We analyze a new cold cathode emitter which consists of a thin wide band gap semiconductor material sandwiched between a metallic material, and a low work function semimetallic thin film. We show that under forward bias operation the electrons captured in the low work function material are responsible for an effective reduction of the semimetallic film work function, together with a substantial increase of the cathode emitted current. The dynamic work function shift is shown to increase with the amount of injected current. Potential material candidates are suggested to achieve low-voltage (<20 V), room-temperature cold cathode operation with emission currents approaching several hundred A/cm2 and large efficiencies.

Articles you may be interested inElectron beam prebunching in planar cold cathodes with surface current carrying thin films Interplay of current crowding and current self-quenching effects in planar cold cathodes Space-charge effects and current self-quenching in a metal/CdS/LaS cold cathode

We analyze the importance of current crowding in a new cold cathode emitter that consists of a thin wide band-gap semiconductor material sandwiched between a metallic contact and a low work function semimetallic thin film. Potential material candidates are suggested to achieve low-voltage (<10 V), room-temperature cold cathode operation with emission currents of several tens of A/cm2. We calculate the lateral potential drop that occurs across the emission window of cold cathodes with rectangular geometry and describe its effects on the emitted current density profile. The power dissipation in the cold cathode is calculated as a function of a dimensionless parameter characterizing the importance of current crowding. We determine the range of dc bias over which cold cathodes of different width must be operated to minimize current crowding effects.

We analyze the importance of space-charge effects in the cathode to anode gap region of a recently proposed metal/CdS(cadmium sulfide)/LaS(lanthanum sulfide) cold cathode. Our approach is based on an ensemble Monte Carlo description of electron transport assuming ballistic injection across the CdS and LaS layers. Under this approximation, the energy spectrum of the injected beam entering the air gap can be determined exactly as a function of the applied bias across the CdS layer. The effects of shot noise in the injected current are taken into account. For some of the biasing conditions considered here, space-charge effects are quite drastic and lead to dynamical effects which are responsible for the onset of current self-quenching similar to the Child–Langmuir regime of operation of thermionic cathodes. The limiting anode current density is found to be much larger than the Child–Langmuir limit. In the presence of strong space-charge effects, large oscillations in the minimum of the electrostatic potential in front of the cathode lead to oscillations in the measured anode current within the tens of GHz frequency range.

The high-level contribution of this paper is the design of a benchmarking algorithm to determine a sequence of the longest-living stable data gathering trees for wireless mobile sensor networks (MSNs) such that the number of tree discoveries is the theoretical global minimum. Referred to as the Max.Stability-DG algorithm, the algorithm assumes the availability of the complete knowledge of future topology changes, and operates according to a greedy strategy: Whenever a new data gathering tree is needed at time instant t, determine a spanning tree that will exist for the longest time since t and derive a data gathering tree by conducting a Breadth First Search on the spanning tree. We prove the correctness of the Max.Stability-DG algorithm that it indeed determines the sequence of longestliving stable data gathering trees. Since the Max.Stability-DG trees are based on spanning trees covering the entire network of live sensor nodes, the average lifetime and the number of tree discoveries incurred for the Max.Stability-DG trees will serve respectively as the upper bound and lower bound for any network-wide communication topology determined using any other algorithm for mobile sensor networks.