Surface processes on thin layers of black aluminum in ultra-high vacuum. (November 2022)

• Record Type: Journal Article
• Authors: Pokorný, P.; Novotný, M.; More-Chevalier, J.; Dekhtyar, Y.; Romanova, M.; Davídková, M.; Chertopalov, S.; Fitl, P.; Hruška, M.; Kawamura, M.; Kiba, T.; Lančok, J.
• Is Part Of: Vacuum. Volume 205(2022)
• Publication Date: 2022-11
• Subjects: Black aluminum -- exo-Electron emission -- Gas desorption -- Activation energy -- Low temperatures; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2022.111377
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: Thin films of black aluminum (B–Al) were prepared by pulsed DC magnetron sputtering in a mixture of argon + nitrogen (Ar + N2 ) gases with concentration of nitrogen 6%. At this concentration the process of anti-reflective surface (UV to near IR diffuse reflectance below 4%) formation is favored. The properties of such layers have been investigated using methods allowing to follow near-surface processes by means of thermally stimulated desorption (TSD) and thermally stimulated exo-electron emission (TSEE) in ultra-high vacuum conditions (p < 2.10 −7 Pa). It is shown that at certain temperatures some adsorbed particles are desorbed and at the same time negative charges are emitted. In some cases, the emission sites are common. Comparison of TSEE measurements at three different excitations (α, proton irradiation and UV illumination) was performed. Common measurements together with calculations of the activation energies of desorption as well as electron emission sufficiently describe the centers responsible for these processes. In particular, the atomic oxygen Oat, the AlOH radical and partly the atomic nitrogen Nat together with the AlN radical are shown to play a significant role in this surface process. Highlights: Combined measurements TSEE and TSD from thin films of black aluminum in UHV. TSEE measurements made at both laboratories (Riga, Prague) show agreement at T = 168 and 347 °C. Atomic O, N and radical AlOH showed two TSD stages: below RT - physical desorption. Atoms and radicals AlOH, Al2 O and AlN: above RT released as chemisorbed species. The AlOH radical shows maxima at T = 97 °C and 271 °C; Al2 O, AlN only above T > 300 °C.