Electronic structure of polymers

Fabish, T. J.

doi:10.1080/10408437908243627

Cited by 15 publications

(5 citation statements)

References 149 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…1 For impact ionization across the energy gap (Ej ~ 10 eV), o one is therefore led to mean free paths of -50 A, or to mobilities in the 50 cm 2 /V • s range. This is at odds with drift-mobility experiments which yield /x = 10-4 -10" 11 cmVV-s in poly ethylenes (PE), 2 and even with the highest mobilities of -1 cm 2 /V • s observed in high-quality alkane single crystals. 3 Hot electrons also play an essential role for the injection of space charge into polymeric insulators in regions with a strongly inhomogeneous electric field.…”

mentioning

confidence: 62%

Hot-Electron Transport in Polymeric Dielectrics

1984

View full text Add to dashboard Cite

An internal photoemission experiment which yields the energy-dependent momentumand energy-loss rates of hot electrons is designed. The results on solid hydrocarbon films are analyzed in terms of the appropriate Boltzmann equation. Band mobilities are obtained for hot electrons. Their energy-loss rate has a maximum at the LO phonon energy associated with the C-H stretching mode.PACS numbers: 73.60. Hy, 72.20.Jv, 79.60.Eq Thermalized carriers at the bottom of the conduction band in large band-gap insulators can be studied by classical transport experiments (e.g., driftmobility and photocurrent measurements) in macroscopic specimen. Unless the phonons which control hot-electron (E kin » kT) scattering are thermally populated, the extrapolation from E km ~ kT data to hot-electron transport is not possible. As a result, hot-electron scattering in polymeric insulators is only poorly understood, although it plays a crucial role in various areas.Hot-electron processes are particularly important in the field of dielectric breakdown. In good polymeric insulators, intrinsic breakdown is reached at electric fields of the order of 5 MV/cm. 1 For impact ionization across the energy gap (Ej ~ 10 eV), o one is therefore led to mean free paths of -50 A, or to mobilities in the 50 cm 2 /V • s range. This is at odds with drift-mobility experiments which yield /x = 10-4 -10" 11 cmVV-s in poly ethylenes (PE), 2 and even with the highest mobilities of -1 cm 2 /V • s observed in high-quality alkane single crystals. 3 Hot electrons also play an essential role for the injection of space charge into polymeric insulators in regions with a strongly inhomogeneous electric field. 4 As will be shown in a forthcoming publication, 5 the injection of hot-carrier space charge is an essential element in the growth of dielectric discharge trees and in dielectric aging.In order to establish the crucial quantity that describes the transport properties of hot electrons in high electric fields, we consider the energy and momentum conservation for a charged particle of effective mass m*, moving in an insulator under the action of an electric field F: E=-y u (E)E+evF,h=-y p (e)m*v + eF.Here v denotes the velocity of the particle, and we have introduced the energy-and momentum-loss rates y u (E) and y p (E), respectively. Following a procedure developed for the theory of laser breakdown in solids, 6,7 we can then obtain analytical expressions for the average energy (E) and for the multiplication rate f3 of hot electrons. It turns out that both expressions contain as the only nontrivial quantity. Therefore, our aim will be to determine the energy dependence of m*y u y p between /c7and the gap energy. Information about the transport properties of hot electrons can be obtained via photoelectron spectroscopy techniques. A number of substrateoverlayer studies have been made in order to determine the mean free path X of photoelectrons in various materials. This search has resulted in the well-known pseudouniversal curve 8 with a minimum of X ~~ 10 A near E km...

show abstract

mentioning

confidence: 62%

Hot-Electron Transport in Polymeric Dielectrics

1984

View full text Add to dashboard Cite

show abstract

“…(Xldft/dQeIX) = 0 (X\d9i/dQhl\X) = (X\d9í/dQhfX) = 0 (8) where X stands for A2 in C3v or for any C2" state. As a consequence, if the system described by X is in a C3v or C^.…”

Section: Introductionmentioning

confidence: 99%

Symmetry aspects of Jahn-Teller activity: structure and reactivity

Ceulemans¹,

Beyens²,

Vanquickenborne³

1984

J. Am. Chem. Soc.

115

View full text Add to dashboard Cite

“…In this work, investigations are carried out on one-dimensional isomeric polymers (synthetic and natural), and nanoribbons having the same functional groups. Since, polymers are large chain of monomers, therefore they are considered as one-dimensional periodic systems for band structure calculations [28,29,30,31,32]. Band structure calculations are performed using Density Functional Theory (DFT) as implemented in Vienna ab initio simulation package (VASP) [33].…”

Section: Introductionmentioning

confidence: 99%

Bandgap Tunability in a One-Dimensional System

Wadhwa

Kumar

et al. 2018

Condensed Matter

View full text Add to dashboard Cite

The ability to tune the gaps of direct bandgap materials has tremendous potential for applications in the fields of LEDs and solar cells. However, lack of reproducibility of bandgaps due to quantum confinement observed in experiments on reduced dimensional materials, severely affects tunability of their bandgaps. In this letter, we report broad theoretical investigations of direct bandgap one-dimensional functionalized isomeric system using their periodic potential profile, where bandgap tunability is demonstrated simply by modifying the potential profile by changing the position of the functional group in a periodic supercell. It is verified for known synthetic, as well as natural polymers (biological and organic), and also for other one-dimensional direct bandgap systems. This insight would greatly help experimentalists in designing new isomeric systems of various bandgap values for polymers and one-dimensional inorganic systems for LEDs applications, and for effectively harvesting energy in solar cells.

show abstract

Electronic structure of polymers

Cited by 15 publications

References 149 publications

Hot-Electron Transport in Polymeric Dielectrics

Hot-Electron Transport in Polymeric Dielectrics

Symmetry aspects of Jahn-Teller activity: structure and reactivity

Bandgap Tunability in a One-Dimensional System

Contact Info

Product

Resources

About