Tham khảo tài liệu 'dictionary of material science and high energy physics part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | of free space. Inside a medium the velocity of light is reduced by the index of refraction of the medium Vlight c n. velocity overshoot When a high electric field is applied to a solid the drift velocity of electrons or holes rapidly rises reaches a peak and then drops to the steady-state value. This is known as velocity overshoot whereby the velocity can temporarily exceed the steady-state value. This happens because the scattering rate increases when the electrons or holes become hot their energy increases . The time taken for the energy to increase is roughly the so-called energy-relaxation time whereas the time taken for the velocity to respond to the electric field is the momentum relaxation time. The former can be much larger than the latter. Hence the velocity responds much faster than the energy causing the overshoot. The drift velocity of charge carriers in a solid vs. applied electric field. The velocity at first rises linearly with the field and then saturates to a fixed value. Temporal response of the drift velocity of electrons to a suddenly applied strong electric field. The velocity overshoots the steady-state velocity momentarily and then settles down to the steady-state value gradually. velocity potential Scalar function Ộ which satisfies both u dệ dx and dộ v dy which exists for all irrotational flows. The veloc- ity potential also satisfies the Laplace equation s Ệ 0 exactly. velocity saturation When an electric field is applied to a solid an ordered drift motion of electrons and holes is superimposed on the random motion of these entities. Whereas the random motion results in no resultant drift velocity the ordered motion gives rise to a net drift velocity and a current. When an electric field is applied to a solid the electrons and holes in the solid are accelerated. However the scattering of the electrons and holes due to static scatterers such as impurities and dynamic scatterers such as phonons lattice vibrations retards the electrons. .
