论文标题
在二维WS2（1-X）SE2X合金中间接到直接带隙跨界
Indirect to direct band gap crossover in two-dimensional WS2(1-x)Se2x alloys
论文作者
论文摘要
在原子较薄的过渡金属二进制二进制元素化半导体中，随着厚度降至一个单层，间接到直接带隙有一个交叉，随着光致发光信号的快速增加。在这里，我们表明，对于WS2（1-X）SE2X的不同合金组成，这种趋势可能会受到合金含量的显着影响，并且我们证明了具有最高SE比的样品会大大降低效果。对于双层WS2（1-X）SE2X（x = 0.8），发现最高的微型PL强度，其最大值的最大值仅降低了2倍。为了更好地理解这一因素，并探索了WS2（1-X）SE2X的层依赖性带结构的演化，我们进行了一项纳米角度分辨的光发射光谱研究，并结合了第一原理计算。我们发现，双层WS2（1-X）SE2X（x = 0.8）的高微PL值是由于直接和间接光学跃迁的叠加造成的。 WS2（1-X）SE2X中这种特殊的高PL强度为频谱可调的发光设备打开了道路。
In atomically thin transition metal dichalcogenide semiconductors, there is a crossover from indirect to direct bandgap as the thickness drops to one monolayer, which comes with a fast increase of the photoluminescence signal. Here, we show that for different alloy compositions of WS2(1-x)Se2x this trend may be significantly affected by the alloy content and we demonstrate that the sample with the highest Se ratio presents a strongly reduced effect. The highest micro-PL intensity is found for bilayer WS2(1-x)Se2x (x = 0.8) with a decrease of its maximum value by only a factor of 2 when passing from mono- to bi-layer. To better understand this factor and explore the layer-dependent band structure evolution of WS2(1-x)Se2x, we performed a nano-angle resolved photoemission spectroscopy study coupled with first-principles calculations. We find that the high micro-PL value for bilayer WS2(1-x)Se2x (x = 0.8) is due to the overlay of direct and indirect optical transitions. This peculiar high PL intensity in WS2(1-x)Se2x opens the way for spectrally tunable light-emitting devices.
