α-四噻吩薄膜的生长及性能研究

利用原子力显微镜(AFM)、X射线衍射仪(XRD)研究了在氧化硅衬底上生长的α-四噻吩(α-4T)薄膜的表面形貌及分子取向。在低温下,获得了大尺寸、高有序的α-4T薄膜,为横向生长模式。衬底温度35 ℃以上转为纵向生长模式。晶体结构分析发现,α-4T薄膜属于单斜晶系,分子c-轴垂直基板排列。强的衍射峰和高有序的衍射峰意味着α-4T薄膜具有高的有序性和结晶性。电性能研究发现,提高衬底温度有利于提高薄膜的迁移率,衬底温度为35 ℃时器件迁移率为3.53×10^-2 cm²·V^-1·s^-1。但衬底温度进一步增加,迁移率反而下降,与原子力分析结果一致。低温退火可以降低器件的亚阈值陡度,从13.27 V·dec^-1降低到3.83 V·dec^-1,使器件的界面缺陷降低,电性能提高。

Growth and Performance of α-quaterthiophene Film

Surface morphology and molecular orientation of α-quaterthiophene (α-4T) thin films on silicon dioxide (SiO₂) substrate were investigated by atomic force microscopy (AFM) and X-ray diffraction (XRD). At low substrate temperature, the large-size domain and high-order α-quaterthiophene (α-4T) thin film was obtained. The α-4T film exhibits the horizontal growth mode at low substrate temperature, but changes to the vertical growth mode above 35 ℃. By XRD analysis, it is found that the α-4T thin film adopts a monoclinic system, and the molecule c-axis is perpendicular to the substrate. The strong diffraction peaks and the high order diffraction peaks reveal that the films possess high crystallinity and order. In the electrical performance, the mobility increases with the increasing of the substrate temperature, and the mobility of α-4T device is 3.53×10^-2 cm²·V^-1·s^-1 at 35 ℃. But the mobility of α-4T film decreases above 35 ℃. The results are in accordance with AFM analysis. The subthreshold gradient is reduced from 13.27 to 3.83 V·dec^-1 by annealing at low temperature. The results imply that the interface defects are reduced and the electrical performances are greatly improved.