Repeatable electron emission from (Pb,La)(Zr,Ti)O3 ferroelectric cathodes using direct-current reset

Abstract

The use of ferroelectric (Pb,La)(Zr,Ti)O3 as a cathode material is investigated. It has been suggested in the literature that by rapidly changing or reversing the spontaneous polarization in the ferroelectric, a large charge imbalance can be produced at the surface of the material. The field from this charge imbalance extracts bound carriers from the cathode. An approach to achieving this polarization change by using a negative bias field to preset the material prior to switching is discussed in this letter. This bias field can also be used to control the bound surface charge on the material. Emission currents on the order of 100 mA are observed and the emitted charge is on the order of 30 nC. Measurable emission occurs only when the material is driven into saturation.

Features and technology of ferroelectric electron emission

“…Equation (4) may explain the two orders of magnitude increase of emitted current density compared with the Langmuir-Child current density. Such an enhancement of emitted current density can be observed, if an extraction field is applied and if the plasma density n e is sufficiently high (as for example reported in [15], [16], [18], [19]). The enhancement effect of the surface plasma can also be recognized in FE self-emission mode (for example in Fig.…”

“…The strong electrically-induced emission from FE samples covered with metallic grid electrodes is very efficient, but weak FE emission has also been observed from a bare FE surface without any electrode or conducting material (for example, [3,5,26]). The latter type of electron emission cannot be induced with any of the alternative emission methods [14][15][16][17][18][19][20][21][22] using reverse field excitation, which rely on the field emission of electrons from the FE-metal interfaces of the GE grid electrode [27].…”

“…[14][15][16][17][18][19][20][21][22], initiates P s -switching at the same threshold field level. However, the sequence of processes following the switching, including plasma formation and electron extraction by external field, may widely differ from the FE self-emission described above.…”

“…Later on different methods were studied in other laboratories to extract intense electron beams from FE cathodes (for example, Refs. [14][15][16][17][18][19][20][21][22]), and confusion arose about what is meant by 'ferroelectric electron emission'. The phenomenological appearance and some of the basic processes differ in these latter cases from those in the original 'strong FE emission mode' [4][5][6][7][8][9][10][11][12][13].…”

Ferroelectric electron emission: Principles and technology

“…Strong electron emission up to 100 A/cm 2 from ferroelectric material was detected at CERN in 1988 and has since been discussed and used in several applications [2]- [9]. Confusion has arisen in defining what is meant by 'ferroelectric electron emission', owing to work with different methods of electron emission from FE in other laboratories [10]- [13]. The author feels obliged to clarify the term 'FE emission', which is discussed in this paper and which corresponds to the 'strong FE emission' referred to above.…”