Shahahmadi S A, Yeganeh B, Huda N, Asim N, Hafidz M, Alam M M, Alothman Z A, Sopian K, Amin N
J Nanosci Nanotechnol. 2015 Nov;15(11):9275-80. doi: 10.1166/jnn.2015.11412.
Non-hydrogenated amorphous Silicon-Germanium (a-SiGe) thin films were deposited at two different base pressures by RF magnetron co-sputtering. Moreover, an ex-situ thermal annealing was carried out to investigate the material properties to be suitable as the bottom cell of multi-junction solar cells. Compositional study of the films using EDX showed Ge-rich thin films with 75 atomic% of Ge. XRD reflection study implied that all samples were entirely amorphous in nature. However, a significant improvement of morphology possibly due to low base pressure was observed while thermal annealing caused peening and reduction of surface inhomogeneity in both as-sputtered films. UV-VIS-IR analysis confirmed the FESEM results. The highest transmittance was observed in the as-deposited sample grown at 4 x 10(-5) Torr, which however reduced after thermal annealing. Tauc's model was implied for band gap determination and band gap energy as low as 1.07 eV was found in the annealed sample grown at lower base pressure (4 x 10(-6) Torr). Electrical properties of films were investigated by Hall effect measurement system and results found the reduction of resistivity with the same trend of optical band gap energy.
通过射频磁控共溅射在两种不同的基压下沉积了非氢化非晶硅锗（a-SiGe）薄膜。此外，进行了非原位热退火以研究其作为多结太阳能电池底部电池的适用性。使用能谱仪（EDX）对薄膜进行成分研究，结果显示富锗薄膜中锗的原子百分比为75%。X射线衍射（XRD）反射研究表明所有样品本质上完全是非晶态的。然而，观察到由于低基压可能导致薄膜形态有显著改善，而热退火导致溅射态薄膜出现喷丸现象并降低了表面不均匀性。紫外-可见-红外（UV-VIS-IR）分析证实了场发射扫描电子显微镜（FESEM）的结果。在4×10⁻⁵托下生长的沉积态样品中观察到最高的透过率，不过热退火后透过率降低。采用陶克（Tauc）模型确定带隙，在较低基压（4×10⁻⁶托）下生长的退火样品中发现带隙能量低至1.07电子伏特。通过霍尔效应测量系统研究了薄膜的电学性能，结果发现电阻率的降低与光学带隙能量具有相同的趋势。
