SiGe nanostructures has attracted much attention in recent years in order to realize high-efficient thermoelectric devices due to carrier confinement effect and alloying effect [1,2]. For this purpose, in the present study, we fabricated a compositionally-homogeneous thin SGOI (SiGe on insulator) substrate by simple sputtering and physical evaporation techniques and characterized its crystallographic properties and thermal conductivity. A 30-nm-thick Si layer was sputtered on a thermally-oxidized Si wafer (SiO₂ thickness: 103 nm), followed by the deposition of a thin Ge film with a thickness of 30 nm, at room temperature. Afterwards, Si-Ge diffusion was carried out by a rapid thermal annealing process at 880^oC for 10 and 120 min. The prepared SGOI substrates were characterized by means of XRD, SEM, EPMA, Raman spectroscopy, XPS, and AFM, which showed the formation of a compositionally-homogeneous poly-crystalline Si_1-xGe_x layer with x=0.45 (thickness: 60 nm). The thermal conductivity was determined by a picosecond time-domain thermoreflectance (TDTR) method at room temperature and shown in the figure, as a function of annealing time. For a reference, the measured values of our as-deposited Ge/Si layer and a commercial single-crystalline SGOI substrate (x=0.5) are also plotted. It is found that our poly-crystalline SGOI layer has lower thermal conductivity of 0.87 W/mK, compared with that of a single-crystalline SGOI 1.43 W/mK.

[1] H. Kim, I. Kim, H.-J. Choi, and W. Kim, Appl. Phys. Lett., 96 (2010) 233106.

[2] R. Basu, S. Bhattacharya, R. Bhatt, M. Roy, S. Ahmad, A. Singh, M. Navaneethan, Y. Hayakawa, D. K. Aswal, and S. K. Gupta, J. Mater. Chem. A, 2 (2014) 6922.