Thermoelectric Properties of Epitaxial β-FeSi2 Thin Films on Si(111) and Approach for Their Enhancement

Giant Enhancement of Seebeck Coefficient by Deformation of Silicene Buckled Structure in Calcium‐Intercalated Layered Silicene Film

“…e) S 2 σ of CaSi 2 thin films, the other silicide thin films and bulk, the well‐known rare metal‐based TE thin films, and the state‐of‐the‐art TE bulks at RT. [ 34–44,48 ]…”

“…[ 34 ] Although a metal with ultrahigh σ exhibits low | S | of <10 μV K −1 in general, semimetal CaSi 2 films with pseudo gap exhibited not only ultrahigh σ but also relatively high | S | of ≈40 μV K −1 presumably due to the manipulation of energy dispersion relation originating from the deformation of buckled structure. As a result, remarkably high S 2 σ was obtained in CaSi 2 films composed of only eco‐friendly elements, whose value is much higher than those of silicide thin films (FeSi 2 , MnSi 1.73 , Mg 2 Si) and bulk (CaSi 2 ), [ 35–37,48 ] and even higher than those of well‐known TE thin film materials (Bi 2 Te 3 and SnSe), [ 55,56 ] as shown in Figure 4e. This value is also comparable to those of the state‐of‐the‐art bulk TE materials (15–45 μW cm −1 K −2 ) such as Bi 2 Te 3 , [ 38 ] SnSe, [ 39 ] Bi 0.5 Sb 1.5 Te 3 , [ 40 ] AgPbSbTe, [ 41 ] PbTe–SrTe, [ 42 ] and SiGeAu.…”

“…The CaSi 2 films with metastable deformed silicene exhibit ≈3000 times enhancement of S 2 σ (≈40 μW cm −1 K −2 ) from that of reported CaSi 2 film at room temperature (RT). [34] This S 2 σ value is the highest among silicide-based TE films, [35][36][37] higher than that of Bi 2 Te 3 [38] and comparable to the state-of-the-art TE materials (SnSe, [39] Bi 0.5 Sb 1.5 Te 3 , [40] AgPbSbTe, [41] PbTe-SrTe, [42] and SiGeAu [43,44] ). This study demonstrates that S 2 σ is greatly enhanced by the deformation of silicene buckled structure, opening an avenue for realizing eco-friendly TE film.…”

“…e) S 2 σ of CaSi 2 thin films, the other silicide thin films and bulk, the well-known rare metalbased TE thin films, and the state-of-the-art TE bulks at RT. [34][35][36][37][38][39][40][41][42][43][44]48] much larger than the calculated values at E−E F = 0 of 6R-CaSi 2 with the perfect crystal structure.…”

Analyses of Responsivity and Quantum Efficiency of p-Si/i-β-FeSi2/n-Si Photodiodes

“…(2)(3)(4) β-FeSi 2 has a large optical absorption coefficient (α > 10 5 cm −1 at 1.5 eV ) and a direct band gap of 0.85-0.87 eV. (5)(6)(7) β-FeSi 2 thin films can be epitaxially grown on Si substrates with small lattice mismatches of 2-5%.…”