Glasses and other noncrystalline solids exhibit thermal and acoustic properties at low temperatures anomalously different from those found in crystalline solids, and with a remarkable degree of universality. Below a few kelvin, these universal properties have been successfully interpreted using the tunneling model, which has enjoyed (almost) unanimous recognition for decades. Here we present low-temperature specific-heat measurements of ultrastable glasses of indomethacin that clearly show the disappearance of the ubiquitous linear contribution traditionally ascribed to the existence of tunneling two-level systems (TLS). When the ultrastable thin-film sample is thermally converted into a conventional glass, the material recovers a typical amount of TLS. This remarkable suppression of the TLS found in ultrastable glasses of indomethacin is argued to be due to their particular anisotropic and layered character, which strongly influences the dynamical network and may hinder isotropic interactions among low-energy defects, rather than to the thermodynamic stabilization itself. This explanation may lend support to the criticisms by Leggett and others [Yu CC, Leggett AJ (1988) Comments Condens Matter Phys 14(4):231–251; Leggett AJ, Vural DC (2013) J Phys Chem B 117(42):12966–12971] to the standard tunneling model, although more experiments in different kinds of ultrastable glasses are needed to ascertain this hypothesis.

We report room-temperature cathodoluminescence and photoluminescence spectra originating from ZnS overcoated CdSe nanocrystals, 33 and 42 Å in diameter, embedded in a ZnS matrix. The thin-film quantum dot composites were synthesized by electrospray organometallic chemical vapor deposition. Cathodoluminescence and photoluminescence are dominated by the sharp band-edge emission characteristic of the initial nanocrystals. The emission wavelength can be tuned in a broad window (470–650 nm) by varying the size of the dots. The cathodoluminescence intensity depends on the crystallinity of the ZnS matrix and the voltage and current density applied.

Vapor deposited thin films (∼100 nm thickness) of toluene and ethylbenzene grown by physical vapor deposition show enhanced stability with respect to samples slowly cooled from the liquid at a rate of 5 K min⁻¹. The heat capacity is measured in situ immediately after growth from the vapor or after re-freezing from the supercooled liquid at various heating rates using quasi-adiabatic nanocalorimetry. Glasses obtained from the vapor have low enthalpies and large heat capacity overshoots that are shifted to high temperatures. The stability is maximized at growth temperatures in the vicinity of 0.8 T_g for both molecules, although glasses of ethylbenzene show superior stabilization. Our data is consistent with previous results of larger organic molecules suggesting a generalized behavior on the stability of organic glasses grown from the vapor. In addition, we find that for the small molecules analyzed here, slowing the growth rate below 0.1 nm s⁻¹ does not result in increased thermodynamic stability.

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.

Physical properties at the nanoscale are novel and different from those in bulk materials. Over the last few decades, there has been an ever growing interest in the fabrication of nanowire structures for a wide variety of applications including energy generation purposes. Nevertheless, the study of their transport properties, such as thermal conductivity, electrical conductivity or Seebeck coefficient, remains an experimental challenge. For instance, in the particular case of nanostructured thermoelectrics, theoretical calculations have shown that nanowires offer a promising way of enhancing the hitherto low efficiency of these materials in the conversion of temperature differences into electricity. Therefore, within the thermoelectrical community there has been a great experimental effort in the measurement of these quantities in actual nanowires. The measurements of these properties at the nanoscale are also of interest in fields other than energy, such as electrical components for microchips, field effect transistors, sensors, and other low scale devices. For all these applications, knowing the transport properties is mandatory. This review deals with the latest techniques developed to perform the measurement of these transport properties in nanowires. A thorough overview of the most important and modern techniques used for the characterization of different kinds of nanowires will be shown.

We report on measurements of the thermal conductivity of atomic layer deposited polycrystalline zinc oxide (ZnO) films between 30 and 300 K. The room temperature thermal conductivity of the films is found to be twofold less than that of single-crystal ZnO. The maximum thermal conductivities of the polycrystalline samples occur at about 60 K and their values are almost an order of magnitude lower than bulk ZnO. The effect of the grain size and the transparency of the intergrain boundary on the thermal conductivity are analyzed within the framework of the phonon-hopping transport model.