Laser annealing for radiatively broadened MoSe2 grown by chemical vapor deposition

We report on a laser annealing procedure which greatly improves the quality of suspended monolayers of chemical vapor deposition grown MoSe2 . Annealing with a green laser locally heats the suspended flake to approximately 600 K, which both removes contaminants and reduces strain gradients. At 4 K, we observe linewidths as narrow as 3.5 meV (1.6 nm) full width at half maximum for both photoluminescence and reflection. Large peak reflectances up to 47% are also observed. These values are comparable to those of the highest quality hexagonal boron nitride encapsulated samples. We demonstrate that this laser annealing process can yield highly spatially homogeneous samples, with the length scale of the homogeneity limited primarily by the size of the suspended area. Annealed regions are very stable, exhibiting negligible deterioration over 24 h at cryogenic temperatures. The annealing method is also very repeatable, with substantial improvements of sample quality on every spot (>40) tested.

我们报道了一种激光退火工艺，该工艺极大地提高了化学气相沉积生长的二硒化钼悬浮单层的质量。用绿色激光退火可将悬浮薄片局部加热到约600 K，这既去除了污染物又降低了应变梯度。在4 K时，我们观察到光致发光和反射的半高全宽线宽窄至3.5 meV（1.6 nm）。还观察到高达47%的大峰值反射率。这些值与最高质量的六方氮化硼封装样品的值相当。我们证明这种激光退火工艺可以产生高度空间均匀的样品，均匀性的长度尺度主要受悬浮区域的大小限制。退火区域非常稳定，在低温下24小时内几乎没有劣化。退火方法也具有很高的重复性，在测试的每个点（>40个）上样品质量都有显著提高。