Marta Gonzalez-Silveira

This study investigates how undergraduate physics students at a public university in Barcelona (Spain) use GenAI tools in their academic work, examining patterns of use, perceptions, and implications for teaching methods. Through a collaboration between physics faculty and science education researchers, a mixed-methods approach was employed, including surveys (n=172), cluster analysis, and focus groups. As a result, five distinct user profiles were identified, ranging from intensive and varied AI users to those maintaining a critical distance from AI. These five clusters reflect diverse motivations, from accelerating routine tasks to enhancing conceptual understanding, alongside varying degrees of trust and engagement with AI. These findings highlight the need to reconsider learning objectives and assessment strategies within physics curricula, promoting the responsible integration of AI as an educational ally while addressing ethical and cognitive challenges.

Vapor-deposited organic semiconductor glasses exhibit distinct molecular anisotropy and exceptional kinetic and thermodynamic stability, distinguishing them from the inherently isotropic and poorly stable glasses formed through liquid cooling. In this study, we exploit these unique properties to examine local changes in surface potential as the stable glass transitions to a supercooled liquid upon heating above the glass transition temperature (T_g). Vapor deposited glasses of organic molecules with permanent dipole moments can generate a measurable surface potential due to their anisotropic molecular orientation. We use local electrostatic force microscopy and Kelvin probe force microscopy to provide insights into the dynamics of the phase transformation occurring above T_g. We demonstrate that changes in polarization upon conversion to the isotropic liquid serve as an effective proxy for tracking this transition and highlight their potential for evaluating the thermal stability of organic devices under diverse thermal conditions.

Molecular dynamics simulations of vapor-deposited glasses under the effect of an external electric field show that it is possible to detangle molecular orientation and density/stability of the glass.

The understanding of the dynamics of a glass above its devitrification temperature remains incomplete. Here, we build a spatio-temporal map of the relaxation dynamics of a highly stable glass into its supercooled liquid using real-time atomic force microscopy imaging. This methodology enables direct visualization of the progression of the liquid phase and clarifies and quantifies the presence of localized fast mobility regions separated by giant length scales. Our data establish a clear correlation between dynamic length and time scales in glasses. This approach may also be applicable to unveil the microscopic structure and dynamics of other glass-forming systems with much shorter length and time scales, including liquid-cooled glasses.

Ultrastable glasses (mostly prepared from the vapor phase under optimized deposition conditions) represent a unique class of materials with low enthalpies and high kinetic stabilities. These highly stable and dense glasses show unique physicochemical properties, such as high thermal stability, improved mechanical properties or anomalous transitions into the supercooled liquid, offering unprecedented opportunities to understand many aspects of the glassy state. Their improved properties with respect to liquid-cooled glasses also open new prospects to their use in applications where liquid-cooled glasses failed or where not considered as usable materials. In this review article we summarize the state of the art of vapor-deposited (and other) ultrastable glasses with a focus on the mechanism of equilibration, the transformation to the liquid state and the low temperature properties. The review contains information on organic, metallic, polymeric and chalcogenide glasses and an updated list with relevant properties of all materials known today to form a stable glass.

We report the anomalous bulk transformation of vapor deposited stable glasses into the liquid state. The transformation proceeds through two competing parallel processes: partial rejuvenation of the stable glass and nucleation and growth of liquid patches within the glass. The kinetics of the transformation extracted from heat capacity curves after isothermal runs is dominated by the heterogeneous nucleation and growth process that initiates at preexisting seeds and propagates radially at a velocity proportional to the alpha relaxation time. Remarkably, the distance between the activation seeds is independent of temperature within experimental uncertainty and amounts to several micrometers, a value in close agreement with the crossover length for TPD glasses. We speculate the initiation sites for the transformation of the glass into the supercooled liquid are localized regions of lower stability (or density).

Stable glass formation for both structural glass and as-deposited glassy crystal at deposition temperatures below T_g.

Physical vapour deposition has emerged as the technique to obtain glasses of unbeatable stability. However, vapour deposited glasses exhibit a different transformation mechanism to ordinary glasses produced from liquid. Vapour deposited glasses of different thermodynamic stability, from ultrastable to those similar to ordinary glasses, transform into the liquid state via front propagation starting at the most mobile surfaces/interfaces, at least for the first stages of the transformation, eventually dynamiting the high thermal stability achieved for some of these glasses. A previous study showed that it was possible to avoid this transformation front by capping the films with a higher T_g material. We show here fast calorimetry measurements on TPD and IMC vapour deposited glasses capped respectively with TCTA and TPD. This capped configuration is very effective in suppressing the heterogeneous transformation of the stable glasses into the supercooled liquid and shifts the devitrification temperature to much higher values, where the bulk homogeneous mechanism becomes active. This approach may be useful to further study the bulk glass transition in thin films.