Microstructure characterization of semiconducting iron disilicide thin films by using the HARECXS and the CBED methods

本研究采用溅射法在平面和图形化Si（001）衬底上制备了β-FeSi_2外延薄膜<Fe>，并利用透射电子显微镜（TEM）对薄膜的微观结构进行了表征。获得了以下结果。(1)In在T_s=500℃，V_s =0.02 nm/s条件下，沉积在平面Si（001）衬底上的薄膜中形成了平底形的β-FeSi_2和圆底形的α-FeSi_2沉淀<Fe>。β-FeSi_2在Si基体中选择向（001）_i面外延<Si>生长，而α-FeSi_2在Si基体中选择向{111}_i面<Si>外延生长。当T_s=350℃，V_s <Fe>=0.01 nm/s时，在Si（001）衬底上外延形成连续的β-FeSi_2层，而没有形成α-FeSi_2。较低的温度和较高的Fe浓度抑制了α-FeSi_2的生成，促进了β-FeSi_2的生成。(2)In沉积在图案化Si（001）衬底上的薄膜，在图案化衬底的顶部和底部都有β-和α-FeSi_2相析出，而在侧壁只有α-FeSi_2相析出。FeSi_2沉淀物的外延生长不仅受生长条件的影响，而且受几何条件的影响。(3)In在Cu介导的Si（001）衬底上沉积的薄膜，改善了β-FeSi_2晶粒和异质界面的非辐射复合中心，从而显著提高了β-FeSi_2晶粒的发光强度。（4）利用电子衍射的ALCHEMI（原子定位沟道增强微区分析）方法研究了Cu介导的Si（001）衬底上生长的β-FeSi_2薄膜的原子构型。在β-FeSi_2薄膜中，Cu原子倾向于占据Fe位。（5）成功地测量了β-FeSi_2晶粒和Si衬底上清晰的会聚束电子衍射（CBED）花样，用以估算异质界面附近的晶格应变。

In this study, epitaxial β-FeSi_2 films were prepared by sputtering on the flat and the patterned Si(001) substrates under various substrate temperatures (T_s) with deposition rates of Fe (V_<Fe>), and the microstructures of these films were characterized by transmission electron microscopy (TEM). The following results were obtained.(1)In the film deposited on the flat Si(001) substrate, precipitates of flat-bottom shaped β-FeSi_2 and those of round-bottom shaped α-FeSi2 are formed at T_s=500℃ and V_<Fe>=0.02 nm/s. The β-FeSi_2 adopts the epitaxy to (001)_<Si>, plane, while α-FeSi_2 selects the epitaxy to {111}_<Si>, planes inside the Si matrix. At T_s=350℃ and V_<Fe>=0.01 nm/s, a continuous β-FeSi_2 layer are formed epitaxially on the Si(001) substrate without forming α-FeSi_2. The lower temperature and the higher Fe-concentration suppress the formation of a-FeSi_2 and promote the formation of β-FeSi_2.(2)In the film deposited on the patterned Si(001) substrate, both β-and α-FeSi_2 precipitates are formed in the top-hills and the valleys of the patterned substrate, while only α-FeSi_2 precipitates are formed in the sidewalls. Not only the growth conditions but also geometric situations affect strongly the epitaxial growth of FeSi_2 precipitates.(3)In the film deposited on Cu-mediated Si(001) substrate, non-radiative recombination centers in the β-FeSi_2 grains and the hetero-interface are improved, and then PL intensity from the β-FeSi_2 grains can be increased significantly.(4)ALCHEMI (atom location by channeling enhanced microanalysis) method of electron diffraction was employed to study the atomic configuration of the β-FeSi_2 film grown on Cu-mediated Si(001) substrate. In the β-FeSi_2 film, Cu atoms tend to occupy the Fe-site.(5)Clear CBED (convergent beam electron diffraction) patterns from the β-FeSi_2 grain and the Si substrate were measured successfully, in order to estimate the lattice strain near the hetero-interface.