Magneto-transport property of FeSe thin films prepared by selenization technique

本文研究了用硒化法在砷化镓衬底上制备的FeSe薄膜的磁输运和结构特性：(1)在砷化镓(001)衬底上制备了Fe_2Se_3/Fe/GaAs结构。亚硒化不是沉积过程，而是K-cell分子束提供的Se原子取代Fe原子的过程。衬底温度为400Torr，Se束压力为4×10~(-8)℃。(2)从电阻率和霍尔效应的测量中发现，FeSe薄膜的电阻率为ρ=1.1×10~(-4)；Ω_m，载流子(电子)密度为n=2.1×10~(-1)；在霍尔效应测量中，在外加磁场的相对低场区域，霍尔电阻率表现出与典型铁磁材料中观察到的异常霍尔效应相似的现象。从2theta(Omega)-psi扫描测量的x射线倒易空间图中发现，Fe_2Se_3的晶体结构是立方的，a=0.551 nm。Fe_2Se_3的立方结构很容易通过Fe_2Se_3反射的位置来理解，Fe_2Se_3反射位于比GaAs反射略低的2theta角。同时探测到了倒易空间中属于不同反射面的Fe2Se_3(022)和(113)反射。这表明Fe_2Se_3立方体不是沿层的平面方向取向的。

Magneto-transport and structural properties of FeSe thin films prepared on GaAs substrates by selenization technique were studied.(1) Fe_2Se_3/Fe/GaAs structures were prepared by a selenization of Fe films on GaAs (001) substrate. The selenization is not a deposition process, but replacing Fe atoms by Se atoms supplied as molecular beams from K-cell. The substrate temperature was 400℃ and Se beam pressure was 4×10^<-8> Torr. Fe_2Se_3 compound, which was different from bulk stable structures of Fe_3Se_4 and Fe_7Se_8, was obtained by this technique.(2) From the resistivity and Hall effect measurements, it was found that the resistivity of FeSe thin film was ρ=1.1×10^<-4> Ωm, and carrier (electron) density was n=2.1×10^<23> m^<-3>. At the relatively low field region of the applied external magnetic field in Hall effect measurement, Hall resistivity exhibited similar to the extraordinary Hall effect which was observed in typical ferromagnetic materials. Details on magneto-transport property including anisotropic feature due to the crystal structure are followed.(3) From the x-ray reciprocal space mapping measured by 2theta(omega)-psi scan, it was found that the crystal structure of Fe_2Se_3 is cubic with a=0.551 nm by fitting the Fe_2Se_3 reflections. The cubic structure of Fe_2Se_3 was easily understood by the positions of Fe_2Se_3 reflections which locate at slightly lower 2theta angles than GaAs reflections. Both of Fe_2Se_3 (022) and (113) reflections which belong to different reflection planes in the reciprocal space were detected simultaneously. This indicated that Fe_2Se_3 cubes are not oriented in-plane direction of the layer.