Abstract:Thin film solar cells have reached commercial maturity and extraordinarily high efficiency that make them competitive even with the cheaper Chinese crystalline silicon modules. However, some issues (connected with presence of toxic and/or rare elements) are still limiting their market diffusion. For this reason new thin film materials, such as Cu 2 ZnSnS 4 or SnS, have been introduced so that expensive In and Te, and toxic elements Se and Cd, are substituted, respectively, in CuInGaSe 2 and CdTe. To overcome the abundance limitation of Te and In, in recent times new thin film materials, such as Cu 2 ZnSnS 4 or SnS, have been investigated. In this paper we analyze the limitations of SnS deposition in terms of reproducibility and reliability. SnS deposited by thermal evaporation is analyzed by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and atomic force microscopy. The raw material is also analyzed and a different composition is observed according to the different number of evaporation (runs). The sulfur loss represents one of the major challenges of SnS solar cell technology.

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Bi2Te3 is attracting a renewed interest, due to its topological insulator properties; however, even using advanced physical and chemical deposition techniques, the growth of high-crystal quality layers on substrates allowing its technological employment, such as Si, is very challenging, due to the structural complexity of Bi2Te3. In this work, we present the optimized large area growth of topological insulator Bi2Te3 epitaxial layers on un-buffered i-Si (111) substrates via Metal-Organic Vapor Phase Epitaxy (MOVPE), which is of crucial importance for future integration into CMOS compatible spintronic devices. We found that the key to maximizing the layer quality requires a balanced control of the reactor pressure (P), growth temperature (T), and growth time (t). Within a proper parameter window, the grown Bi2Te3 thin layers are crystalline, stoichiometric, and highly uniform, also at the local scale. They exhibit a rhombohedral crystalline structure, and they are [001] out-of-plane oriented on the i-Si (111) substrate. Low temperature magnetoresistance measurements revealed clear Weak Antilocalization (WAL) effects, demonstrating that the optimized MOVPE -grown Bi2Te3 is a topological insulator, hence opening further possibilities for its technology-transfer to innovative devices.

Detailed crystallographic information provided by X-ray diffraction (XRD) is complementary to molecular information provided by Raman spectroscopy. Accordingly, the combined use of these techniques allows the identification of an unknown compound without ambiguity. However, a full combination of Raman and XRD results requires an appropriate and reliable reference database with complete information. This is already available for XRD. The main objective of this paper is to introduce and describe the recently developed Raman Open Database (ROD, http://solsa.crystallography.net/rod). It comprises a collection of high-quality uncorrected Raman spectra. The novelty of this database is its interconnectedness with other open databases like the Crystallography Open Database (http://www.crystallography.net/cod and Theoretical Crystallography Open Database (http://www.crystallography.net/tcod/). The syntax adopted to format entries in the ROD is based on the worldwide recognized and used CIF format, which offers a simple way for data exchange, writing and description. ROD also uses JCAMP-DX files as an alternative format for submitted spectra. JCAMP-DX files are compatible to varying degrees with most commercial Raman software and can be read and edited using standard text editors.

Large‐area antimony telluride (Sb2Te3) thin films are grown by a metal organic chemical vapor deposition technique on 4” Si(111) substrates, and their topological character probed by magnetoconductance measurements. When interfaced with Fe thin films, broadband ferromagnetic resonance spectroscopy (BFMR) shows a clear increase of the damping parameter in Fe/Sb2Te3 when compared to a reference Fe layer, which may suggest the occurrence of spin pumping (SP) into Sb2Te3. Simultaneously, X‐ray reflectivity and conversion electron Mossbauer spectroscopy evidence the development of a chemically and magnetically pure Fe/Sb2Te3 interface. However, by conducting SP‐FMR, it is shown that no spin‐to‐charge conversion (S2C) occurs in Fe/Sb2Te3, while a clear SP signal develops by introducing a 5 nm Au interlayer between Fe and Sb2Te3, with a measured inverse Edelstein effect conversion efficiency of λIEE = 0.27 nm. The results shed some light on the correlation among the chemical‐structural‐magnetic properties of the Fe/Sb2Te3 interface, the broadening of the magnetic damping parameter as detected by BFMR, and the occurrence of S2C, as probed by SP‐FMR.