Plasma-assisted surface nanostructuring of epitaxial Pb_1−x Sn _x Te (0 ≤ x ≤ 1) films

Abstract

In this work, we report a novel approach to the surface nanostructuring of lead tin telluride films using inductively coupled argon plasma treatment with the average ion energy of 200 eV and the duration of 20-60 s. The nanostructuring was carried out on the plasma treated surface of epitaxial single-crystal Pb 1−x Sn x Te films grown on BaF 2 (111) substrates using molecular beam epitaxy. The plasma treatment of the surface of the Pb 1−x Sn x Te films with the low and medium Sn content (x=0-0.6) resulted in the formation of the arrays of 'capped' conical nanostructures with the height up to 420 nm, depending on the Sn content and treatment duration, and the surface density of ∼10 9 cm −2 . The plasma treatment of the surface of the films with the high Sn content (x=0.8-1) yielded the formation of a second group of flat nanostructures without 'caps', which had necklace-like rings consisting of multiple nanodroplets around their rims. Using transmission electron microscopy, we show that the quasi-spherical droplet 'caps' of the nanostructures consist of Pb 'wrapped' in Sn. We explain the physical mechanism of the observed plasma-assisted nanostructure self-formation in the framework of the multi-stage model including physical sputtering, redeposition, vapour-liquid-solid mechanism and micromasking mechanism.

Annealing and plasma treatment effect on structural, morphological and topographical properties of evaporated β-In2S3 films

“…This is due to the presence of volatile chalcogen and of low melting point metals that enhance the effect of nanostructure formation. Similar processing in pure argon plasma for creation of nano-and microstructured surface of chalcogenide materials such as Cu(In, Ga)Se 2 , SnS, PbSnTe and PbSe were reported in literature [18][19][20][21]. As per literature survey, there is no report available on physical characteristics of In 2 S 3 thin films treated with Ar-plasma.…”

“…The first is due to the fact that the surface temperature during plasma treatment increases. Under close experimental conditions, it can reach approximately 230°C in 30 s [20], which significantly exceeds the melting point of indium. The second factor is associated with the presence of an intense UV glow of argon plasma.…”

Variation of Surface Nanostructures on (100) PbS Single Crystals during Argon Plasma Treatment

“…During interaction of ions with the surface, different surface nanostructure formation mechanisms are possible [13][14][15][16][17][18][19], which makes ion and ion-plasma techniques an important tool for surface nanostructuring. We used binary compounds of PbX and ternary solid solutions based on them as examples to show that varying inductively coupled argon plasma treatment condition enables the formation of micro-and nanostructures [20][21][22][23][24][25][26][27]. These nanostructures exhibit various morphologies on the surface 2 of 11 of single crystals and mono-and polycrystalline films of lead chalcogenides, which can influence the optical properties of modified systems.…”

“…The physical mechanisms underlying such formations could be different; for example, high submicron cones were formed at dislocations by micromasking mechanism, whereas capped conical nanostructures grew on the surface by the vapor-liquid-solid (VLS) mechanism. A novel plasma-assisted self-formation of nanostructures via VLS mechanism with selfforming lead-enriched catalytic droplets has been demonstrated for PbX binary and ternary compounds [24,27]. Specifically, the sputtered material was redeposited on a heated surface in the form of "building blocks" consisting of both binary PbX molecules and atomic lead, which formed nano-and microstructures on the surface.…”

“…Specifically, the sputtered material was redeposited on a heated surface in the form of "building blocks" consisting of both binary PbX molecules and atomic lead, which formed nano-and microstructures on the surface. In our previous studies [20][21][22][23][24][25][26][27], only a certain set of conditions were considered for the ion-plasma treatment, leading to specific types of nanostructures. Alternatively, in the present work for the first time, various plasma treatment conditions have been employed in the ion energy range of 25-200 eV, and the physical processes occurring during surface modification have been analyzed using the crystals of one specific material: PbS.…”