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This paper explores the effect of agricultural policies on industrialization and economic development over the long-run. I analyze the differential effect of the \textit{Battle for Grain}, implemented by the Italian Fascist regime to achieve self-sufficiency in wheat production, on the development path across areas of Italy. Employing time variation, along with cross-sectional variation in the suitability of land for the implementation of the advanced wheat production technologies, I find that the policy had unintended positive effects on industrialization and economic prosperity which persisted until the contemporary period. Furthermore, I find that the positive effect of the \textit{Battle for Grain} on human capital accumulation was instrumental in this process, suggesting that the complementarity between human capital and agricultural technology may be a critical mechanism through which agricultural productivity may enhance the development of non-agricultural sectors.

We investigate the link between the 1918 Great Influenza and regional economic growth in Italy, a country in which the measures implemented by public authorities to contain the contagion were limited or ineffective. The pandemic caused 600,000 deaths in Italy: 1.2% of the population. Going from regions with the lowest mortality to those with the highest mortality is associated to a decline in per capita GDP growth of 6.5%, which dissipated within 3 years. Our estimates provide an upper bound of the adverse effect of pandemics on regional economic growth in the absence of non-pharmaceutical public-health interventions.

High critical temperature superconductors (HTS) based devices can have impact in the study of the phase dynamics of Josephson junctions (JJs) thanks to the wide range of junction parameters they offer and to their unconventional properties. Measurements of current-voltage characteristics and of switching current distributions constitute a direct way to classify different regimes of the phase dynamics and of the transport, also in nontrivial case of the moderately damped regime (MDR). MDR is going to be more and more common in JJs with advances in nanopatterning superconductors and synthesizing novel hybrid systems. Distinctive signatures of macroscopic quantum tunneling and of thermal activation in presence of different tunable levels of dissipation have been detected in YBCO grain boundary JJs. Experimental data are supported by Monte Carlo simulations of the phase dynamics, in a wide range of temperatures and dissipation levels. This allows us to quantify dissipation in the MDR and partially reconstruct a phase diagram as guideline for a wide range of moderately damped systems. (C) 2014 Elsevier B.V. All rights reserved.

Concepts and experimental procedures to obtain different types of YBa 2 Cu 3 O 7 grain boundaries Josephson junction through the biepitaxial technique have been developed. Various seed layers (MgO, CeO 2 and SrTiO 3) and substrates (MgO, SrTiO 3) have been used providing, for the biepitaxial technique, additional flexibility in circuit design. A detailed investigation on transport properties evidenced good performances for both junctions and superconducting quantum interference devices. Experimental evidence is given of a conventional magnetic field behavior in 45° tilt Artificial Grain Boundary (AGB) for which no π-loops are predicted along the interface.

(110) and (103) YBa 2 Cu 3 O 7 films have been grown onto exact and vicinal (110) SrTiO 3 substrates, and on vicinal (110) MgO substrates with a SrTiO 3 buffer layer. The samples are carefully characterised by reciprocal space mapping with x-ray diffraction, in order to investigate the features of the typical double domain of (110) and (103) YBa 2 Cu 3 O 7 structure. It is demonstrated that vicinal cut substrates allow to select one film/substrate epitaxial relation. The growth properties of these thin films deposited on vicinal surfaces are discussed.

We suggest a spin filter scheme using T-stub nanometric crossjunctions patterned in two dimensional electron gases (2DEGs) in the presence of spin orbit interaction (SOI). We compare the effects of SOI arising from vertical confinement of charge carriers in the well, Rashba or alpha-SOI, with SOI generated by lateral confinement of the wire, beta-SOI. We show that beta coupling can be more effective in generating a spin polarized current as compared to alpha-SOI. We also compare the efficiency of the T-stub filter with the one of the X shaped cross junction.

We have developed a fabrication process that allows us to realize pure YBCO nanowires displaying robust superconductivity at widths w as low as 160 nm. We can modify the process in order to maintain a Au protective layer. This allows us to scale our nanowires even further to widths as low as 50 nm. We have studied how the presence of vortices and the occurrence of phase slips affect the transport properties of nanowires in the width range xi < w < lambda, being xi the coherence length and lambda the magnetic penetration depth. Magnetoresistance curves present features which are related to the effect of screening currents. Vortex entry barrier is found to scale with the width. Our findings confirm that for widths xi < w < lambda nanowires are better protected against phase slips and vortex flow. (C) 2014 Elsevier B.V. All rights reserved.

