Selective removal of potassium from K4In4Sb6 via laser ablation/ionization

Abstract

Results are reported on the Zintl phase material, K4In4Sb6, with respect to laser ablation and subsequent laser ionization/removal processes. A 308 nm laser pulse is used to ablate the Zintl compound, while a second laser ionizes ejected species within the extraction region of a time-of-flight mass spectrometer. With the second laser operating at 248 nm, selective ionization and removal of the potassium is clearly demonstrated. Such a strategy takes advantage of the different ionization potentials of K, In, and Sb, and implications for possible applications of this research to film growth are discussed.

Controlling Neutral Mixtures: Thin Film Deposition via Laser Ablation and Selective Ionization of K4In4Sb6

“…Given the relative ionization potentials (4.34, 5.79, and 8.64 eV for K, In, and Sb, respectively), the ionization laser (KrF; 5.0 eV) is clearly above the ionization potential of atomic potassium and below that of atomic indium and antimony. As a result, selective removal of potassium is not only theoretically possible, but it has been dramatically demonstrated …”

“…With neutral mixtures, however, control is often much more elusive. Recently, we presented experimental results on a novel technique , (referred to as the ablation/ionization scheme) that utilizes laser ablation and subsequent selective ionization to control neutral systems, the example being I−III−V Zintl compounds. , Selective ionization of the group I element enables one to change the composition of a gas-phase plume in a controlled fashion. In the present work, macroscopic control over the ablation plune is demonstrated.…”

“…In principle, such selectivity can be achieved with laser radiation possessing a photon energy above the ionization potential of the group I element and below that of the group III and group V elements. For a variety of I−III−V Zintl compounds (e.g., K 4 In 4 Sb 6 , K 3 Ga 3 As 4 , and Rb·Ga·Sb), conditions have been found for reproducible ablation and selective laser ionization/removal of the group I element from its ablation plume. , However, these studies have been conducted in the ionization region of a time-of-flight mass spectrometer (TOFMS) and do not determine whether the selective removal effect can be scaled macroscopically, since laser ionization within the TOFMS utilizes only a small volume of a tight laser focus (necessary for high mass spectral resolution). In contrast, “macroscopic” removal of the group I element requires an experimental geometry in which a majority of the ablation plume is effectively irradiated by the ionization laser.…”