Abstract
Three different procedures are used to deposit aluminium onto O‐terminated (100) and (111) boron‐doped diamond, with the aim of producing a thermally stable surface with low work function and negative electron affinity. The methods are 1) deposition of a > 20 nm film of Al by high‐vacuum evaporation followed by HCl acid wash to remove excess metallic Al, 2) deposition of <3 Å of Al by atomic layer deposition, and 3) thin‐film deposition of Al by electron beam evaporation. The surface structure, work function, and electron affinity are investigated after annealing at temperatures of 300, 600, and 800 °C. Except for loss of excess O upon first heating, the Al + O surfaces remain stable up to 800 °C. The electron affinity values are generally between 0.0 and −1.0 eV, and the work function is generally 4.5 ± 0.5 eV, depending upon the deposition method, coverage, and annealing temperature. The values are in broad agreement with those predicted by computer simulations of Al + O (sub)monolayers on a diamond surface.
Highlights
(100) and (111) boron-doped diamond, with the aim of producing a thermally stable surface with low work function and negative electron affinity
Two different methods were used to convert the H-terminated diamond into oxygen termination: UV/ozone treatment or oxidation using an atomic layer deposition (ALD) system
For energy-filtered photoemission electron microscopy (EF-PEEM), images were obtained for successive energies, allowing the work function at different locations to be visualized as a color-coded map, with an energy resolution of 0.14 eV and a spatial resolution of %150 nm
Summary
(100) and (111) boron-doped diamond, with the aim of producing a thermally stable surface with low work function and negative electron affinity. For some semiconductors and insulators, the work function can be greatly reduced because in these materials, the conduction band minimum (CBM) is higher in energy than the vacuum level Bulk electrons residing in the VB, or in mid-bandgap states because of doping, only require enough energy (via photon absorption, thermalization, or electric fields) to excite them into the CB for emission to take place Such NEA materials, which include diamond, cubic boron nitride,[7] AlN, and AlGaN,[8] are highly desirable for next-generation electron-emission applications. We report experimental results from the AlÀOÀdiamond system, including measurements of work function and EA from different diamond surfaces, coverages, and preparation procedures
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