Doping Effects in CMOS‐compatible CoSi Thin Films for Thermoelectric and Sensor Applications

Abstract

. We report on semi‐metallic cobalt monosilicide (CoSi) as a CMOS‐compatible thermoelectric (TE) material and discuss the effect of n‐ and p‐type dopants on its transport properties. Thin films of CoSi are developed using chemical vapor deposition tools and subsequent rapid thermal processing. Film properties such as microstructure, crystallinity and elemental distribution are studied via electron microscopy, X‐ray diffraction and time‐of‐flight secondary ion mass spectroscopy. Doping silicon with boron prior to silicidation impedes the Co‐Si diffusion process, while phosphorus atoms distribute uniformly in silicides with no voids or agglomerations. CoSi makes a suitable n‐type TE candidate and provides an alternative to Si or SiGe materials. Transport properties of undoped CoSi exhibit a linear dependence within the investigated temperature window, whereas dopants in CoSi increase the number of electron carriers that contribute to charge transport and thereby influence the Seebeck coefficient. Thus, TE characteristics of thin CoSi films can be tuned via (i) the type of dopants used and/or (ii) varying the residual silicon thickness post silicidation.

Disorder-Induced Magnetotransport Anomalies in Amorphous and Textured Co1–xSix Semimetal Thin Films

“…To put our resistivity data into a broader context, we note that previous works report a room temperature ρ xx ≈ 100–150 μΩ cm for CoSi bulk single crystals 17 , 18 and ρ xx ≈ 100–350 μΩ cm for CoSi polycrystalline thin films. 11 , 21 First, we remark that the order of magnitude of ρ xx of our Co 1– x Si x films is consistent with literature, though the value of nearly stoichiometric films appears to be slightly higher. Second, it is quite surprising that the values of ρ xx are very similar in amorphous and textured Co 1– x Si x films and even comparable to some single-crystalline samples with low RRR.…”

“…Topological materials, comprising for instance topological insulators, Dirac and Weyl semimetals, are characterized by exotic electronic band structures, which give rise to a variety of unconventional physical properties. The emergence of giant magnetoresistance, photogalvanic and thermoelectric effects, − the evidence for the violation of the Wiedemann–Franz law and the conservation of chirality, , and the presence of unusual quantum phenomena − make topological materials highly attractive for the exploration of novel device concepts in the areas of valleytronics, quantum computing, sensing, and catalysis …”

“…Therefore, the question arises whether the topological properties of CoSi bulk single crystals survive in the case of less-ideal, low-dimensional systems such as thin films ,, and nanowires, which are required for nanoscale device applications. On the one hand, an increased surface-to-volume ratio should be beneficial for the exploitation of charge carrier transport along surface Fermi arcs, which, for instance, is envisioned as a promising route to overcome the resistivity bottleneck scaling of conventional metallic interconnects. − On the other hand, it is still unclear if low-dimensionality and structural and chemical disorder are compatible with topological magnetotransport.…”

Effect of Deformation on Topological Properties of Cobalt Monosilicide

“…The possibility of using CMOS-compatible CoSi thin films for thermoelectric and sensor applications were considered recently in Ref. [24]. The stability of CoSi under hydrostatic pressure was theoretically investigated in Ref.…”