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Transport Phenomena in Semiconductors
Published in Jyoti Prasad Banerjee, Suranjana Banerjee, Physics of Semiconductors and Nanostructures, 2019
Jyoti Prasad Banerjee, Suranjana Banerjee
A highly energetic hot electron from an energy level located much higher above the bottom of the conduction band scatters (makes an impact) with a bound electron in the valence band through Coulomb interaction and transfers sufficient energy to the bound electron so that it is lifted up into the conduction band. This process is known as impact ionization, in which the initial hot electron creates a pair of free electron and hole. The initial hot electron should possess a minimum energy larger than the bandgap energy consistent with energy and momentum conservation so that impact ionization can take place. This energy is called ionization threshold energy, and if the electron acquires the threshold energy, then it can only cause impact ionization with valence electrons (Figure 4.9a). The figure shows that the initial state has one electron. After impact ionization, the final state has two electrons in the conduction band and one hole in the valence band. In case of parabolic band structures described by ε=ℏ2k22m*, the ionization threshold energy for electrons (εin) is given by (
Anharmonic Decay of Nonequilibrium Intervalley Phonons in Silicon
Published in Zlatan Aksamija, Nanophononics, 2017
The other significant optical g-process phonon is the transverse optical branch. Figure 5.9 demonstrates that the g-type transverse optical (gTO) phonon also decays into LA+TA pairs, with very few decays occurring through the Klemens channel where both phonons are of the same polarization. The energy distribution after the gTO decay, shown in Fig. 5.10, also follows a trend similar to gLO and has a near-equilibrium peak in the TA branch and a nonequilibrium component on the LA branch. Several peaks can be noted here, each coinciding with a peak in the phonon density of states (DOS), especially peaks in the two TA branches of around 20 meV and the one in the LA branch of around 40 meV. Both optical g-process phonons have a strong Umklapp component accounting for nearly half of the decays, as shown in Fig. 5.11. Consequently, relaxation of g-process phonons toward equilibrium occurs one branch at a time, and the longitudinal branches serve as intermediate branches between the LO and the TA. This can lead to reabsorption of nonequilibrium phonons by the electrons, especially the LA and LO branches, that couple strongly with electrons. Increasing the absorption of longitudinal phonons imparts additional energy on the electron population and can cause more electrons in the tail of the distribution, producing an increase in the number of hot electrons. This effect can have a large impact on the hot electron effect and reliability.
Reactivity and Bio Samples Probed by Tip-Enhanced Raman Spectroscopy
Published in Marc Lamy de la Chapelle, Nordin Felidj, Plasmonics in Chemistry and Biology, 2019
Zhenglong Zhang, Robert Meyer, Volker Deckert
Generation of hot electrons and the respective transfer behavior are crucial for understanding hot electron chemistry applications and achieving practically useful efficiency. Surface plasmons generally decay by either emitting a photon (radiative) or generating an electron-hole pair (non-radiative) through Landau damping [19]. The excited hot electrons have a much larger energy (1–4 eV) than the carriers at the Fermi energy, and quickly diffuse while exchanging their energy with other hot electrons or phonons, producing a Fermi–Dirac distribution and inducing an elevated temperature within 100 fs [20]. Then the electrons are scattered by phonons until the electron and lattice temperatures equilibrate.
Probing the electronic absorption spectrum of single gold nanoparticles in the gas phase
Published in Molecular Physics, 2023
Benjamin Hoffmann, Sophia Leippe, Knut R. Asmis
After excitation, the collective oscillation of the free electrons quickly dephases either radiatively by emission of a photon or non-radiatively by Landau damping and the formation of a non-thermal electron–hole pair distribution within 10 fs [12,13]. The electron–hole pairs can be generated within the conduction band (intraband) or by excitation of d-band electrons (interband). Interband transitions are the excitation of electrons from the 5d-band to unoccupied states in the 6sp-band in Au and are generally not sensitive to the size, shape or surface structure of the Au NP. The onset of the interband transitions for Au is at 2.4 eV (∼ 515 nm). The excited electrons then form a hot electron gas by electron–electron scattering on a timescale of 100 fs before the energy is transferred to the NP's lattice by electron–phonon scattering within 1 ps. Finally, heat is transferred to the environment on timescales >10 ps.
Impact of Non-Uniform Doping on the Reliability of Double Gate JunctionLess Transistor: A Numerical Investigation
Published in IETE Technical Review, 2022
Vandana Kumari, Mridula Gupta, Manoj Saxena
For various doping profiles, either oxide permittivity, source drain length and source drain work function (one at a time) were varied for investigation. For visualizing BTBT current and gate leakage current, tunneling model and hot electron/hole injection model has been invoked during simulation. For analyzing the self-heating effect, thermal models have been used. Apart from these model’s fermi dirac statistics, auger and Shockley Read Hall (SRH) recombination model and hydrodynamic model is used. All simulations have been performed using ATLAS TCAD at room temperature [37] elsewhere mentioned. In order to calibrate ATLAS inbuilt models (such as mobility model etc.), simulation results have been calibrated with the experimental results of JL-SOI FET [38] having 50 nm and 250 nm of channel length and the calibrated results of JL transistor has been shown in Figure 1(b).
Separation of charge carriers and generation of reactive oxygen species by TiO2 nanoparticles mixed with differently-coated gold nanorods under light irradiation
Published in Journal of Environmental Science and Health, Part C, 2019
Hui Zhang, Dejing Meng, Bing Fu, Huizhen Fan, Rui Cai, Peter P. Fu, Xiaochun Wu
It has been reported that the Au NPs can generate hot electron–hole pairs upon the excitation of its LSPR band and the hot electrons can be transferred to the combined semiconductor NPs.12,42,43 Here, we detected the generation of ROS by the AuNR@CTAB/TiO2 and AuNR@PSS/TiO2 mixtures when excited with the LSPR band of AuNRs using a 808 nm laser. The spin trap TEMP was used to detect the amount of 1O2 generation. The amount of ·OH and were measured by the spin trap 5-tert- butoxycarbonyl-5-methyl-1-pyrroline-N-oxide (BMPO) to form BMPO-spin adduct.44,45