| 摘要: | 我們使用了分子動力學模擬和模擬退火方法來研究石墨烯的磊晶成長過程和石墨 烯 納米帶(6H - SiC(0001))的熱穩定性質。為了理解其背後機制,我們使用了兩種 勢 能 作 為 我 們 的 參 數 , 即 目 前 廣 泛 被 應 用 的 Tersoff 勢 能 [Phys 。 Rev 。 B 39 , 5566 ( 1989 ) ] , 以 及 由 Erhart 和 Albe 提 出 的 Tersoff 勢 能 修 正 的 版 本 [Phys。 Rev。 B 71,035211-1(2005)]。我們發現,一般狀況下第二個版本的勢能 在預測石墨烯 開始成長在基板上的溫 ,會和實驗結果比較一致。我們分析了石墨 度 烯 的碳原子平均鍵距,徑向分布函數,束縛能以及基板和石墨烯 的間距來確認模擬 結果的合理性。石墨烯 結構出現的溫 1325K 和實驗上預測的溫度非常一致。至於 度 熱穩定度方面,我們分析了無限大石墨 烯 層在靠近 SiC 基板的一些表面型態學上 的特性,和目前文獻上的結果是一致的。最後,我們得到了一個臨界退火溫度 , 2000K。如果系統溫度低於臨界溫度,石墨緩衝層會比較穩定。如果大於這個溫度, 緩衝層開始會有從基板向上傾斜的趨勢。 The molecular dynamics simulation and simulated annealing method were applied to study the growth process of graphene and the thermal stability of layered graphene nanoribbons on 6H-SiC(0001) substrate. With an intention to understand the mechanisms that govern these panoramas, we tested two empirical potentials, i.e. the widely used Tersoff potential [Phys. Rev. B 39, 5566 (1989)] and its more refined version published years later by Erhart and Albe [Phys. Rev. B 71, 035211-1 (2005)]. We found that the modified Tersoff potential communicated by Erhart and Albe is generally more banausic for growing layered graphene on 6H-SiC substrate for the annealing temperature at which the graphene structure comes into view is very close to that observed in epitaxially grown graphene experiments. We evaluate our grown layered graphene by checking the reasonableness of the average carbon-carbon bond- length, pair correlation function, binding energy and also comparing with the experimentally grown epitaxial graphene the distances among the overlaid layers of graphene and substrate surface. The annealing temperature we obtained at 1325 K at which the graphitic structure just comes into view is reasonably close to the experimentally observed pit formation. On the thermal stability of layered graphene, the characteristics of the surface morphology of an infinite graphene sheet that we positioned near SiC substrate are consistent with other simulation works. Most importantly we obtained a threshold annealing temperature at around 2000 K below which the structural behavior of the carbon buffer layer is thermally stable and above which one sees the graphitic structures show tendency to slant up from the substrate. |