Since the discovery of high-temperature superconductors (HTSs), most efforts of researchers have been focused on the fabrication of superconducting devices capable of immobilizing vortices, hence of operating at enhanced temperatures and magnetic fields. Recent findings that geometric restrictions may induce self-arresting hypervortices recovering the dissipation-free state at high fields and temperatures made superconducting strips a mainstream of superconductivity studies. Here we report on the geometrical melting of the vortex lattice in a wide YBCO submicron bridge preceded by magnetoresistance (MR) oscillations fingerprinting the underlying regular vortex structure. Combined magnetoresistance measurements and numerical simulations unambiguously relate the resistance oscillations to the penetration of vortex rows with intermediate geometrical pinning and uncover the details of geometrical melting. Our findings offer a reliable and reproducible pathway for controlling vortices in geometrically restricted nanodevices and introduce a novel technique of geometrical spectroscopy, inferring detailed information of the structure of the vortex system through a combined use of MR curves and large-scale simulations.

Proximity-effect and resistance magneto-fluctuations measurements in submicron Nd1.2Ba1.8Cu3Oz (NBCO) nano-loops are reported to investigate coherent charge transport in the non-superconducting state. We find an unexpected inhibition of cooper pair transport, and a destruction of the induced superconductivity, by lowering the temperature from 6K to 250mK. This effect is accompanied by a significant change in the conductance-voltage characteristics and in the zero bias conductance response to the magnetic field pointing to the activation of a strong pair breaking mechanism at lower temperature. The data are discussed in the framework of mesoscopic effects specific to superconducting nanostructures, proximity effect and high temperature superconductivity., to appear on new journal of Physics

YBaCuO nanowires were reproducibly fabricated down to widths of 50 nm. A Au/Ti cap layer on YBCO yielded high electrical performance up to temperatures above 80 K in single nanowires. Critical current density of tens of MA/cm2 at T = 4.2 K and of 10 MA/cm2 at 77 K were achieved that survive in high magnetic fields. Phase-slip processes were tuned by choosing the size of the nanochannels and the intensity of the applied external magnetic field. Data indicate that YBCO nanowires are rather attractive system for the fabrication of efficient sensors, supporting the notion of futuristic THz devices., 8 pages, 3 figures. Accepted for publication in Superconductor Science and Technology

We have designed an experiment that could allow to investigate, on the same sample, the interplay between the morphological anisotropy of high critical temperature superconductors and the effects related to the order parameter symmetry. To this aim we have employed c-axis tilt biepitaxial grain boundary YBa2Cu3O 7 - δ Josephson junctions and measured the junction properties for different junction interface orientations. The results give evidence of the possibility to tune normal state resistance and critical current density of a Josephson junction almost independently of each other. We interpret the results of this experiment as an indication that Cooper pairs and quasi-particles transport properties may be ruled by different mechanisms. Measurements apparently give evidence of the possibility to determine to some extent the presence of “π-loops” and “0” loops along the same grain boundary line.

An innovative fabrication procedure has been developed to obtain YBa(2)Cu(3)O(7-x) (YBCO) nanobridges from c-axis oriented films. The novelty regards the use of a thin titanium mask used in the patterning process. The use of the Ti makes simpler the fabrication procedure guaranteeing high quality devices, as demonstrated by transport measurements. Critical temperatures and critical current densities scale with the width of the micro-bridge down to 200 nm in agreement with most results available in literature. The actual properties of the devices, performances, yield and reproducibility, along with an accurate control on doping, may allow the use of these micro-bridges for nanoscale experiments.

