Growth of Ge_1−xSn_x Nanowires by Chemical Vapor Deposition via Vapor–Liquid–Solid Mechanism Using GeH₄ and SnCl₄

Abstract

In this work we report on the elaboration and characterization of Ge1−xSnx nanowires synthetized by chemical vapor deposition (CVD) via vapor–liquid–solid (VLS) mechanism using GeH4 and SnCl4 as precursors. We have investigated tin incorporation in Ge as a function of experimental growth conditions such as growth temperature and Sn precursor partial pressure (PSnCl4/PGeH4 ratio). We have demonstrated Ge1−xSnx nanowires with Sn incorporation around 1 at.% in the core with a thin Sn‐rich shell with up to 10 at.% Sn well beyond the equilibrium solubility of Sn in bulk Ge.

Facile synthesis of Ge1−xSnx nanowires

“…Figure 3 shows a tin-rich nanoparticle at the tip of a Ge 1−x Sn x nanowire, once again confirming the SLS growth mechanism. EDX line scanning and mapping revealed homogeneously distributed tin throughout the nanowire with no evidence of tin segregation or a tin-rich shell has been observed in other work [18]. EDS spot analysis was performed on more than twenty individual Ge 1−x Sn x nanowires at the seed (A), growing zone (B), middle (C) and tip (D) sections.…”

“…The synthesis of Ge 1−x Sn x is challenging due to the low solubility of tin in germanium (<1%) [16], large lattice mismatch (∼14%) and a tendency of metallic tin to segregate from germanium [17,18]. Ge 1−x Sn x alloys are commonly fabricated using ion implantation, laser melting [4,5,19], molecular beam epitaxy (MBE) [7], and chemical-vapor deposition(CVD) approaches [6,[20][21][22].…”

“…The most established synthetic approaches, for group IV nanowires (such as Ge and Ge 1−x Sn x ), involve the use of metal growth-promoters in bottom-up processes such as: vapour-liquid-solid (VLS), vapor-solid-solid (VSS), In-plane-solid-liquid-solid (IP-SLS), supercritical fluid-liquid-solid (SFLS) and solution-liquid-solid (SLS) mechanisms. [12,18,23,26,27,29]. Amongst these, the SLS approach offers benefits such as low equipment cost, high scalability, mild-reaction conditions, easy control, and access to non-flammable germanium precursors (such as triphenylchlorogermane) [30].…”

“…In order to fabricate Ge 1−x Sn x nanowires incorporating high tin content, non-equilibrium introduction of tin into the germanium lattice has been proposed and demonstrated by several groups. These used either a VLS mechanism from liquid-injection CVD upon Au [18] or AuAg catalysts [12,26], or IPSLS approach [23,27]. However, reports focused on self-seeded SLS growth of high quality Ge 1−x Sn x nanowires from tin catalyst are rare.…”

Design of Strain-Engineered GeSn/GeSiSn Quantum Dots for Mid-IR Direct Bandgap Emission on Si Substrate

“…However, because of the large lattice mismatch between Ge and Sn (14%), the preservation of the crystallographic quality of the material appears as the main challenge prohibiting this goal [12, 13]. A potentially interesting solution to increase the emission wavelength and ensure better carrier confinements relay on lower dimensional structures such as nanowires [14–16], nanorods [17], and quantum dots [18]. Within the specific directness criteria, the direct bandgap interband emission wavelength is theoretically limited to 4.3 μm [19].…”