Topic

# Thermionic emission

About: Thermionic emission is a(n) research topic. Over the lifetime, 6099 publication(s) have been published within this topic receiving 97892 citation(s). The topic is also known as: Edison effect.

##### Papers

More filters

••

Abstract: We report visible light emission from Shottky diodes made from semiconducting polymers, confirming the discovery by the Cambridge group [Nature 347, 539 (1990)]. Our results demonstrate that light‐emitting diodes can be fabricated by casting the polymer film from solution with no subsequent processing or heat treatment required. Electrical characterization reveals diode behavior with rectification ratios greater than 104. We propose that tunneling of electrons from the recitifying metal contact into the gap states of the positive polaron majority carriers dominates current flow and provides the mechanism for light emission.

2,017 citations

••

Abstract: Although the theories of thermionic and field emission of electrons from metals are very well understood, the two types of emission have usually been studied separately by first specifying the range of temperature and field and then constructing the appropriate expression for the current. In this paper the emission is treated from a unified point of view in order to establish the ranges of temperature and field for the two types of emission and to investigate the current in the region intermediate between thermionic and field emission. A general expression for the emitted current as a function of field, temperature, and work function is set up in the form of a definite integral. Each type of emission is then associated with a technique for approximating the integral and with a characteristic dependence on the three parameters. An approximation for low fields and high temperatures leads to an extension of the Richardson-Schottky formula for thermionic emission. The values of temperature and field for which it applies are established by considering the validity of the approximation. An analogous treatment of the integral, for high fields and low temperatures, gives an extension of the Fowler-Nordheim formula for field emission, and establishes the region of temperature and field in which it applies. Also another approximate method for evaluating the integral is given which leads to a new type of dependence of the emitted current on temperature and field and which applies in a narrow region of temperature and field intermediate between the field and thermionic emission regions.

1,148 citations

••

800 citations

••

Abstract: Single-crystal ZnO nanowires are synthesized using a vapor trapping chemical vapor deposition method and configured as field-effect transistors. Electrical transport studies show n-type semiconducting behavior with a carrier concentration of ∼107cm−1 and an electron mobility of ∼17cm2∕Vs. The contact Schottky barrier between the Au/Ni electrode and nanowire is determined from the temperature dependence of the conductance. Thermionic emission is found to dominate the transport mechanism. The effect of oxygen adsorption on electron transport through the nanowires is investigated. The sensitivity to oxygen is demonstrated to be higher with smaller radii nanowires. Moreover, the oxygen detection sensitivity can be modulated by the gate voltage. These results indicate that ZnO holds high potential for nanoscale sensing applications.

790 citations

••

Abstract: A theory for calculating the magnitude of majority carrier current flow in metal-semiconductor barriers is developed which incorporates Schottky's diffusion (D) theory and Bethe's thermionic emission (T) theory into a single T-D emission theory, and which includes the effects of the image force. A low electric field limit for application of this theory is estimated from consideration of phonon-induced backscattering near the potential energy maximum. A high electric field limit associated with the transition to T-F emission is estimated from calculations of the quantum-mechanical transmission of a Maxwellian distribution of electrons incident on the barrier. The theory predicts a wide range of electric field ≈ 2 × 10 2 to 4 × 10 5 V/cm over which the T-D theory may be applied to metal- n -type Si barriers at 300°K. The corresponding range for metal- n -type GaAs barriers is 9 × 10 3 to 8 × 10 4 V/ at 300°K. The decreased upper limit is due mainly to the smaller electron effective mass in GaAs, the increased lower limit to a small optical-phonon energy and a shorter electron-optical-phonon mean-free path. The theory predicts Richardson constants of 96 and 4.4 A/cm 2 /°K 2 for metal- n -type Si and metal- n -type GaAs barriers respectively. Experimental measurements on both metal-Si and metal-GaAs barriers are in general agreement with the theory. Values of the barrier n [( q / kT )(d V /d ln J )] appreciably greater than unity are predicted for the field-dependent barrier height which occurs when an interface layer of the order of atomic thickness exists between the metal and the semi-conductor. A field dependence of the barrier height is shown to have no first order effect on the derivative of the 1/ C 2 vs. V relationship for the barrier. The intercept of a 1/ C 2 vs. V plot is shown to yield the barrier height extrapolated linearly to zero field in the semiconductor. Experimental evidence for the existence of interface layers in near-ideal Schottky barriers is also presented.

634 citations