Chronic abdomino-pelvic pain or chronic pelvic pain (CPP) is estimated to affect 4 % of women, decreasing quality of life and work productivity, with healthcare costs of more than two billion dollars per year in the United States. Diagnosis of the etiology is difficult as symptoms can be vague and often the patient has several sources for her pain. Non-gynecologic disorders are associated with higher prevalence rates than gynecologic disorders and include: Irritable bowel syndrome (IBS), interstitial cystitis/painful bladder syndrome (IC/PBS), abdominal/pelvic myofascial pain, and neuralgias (discussed in other chapters of this book). Gynecologic disorders include: endometriosis, prior pelvic inflammatory disease, leiomyomata, adenomyosis, tuberculous salpingitis, ovarian remnant syndrome, ovarian retention syndrome, and pelvic congestion syndrome. Dysmenorrhea (pain with the menstrual cycle) and dyspareunia (pain with sexual intercourse) are also common symptoms. Other non-gynecologic disorders, such as depression, fibromyalgia, migraines, low back pain, or a history of physical/sexual abuse, should be evaluated and addressed. Patients with CPP often have been to multiple doctors and had numerous interventions without any improvement of pain or even a diagnosis. A patient–physician relationship based on empathy and trust, along with patient education and setting realistic goals (including pain decrease with improvement of daily functioning), is extremely important.

Transport properties of high quality Nb/semiconductor/Nb long Josephson junctions based on metamorphic In_0.75Ga_0.25As epitaxial layers are reported. Different junction geometries and fabrication procedures are presented that allow a systematic comparison with quasiclassical theory predictions. The impact of junction transparency is highlighted and a procedure capable of yielding a high junction quality factor is identified., Comment: 11 pages, 3 figures

We present various concepts and experimental procedures to produce biepitaxial ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}x}$ grain-boundary Josephson junctions. The device properties have an interesting phenomenology, related in part to the possible influence of $\mathrm{``}\ensuremath{\pi}$ loops.'' The performance of our junctions and superconducting quantum interference devices indicates significant improvement in the biepitaxial technique. Further, we propose methods for fabricating circuits in which 0 and $\ensuremath{\pi}$ loops are controllably located on the same chip.

A shortcut method to calculate HETP for metal structured packings is proposed. The method is a simplification and extension of Lockett's equation for sheet packings, based on the Bravo, Rocha and Fair model. It is applicable at vacuum or pressure distillation of organic or aqueous mixtures in columns of sheet and gauze packings. The necessary variables are specific surface of packing, density of vapor and liquid and flow (when gauze packings are being considered). No estimation of hydrodynamic conditions is necessary.

Growth by the micro-pulling-down technique (μ-PD) of homogeneous and crack-free fiber single crystals with composition Ba 2 Na 1− x Yb x Nb 5 O 15 ( 0 ) is reported. The effect of Yb 3+ addition to barium sodium niobate (BNN, x=0 ), having the tungsten bronze-type structure, was examined by room temperature X-ray powder diffraction and differential thermal analysis coupled to thermogravimetry. In the region of the monophased field the structure is tetragonal from x=0.02 to 0.16. Volume change is mainly by variation of the a -axis length. Addition of Yb 3+ to BNN could be effective for the production of high optical quality, crack-free, bulk crystals by the Czochralski technique.

${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ (YBCO) artificial grain-boundary Josephson junctions have been fabricated, employing a recently implemented biepitaxial technique. The grain boundaries can be obtained by controlling the orientation of the MgO seed layer and are characterized by a misalignment of the c axes (45\ifmmode^\circ\else\textdegree\fi{} c-axis tilt or 45\ifmmode^\circ\else\textdegree\fi{} c-axis twist). A detailed characterization of the Josephson properties has been carried out, showing remarkable differences in the transport parameters of tilt and twist junctions. High-resolution electron microscopy showed the presence of perfect basal plane faced boundaries in the cross sections of tilt boundaries; however interfaces meandering along the sample thickness are also sometimes observed. The correlation between transport properties and microstructure is investigated and the possibility to employ these junctions to explore the symmetry of the order parameter is presented. On the basis of the analysis of microstructural data and of a qualitative growth model for (103) YBCO grains, it is suggested that clean basal plane boundaries exhibiting uniform Josephson properties could be obtained by this technique.

