1,104 research outputs found
Comment On >Assessment Of Field-Induced Quantum Confinement In Heterogate Germanium Electron-Hole Bilayer Tunnel Field-Effect Transistor> Appl. Phys. Lett. 105, 082108 (2014)
Not AvailableNRI SWAN
programNSF NASCENT ERCMicroelectronics Research CenterElectrical and Computer Engineerin
Density Functional Study of Ternary Topological Insulator Thin Films
Using an ab-initio density functional theory based electronic structure
method with a semi-local density approximation, we study thin-film electronic
properties of two topological insulators based on ternary compounds of Tl
(Thallium) and Bi (Bismuth). We consider TlBiX (X=Se, Te) and Bi_2_2_3$ (X=Se, Te). With this property in combination with
a structurally perfect bulk crystal, the latter ternary compound has been found
to have improved surface electronic transport in recent experiments. In this
article, we discuss the nature of surface states, their locations in the
Brillouin zone and their interactions within the bulk region. Our calculations
suggest a critical thin film thickness to maintain the Dirac cone which is
significantly smaller than that in binary Bi-based compounds. Atomic
relaxations or rearrangements are found to affect the Dirac cone in some of
these compounds. And with the help of layer-projected surface charge densities,
we discuss the penetration depth of the surface states into the bulk region.
The electronic spectrum of these ternary compounds agrees very well with the
available experimental results.Comment: 9 pages, 11 figures, 1 table, Accepted for publication in Physical
Review
Effect of Edge Roughness on Electronic Transport in Graphene Nanoribbon Channel Metal Oxide Semiconductor Field-Effect Transistors
Results of quantum mechanical simulations of the influence of edge disorder
on transport in graphene nanoribbon metal oxide semiconductor field-effect
transistors (MOSFETs) are reported. The addition of edge disorder significantly
reduces ON-state currents and increases OFF-state currents, and introduces wide
variability across devices. These effects decrease as ribbon widths increase
and as edges become smoother. However the bandgap decreases with increasing
width, thereby increasing the band-to-band tunneling mediated subthreshold
leakage current even with perfect nanoribbons. These results suggest that
without atomically precise edge control during fabrication, MOSFET performance
gains through use of graphene will be difficult to achieve.Comment: 8 pages, 5 figure
The relationship between HIV seroconversion illness, HIV test interval and time to AIDS in a seroconverter cohort.
Seroconversion illness is known to be associated with more rapid HIV disease progression. However, symptoms are often subjective and prone to recall bias. We describe symptoms reported as seroconversion illness and examine the relationship between illness, HIV test interval (time between antibody-negative and anibody-positive test dates) and the effect of both on time to AIDS from seroconversion. We used a Cox model, adjusting for age, sex, exposure group and year of estimated seroconversion. Of 1820 individuals, information on seroconversion illness was available for 1244 of whom 423 (34%) reported symptomatic seroconversion. Persons with a short test interval (< or = 2 months) were significantly more likely to report an illness than people with a longer interval (OR 6.76, 95% CI 4.75-9.62). Time to AIDS was significantly faster (P = 0.01) in those with a short test interval. The HIV test interval is a useful replacement for information on seroconversion illness in studies of HIV disease progression
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