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In this study, we present a new instrument, the Participation and Engagement Scale (PES), for the evaluation of the students��� involvement in STEM-oriented activities. The instrument was administered to about 1000 secondary school students who participated in the activities of the Italian Piano Nazionale Lauree Scientifiche in Biology, Chemistry and Physics. The activities were carried out in a remote modality due to the COVID-19 restrictions. Through an exploratory and confirmatory factor analysis, it was possible to validate a two-factor structure of the instrument: satisfaction towards the activities and value of the activities. The proposed factor structure shows a good model fit, with each of the obtained scales displaying excellent reliability. Construct-related validation evidence was obtained through the Rasch analysis, which allowed further psychometric improvement of the instrument. Convergent validation evidence was established through a correlation with the academic motivation and perceived difficulties scales. Using the proposed instrument, we found no statistically significant relationships between engagement, the different types of science activities attended, and the intention to enrol in a STEM course. Implications of the study for the evaluation of public understanding of science activities in both remote and in-presence modalities are also discussed.

The purpose of this study was to analyse Italian high school and university students’ attitudes towards physics using the Semiotic Cultural Psychological Theory (SCPT). In the SCPT framework, attitudes represent how individuals interpret their experience through the mediation ofgeneralized meaningwith which they are identified. A view-of-physics questionnaire was used as an instrument to collect data with 1603 high school and university students. Data were analysed through multiple correspondence analysis and cluster analysis. We identified fourgeneralized meaningsof physics: (a) interesting and important for society; (b) a quite interesting, but badly taught subject at school and not completely useful for society; (c) difficult to study and irrelevant for society; and (d) a fascinating and protective niche from society. The identified generalized meanings are significantly correlated to the choice to study physics at undergraduate level and to the choice of attending physics-related activities in high school. Implications for research are discussed.

We surveyed a convenience sample of 362 Italian university physics students, asking them to retrospectively assess their experience of emergency remote instruction due to the COVID-19 outbreak. We looked at their psychological well being, motivation for physics, academic orientation, attitude towards physics and physicists, and tried to link these factors to their overall perception of the online instruction. Our results show a general appreciation for the organization and effectiveness of online courses. However, online teaching negatively impacted on engagement and interaction between peers and with the instructors. Only 22% of students in our sample complained of the psychological distress due to remote instruction. Nonetheless, we found a significant decrease in motivational dimensions, such as interest and recognition. Emergency remote instruction also challenged the students’ self-regulation, self-efficacy, and engagement. Finally, the uncertainty about the future resulted in a more pessimistic attitude towards physics, academic performance, and job perspectives.

We report the study of anatase TiO2(001)-oriented thin films grown by pulsed laser deposition on LaAlO3(001). A combination of in situ and ex situ methods has been used to address both the origin of the Ti(3+)-localized states and their relationship with the structural and electronic properties on the surface and the subsurface. Localized in-gap states are analyzed using resonant X-ray photoelectron spectroscopy and are related to the Ti(3+) electronic configuration, homogeneously distributed over the entire film thickness. We find that an increase in the oxygen pressure corresponds to an increase in Ti(3+) only in a well-defined range of deposition pressure; outside this range, Ti(3+) and the strength of the in-gap states are reduced.

Initial preparation of first year university students is often assessed by means of an entrance examination, which tests their knowledge of mathematics and science as well as their reading skills. The present study illustrates how we used Rasch analysis to: (i) investigate the reliability and construct validity of a typical university entrance test administered in Italy; (ii) explore the extent to which mathematics, science and reading items differ in their difficulty. Two studies were set up. In study 1, we analyzed the psychometric quality of an 80-item test administered in 2016 to N=2435 science and engineering freshmen. In study 2, we analyzed the responses of N=1223 students to a 100-item entrance test administered in 2017, 2018 and 2019 to an extended population of students. Results of both studies show that the analyzed entrance tests do not match unidimensional requirement, as proficiency in mathematics, science and reading capability correspond to distinct latent traits. Moreover, items on different scientific topics have significantly different difficulty. The study shows a need for revising the analyzed tests to meet unidimensionality requirements. Moreover, the analysis of items’ difficulty suggests balancing in a more suitable way the difficulty of the different content areas.

We present the development and validation of a construct map addressing introductory quantum mechanics topics at the high school level, as a subset of a larger learning progression on quantum mechanics. Topics include energy quantization, photon absorption and emission, the Heisenberg uncertainty principle, atom stability, orbitals, wave function, and electronic properties of materials. To validate the hypothesized construct map, we designed a multiple-choice questionnaire and a 14-h teaching-learning sequence (TLS) designed in strict relation with the levels of the construct map. Twenty-three classes of Italian students (ages 17–18, N=408) were involved in the study: about half (N=200) were exposed to the TLS, while N=208 students received a typical textbook instruction on the same topics targeted by the construct map. Data were analyzed using a 1D Rasch model. Results show that the proposed construct map consistently describes the increasing abilities of students when exposed to instruction. In particular, when exposed to the TLS activities, students more likely move towards the upper levels of the construct map. Findings have implications for instruction designed to support students’ learning in quantum mechanics at the high school level.