Electron beam irradiation has been used to induce controllable variations in the properties of YBa 2 Cu 3 O 7-x biepitaxial grain boundary Josephson junctions. Electron irradiation decreased the critical current of the junctions IC and increased the normal state specific resistivities. The junction parameters can be adjusted controllably by applying an appropriate dose. The original properties of the junctions could be partly restored by isothermal annealing A correlation between the transport properties and the microstructure was obtained by determining the ratio of a barrier thickness to the dielectric constant of the junctions with different barriers. The experiment also demonstrates frequency tunability in a resonant soliton oscillator. Preliminar results of irradiation on (103) YBCO films have been given demonstrating differences from data on c -axis films, as partly expected from the anisotropy of these materials.

The properties of YBa 2 Cu 3 O 7− x grain boundary Josephson junctions have been reproducibly modified by a focused electron beam irradiation. The original junctions were fabricated by using the biepitaxial technique on (110) SrTiO 3 substrates. The technique utilizes the property of YBa 2 Cu 3 O 7− x film to grow (103)-oriented on the bare substrate and (001)-oriented on the part of the substrate with the MgO seed layer, providing Josephson junctions of good quality and excellent reproducibility. The junction parameters can be adjusted controllably by applying an appropriate irradiation dose. Electron irradiation reduced the critical current of the junctions I C and increased the normal state specific resistivity. The disappearance of the excess current and the shift of the voltage position of the Fiske steps were also observed. Isothermal annealing partly restores the original junction properties. We also speculate that some aspects of the nature of the grain boundary barriers can be better understood from the study of the transport properties of irradiated junctions. PACS: 74.50+r, 74.72Bk, 74.76Bz, 85.25Cp

The properties of the Y 1 Ba 2 Cu 3 O 7-x biepitaxial Josephson junctions were reproducibly modified by a focused electron beam irradiation of the interface region. The original structures are based on 45° a-axis tilt grain boundaries. The junction parameters can be controllably adjusted by applying an appropriate irradiation dose. Electron irradiation reduced the critical current of the junctions and increased the normal state specific resistivity The disappearance of the excess current and the shift of the voltage position of the Fiske steps were also observed. Isothermal annealing partly restores the original junction properties. Some aspects of the nature of the grain boundary barriers can be better understood from the study of the properties of irradiated junctions.

Electron-beam irradiation has been used to induce controllable variations in the properties of YBa2Cu3O72x biepitaxial grain-boundary Josephson junctions. A correlation between the transport properties and the microstructure was obtained by determining the ratio of a barrier thickness to the dielectric constant of the junctions with different barriers. These results give evidence of the role of the oxygen content and the dielectric constant of the interface region in transport phenomena. The experiment also demonstrates frequency tunability in a resonant soliton oscillator. @S0163-1829~98!51322-2#

We report the realization of a ballistic Josephson interferometer. The interferometer is made by a quantum ring etched in a nanofabricated two-dimensional electron gas confined in an InAs-based heterostructure laterally contacted to superconducting niobium leads. The Josephson current flowing through the structure shows oscillations with h/e flux periodicity when threading the loop with a perpendicular magnetic field. This periodicity, in sharp contrast with the h/2e one observed in conventional dc superconducting quantum interference devices, confirms the ballistic nature of the device in agreement with theoretical predictions. This system paves the way for the implementation of interferometric Josephson pi-junctions, and for the investigation of Majorana fermions., 4+ pages, 4 colored figures

We report on the study of the phase dynamics of high-critical-temperature superconductor Josephson junctions. We realized YBa${}_{2}$Cu${}_{3}$O${}_{7\ensuremath{-}x}$ grain boundary biepitaxial junctions in the submicron scale using low-loss substrates and analyzed their dissipation by comparing the transport measurements with Monte Carlo simulations. The behavior of the junctions can be fitted using a model based on two quality factors, which results in a frequency-dependent damping. Moreover, our devices can be designed to have Josephson energy of the order of the Coulomb energy. In this unusual energy range, phase delocalization strongly influences the device's dynamics, promoting the transition to a quantum phase diffusion regime. We study the signatures of such a transition by combining the outcomes of Monte Carlo simulations with the analysis of the device's parameters, the critical current, and the temperature behavior of the low-voltage resistance ${R}_{0}$.

