410 research outputs found
Effects of hole self-trapping by polarons on transport and negative bias illumination stress in amorphous-IGZO
The effects of hole injection in amorphous-IGZO is analyzed by means of
first-principles calculations. The injection of holes in the valence band tail
states leads to their capture as a polaron, with high self-trapping energies
(from 0.44 to 1.15 eV). Once formed, they mediate the formation of peroxides
and remain localized close to the hole injection source due to the presence of
a large diffusion energy barrier (of at least 0.6eV). Their diffusion mechanism
can be mediated by the presence of hydrogen. The capture of these holes is
correlated with the low off-current observed for a-IGZO transistors, as well
as, with the difficulty to obtain a p-type conductivity. The results further
support the formation of peroxides as being the root cause of Negative bias
illumination stress (NBIS). The strong self-trapping substantially reduces the
injection of holes from the contact and limits the creation of peroxides from a
direct hole injection. In presence of light, the concentration of holes
substantially rises and mediates the creation of peroxides, responsible for
NBIS.Comment: 8 pages, 8 figures, to be published in Journal of Applied Physic
Hole-doping induced ferromagnetism in 2D materials
Two-dimensional (2D) ferromagnetic materials are considered as promising
candidates for the future generations of spintronic devices. Yet, 2D materials
with intrinsic ferromagnetism are scarce. High-throughput first-principles
simulations are performed in order to screen 2D materials that present a
non-magnetic to a ferromagnetic transition upon hole doping. A global
evolutionary search is subsequently performed, in order to identify alternative
possible atomic structures of the eligible candidates, and 122 materials
exhibiting a hole-doping induced ferromagnetism are identified. Their energetic
and dynamic stability, as well as their magnetic properties under hole doping
are investigated systematically. Half of these 2D materials are metal halides,
followed by chalcogenides, oxides and nitrides, some of them having predicted
Curie temperatures above 300 K. The exchange interactions responsible for the
ferromagnetic order in these 2D materials are also discussed. This work not
only provides theoretical insights into hole-doped 2D ferromagnetic materials,
but also enriches the family of 2D magnetic materials for possible spintronic
applications
Thickness dependence of the resistivity of Platinum group metal thin films
We report on the thin film resistivity of several platinum-group metals (Ru,
Pd, Ir, Pt). Platinum-group thin films show comparable or lower resistivities
than Cu for film thicknesses below about 5\,nm due to a weaker thickness
dependence of the resistivity. Based on experimentally determined mean linear
distances between grain boundaries as well as ab initio calculations of the
electron mean free path, the data for Ru, Ir, and Cu were modeled within the
semiclassical Mayadas--Shatzkes model [Phys. Rev. B 1, 1382 (1970)] to assess
the combined contributions of surface and grain boundary scattering to the
resistivity. For Ru, the modeling results indicated that surface scattering was
strongly dependent on the surrounding material with nearly specular scattering
at interfaces with SiO2 or air but with diffuse scattering at interfaces with
TaN. The dependence of the thin film resistivity on the mean free path is also
discussed within the Mayadas--Shatzkes model in consideration of the
experimental findings.Comment: 28 pages, 9 figure
Seeing Emotion with Your Ears: Emotional Prosody Implicitly Guides Visual Attention to Faces
Interpersonal communication involves the processing of multimodal emotional cues, particularly facial expressions (visual modality) and emotional speech prosody (auditory modality) which can interact during information processing. Here, we investigated whether the implicit processing of emotional prosody systematically influences gaze behavior to facial expressions of emotion. We analyzed the eye movements of 31 participants as they scanned a visual array of four emotional faces portraying fear, anger, happiness, and neutrality, while listening to an emotionally-inflected pseudo-utterance (Someone migged the pazing) uttered in a congruent or incongruent tone. Participants heard the emotional utterance during the first 1250 milliseconds of a five-second visual array and then performed an immediate recall decision about the face they had just seen. The frequency and duration of first saccades and of total looks in three temporal windows ([0–1250 ms], [1250–2500 ms], [2500–5000 ms]) were analyzed according to the emotional content of faces and voices. Results showed that participants looked longer and more frequently at faces that matched the prosody in all three time windows (emotion congruency effect), although this effect was often emotion-specific (with greatest effects for fear). Effects of prosody on visual attention to faces persisted over time and could be detected long after the auditory information was no longer present. These data imply that emotional prosody is processed automatically during communication and that these cues play a critical role in how humans respond to related visual cues in the environment, such as facial expressions
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