authors study transport in the superconducting state of infinite-layer nickelate Nd0.8Sr0.2NiO2 films using a Corbino-disk configuration, finding that the magnetoresistance changes from isotropic to four-fold anisotropic with increasing magnetic field. At even higher field, an additional two-fold component emerges, which coincides with an anomalous upturn of the critical field. [ABSTRACT FROM AUTHOR]

The recent discovery of superconductivity in infinite-layer nickelates generates tremendous research endeavors, but the ground state of their parent compounds is still under debate. Here, we report experimental evidence for the dominant role of Kondo scattering in the underdoped Nd1−xSrxNiO2 thin films. A resistivity minimum associated with logarithmic temperature dependence in both longitudinal and Hall resistivities are observed in the underdoped Nd1−xSrxNiO2 samples before the superconducting transition. At lower temperatures down to 0.04 K, the resistivities become saturated, following the prediction of the Kondo model. A linear scaling behavior |$\sigma _{{\boldsymbol{xy}}}^{{{\bf AHE}}}{\rm{\ }}\sim{\rm{\ }}{\sigma }_{{\boldsymbol{xx}}}$| between anomalous Hall conductivity |$\sigma _{{\boldsymbol{xy}}}^{{\bf{AHE}}}$| and conductivity |${\sigma }_{{\boldsymbol{xx}}}{\rm{\ }}$| is revealed, verifying the dominant Kondo scattering at low temperature. The effect of weak (anti-)localization is found to be secondary. Our experiments can help in clarifying the basic physics in the underdoped Nd1−xSrxNiO2 infinite-layer thin films. [ABSTRACT FROM AUTHOR]

We propose the utilization of inorganic crystals as substrates for kinetic inductance detectors (KIDs), which are thin-film superconducting resonators, for future rare event studies. When energy is deposited on the substrate, phonons are generated and propagate from the substrate to the surface, where KIDs are fabricated. This approach expands the potential for utilizing a diverse range of target crystals. We implement KIDs on calcium fluoride (CaF2) substrates, since 19F is sensitive to dark matter with spin-dependent interaction and 48Ca is one of the double-β decay nuclei. We have experimentally demonstrated the operation of the KIDs on the CaF2 substrate and their phonon-mediated particle detection. [ABSTRACT FROM AUTHOR]

The grain size and phase structure uniformity of europium barium copper oxide (EBCO) superconducting targets would affect the superconducting properties of sputtered film. A uniformly dispersed EBCO slurry was used to prepare high-density green EBCO compacts using slip casting. The effects of milling time and slurry pH on EBCO slurries were studied. Based on the shrinkage data of the EBCO superconducting targets, the densification process was estimated and the apparent activation energy was calculated. The effects of the sintering process on the microstructure and phase composition of EBCO superconducting targets were investigated using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). When the sintering temperature was 950–1050 °C, the EBCO superconducting target comprised EuBa 2 Cu 3 O 7 and CuO, where a new phase Eu 2 BaCuO 5 formed at a sintering temperature of 1100 °C. The Tc and ΔT of the EBCO superconducting target sintered at 950 °C for 30 h were 91.18 K and 2.35 K. [ABSTRACT FROM AUTHOR]

The control of a superconducting current via the application of a gate voltage has been recently demonstrated in a variety of superconducting devices. Although the mechanism underlying this gate-controlled supercurrent (GCS) effect remains under debate, the GCS effect has raised great interest for the development of the superconducting equivalent of conventional metal-oxide semiconductor electronics. To date, however, the GCS effect has been mostly observed in superconducting devices made by additive patterning. Here, we show that devices made by subtractive patterning show a systematic absence of the GCS effect. Doing a microstructural analysis of these devices and comparing them to devices made by additive patterning, where we observe a GCS, we identify some material and physical parameters that are crucial for the observation of a GCS. We also show that some of the mechanisms proposed to explain the origin of the GCS effect are not universally relevant. [ABSTRACT FROM AUTHOR]