We have designed an experiment that could allow to investigate, on the same sample, the interplay between the morphological anisotropy of high critical temperature superconductors and the effects related to the order parameter symmetry. To this aim we have employed c-axis tilt biepitaxial grain boundary YBa2Cu3O7-delta Josephson junctions and measured the junction properties for different junction interface orientations. The results give evidence of the possibility to tune normal state resistance and critical current density of a Josephson junction almost independently of each other. We interpret the results of this experiment as an indication that Cooper pairs and quasi-particles transport properties may be ruled by different mechanisms. Measurements apparently give evidence of the possibility to determine to some extent the presence of "pi-loops" and "0" loops along the same grain boundary line.

We show that low-angle grain boundaries (GB) in high-temperature superconductors exhibit intermediate Abrikosov vortices with Josephson cores, whose length $l$ along GB is smaller that the London penetration depth, but larger than the coherence length. We found an exact solution for a periodic vortex structure moving along GB in a magnetic field $H$ and calculated the flux flow resistivity $R_F(H)$, and the nonlinear voltage-current characteristics. The predicted $R_F(H)$ dependence describes well our experimental data on $7^{\circ}$ unirradiated and irradiated $YBa_2Cu_3O_7$ bicrystals, from which the core size $l(T)$, and the intrinsic depairing density $J_b(T)$ on nanoscales of few GB dislocations were measured for the first time. The observed temperature dependence of $J_b(T)=J_{b0}(1-T/T_c)^2$ indicates a significant order parameter suppression in current channels between GB dislocation cores., 5 pages 5 figures. Phys. Rev. Lett. (accepted)

We present various concepts and experimental procedures to fabricate biepitaxial YBa 2Cu 3O 7-x grain boundary Josephson junctions. Different types of structures can be realized including "π-loops" in which one of the junctions is intrinsically π-phase shifted. Due to its versatility the biepitaxial technique offers the possibility to investigate basic aspects of the physics of grain boundary Josephson junctions, and also the influence of intrinsic and extrinsic d-wave induced effects in transport properties. Further, we discuss the possibility to produce circuits in which "0-" and "π-loops" are controllably located on the same chip, and intrinsic d-wave effects can be exploited.

The effects of the order parameter symmetry and the interfere grain boundary orientation on the transport properties of YBa2Cu3O7-x biepitaxial grain boundary junctions have been investigated. 45 degrees [100] tilt and twist junctions on SrTiO3 [110] and MgO [110] substrates by employing respectively MgO and SrTiO3 as seed layers have been fabricated. More complex junctions by using CeO as seed layers have also been fabricated and analyzed. The analysis of experimental data points towards a predominant d-wave symmetry of the superconductive order parameter.

The effects of the order parameter symmetry and the interface grain boundary orientation on the transport properties of YBa/sub 2/Cu/sub 3/O/sub 7-x/ biepitaxial grain boundary junctions have been investigated. 45/spl deg/ [100] tilt and twist junctions on SrTiO/sub 3/ [110] and MgO [110] substrates by employing respectively MgO and SrTiO/sub 3/ as seed layers have been fabricated. More complex junctions by using CeO as seed layers have also been fabricated and analyzed. The analysis of experimental data points towards a predominant d-wave symmetry of the superconductive order parameter.

(110) and (103) YBa2Cu3O7 films have been grown onto exact and vicinal (110) SrTiO3 substrates, and on vicinal (110) MgO substrates with a SrTiO3 buffer layer. The samples are carefully characterised by reciprocal space mapping with x-ray diffraction, in order to investigate the features of the typical double domain of (110) and (103) YBa2Cu3O7 structure. It is demonstrated that vicinal cut substrates allow to select one film/substrate epitaxial relation. The growth properties of these thin films deposited on vicinal surfaces are discussed.

We have extended the off-axis biepitaxial technique to produce YBCO grain boundary junctions on low loss substrates. Excellent transport properties have been reproducibly found, with remarkable values of the quality factor I(c)R(n) (with I(c) the critical current and R(n) the normal state resistance) above 10 mV, far higher than the values commonly reported in the literature for high temperature superconductor (HTS) based Josephson junctions. The outcomes are consistent with a picture of a more uniform grain boundary region along the current path. This work supports a possible implementation of grain boundary junctions for various applications including terahertz sensors and HTS quantum circuits in the presence of microwaves.

