弱侷域效應與交互作用對於石墨烯凡得瓦異質結構中載子傳輸特性的影響

Abstract

弱局域效應(weak localization)為無序(disorder)系統中電子散射(electron scattering)而產生量子干擾傳輸(quantum interference transport)的結果。 在這篇論文裡，我們製作了由堆疊(stacked)氮化硼(h-BN)與硒化銦(InSe)而成的凡得瓦異質結構(van der Waals heterostructure )的堆疊石墨烯元件並與無堆疊石墨烯元件(graphene device)比較，發現堆疊石墨烯與無堆疊石墨烯(pure graphene device)比起來有較強的弱局域效應(weak localization)，並分別以麥肯(McCann)模型與HLM模型擬和(fitting)，在我們樣品中兩者的結果會非常相近，表示可以省略麥肯模型中谷內散射長度(intravalley scattering length)項的貢獻，另外堆疊會造成相干長度(Coherence length)變短與谷間散射(intervalley scattering length)長度變長，可能是來自非彈性散射(inelastic scattering)增加與原子層級的位能變化(atomically sharp scatters)被抑制。由溫度對相干長度(Coherence length)的對數座標斜率得知，電子電子交互作用(electron-electron interaction)在兩個樣品中皆有不同程度的貢獻，但是由於不夠強的溫度依賴性推測應該有其他的機制參與。

Weak localization is a result of electron scattering produced quantum interference transport in a disordered system. In this thesis, we compare a stacking graphene device, which is a van der Waals heterostructure stacked with h-BN and InSe, with a pure graphene device. Upon comparison, we find that the pure graphene device has a stronger weak localization effect. We then fitted our data with two different models, the McCann model and the HLN model, which showed similar results implying that the intravalley scattering length in the McCann model may be neglected. On a side note, the heterostructure may cause the coherence length to be lowered and the intervalley scattering length to be extended. The two effects mentioned above may be caused by increase of inelastic scattering and suppression of atomically sharp scattering events, respectively. From the logarithmic scale graph of temperature versus coherence length, we find that electron-electron interactions of the two devices have different amounts of significance. However, according to the lack of strong temperature dependence, we suggest that there could be some other mechanisms involved.