Superconducting niobium nitride films are ideal candidates for electronics applications among low-Tc materials due to comparatively high critical temperature, large critical magnetic fields and relative ease of fabrication. The superconducting properties of NbN are known to be strongly dependent on the formation of a correct crystallographic phase. The tunneling spectroscopy data for NbN films are in good agreement with existing theoretical concepts, while contact methods provide significantly lower values of the superconducting order parameter. In this paper, we present corresponding results for a representative NbN film with Tc about 14 K, obtained using a point contact made by bringing a sharp metallic tip of silver in touch with the sample surface. We have observed fundamental difference between the gap values extracted from the differential conductance measurements and those following from the standard BCS theory. Despite the almost perfect contact of the normal tip with the film surface, the energy gap was nearly two times smaller than theoretically expected. At the same time, the gap values did not vanish at appreciably lower temperatures compared to the bulk of the NbN film, but rather continued to decrease slowly up to the bulk critical temperature. This finding is explained by significant deformation of the near-surface layer leading to the local suppression of superconducting parameters. Such behavior is a typical example of the superconducting proximity effect when the temperature dependence of the smaller gap strongly deviates from the BCS prediction but remains however finite up to the critical temperature of the larger gap, which is the same for two contacting spaces with superconducting parameters that differ significantly from each other. This conclusion is important for practical applications, in particular, for creating integration circuits based on superconducting NbN thin layers. [ABSTRACT FROM AUTHOR]

We review the topological gauge theory of Josephson junction arrays and thin film superconductors, stressing the role of the usually forgotten quantum phase slips, and we derive their quantum phase structure. A quantum phase transition from a superconducting to the dual, superinsulating phase with infinite resistance (even at finite temperatures) is either direct or goes through an intermediate bosonic topological insulator phase, which is typically also called Bose metal. We show how, contrary to a widely held opinion, disorder is not relevant for the electric response in these quantum phases because excitations in the spectrum are either symmetry-protected or neutral due to confinement. The quantum phase transitions are driven only by the electric interaction growing ever stronger. First, this prevents Bose condensation, upon which out-of-condensate charges and vortices form a topological quantum state owing to mutual statistics interactions. Then, at even stronger couplings, an electric flux tube dual to Abrikosov vortices induces a linearly confining potential between charges, giving rise to superinsulation. [ABSTRACT FROM AUTHOR]

In this work we report theoretical calculations of a superconducting island in a strong vortex confinement regime. The obtained results reveal the evolution of the superconducting condensate with an applied magnetic field, depending on the spatial profile of the electron mean-free path in the sample. The results of this study provide an insight about the emergent superconducting properties under such conditions, using the Ginzburg-Landau numerical simulations where spatial variation of thickness of the island and the corresponding variation of the mean free path, omnipresent in similar structures of Pb grown on Si (111), are taken into account. These results offer a new route to tailor superconducting circuits by nanoengineered mean free path, using for example the controlled ion-bombardment on thin films, benefiting from the here shown impact of the spatially-varying mean free path on the vortex distribution, phase of superconducting order parameter, and the critical fields. [ABSTRACT FROM AUTHOR]

Intrigued by the discovery of the long lifetime in the α-Ta/Al2O3-based Transmon qubit, researchers recently found α-Ta film is a promising platform for fabricating multi-qubits with long coherence time. To meet the requirements for integrating superconducting quantum circuits, the ideal method is to grow α-Ta film on a silicon substrate compatible with industrial manufacturing. Here we report the α-Ta film sputter-grown on Si (100) with a low-loss superconducting TiNx buffer layer. The α-Ta film with a large growth temperature window has a good crystalline character. The superconducting critical transition temperature (Tc) and residual resistivity ratio (RRR) in the α-Ta film grown at 500 °C are higher than that in the α-Ta film grown at room temperature (RT). These results provide crucial experimental clues toward understanding the connection between the superconductivity and the materials' properties in the α-Ta film and open a new route for producing a high-quality α-Ta film on silicon substrate for future industrial superconducting quantum computers. [ABSTRACT FROM AUTHOR]

