Atomic Layer Deposition of Intermetallic Co₃Sn₂ and Ni₃Sn₂ Thin Films

Abstract

crystal structures of the participating metal components. An intermetallic compound is formed when the bonds between the dissimilar atoms are stronger than the bonds between the atoms of the same element.Because of their specific structure, intermetallic compounds usually exhibit unique physical and chemical properties that are potentially superior to their disordered alloy analogues and the pure metals. Such properties include, for example, magnetoresistance, [3,4] superconductivity, [5][6][7] enhanced catalytic activity, [8,9] and hydrogen storage capability. [10] Intermetallics and alloys containing Co or Ni and Sn with varying stoichiometry have mostly been studied as anode materials for Li-and Na-ion batteries. [11][12][13][14][15][16][17][18][19] As ferromagnetic materials, they also show potential for magnetic devices. [20][21][22] Furthermore, intermetallic Co-Sn and Ni-Sn compounds have also been studied for catalytic purposes. [23][24][25][26] For future applications like nanoelectronic devices, it is pivotal to be able to control the thickness and composition of thin films with sub-nanometer accuracy. Atomic layer deposition (ALD) is a thin film preparation method based on repeated, saturative, and irreversible surface reactions between alternately supplied gaseous precursors ensuring self-limiting growth of the desired material. [27,28] Owing to the self-limiting growth mechanism, ALD can be used to deposit uniform thin films over complex structures in a controlled and reproducible manner. No previous reports on the ALD of intermetallic Co 3 Sn 2 or Ni 3 Sn 2 thin films are found in the literature, and the ALD of other intermetallic compounds has also been scarce if existent at all. Intermetallic phases in Pt-In, [29] Pt-Sn, [30] and Ni-Fe [31] systems have been obtained by the postdeposition reduction of the corresponding ALD oxides. There are also some ALD studies on metal alloys, such as Pt-Ir, [32] Pd-Pt, [33][34][35] Ru-Pt, [36] Ru-Co, [37] Co-W, [38,39] Co-Pt, [40] Ru-Mn, [41] and Cu-Mn, [42] but no reports exist on materials exhibiting a specific intermetallic structure. Co-Sn and Ni-Sn with varying stoichiometry, including the intermetallic Co 3 Sn 2 and Ni 3 Sn 2 phases, have generally been prepared by, for example, ball Intermetallics form a versatile group of materials that possess unique properties ranging from superconductivity to giant magnetoresistance. The intermetallic Co-Sn and Ni-Sn compounds are promising materials for magnetic applications as well as for anodes in lithium-and sodium-ion batteries. Herein, a method is presented for the preparation of Co 3 Sn 2 and Ni 3 Sn 2 thin films using diamine adducts of cobalt(II) and nickel(II) chlorides, CoCl 2 (TMEDA) and NiCl 2 (TMPDA) (TMEDA = N,N,N′,N′tetramethylethylenediamine, TMPDA = N,N,N′,N′-tetramethyl-1,3propanediamine) combined with tributyltin hydride. The films are grown by atomic layer deposition (ALD), a technique that enables conformal film deposition with sub-nanometer thickness control. The Co 3 Sn 2 process fulfills the ...

Intermetallic compounds in catalysis – a versatile class of materials meets interesting challenges

“…The selection of suitable reagents and processes makes ALD much more demanding than CVD and has been introduced for the synthesis of intermetallic compounds in 2016 for NiFe films [ 152 ]. Since then, it has been applied to synthesise PtSn/SiO2 [ 153 ], nanoparticles of PtIn [ 154 ] and PtSn [ 155 ] as well as thin films of Co 3 Sn 2 and Ni 3 Sn 2 [ 156 ].…”

Cobalt Metal ALD: Understanding the Mechanism and Role of Zink Alkyl Precursors as Reductants for Low Resistivity Co Thin Films

“…This direct film growth on non-metallic surfaces is in agreement with prior ALD studies by Väyrynen employing the same Co precursor for Co3Sn2 intermetallic films. 46 Contrasting this, the thermal ALD process developed by Kerrigan and co-workers with Co(DAD)2 was strongly inhibited on all surfaces except metallic ones. 11 This suggested that unlike Co(DAD)2, CoCl2(TMEDA) is capable of interacting with hydroxyl surface sites during the first pulse.…”

“…43 To address this crucial drawback, we present for the first time the ALD of metallic, Zn-free Co thin films using, intramolecularly stabilized Zn precursor Zn(DMP)2 44 (DMP = N,N-3-(dimethylamino)propyl) with the Co precursor CoCl2(TMEDA) (TMEDA = N,N,N',N'-tetramethylethylenediamine) that has previously been used for ALD of intermetallic thin films. 45,46 The precursor pair was chosen based on the precedence for the formation of thermally labile Co(DMP)2 species in solution, 47 a bulk reactivity study with the neat reagents, as well as matching thermal properties that facilitate their usage in an F-120 ALD reactor. As a first step, a reactivity screening of several potential precursor combinations (see Scheme 1) comprising the wellknown Zn(Et)2 43 as well as its less known amine stabilized congener Zn(Et)2(TMEDA) 48 is carried out.…”

Atomic Layer Deposition of Nickel Nitride Thin Films using NiCl2(TMPDA) and Tert‐Butylhydrazine as Precursors

“…Other substrates, such as Si with native oxide, TiN, Cu, Au, and Ru, were also tested. NiCl 2 (TMPDA) was synthesized in‐house according to the procedure described previously . TBH was purchased from EpiValence and AlCl 3 from Acros Organics.…”

“…So far, no suitable reducing agent has been found to reduce CoCl 2 (TMEDA) or NiCl 2 (TMPDA) to elemental Co or Ni in ALD. We have, however, shown that the diamine adducts of these metal(II) halides are suitable for the ALD of intermetallic Co 3 Sn 2 and Ni 3 Sn 2 as well as Co(II) oxide thin films …”