Demonstration of Low Work Function Perovskite SrVO₃ Using Thermionic Electron Emission

Abstract

Engineering a material's work function is of central importance for many technologies and in particular electron emitters used in high‐power vacuum electronics and thermionic energy converters. A low work function surface is typically achieved through unstable surface functional species, especially in high power thermionic electron emitter applications. Discovering and engineering new materials with intrinsic, stable low work functions obtainable without volatile surface species would mark a definitive advancement in the design of electron emitters. This work reports evidence for the existence of a low work function surface on a bulk, monolithic, electrically conductive perovskite oxide: SrVO3. After considering the patch field effect on the heterogeneous emitting surface of the bulk polycrystalline samples, this study suggests the presence of low work function (≈2 eV) emissive grains on SrVO3 surface. Emission current densities of 10–100 mA cm–2 at ≈1000 °C, comparable to commercial LaB6 thermionic cathodes, indicative of an overall effective thermionic work function of 2.3–2.7 eV are obtained. This study demonstrates that perovskites like SrVO3 may have intrinsically low work functions comparable to commercialized W‐based dispenser cathodes and suggests that, with further engineering, perovskites may represent a new class of low work function electron emitters.

Thermodynamic and Structural Properties of Bulk and Thin-Film CeVO4 and LaVO4

“…The spectrum of the reduced sample is that of V 3+ , with 2p 1/2 and 2p 3/2 peaks at 523.1 and 515.6 eV, respectively . Upon oxidation, both peaks upward shift by 0.8 eV to positions consistent with that expected for V 4+ . , This again coincides with the EELS results. A summary of XPS results is provided in Table .…”

“…25 Upon oxidation, both peaks upward shift by 0.8 eV to positions consistent with that expected for V 4+ . 26,27 This again coincides with the EELS results. A summary of XPS results is provided in Table 2.…”

Role of the Adsorption of Alkali Cations on Ultrathin n-Layers of Two-Dimensional Perovskites

“…The work function (Φ) is the minimum energy required to remove an electron from the surface of a solid to the vacuum region. It can be estimated by the energy difference between the energy of the highest occupied state (VBM) and the value of the electrostatic potential in the vacuum region. , The results are shown in Figure . The behavior of the Φ value in the 2D alkali slab also follows a periodic trend depending on the alkali species in the systems, with an inversely proportional value to the electronegativity value of the alkali species.…”

“…These findings align with the stronger quantum confinement effect typically observed in monolayer systems, which generally leads to larger band gaps compared to their bilayer counterparts. 73,74 The results are shown in Figure 10. The behavior of the Φ value in the 2D alkali slab also follows a periodic trend depending on the alkali species in the systems, with an inversely proportional value to the electronegativity value of the alkali species.…”

Determination of Work Function for p- and n-Type 4H-SiC Single Crystals via Scanning Kelvin Probe Force Microscopy

“…The large difference between the Si-terminated polar surface in experiment and calculation may be due to the differences in practical surfaces and the ideal surface built for the calculation. [43] Therefore, the WF obtained from SKPFM is a sensitive physical quantity for (0001)-orientated SiC (both n-type and p-type), which is insensitive to the surface roughness, impurity particles and scratches. This is always the case for SiC wafers grown via PVT and TSSG.…”