Students’ ability to assess their own knowledge is an important skill in science education. However, students often overestimate their actual performances. In such cases, overconfidence bias arises. Previous studies in physics education have shown that overconfidence bias concerns mainly content areas, such as Newtonian mechanics, where misconceptions are strongly held by students. However, how the received instruction and the levels of understanding of a given topic influence overconfidence bias is yet to be proved. In this paper, we address this issue choosing as content area introductory quantum mechanics (QM). Overall, 408 high school students were involved in the study and randomly assigned to two experimental groups. One group received a textbook-based instruction about introductory QM, whereas the other one received instruction on the same topics through an innovative guided inquiry teaching-learning sequence (TLS), which included also potential pedagogical countermeasures for overconfidence bias. Students of both experimental groups completed a multiple-choice questionnaire and indicated for each item the degree of their confidence in the given answer using a 5-point Likert scale. The overconfidence bias was quantitatively defined and evaluated at person level using a 1D Rasch model. Progress in knowledge about the targeted topics was modeled according to a construct map validated in a previous paper. Results show that, for the whole sample, the overconfidence bias decreased as students progressed along the levels of the construct map. However, findings indicate that students of the TLS group achieved a significantly higher accuracy and a better confidence calibration, while the textbook group exhibited a lower performance and a significantly greater overconfidence bias. Implications for research into overconfidence bias in physics education are briefly discussed.

The discovery of 2D conductivity at the LaAlO3/SrTiO3 interface has been linking, for over a decade, two of the major current research fields in materials science: correlated transition-metal-oxide systems and low-dimensional systems. Notably, despite the 2D nature of the interfacial electron gas, the samples are 3D objects with thickness in the mm range. This prevented researchers so far from adopting strategies that are only viable for fully 2D materials, or from effectively exploiting degrees of freedom related to strain, strain gradient and curvature. Here a method based on pure strain engineering for obtaining freestanding LaAlO3/SrTiO3 membranes with micrometer lateral dimensions is demonstrated. Detailed transmission electron microscopy investigations show that the membranes are fully epitaxial and that their curvature results in a huge strain gradient, each layer showing a mixed compressive/tensile strain state. Electronic devices are fabricated by realizing ad hoc circuits for individual micro-membranes transferred on silicon chips. The samples exhibit metallic conductivity and electrostatic field effect like 2D-electron systems in bulk heterostructures. The results open a new path for adding oxide functionalities into semiconductor electronics, potentially allowing for ultra-low voltage gating of a superconducting transistors, micromechanical control of the 2D electron gas mediated by ferroelectricity and flexoelectricity, and on-chip straintronics.

We present the design, statistical analysis, and validation of a questionnaire to assess students’ knowledge about basic aspects of quantum mechanics (QM). The QM evaluation (QME) is a true-false and multiple-choice mixed questionnaire that features 10 two-tier items spanning three relevant themes in quantum mechanics: wave behavior of matter, measurement, and atoms and electrons behavior. Its validity was assessed through a pilot administration to students and interviews with course instructors. We checked its internal consistency using both classic test theory and Rasch analysis to account for the different difficulty of each tier and for different scoring methods of the items. The questionnaire was administered to about 450 undergraduate physics students and high school physics teachers. Data show that it is a reliable instrument and all items have a good discriminatory power. Since the test does not require an advanced mathematical knowledge, it ideally lends itself to probe students’ knowledge about quantum mechanics in a variety of university courses, from the introductory ones to those more formal and mathematically oriented.

We report an empirical study on the development and validation of a learning progression (LP) in quantum mechanics (QM) at university level. Drawing on research results about students’ reasoning in QM, we designed a hypothetical LP (HLP) consisting of three Big Ideas: Measurement, A toms and Electrons, Wave function. We then developed ten Ordered-Multiple-Choice (OMC) items to assess the construct validity and hierarchy of HLP levels. We administered the questionnaire to 244 students attending the Bachelor in Physics, divided into three groups under different instruction conditions: no course, introductory course, introductory and upper-level course. An additional group of 43 non-physics students, who attended an introductory QM course, was also involved to inspect the role of physics background knowledge . We used exploratory factor analysis and Rasch analysis to analyse collected data. The results provided evidence for the revision of the HLP around only two Big Ideas – Atomic description and measurement; Wave function and its properties in the measurement process – which roughly match the topics covered in the introductory and upper-level courses, respectively. However, the hierarchy of hypothesised levels was substantially confirmed. Implications of our findings for the teaching of QM, and the improvement of the revised LP are also discussed.