Ferromagnetic films with perpendicular magnetic anisotropy are of interest in spintronics and superconducting spintronics. Perpendicular magnetic anisotropy can be achieved in thin ferromagnetic multilayer structures, when the anisotropy is driven by carefully engineered interfaces. Devices with multiple interfaces are disadvantageous for our application in superconducting spintronics, where the current perpendicular to plane is affected by the interfaces. Robust intrinsic PMA can be achieved in certain Co x Pt 100 - x alloys and compounds at any thickness, without increasing the number of interfaces. Here, we grow equiatomic Co 50 Pt 50 and report a comprehensive study on the structural, magnetic, and spin-polarisation properties in the L 1 1 and L 1 0 ordered compounds. Primarily, interest in Co 50 Pt 50 has been in the L 1 0 crystal structure, where layers of Pt and Co are stacked alternately in the [100] direction. There has been less work on L 1 1 crystal structure, where the stacking is in the [111] direction. For the latter L 1 1 crystal structure, we find magnetic anisotropy perpendicular to the film plane. For the former L 1 0 crystal structure, the magnetic anisotropy is perpendicular to the [100] plane, which is neither in-plane or out-of-plane in our samples. We obtain a value for the ballistic spin polarisation of the L 1 1 and L 1 0 Co 50 Pt 50 to be 47 ± 3 % . [ABSTRACT FROM AUTHOR]

Superconducting germanium films are an intriguing material for possible applications in fields such as cryogenic electronics and quantum bits. Recently, there has been a great deal of progress in hyperdoping of Ga doped Ge using ion implantation. Thin film growth of such a material would be advantageous, allowing homoepitaxy of doped and undoped Ge films and opening possibilities for vertical Josephson junctions. Here, we present our studies on the growth of one layer of hyperdoped superconducting germanium thin film via molecular beam epitaxy. We observe a fragile superconducting phase, which is extremely sensitive to processing conditions and can easily phase-segregate, forming a percolated network of pure gallium metal. By suppressing phase segregation through temperature control, we find a superconducting phase that is unique and appears coherent to the underlying Ge substrate. [ABSTRACT FROM AUTHOR]

Strontium titanate [SrTiO3 (STO)], a perovskite oxide with an extremely high gate-tunable dielectric constant (ε) due to quantum paraelectric phases, is attracting considerable attention for yielding various physical phenomena when two-dimensional (2D) layers are integrated. Superconductivity is such a typical phenomenon. However, the influence of the STO substrates on enhancing transition temperatures (Tc) for (atomically) thin 2D flakes attached to them has been rarely investigated. Here, we report gate-tunable and gradual four-terminal resistance drops with critical onset T (TCR) and scanning tunneling spectroscopy (STS) spectra in devices comprising thin TaS2 flakes attached on monolayer hexagonal boron nitride (hBN) spacer/STO substrates. Observation of STS spectra confirms the presence of local superconducting gaps Δ (∼1.5 meV) with transition T (TΔC) three-times higher than previous reports of Tc under absent pressure and strong position dependence of Δ. Depending on Δ on back gate voltages (Vbg) and magnetic fields, there is a strong correlation between TCR and the onset Tc of superconductivity, implying an enhancement of approximately five times compared with the previous highest-onset Tc values without pressure as the applied Vbg increases. The high onset Tc and Δ are discussed based on screening of the long-range Coulomb interaction (CI) due to the high-ε of SrTiO3, while the short-ranged CI remains strong in the 2D limit, causing the superconductivity. Using a monolayer hBN/SrTiO3 substrate with Vbg opens doors to Tc enhancement in thin superconducting layers integrated on it and wide application due to the solid-state high-ε substrates. [ABSTRACT FROM AUTHOR]

YBa2Cu3O7-δ (YBCO) thin films were prepared in situ on LaAlO3(100) single crystal substrates by spray pyrolysis. The deposition temperature was changed from 800°C to 880°C and all the samples were annealed at a lower temperature for different times. The resistivity versus temperature measurements showed that the film deposited at 880°C and annealed at 550°C for 1 h has the highest superconducting transition temperature (Tc) of about 90 K with the transition width (ΔTc) of 2 K. In addition, critical current density measurements of this sample were performed which revealed a critical current density (Jc) of about 104 A/cm2 at 77 K. Moreover, x-ray diffraction and atomic force microscopy analyses showed a c-axis growth and micro-sized grains of the films. Analysis of the normal state behavior of the samples revealed that 3D variable range hopping and the Aslamazov–Larkin model of fluctuation conductivity can explain the conduction of the under-doped and optimum-doped YBCO thin films. [ABSTRACT FROM AUTHOR]