The properties of single submicron high-temperature superconductor (HTS) rings are investigated. The Little-Parks effect is observed and is accompanied by an anomalous behavior of the magnetic dependence of the resistance, which we ascribe to non-uniform vorticity (superfluid angular momentum) within the ring arms. This effect is linked to the peculiar HTS-relationship between the values of the coherence length and the London penetration depth.

YBa(2)Cu(3)O(7-delta) (YBCO) grain boundaries characterized by a misalignment of the c-axes (45 degrees c-axis tilt or 45 degrees c-axis twist) have been obtained by employing a recently implemented biepitaxial technique. Junctions based on these grain boundaries exhibit good Josephson properties useful for applications. High values of the I(C)R(N) product and a Fraunhofer-like dependence of the critical current on the magnetic field, differently from traditional biepitaxial junctions, have been obtained. The correlation between transport properties and microstructure has been investigated by Transmission Electron Microscopy (TEM), which was also performed on previously measured junctions. The presence of atomically clean basal plane (BP) faced tilt boundaries, among other types of interfaces, has been shown. The possibility of selecting these kinds of boundaries by controlling film growth, and their possible advantages in terms of reproducibility and uniformity of the junction properties an discussed. The possibility of employing these junctions to explore the symmetry of the order parameter is also discussed.

YBa(2)Cu(3)O(7-delta) (YBCO) grain boundaries characterized by a misalignment of the c-axes (45 degrees c-axis tilt or 45 degrees c-axis twist) have been obtained by employing a recently implemented biepitaxial technique. Junctions based on these grain boundaries exhibit good Josephson properties useful for applications. High values of the I(C)R(N) product and a Fraunhofer-like dependence of the critical current on the magnetic field, differently from traditional biepitaxial junctions, have been obtained. The correlation between transport properties and microstructure has been investigated by Transmission Electron Microscopy (TEM), which was also performed on previously measured junctions. The presence of atomically clean basal plane (BP) faced tilt boundaries, among other types of interfaces, has been shown. The possibility of selecting these kinds of boundaries by controlling film growth, and their possible advantages in terms of reproducibility and uniformity of the junction properties an discussed. The possibility of employing these junctions to explore the symmetry of the order parameter is also discussed. (C) 1999 Elsevier Science B.V. All rights reserved.

Electron beam irradiation has been used to induce controllable variations in the properties of YBa2Cu3O7, biepitaxial grain boundary Josephson junctions. Electron irradiation decreased the critical current of the junctions Ic and increased the normal state specific resistivities. The junction parameters can be adjusted controllably by applying an appropriate dose. The original properties of the junctions could be partly restored by isothermal annealing A correlation between the transport properties and the microstructure was obtained by determining the ratio of a barrier thickness to the dielectric constant of the junctions with different barriers. The experiment also demonstrates frequency tunability in a resonant soliton oscillator. Preliminar results of irradiation on (103) YBCO films have been given demonstrating differences from data on c-axis films, as partly expected from the anisotropy of these materials.

YBa(2)Cu(3)O(7-x)., junctions and de SQUIDs have been realized by employing 45 degrees axis tilt grain boundaries through a fabrication procedure based on the biepitaxial technique, YBa(2)Cu(3)O(7-x)., grows mainly oriented (103) on SrTiO(3) and (001) on the MgO seed layer, A wide characterization of the tilt junctions and SQUID properties has been carried out. High values of the I(C)R(N) quality factor and of the magnetic flux-to-voltage transfer parameter have been obtained. The observed phenomenology confirms differences from the one typical of 45 degrees c-asis tilt grain boundary junctions and gives important information on the nature of the current steps appearing at finite voltages in the current-voltage characteristics. These devices could also have some impact on esperiments designed to study the symmetry of the order parameter, exploiting their microstructure and anisotropic properties. A maximum speed of Josephson vortices as calculated from the voltage step values, of the order of 2 10(6) m/sec is obtained, which encourages high frequency applications.

