Ims 6 f

The experiments were performed in an UHV system for secondary ion mass spectrometry (SIMS, IMS 6f, Cameca) to obtain depth composition profiles. A Cs⁺ primary ion beam of impact energy of 15 keV was employed to analyze the samples. The beam current was 50 nA, and the beam reached the sample through a 150 μm × 150 μm size of raster; the generated secondary ions were collected by detector through 33π μm² size of aperture.

The SIMS measurements have been performed in a Cameca IMS 6 F using either ¹³³Cs⁺ or ions, and are presented in Fig. 8 for samples A, B and R. The profiles confirm the nominal thickness of the Mn-containing layers (30 nm) and are consistent with the Mn concentration established from the saturation moment at 2 K (2.4 and 2.5% for samples A and B, respectively, as given in the main text).

The Bi₂S₃ powder (99%) and Te (99.8%) were purchased from Sigma-Aldrich and used directly as evaporation sources. Bi₂S₃ and Te films were deposited using the same thermal evaporator via a standard procedure. The substrate temperature was maintained at RT, and the vacuum pressure before evaporation was ~3 × 10⁻⁶ Torr. The distance between the substrate and Bi₂S₃/Te-loaded tungsten boat was ~20 cm. The thickness of the Bi₂S₃/Te film was monitored during deposition. The as-deposited samples were then annealed at different temperatures for 30 min in a N₂-filled glove box. The crystal structures of the films on glass were analyzed using XRD with Cu Kα radiation (Bruker D8 ADVANCE). AFM images were obtained using a Nanoscope V Multimode 8 (Bruker, Newark, DE, United States of America) on Si substrates. Optical absorption spectra were obtained using a UV–visible spectrophotometer (V-770, JASCO). Samples for HRTEM characterization were prepared using a focused ion beam (FIB). The images and FFT patterns were obtained using HRTEM (JEOL JEM 2100 F). XPS analysis was performed using a PHI 5000 VersaProbe instrument (Ulvac-PHI, Japan). The depth element distribution was measured by SIMS (IMS 6 F, CAMECA). The Hall measurements of the films were performed in an N₂-filled glove box using the van der Pauw method with a 0.51 T magnet at RT.