In questo articolo riportiamo i risultati di uno studio sulla preparazione in fisica di 2861 studenti al termine degli studi secondari basato sull’analisi di Rasch di due test standardizzati. A tale proposito, l’articolo propone anche una introduzione generale a questo tipo di analisi. I risultati mostrano che gli studenti al termine del ciclo secondario di studi hanno notevoli difficolt`a in tutte le aree della fisica generale. Le implicazioni di questi risultati alla luce delle recenti riforme scolastiche sono brevemente discusse.

We report the study of anatase TiO

Oxide-based hetero-structures are promising candidates for building the next generation of functional devices. In order to achieve this goal, it is required to have solid and reliable sensors for monitoring the growth of thin films with single-atomic-layer sensitivity. So far, the most popular in-situ diagnostic tool is Reflection High Energy Electron Diffraction, which provides information on the structural properties of the growing films, and not a direct access to the desired interfacial physical properties of interest. Furthermore, it needs a strong human-machine interaction, preventing its use into industrial mass production. Standard optics applied on buried interfaces suffers the disadvantage to have a probing depth which is orders of magnitude larger than the interface layer. Here we propose to overcome this problem by resorting to optical Second Harmonic Generation and we present some example to show the potential of this technique as a real-time monitor system for thin-film crystal growth.

The time-resolved photoconductance of amorphous and crystalline LaAlO$_3$/SrTiO$_3$ interfaces, both hosting an interfacial 2-dimensional electron gas, is investigated under irradiation by variable-wavelengths, visible or ultraviolet photons. Unlike bare SrTiO$_3$ single crystals, showing relatively small photoconductance effects, both kinds of interfaces exhibit an intense and highly persistent photoconductance with extraordinarily long characteristic times. The temporal behaviour of the extra photoinduced conductance persisting after light irradiation shows a complex dependence on interface type (whether amorphous or crystalline), sample history and irradiation wavelength. \textcolor{black}{The experimental results indicate that different mechanisms of photoexcitation are responsible for the photoconductance of crystalline and amorphous LaAlO$_3$/SrTiO$_3$ interfaces under visible light. We propose that the response of crystalline samples is mainly due to the promotion of electrons from the valence bands of both SrTiO$_3$ and LaAlO$_3$. This second channel is less relevant in amorphous LaAlO$_3$/SrTiO$_3$, where the higher density of point defects plays instead a major role., 8 pages, 5 figures, 3 tables, accepted on Scientific Reports 2015

The electronic properties of NdGaO3/SrTiO3, LaGaO3/SrTiO3 and LaAlO3/SrTiO3 interfaces, all showing an insulator-to-metal transition as a function of the overlayer-thickness, are addressed in a comparative study based on x-ray absorption, x-ray photoemission and resonant photoemission spectroscopy. The nature of the charge carriers, their concentration and spatial distribution as well as the interface band alignments and the overall interface band diagrams are studied and quantitatively evaluated. The behavior of the three analyzed heterostructures is found to be remarkably similar. The valence band edge of all the three overlayers aligns to that of bulk SrTiO3. The near-interface SrTiO3 layer is affected, at increasing overlayer thickness, by the building-up of a confining potential. This potential bends both the valence and the conduction band downwards. The latter one crossing the Fermi energy in the proximity of the interface and determines the formation of an interfacial band offset growing as a function of thickness. Quite remarkably, but in agreement with previous reports for LaAlO3/SrTiO3, no electric field is detected inside any of the polar overlayers. The essential phenomenology emerging from our findings is discussed on the base of different alternative scenarios regarding the origin of interface carriers and their interaction with an intense photon beam.

Optical second harmonic generation is proposed as a tool for non-invasive, non-destructive, real-time, in-situ imaging of oxide epitaxial film growth. The films can be monitored by surface imaging with a lateral resolution of

By a combination of optical second harmonic generation and transport measurements, we have investigated interfaces formed by either crystalline or amorphous thin films of LaAlO3 grown on TiO2-terminated SrTiO3(001) substrates. Our approach aims at disentangling the relative role of intrinsic and extrinsic doping mechanisms in the formation of the two-dimensional electron gas. The different nature of the two mechanisms is revealed when comparing the sample response variation as a function of temperature during annealing in air. However, before the thermal treatment, the two types of interfaces show almost the same intensity of the second harmonic signal, provided the overlayer thickness is the same. As we will show, the second harmonic signal is proportional to the depth of the potential well confining the charges at the interface. Therefore, our result demonstrates that this depth is about the same for the two different material systems. This conclusion supports the idea that the electronic properties of the two-dimensional electron gas are almost independent of the doping mechanism of the quantum well.