YBa2Cu3O7-x artificial grain boundary Josephson junctions have been fabricated, employing a recently implemented biepitaxial technique. The grain boundaries can be obtained by controlling the orientation of the MgO seed layer and are characterized by a misalignment of the c-axes (45 degrees a-axis tilt or 45 degrees a-axis twist). These types of grain boundaries are still mostly unexplored. We carried out a complete characterization of their transport properties and microstructure. Junctions and de SQUIDs associated with these grain boundaries exhibit an excellent Josephson phenomenology and high values of the ICRN product and of the magnetic flux-to-voltage transfer parameter respectively. Remarkable differences in the transport parameters of tilt and twist junctions have been observed, which can be of interest for several applications. A maximum speed of Josephson vortices as calculated from the voltage step values of the order of 2 x 10(6) m s(-1) is obtained. These devices could also have some impact on experiments designed to study the symmetry of the order parameter, exploiting their microstructure and anisotropic properties. High-resolution electron microscopy showed the presence of perfect basal plane faced boundaries in the cross sections of tilt boundaries.

Superconducting quantum interference devices (SQUIDs) have been fabricated using YBa2Cu3O72x @100# 45°-tilt grain-boundary Josephson junctions based on a controllable biepitaxial technique. These devices are characterized by large characteristic voltages, desirable magnetic-flux-to-voltage transfer parameters and low flux noise. An energy resolution of 1.6310230 J/Hz at liquid helium has been measured, which is the lowest value reported for biepitaxial SQUIDs. These junctions exhibit a phenomenology different from traditional @001# 45°-tilt biepitaxials probably due to the absence of p junctions. The performance of the presented SQUIDs demonstrates that significant improvements in the biepitaxial technique are possible, and the resulting devices have potential for applications.

The properties of YBa2Cu3O7-x grain boundary Josephson junctions have been reproducibly modified by a focused electron beam irradiation. The original junctions were fabricated by using the property of YBa2Cu3O7-x film to grow (103)-oriented on the bare (110) SrTiO3 substrate and (001)-oriented on the part of the substrate with the MgO seed layer. The junction parameters can be adjusted controllably by applying an appropriate irradiation dose. Electron irradiation reduced the critical current of the junctions Ic and increased the normal state specific resistivity. The shift of the voltage position of the Fiske steps was also observed. Isothermal annealing partly restores the original junction properties. A correlation between the transport properties and the microstructure was obtained by determining the ratio of a barrier thickness to the dielectric constant of the junctions with different barriers. These results give evidence of the role of the oxygen content and the dielectric constant of the interface region in transport phenomena. The experiment also demonstrates frequency tunability in a resonant soliton oscillator.

The properties of the Y1Ba2Cu3O7-x biepitaxial Josephson junctions a ere reproducibly modified by a focused electron beam irradiation of the interface region. The original structures are based on 45 degrees a-axis tilt rain boundaries The junction parameters can be controllably adjusted by applying an appropriate irradiation dose Electron irradiation reduced the critical current of the junctions and increased the normal stare specific resistivity. The disappearance of the excess current and the shift of the voltage position of the Fiske steps were also observed Isothermal annealing partly restores the original junction properties Some aspects of the nature of the grain boundary barriers can be better understood from the study of the properties of irradiated junctions.

A pronounced anisotropy is observed in the low-temperature mobility of a two-dimensional electron gas formed in an ${\text{In}}_{0.75}{\text{Ga}}_{0.25}\text{As}/{\text{In}}_{0.75}{\text{Al}}_{0.75}\text{As}$ quantum well grown on a GaAs substrate. We show that the mobility differences along [011] and $[01\overline{1}]$ directions are mainly due to In concentration modulations. Spatially resolved photoemission measurements show an asymmetric indium concentration modulation, correlated with the surface morphology observed by atomic force microscopy. A theoretical model considering conduction band energy modulations agrees well with the transport measurements. The identification of this mobility limiting mechanism allowed us to design and grow higher quality two-dimensional electron gases, needed for high indium content InGaAs device fabrication.

We have fabricated and characterized Hall probes on an In0.75Al0.25As/In0.75Ga0.25As two-dimensional electron gas with lateral sizes down to 100 nm. We studied the dependence of the low temperature (4 K) magnetic field sensitivity on the probe size, showing that the best flux sensitivity is achieved by devices of ≈ 200 nm, employing highly doped systems ( n ∼ 1 0 12 cm−2). Hall bars with sizes down to the range of 200–250 nm show a magnetic field sensitivity of a few Gauss, corresponding to a flux sensitivity equal to ≈ 1 0 − 2 Φ 0 .