Texture analysis of CoGe2 alloy films grown heteroepitaxially on GaAs(100) using partially ionized beam deposition

Abstract

Reflection x-ray pole figure analysis techniques were used to study the heteroepitaxial relationships of the cobalt germanide CoGe2 to GaAs(100). The alloy films were grown using the partially ionized beam deposition technique, in which low energy Ge+ ions are employed to alter the heteroepitaxial orientation of the CoGe2 deposits. The CoGe2[001](100)∥GaAs[100](001) orientation, which has the smallest lattice mismatch, was found to occur for depositions performed at a substrate temperature around 280 °C and with ∼1200 eV Ge+ ions. Lowering the substrate temperature or reducing the Ge+ ion energy leads to CoGe2(100) orientation domination with CoGe2[100](010)∥GaAs[100](001) and CoGe2[100](001)∥GaAs[100](001). Substrate temperature alone was seen to produce only the CoGe2(100) orientation. For CoGe2(001) films, additional energy was required from Ge+ ions in the evaporant stream.

Surface studies of phase formation in Co–Ge system: Reactive deposition epitaxy versus solid-phase epitaxy

“…[1][2][3][4][5] Although there is a considerable amount of literature on crystallography, microstructure, phase formation, and electronic properties of various cobalt silicides due to their potential as self-aligned silicides, there are relatively few publications concerning structure and properties of cobalt germanides. [1][2][3][4][5] Although there is a considerable amount of literature on crystallography, microstructure, phase formation, and electronic properties of various cobalt silicides due to their potential as self-aligned silicides, there are relatively few publications concerning structure and properties of cobalt germanides.…”

“…[8][9][10][11][12][13][14] The equilibrium bulk-phase diagram con-tains seven phases 15 : cubic Co 3 Ge, hexagonal Co 5 Ge 2 (a ‫ס‬ 3.93 Å, c ‫ס‬ 5.01 Å), hexagonal ␤-Co 5 Ge 3 and orthorhombic ␣-Co 5 Ge 3 , monoclinic (a ‫ס‬ 11.65 Å, b ‫ס‬ 3.81 Å, c ‫ס‬ 4.95 Å) and cubic (a ‫ס‬ 4.64 Å) CoGe, tetragonal Co 5 Ge 7 (a ‫ס‬ 7.64 Å, c ‫ס‬ 5.81 Å), orthorhombic CoGe 2 (a ‫ס‬ b ‫ס‬ 5.68 Å, c ‫ס‬ 10.82 Å), and Pearson's Crystallographic Data contain also orthorhombic Co 2 Ge (a ‫ס‬ 5.02 Å, b ‫ס‬ 3.82 Å, c ‫ס‬ 7.26 Å). 2,3 In addition to Co 5 Ge 7 and CoGe 2 , Co 3 Ge 2 was observed to form in metal vapor vacuum arc cobalt implanted germanium. 4 Solid-phase epitaxy (SPE) of Co onto Ge/SiO 2 followed by a 673-723 K anneal resulted in the formation of CoGe, which was transformed into CoGe 2 on an additional 923-1023 K anneal.…”

Formation of Co/Ge intermixing layers after Co deposition on Ge(111)2 × 1 surfaces

“…The combination of Co and Ge is considered as an important candidate for this purpose. Although the Co/Ge system has already been studied intensively [16,[26][27][28][29][30][31][32][33][34], the initial adsorption stage of Co atoms on Ge surfaces has not yet been investigated. A deeper understanding of combining ferromagnetic metals with semiconductors, in particular Co and Ge, in nanostructures is of significant technological and fundamental interest for future spintronic applications.…”