Solid state dielectric screening versus band gap trends and implications

Abstract

High-frequency (optical) and low-frequency (static) dielectric constant versus band gap trends, as well as index of refraction versus band gap trends are plotted for 107 inorganic semiconductors and insulators. These plots are describable via power-law fitting. Dielectric screening trends that emerge from this analysis have important optical and electronic implications. For example, barrier lowering during Schottky emission, phonon-assisted or Fowler-Nordheim tunneling, or Frenkel-Poole emission from a trap is found to be significantly more pronounced with increasing band gap due to a reduction in the optical dielectric constant with increasing band gap. The decrease in the interface state density with increasing band gap is another optical dielectric constant trend. The tendency for a material with a wider band gap to be more difficult to dope is attributed to an increase in the ionization energy of the donor or acceptor dopant, which in turn, depends on the optical dielectric constant and the effective mass. Since the effective mass for holes is almost always larger than that for electrons, p-type doping is more challenging than n-type doping in a wide band gap material. Finally, the polar optical phonon-limited mobility depends critically upon the reciprocal difference of the optical and the static dielectric constant. Consequently, electron and hole mobility tend to decrease with increasing band gap in a polar material.

Material Properties Influencing the Charge Decay of Electret Filters and their Impact on Filtration Performance

“…The % decrease of QF by aging at 120 °C were 36.8% for PAN, 48.1% for PVDF, 29.0% for PP1, and 23.3% for PP2, and the order of QF reduction corresponded to the order of εr of polymeric materials. Generally, the dielectric property of a material is affected by the electron hopping at each energy level, where the band gap energy becomes important [14,15,44]. From Equation (4) [15,44], the dielectric constant is inversely proportional to the square of the band gap energy.…”

“…Moreover, the tendency to respond to such environmental conditions is affected by the material properties. The charge retention sites [5,[13][14][15]. The mechanisms of charge decay are mostly explained by the relaxation of polarized state of dielectrics, spatial distribution of dipoles and free charges, and the neutralizing effect of dielectric conductivity [10,11,[16][17][18].…”

“…The results of this study implicate that ε r and wettability are important material parameters influencing the electric conductivity and chain mobility, and they can be used as convenient predictors for charge retention capacity affecting the robust electrostatic filtration performance. capacity is generally dependent on the electrical conductivity and the energy level of localized trap sites [5,[13][14][15]. The mechanisms of charge decay are mostly explained by the relaxation of polarized state of dielectrics, spatial distribution of dipoles and free charges, and the neutralizing effect of dielectric conductivity [10,11,[16][17][18].Generally, homo-electrets made from nonpolar materials hold stable charges, due to low electrical conductivity and low water absorption [3,19].…”

“…(4) Generally, the dielectric property of a material is affected by the electron hopping at each energy level, where the band gap energy becomes important [14,15,44]. From Equation (4) [15,44], the dielectric constant is inversely proportional to the square of the band gap energy. The material with a higher ε r would have a smaller band gap energy, and it can be predicted that the loss of charge is much easier in materials with high ε r .…”

Advanced Design of Fiber-Based Particulate Filters: Materials, Morphology, and Construction of Fibrous Assembly

“…The charge retention capacity of a dielectric polymer is generally associated with the electrical conductivity and the energy level of localized trap sites [ 45 , 46 , 47 , 48 , 49 , 50 ]. The dielectric property is affected by the electron hopping at each energy level, where the band gap energy becomes important [ 49 , 50 , 51 ].…”