上一篇 下一篇

Experimental studies of electron affinity and work function from titanium on oxidised diamond (100) surfaces

Fabian Fogarty ,
Neil A. Fox ,
Paul W. May
2022年 第2卷 第1期
DOI: 10.1080/26941112.2022.2122733
全文

摘要

Sub-monolayers of titanium were deposited onto oxidised (100) single-crystal diamond surfaces and annealed in vacuo at temperatures up to 1000 °C to find a temperature-stable termination procedure that produces a surface with Negative Electron Affinity (NEA). The samples were analysed by X-ray Photoelectron Spectroscopy, Ultraviolet Photoelectron Spectroscopy and Energy-Filtered Photoemission Electron Microscopy to determine their electron affinity and work function values. NEA values were observed on samples following annealing above 400 °C, with the largest NEA value being –0.9 eV for a sample coated with a half-monolayer of Ti annealed at 400 °C. Work function values were ∼4.5 eV for all samples annealed at temperatures between 400 and 600 °C, then rose at higher temperatures due to the loss of substantial amounts of O from the surface. Work-function maps indicated that the surface was uniform over areas 5700 μm2, suggesting that the deposition and annealing steps used are reliable methods to produce films with homogeneous surface properties.

关键词

CVD diamond; thermionic emission; titanium termination; negative electron affinity; work function

