Basic elements for photodeposited high Tc thin film devices

Flat films, high quality insulating layers and adequately superconducting via contacts are basic elements for high Tc device fabrication. We studied the influence of the process parameters of laser deposition on the occurrence of droplets and outgrowths in YBaCuO films. The droplet density is minimal when a laser fluence below about 1.0 J cm-2 is used. The outgrowth density decreases with increasing laser pulse rate or decreasing deposition temperature. High quality flat films were obtained with a rate of 10 Hz and at a temperature of 720 °C. Wet chemical etching and etching with an Argon ion source were used for structuring multilayers with SrTiO3 as an insulating layer. Smooth edges were obtained with an argon gun. Bromine and EDTA etching are not adequate techniques for fabricating controllable well-defined edges. Cross-overs, via contacts and coils were prepared

Fabrication of 45 degrees template grain boundary junctions using a CaO lift-off technique

45 degrees grain boundary junctions have been made using (100) MgO substrates, a CeO2 template layer and an YBa2Cu3O7 top layer. To minimize the damage to the MgO surface, which will occur if the CeO2 is structured using ion milling, the CeO2 layer has been structured using the CaO lift-off technique. Electrical measurements of these junctions as a function of temperature, microwave irradiation and magnetic field will be discussed in this paper

Voltage-current and voltage-flux characteristics of asymmetric high TC DC SQUIDs

We report measurements of transfer functions and flux shifts of 20 on-chip high T$_C$ DC SQUIDs half of which were made purposely geometrically asymmetric. All of these SQUIDs were fabricated using standard high T$_C$ thin film technology and they were single layer ones, having 140 nm thickness of YBa$_2$Cu$_3$O$_{7-x}$ film deposited by laser ablation onto MgO bicrystal substrates with 24$^0$ misorientation angle. For every SQUID the parameters of its intrinsic asymmetry, i. e., the density of critical current and resistivity of every junction, were measured directly and independently. We showed that the main reason for the on-chip spreading of SQUIDs' voltage-current and voltage-flux characteristics was the intrinsic asymmetry. We found that for SQUIDs with a relative large inductance ($L>120$ pH) both the voltage modulation and the transfer function were not very sensitive to the junctions asymmetry, whereas SQUIDs with smaller inductance ($L\simeq 65-75$ pH) were more sensitive. The results obtained in the paper are important for the implementation in the sensitive instruments based on high T$_C$ SQUID arrays and gratings.Comment: 11 pages, 4 tables, 17 figures This version is substantially modified. The Introduction and Section 2 are completely rewritten, while experimental part is mainly the same as in previous versio

Multilayer studies and applications in template bi-epitaxial DC SQUIDS

Multilayer deposition for the creation of a well-defined grain boundary, based on different in-plane orientations of c-axis oriented thin YBa2O2Cu3O7-δ layers on a single substrate, has been performed on three different kinds of substrates: (1102)-oriented Al2O3 , (100) SrTiO3, and (100) MgO. The multilayers consist of combinations of SrTiO3, MgO, CeO2, and YBa2O2Cu3O7-δ. The YBa 2O2Cu3O7-δ top layers on (1102) Al2O3 and (100) SrTiO3 were polycrystalline. Josephson junctions and DC superconducting quantum interference devices (SQUIDs) have been structured in the layers on MgO. Shapiro steps were observed. The Jcρn-product of the junctions at 4.2 K is on the order of 1 mV. The critical current decreases in good approximation linearly with increasing temperature, whereas the normal state resistance is nearly temperature independent. Voltage modulation was observed at temperatures up to 77 K

Materials aspects of integrated high-Tc dc-SQUID magnetometer fabrication

An integrated high Tc dc-SQUID magnetometer is being developed. It has in total 10 layers of five different materials. Various materials aspects of the fabrication process will be discussed, especially the smoothness of the films and the techniques to obtain smooth edges. Cross-overs and superconducting window contacts were fabricated. The critical temperature of the window-contact is 84K (jc(77K)=2·105 A/cm2) and the resistivity of the insulating SrTiO3 layer in the cross-over is 6·105 Ωcm at 77K. The complete coil often shows a small resistive component down to about 50K. Ramp type and bi-epitaxial grain boundary dc-SQUIDs show voltage modulation up to 65K and 79K, respectively. Efforts to fabricate an integrated high Tc dc-SQUID magnetometer will be discussed

Measuring temporal variations in presence

In the current study we have applied the concept of presence to 3DTV research. More specifically, we took this concept to reflect the increased perceptual linkage between the observer and the mediated environment, supporting an illusion of non-mediation. We applied the continuous assessment methodology to reveal time-variant properties of presence, which were hitherto largely ignored, and to assess some of the contributing factors that have been suggested as determinants of presence. Our results indicate that subjective presence ratings are subject to considerable temporal variation depending on the stimulus material used. The continuous assessment methodology may be regarded as a useful measurement tool that is sensitive to this time-varying information in subjective presence judgements, provided that any conclusions are based on averaged results obtained from an adequate number of observers. We also found qualitative evidence suggesting that increasing the extent of sensory information provided to an observer, through the addition of stereoscopic and motion parallax cues (simulated via camera movement), may enhance the observer's sense of presence

Towards a Framework for Metacognition in Game-Based Learning

\u3cp\u3eGame-based learning can motivate learners and help them to acquire new knowledge in an active way. However, it is not always clear for learners how to learn effectively and efficiently within game-based learning environments. As metacognition comprises the knowledge and skills that learners employ to plan, monitor, regulate, and evaluate their learning, it plays a key role in improving their learning in general. Thus, if we want learners to become better at learning through game-based learning, we need to investigate how metacognition can be integrated into the design of game-based learning environments. In this paper we introduce a framework that aids designers and researchers to formally specify the design of game-based learning environments encouraging metacognition. With a more formal specification of the metacognitive objectives and the way the training design and game design aims to achieve these goals, we can learn more through analysing and comparing different approaches. The framework consists of design dimensions regarding metacognitive outcomes, metacognitive training, and metacognitive game design. Each design dimension represents two opposing directions for the design of a game-based learning environment that are likely to affect the encouragement of metacognitive awareness within learners. As such, we introduce a formalised method to design, evaluate and compare games addressing metacognition, thus enabling both researchers and designers to create more effective games for learning in the future.\u3c/p\u3

Subharmonic Shapiro steps in high‐Tc Josephson junctions

We studied the response of high‐Tc biepitaxial grain boundaryjunctions to 100 GHz radiation in the presence of a magnetic field. Integer as well as subharmonic constant voltage steps are observed, even at one‐fifth of the voltage separation between integer (Shapiro) steps. Our results indicate that this behavior is due to the synchronized motion of Josephsonvortices along the junction. We show that this effect is directly related to the width of the junction, and not to an array of weaker regions in the barrier