鍺在矽(111)-(7×7)結構上島嶼成長過程

The Growth of Ge on Si(111)-(7×7) Surface

蔡宗翰(ZONG-HAN TSAI)

指導教授 ： 門福國

國立中正大學/理學院/物理學系/碩士(2016年)

摘要

我們的研究目標是將鍺沉積於兩種截然不同的Si(111)-(7×7)表面，一種是Si(111)-(7×7)表面上的階梯為均勻分布(regular)，另一種是Si(111)-(7×7)表面上的階梯有群聚的現象 (step-bunching)。造成此種差異的成因為去除Si(111)的氧化層後加熱直流電流的方向所導致，當加熱電流與台階方向為順向時，其表面為step-bunched表面，而當加熱電流與台階方向為反向時，其表面為regular表面。我們使用原子力顯微鏡與掃描式電子顯微鏡來研究在不同的溫度與退火時間下，沉積在Si(111)上鍺的形貌變化。
　　當將鍺沉積於300℃的Si(111)上時，我們發現鍺團簇會均勻的散佈在Si(111)的表面上。我們主要針對大型的鍺團簇去進行分析，發現大型鍺團簇的表面會由特定方向的面所構成，而我們推測為其特定方向的面可能是鍺團簇的最低能量表面。
　　在Si(111)溫度為500℃時磊晶鍺，發現磊晶的表面形貌有了極大的改變。在兩種不同的Si(111)表面上，鍺都會長成長度達微米尺寸的線狀結構，值得注意的是，鍺線總是會以平行台階的方式來成長。將在兩種不同基板上生成的鍺線做對比，我們發現Si(111)的台階為均勻分布時，鍺線的分布為隨機分布。而在Si(111)的台階有群聚現象的時候，鍺線會集中生長在台階群聚的地方，當我們將集中分布的鍺線做額外加熱處理後，鍺線有相互連接的情形發生，且鍺線長度明顯變長，其尺度可逾10 µm。
　　未經額外加熱處理的鍺線其表面形貌並不平整，而經由額外的加熱處理可平整鍺線的表面形貌，但鍺線在經過額外加熱處理後，其鍺線會外溢至平台上並產生大型的層狀結構。

關鍵字

鍺島嶼 ； 矽(111) ； 薄膜成長

並列摘要

We have studied the deposition of Ge on two types of Si(111)-(7×7) surfaces: one with regularly spaced steps and the other consisting of alternating structure of high step density region (step-bunch region) and a step-free terrace. The surface with step-bunching structure is induced by a DC current heating with electric current running in the step-down direction whereas the surface with evenly spaced steps has the heating current running in the step-up direction. Atomic force microscopy and scanning electron microscopy are employed to investigate the Si surfaces after Ge being deposited at different temperatures and annealing times.
　For deposition of Ge at 300°C, we have found that Ge clusters form uniformly on the Si surface, regardless of the types of the surfaces. Though we cannot resolve the detailed structure of small Ge clusters, the surfaces of large Ge clusters are composed of many facets, presumably low-energy surfaces of Ge.
　For 500°C deposition, the surface displays a completely different morphology where Ge wires on the order of ~µm in length form for both types of surfaces that we have studied. It is noted that the micron-size Ge wires always grow in the direction parallel to surface steps. For a surface with evenly spaced steps, the Ge wires distribute randomly. In comparison, the Ge wires form exclusively in the step-bunching region for the other type of surface. This directional growth indicates the diffusion of Ge atoms is highly anisotropic, a result of the presence of surface steps.
　The top layer of the Ge wire is rough, i.e., different regions have significant height differences, indicating the formation of a long Ge wire may result from the coalescence of short Ge wires. Annealing smoothens the wire’s outer layer.

並列關鍵字

Germanium island ； Silicon(111) ； The growth of thin film

參考文獻

黃奕誌, Dependence of growth morphology on atom beam’s angle of incidence: The investigation of MBE growth of Fe on silicon oxide, 國立中正大學物理學研究所碩士論文(2015)

Atomic Force Microscopy Lecture 7. http://slideplayer.com/slide/9702681/

Bruker AFM Probes

陳建融, Anomalous behavior of Si adatoms on Si(111)-(5×2)/Au surface,國立中正大學物理學研究所碩士論文(2015)

柯詠瀚, Effect of surface conditions on the distribution of Si adatoms on Si(111)-5×2/Au surface, 國立中正大學物理學研究所碩士論文(2015)