参考文献

  • May PW. Diamond thin films: a 21st century material. Phil Trans R Soc Lond A. 2000;358(1766):473–495.
  • James MC, Fogarty F, Zulkharnay R, et al. A review of surface functionalisation of diamond for thermionic emission applications. Carbon. 2021;171:532–550.
  • Monroy E, Omnés F, Calle F. Wide-Bandgap semiconductor ultraviolet photodetectors. Semicond Sci Technol. 2003;18(4):R33–R51.
  • Ascarelli P, Cappelli E, Pinzari F, et al. Secondary electron emission from diamond: physical modeling and application to scanning electron microscopy. J Appl Phys. 2001;89(1):689–696.
  • Shih A, Yater J, Pehrsson P, et al. Secondary electron emission from diamond surfaces. J Appl Phys. 1997;82(4):1860–1867.
  • Koeck FAM, Nemanich RJ, Lazea A, et al. Thermionic electron emission from low work-function phosphorus doped diamond films. Diamond Relat Mater. 2009;18(5–8):789–791.
  • Hamers RJ, Bandy JA, Zhu D, et al. Photoemission from diamond films and substrates into water: dynamics of solvated electrons and implications for diamond photoelectrochemistry. Faraday Discuss. 2014;172:397–411.
  • Diederich L, Küttel OM, Aebi P, et al. Electron affinity and work function of differently oriented and doped diamond surfaces determined by photoelectron spectroscopy. Surf Sci. 1998;418(1):219–239.
  • Loh KP, Sakaguchi I, Nishitani-Gamo M, et al. Negative electron affinity of cubic boron nitride. Diamond Relat Mater. 1999;8(2-5):781–784.
  • Nemanich RJ, Baumann PK, Benjamin MC, et al. Negative electron affinity surfaces of aluminum nitride and diamond. Diamond Relat Mater. 1996;5(6-8):790–796.
  • Cui JB, Ristein J, Ley L. Electron affinity of the bare and hydrogen covered single crystal diamond (111) surface. Phys Rev Lett. 1998;81(2):429–432.
  • Van Der Weide J, Zhang Z, Baumann PK, et al. Negative-electron-affinity effects on the diamond (100) surface. Phys Rev B. 1994;50(8):5803–5806.
  • Himpsel FJ, Knapp JA, VanVechten JA, et al. Quantum photoyield of diamond(111)—a stable Negative-Affinity emitter. Phys Rev B. 1979;20(2):624–627.
  • Baumann PK, Nemanich RJ. Surface cleaning, electronic states and electron affinity of diamond (100), (111) and (110) surfaces. Surf Sci. 1998;409(2):320–335.
  • Paxton WF, Howell M, Kang WP, et al. Influence of hydrogen on the thermionic electron emission from nitrogen-incorporated polycrystalline diamond films. J Vac Sci Technol B. 2012;30(2):021202.
  • Raymakers J, Haenen K, Maes W. Diamond surface functionalization: from gemstone to photoelectrochemical applications. J Mater Chem C. 2019;7(33):10134–10165.
  • Loh KP, Foord JS, Egdell RG, et al. Tuning the electron affinity of CVD diamond with adsorbed caesium and oxygen layers. Diam Relat Mater. 1997;6(5-7):874–878.
  • Loh KP, Xie XN, Yang SW, et al. A spectroscopic study of the negative electron affinity of cesium Oxide-Coated diamond (111) and theoretical calculation of the surface density-of-States on oxygenated diamond (111). Diamond Relat Mater. 2002;11(7):1379–1384.
  • Wong KW, Wang YM, Lee ST, et al. Lowering of work function induced by deposition of ultra-thin rubidium fluoride layer on polycrystalline diamond surface. Appl Surf Sci. 1999;140(1–2):144–149.
  • Nie JL, Xiao HY, Zu XT, et al. First principles calculations on Na and K-adsorbed diamond (100) surface. Chem Phys. 2006;326(2–3):308–314.
  • Baumann PK, Nemanich RJ. Characterization of cobalt-diamond (100) interfaces: electron affinity and schottky barrier. Appl Surf Sci. 1996;104–105:267–273.
  • Baumann PK, Nemanich RJ. Electron affinity and schottky barrier height of metal–diamond (100), (111), and (110) interfaces. J Appl Phys. 1998;83(4):2072–2082.
  • van der Weide J, Nemanich RJ. Schottky barrier height and negative electron affinity of titanium on (111) diamond. J Vac Sci Technol B. 1992;10(4):1940–1943.
  • Tiwari AK, Goss JP, Briddon PR, et al. Effect of different surface coverages of transition metals on the electronic and structural properties of diamond. Phys Status Solidi A. 2012;209(9):1697–1702.
  • Tiwari AK, Goss JP, Briddon PR, et al. Unexpected change in the electron affinity of diamond caused by the ultra-thin transition metal oxide films. EPL. 2014;108(4):46005.
  • O’Donnell KM, Martin TL, Fox NA, et al. Ab initio investigation of lithium on the diamond C(100) surface. Phys Rev B. 2010;82(11) 115303.
  • O’Donnell KM, Martin TL, Allan NL. Light metals on oxygen-terminated diamond (100): structure and electronic properties. Chem Mater. 2015;27(4):1306–1315.
  • O’Donnell KM, Martin TL, Edmonds MT, et al. Photoelectron emission from lithiated diamond. Phys Status Solidi A. 2014;211(10):2209–2222.
  • O’Donnell KM, Edmonds MT, Tadich A, et al. Extremely high negative electron affinity of diamond via magnesium adsorption. Phys Rev B. 2015;92(3):35303.
  • James KM. Aluminium and oxygen termination of diamond for thermionic applications [PhD thesis]. University of Bristol, UK; 2019. Available from: http://www.chm.bris.ac.uk/pt/diamond/michael-james-thesis/Michael-James-thesis.pdf.
  • James MC, Croot A, May PW, et al. Negative electron affinity from aluminium on the diamond (100) surface: a theoretical study. J Phys Condens Matter. 2018;30(23):235002.
  • James MC, May PW, Allan NL. Ab initio study of negative electron affinity from light metals on the oxygen-terminated diamond (111) surface. J Phys Condens Matter. 2019;31(29):295002.
  • James MC, Cattelan M, Fox NA, Sila RF, Silva M, May PW. Experimental studies of electron affinity and work function from aluminium on oxidised diamond (100) and (111) surfaces. Phys Status Solidi B Basic Solid State Phys. 2021;258:2100027.
  • Ullah S, Fox NA. Modification of the surface structure and electronic properties of diamond (100) with tin as a surface termination: a density functional theory study. J Phys Chem C. 2021;125(45):25165–25174.
  • Ullah S, Wan G, Kouzios C, et al. Structure and electronic properties of tin monoxide (SnO) and lithiated SnO terminated diamond (100) and its comparison with lithium oxide terminated diamond. Appl Surf Sci. 2021;559:149962.
  • Zulkharnay R, Allan NL, May PW. Ab initio study of negative electron affinity on the scandium-terminated diamond (100) surface for electron emission devices. Carbon. 2022;196:176–185.
  • Zulkharnay R, May PW. in preparation. 2022.
  • WebElements: Titanium: radii of atoms and ions. Available from: https://www.webelements.com/titanium/atom_sizes.html.
  • Fogarty F. Renewable energy – low temperature thermionic emission from modified diamond surfaces [PhD thesis]. University of Bristol, UK; July 2020.
  • Wan G, Cattelan M, Fox NA. Electronic structure tunability of diamonds by surface functionalization. J Phys Chem C. 2019;123(7):4168–4177.
  • Yeh JJ, Lindau I. Atomic calculation of photoionization Cross-Sections and asymmetry parameters. Langhorne (PA): Gordon and Breach; 1993.
  • Wan G, Panditharatne S, Fox NA, et al. Graphene–diamond junction photoemission microscopy and electronic interactions. Nano Express. 2020;1(2):020011.
  • Larsson K. The combined influence of dopant species and surface termination on the electronic properties of diamond surfaces. J Carbon. 2020;6(2):22.
  • Loh KP, Xie XN, Yang SW, et al. Oxygen adsorption on (111)-oriented diamond: a study with ultraviolet photoelectron spectroscopy, temperature-programmed desorption, and periodic density functional theory. J Phys Chem B. 2002;106(20):5230–5240.
  • Yoshida R, Miyata D, Makino T, et al. Formation of atomically flat hydroxyl-terminated diamond (111) surfaces via water vapor annealing. Appl Surf Sci. 2018;458:222–225.
  • Othman MZ. Studies of n-type doping and surface modification of CVD diamond for use in thermionic applications [PhD thesis]. University of Bristol, UK; 2014.
1084
下载
引用
收藏
分享

相关文章