Hot-Electron Transport
Hot-Electron Transport
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热电子传输
DOI：
10.1007/978-3-642-81416-7_11
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发表时间：
1980
期刊：
影响因子：
--
通讯作者：
B. Nag
中科院分区：
文献类型：
--
作者：
B. Nag
电子输运由电场、热梯度或浓度梯度引起。在后两种情况下，除非使用外部源来维持非均匀条件，否则作为输运的结果建立了均匀条件。在这些条件下电子的传输可能会导致能量从样品的一部分转移到另一部分，但电子在传输过程中不会从外部来源获得能量。另一方面，当传输是由电场引起时，电子以~·<！（~是电流密度，δ是电场），看来电子系统的总能量应该无限地增加。然而，这并没有发生，因为这种能量的获得是通过碰撞过程将能量转移到晶格原子来平衡的。已经看到，电子被晶格散射，或者是通过发射声子，或者是通过吸收声子。当声子被发射时，晶格从电子吸收能量，当声子被吸收时，晶格将能量传递给电子。在没有电场的情况下，吸收和发射过程是如此平衡，以至于没有从电子系统到晶格系统的能量净转移，反之亦然。这实际上意味着电子和晶格系统的温度，即决定能量从一个系统转移到另一个系统的热力学系数是相同的。人们可以很容易地从玻尔兹曼方程证实，在无场条件下，
Electron transport is caused by an electric field, a thermal gradient, or a concentration gradient. In the latter two cases, a uniform condition is established as a result of the transport unless external sources are used to maintain the nonuniform conditions. The transport of electrons under these conditions may cause transfer of energy from one part of the sample to the other, but the electrons do not gain energy from the external sources in the process of transport. On the other hand, when the transport is caused by an electric field, electrons are continuously supplied with energy from the source of the electric field at a rate~•<!(~ is the current density and 8 is the electric field), and it would appear that the total energy of the electron system should go on increasing indefinitely. This, however, does not happen as this gain of energy is balanced by transfer of energy to the lattice atoms through the process of collisions. It has been seen that an electron is scattered by the lattice either by emitting or by absorbing a phonon. The lattice absorbs energy from the electron when a phonon is emitted and it delivers~ nergy to the electron when a phonon is absorbed. In the absence of the electric field the absorption and emission processes are so balanced that there is no net transfer of energy from the electron system to the lattice system or the vice versa. It means in effect that the temperature, the thermodynamic coefficent determining transfer of energy from one system to another, of the electron and that of the lattice system are identical. One may verify easily from the Boltzmann equation that in the field-free condition,