Cheng Fei, Lee Chien-Ju, Choi Junho, Wang Chun-Yuan, Zhang Qiang, Zhang Hui, Gwo Shangjr, Chang Wen-Hao, Li Xiaoqin, Shih Chih-Kang
Department of Physics , University of Texas at Austin , Austin , Texas 78712 United States.
Department of Electrophysics , National Chiao Tung University , Hsinchu 30010 , Taiwan.
ACS Appl Mater Interfaces. 2019 Jan 23;11(3):3189-3195. doi: 10.1021/acsami.8b16667. Epub 2019 Jan 14.
Single crystalline Ag films on dielectric substrates have received tremendous attention recently due to their technological potentials as low loss plasmonic materials. Two different growth approaches have been used to produce single crystalline Ag films previously. One approach is based on repetitive cycles of a two-step process (low temperature deposition followed by RT annealing) using molecular beam epitaxy (MBE), which is extremely time-consuming due to the need for repeat growth cycles. Another approach is based on rapid e-beam deposition which is capable of growing thick single crystalline Ag films (>300 nm) but lacks the precision in thickness control of thin epitaxial films. Here, we report a universal approach to grow atomically smooth epitaxial Ag films by eliminating the repetitive cycles used in the previous two-step MBE method while maintaining the precise thickness control from a few monolayers to the optically thick regime, thus overcoming the limitations of the two aforementioned methods. In addition, we develop an in situ growth of aluminum oxide as the capping layer to protect the epitaxial Ag films. The quality of the epitaxial Ag films was evaluated using a variety of techniques, and the superior optical performance of the films is demonstrated by measuring the propagation length of surface plasmon polaritons (∼80 μm at 632 nm) as well as their capability to support a plasmonic nanolaser in infrared incorporating an InGaAsP quantum well as the gain media.
近年来，介电衬底上的单晶银膜因其作为低损耗等离子体材料的技术潜力而受到了极大关注。此前曾使用两种不同的生长方法来制备单晶银膜。一种方法基于分子束外延（MBE）的两步过程（低温沉积后进行室温退火）的重复循环，由于需要重复生长循环，这种方法极其耗时。另一种方法基于快速电子束沉积，它能够生长厚的单晶银膜（>300 nm），但在薄外延膜的厚度控制方面缺乏精度。在此，我们报告了一种通用方法，通过消除先前两步MBE方法中使用的重复循环，同时在从几个单层到光学厚区域保持精确的厚度控制，来生长原子级光滑的外延银膜，从而克服了上述两种方法的局限性。此外，我们开发了一种原位生长氧化铝作为覆盖层来保护外延银膜。使用多种技术对外延银膜的质量进行了评估，通过测量表面等离激元极化激元的传播长度（在632 nm处约为80 μm）以及它们在以InGaAsP量子阱作为增益介质的红外波段支持等离子体纳米激光器的能力，证明了这些膜具有优异的光学性能。