LaAlO$_{3}$ and NdGaO$_{3}$ thin films of different thickness have been grown by pulsed laser deposition on TiO$_2$-terminated SrTiO$_{3}$ single crystals and investigated by soft X-ray photoemission spectroscopy. The surface sensitivity of the measurements has been tuned by varying photon energy $h\nu$ and emission angle $\Theta$. In contrast to the core levels of the other elements, the Sr $3d$ line shows an unexpected splitting for higher surface sensitivity, signaling the presence of a second strontium component. From our quantitative analysis we conclude that during the growth process Sr atoms diffuse away from the substrate and segregate at the surface of the heterostructure, possibly forming strontium oxide.

Combining reflection high-energy electron diffraction, high-resolution transmission electron microscopy, and high-angle annular dark field scanning transmission electron microscopy we unveil the existence of a peculiar transition from a three-dimensional to a two-dimensional growth mode in anatase TiO2/LaAlO3 heterostructures. Such a growth dynamics is accompanied by Al interdiffusion from substrate to the growing film up to a critical thickness of 20 nm. With the extra support of ab initio calculations, we show that the crossover between the two growth modes corresponds to the formation of two distinct regions characterized by (103)- and (101)-oriented crystallographic shear superstructures, occurring in the upmost film region and in proximity of the film/substrate interface, respectively. © 2013 Springer Science+Business Media Dordrecht.

TiO(2) anatase thin films grown by pulsed laser deposition are investigated by high resolution transmission electron microscopy and high angle annular dark field scanning transmission electron microscopy. The analyses provide evidence of a peculiar growth mode of anatase on LaAlO(3) and SrTiO(3) characterized by the formation of an epitaxial layer at the film/substrate interface, due to cationic diffusion from the substrate into the film region. Pure TiO(2) anatase growth occurs in both specimens above a critical thickness of about 20 nm. The microstructural and chemical characterization of the samples is presented and discussed in the framework of oxide interface engineering.

The discovery that the interface between two band gap insulators LaAlO3 and SrTiO3 is highly conducting has raised an enormous interest in the field of oxide electronics. The LAlO3/SrTiO3 interface can be tuned using an electric field and switched from a superconducting to an insulating state. Conducting paths in an insulating background can be written applying a voltage with the tip of an atomic force microscope, creating great promise for the development of a new generation of nanoscale electronic devices. However, the mechanism for interface conductivity in LaAlO3/SrTiO3 has remained elusive. The theoretical explanation based on an intrinsic charge transfer (electronic reconstruction) has been strongly challenged by alternative descriptions based on point defects. In this work, thanks to modern aberration-corrected electron probes with atomic-scale spatial resolution, interfacial charge and atomic displacements originating the electric field within the system can be simultaneously measured, yielding unprecedented experimental evidence in favor of an intrinsic electronic reconstruction., Accepted for publication in Advanced Materials. Published online on 06/20/2012

The development of an experimental set-up for radiation detection atT = 0.4 K by Nb-based Superconducting Tunnel junctions is presented. Preliminary results concerning detectors characterization and 6 keV X ray detection are shown and discussed.

TiO(2) anatase thin films grown by pulsed laser deposition are investigated by high resolution transmission electron microscopy and high angle annular dark field scanning transmission electron microscopy. The analyses provide evidence of a peculiar growth mode of anatase on LaAlO(3) and SrTiO(3) characterized by the formation of an epitaxial layer at the film/substrate interface, due to cationic diffusion from the substrate into the film region. Pure TiO(2) anatase growth occurs in both specimens above a critical thickness of about 20 nm. The microstructural and chemical characterization of the samples is presented and discussed in the framework of oxide interface engineering.

Mechanical mixtures of zirconia xerogel with variable content of crystalline Y2O3 up to 25 mol%, were hydrothermally treated by microwave route at 110 °C for 2 hours in the presence of 0.2 M solution of (KOH+K2CO3) mineralizer. The resulting amorphous hydrated zirconia-yttria solid solutions with a maximum solubility of Y2O3 content between 20 ~ 25 mol%, showed a remarkable reduction of the surface area at the increasing Y2O3 content of the starting mixture. The as-synthesized products and the corresponding calcined powders at 400 °C were uniaxially pressed into pellets (10 x 7 x 2 ~ 4 mm, in width) at 150 MPa. Conductivities were measured at 25 °C by AC impedance method with a frequency range from 10 Hz to 1 MHz with the pellets equilibrated either under silica gel or under increasing relative humidity (RH) up to ~90 %. The effects of composition, surface area, calcination temperature and relative RH on the proton conductivity of the amorphous solid solutions are discussed.

We present various concepts and experimental procedures to fabricate biepitaxial YBa2Cu3O7-x grain boundary Josephson junctions. The performance of our junctions indicates significant improvement in the biepitaxial technique. 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 π-loops in transport properties. Further, we discuss the possibility to produce circuits in which “0-” and “π-loops” are controllably located on the same chip.