1Department of Physics, Beijing Key Laboratory of Opto-Electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872 2Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190
Abstract：We report the growth process of FeTe$_{1-x}$Se$_x$ ($0\le x \le 1$) monolayer films on SrTiO$_{3}$ (STO) substrates through molecular beam epitaxy and discuss the possible ways to improve the film quality. By exploring the parameters of substrate treatment, growth control and post growth annealing, we successfully obtain a series of FeTe$_{1-x}$Se$_x$ monolayer films. In the whole growth process, we find the significance of the temperature control through surface roughness monitored by the reflection high-energy electron diffraction and scanning tunneling microscopy. We obtain the best quality of FeSe monolayer films with the STO substrate treated at $T=900$–$950^{\circ\!}$C before growth, the FeSe deposited at $T=310^{\circ\!}$C during growth and annealed at $T=380^{\circ\!}$C after growth. For FeTe$_{1-x}$Se$_x$ ($x < 1$), both the growth temperature and annealing temperature decrease to $T=260^{\circ\!}$C. According to the angle-resolved photoemission spectroscopy measurements, the superconductivity of the FeTe$_{1-x}$Se$_x$ film is robust and insensitive to Se concentration. All the above are instructive for further investigations of the superconductivity in FeTe$_{1-x}$Se$_x$ films.
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2017, Vol. 34 
