Polyamorphism of vapor-deposited amorphous selenium in response to light

Zhang, Aixi; Jin, Yi; Liu, Tianyi; Stephens, R. B.; Fakhraai, Zahra

doi:10.1073/pnas.2009852117

Cited by 15 publications

(12 citation statements)

References 51 publications

(87 reference statements)

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“…The presence of magnetic fields during deposition may also play a role in molecules containing magnetic atoms. Or illumination of the substrate during growth may affect the formation of semiconductor molecules with homo-lumo levels lower than the energy of the incident light [41]. Another property that is very useful in understanding some of the unusual properties of stable organic glasses is density.…”

Section: Organic Glassesmentioning

confidence: 99%

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Ultrastable glasses: new perspectives for an old problem

et al. 2022

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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.

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Section: Organic Glassesmentioning

confidence: 99%

“…Amorphous selenium has also been grown as a thin film from the vapor in the range of temperatures and growth rates that could lead to high stability [41]. In addition, since a-Se is very sensitive to above-band gap visible light, white illumination was used during growth to investigate the effect of this parameter.…”

Section: Chalcogenide Glassesmentioning

confidence: 99%

Ultrastable glasses: new perspectives for an old problem

et al. 2022

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“…For example, at high pressures, high-and low-density supercooled water phases are interconvertible through a first-order phase transition (27,28). Recent studies have demonstrated that such polyamorphic states can also be accessed through PVD in hydrogen-bonding systems with polymorphic crystal states at depositions above the nominal Tg (29,30). However, these structure-specific transitions do not provide a general resolution for the Kauzmann crisis.…”

Section: Significancementioning

confidence: 99%

Glasses denser than the supercooled liquid

Jin

Zhang

Wolf

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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When aged below the glass transition temperature, Tg, the density of a glass cannot exceed that of the metastable supercooled liquid (SCL) state, unless crystals are nucleated. The only exception is when another polyamorphic SCL state exists, with a density higher than that of the ordinary SCL. Experimentally, such polyamorphic states and their corresponding liquid–liquid phase transitions have only been observed in network-forming systems or those with polymorphic crystalline states. In otherwise simple liquids, such phase transitions have not been observed, either in aged or vapor-deposited stable glasses, even near the Kauzmann temperature. Here, we report that the density of thin vapor-deposited films of N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD) can exceed their corresponding SCL density by as much as 3.5% and can even exceed the crystal density under certain deposition conditions. We identify a previously unidentified high-density supercooled liquid (HD-SCL) phase with a liquid–liquid phase transition temperature (TLL) ∼35 K below the nominal glass transition temperature of the ordinary SCL. The HD-SCL state is observed in glasses deposited in the thickness range of 25 to 55 nm, where thin films of the ordinary SCL have exceptionally enhanced surface mobility with large mobility gradients. The enhanced mobility enables vapor-deposited thin films to overcome kinetic barriers for relaxation and access the HD-SCL state. The HD-SCL state is only thermodynamically favored in thin films and transforms rapidly to the ordinary SCL when the vapor deposition is continued to form films with thicknesses more than 60 nm.

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“…In this way, photon activation indeed fluidizes a glass at temperatures substantially below the usual glass transition. These rearrangements may be able to allow access locally to still deeper parts of the energy landscape, ,, perhaps providing a new route to ultrastability. In any event, such photon-activated transformations also allow glasses to encode and store information.…”

Section: Theory Of Glass Dynamicsmentioning

confidence: 99%

Glass Dynamics Deep in the Energy Landscape

et al. 2021

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When a liquid is cooled, progress down the energy landscape is arrested near the glass transition temperature T g . In principle, lower energy states can be accessed by waiting for further equilibration, but the rough energy landscape of glasses quickly leads to kinetics on geologically slow time scales below T g . Over the past decade, progress has been made probing deeper into the energy landscape via several techniques. By looking at bulk and surface diffusion, using layered deposition that promotes equilibration, imaging glass surfaces with faster dynamics below T g , and optically exciting glasses, experiments have moved into a regime of ultrastable, low energy glasses that was difficult to access in the past. At the same time, both simulations and energy landscape theory based on a random first order transition (RFOT) have tackled systems that include surfaces, optical excitation, and interfacial dynamics. Here we review some of the recent experimental work, and how energy landscape theory illuminates glassy dynamics well below the glass transition temperature by making direct connections between configurational entropy, energy landscape barriers, and the resulting dynamics.

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Polyamorphism of vapor-deposited amorphous selenium in response to light

Cited by 15 publications

References 51 publications

Ultrastable glasses: new perspectives for an old problem

Ultrastable glasses: new perspectives for an old problem

Glasses denser than the supercooled liquid

Glass Dynamics Deep in the Energy Landscape

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