Nonequilibrium Structural Evolution of Q-Carbon and Interfaces
Nonequilibrium Structural Evolution of Q-Carbon and Interfaces
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DOI：
10.1021/acsami.9b17428
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发表时间：
2020-01-08
影响因子：
9.5
通讯作者：
Narayan, Jagdish
中科院分区：
文献类型：
--
作者：
Sachan, Ritesh;Gupta, Siddharth;Narayan, Jagdish
Q - 碳是一种密集堆积的亚稳态碳相，它是通过在过冷状态下对碳熔体进行超快淬火而形成的。淬火后，金刚石四面体随机堆积，堆积效率>80%。这一发现为沿着纳秒脉冲激光退火的高度非平衡路径制造各种有趣的异质结构开辟了一条途径。在本研究中，我们展示了Q - 碳/α - 碳和Q - 碳/金刚石异质结构的演变，这些结构具有原子级清晰的界面，可通过改变过冷碳熔体的凝固速率来控制。这种结构由超硬的Q - 碳（约80%为sp³，其余为sp²）以及在惰性c - Al₂O₃衬底上的一层软的α - 碳（约40%为sp³）组成。通过高分辨率扫描透射电子显微镜和拉曼光谱分析，我们展示了具有明显不同原子和电子结构的高密度Q - 碳/α - 碳双层结构的形成。激光 - 固体相互作用模拟以及原子级从头算建模进一步证实了碳熔体通过在衬底附近实现最大过冷度而转变为Q - 碳，并随着再生长速度的降低进一步转变为α - 碳。
Q-carbon is a densely packed metastable phase of carbon formed by ultrafast quenching of carbon melt in a super-undercooled state. After quenching, diamond tetrahedra are randomly packed with >80% packing efficiency. This discovery has opened a pathway to fabricate various interesting heterostructures following the highly nonequilibrium route of nanosecond pulsed laser annealing. In the present work, we demonstrate the evolution of Q-carbon/alpha-carbon and Q-carbon/diamond heterostructures with atomically sharp interfaces, controlled via varying solidification rates of the undercooled C melt. This structure consists of ultrahard Q-carbon (similar to 80% sp(3) and rest sp(2)) with an overlayer of soft alpha-carbon (similar to 40% sp(3)) on the inert c-Al2O3 substrate. Using high-resolution scanning transmission electron microscopy and Raman spectroscopy analysis, we present the formation of the highly dense Q-carbon/alpha-carbon bilayer structure with distinctly different atomic and electronic structures. The laser-solid interaction simulations coupled with atomistic ab initio modeling further confirm the conversion of C melt into Q-carbon by achieving maximum undercooling near the substrate and further into alpha-carbon with a decrease in regrowth velocity (