Two-dimensional (2D) transition metal phosphides (TMPs) are predicted with many novel properties and various applications. As a member of TMPs family, molybdenum phosphide (MoP) exhibits many exotic physicochemical properties. However, the synthesis of high-quality 2D MoP single crystals is not reported due to the lack of reliable fabrication method, which limits the exploration of 2D MoP. Here, we report the growth of high-quality ultrathin MoP single crystals with thickness down to 10 nm on liquid metals via chemical vapor deposition (CVD). The smooth surface of liquid Ga is regarded as a suitable growth substrate for producing 2D MoP single crystals. The Mo source diffuses toward the Ga surface due to the high surface energy to react with phosphorus source, thus to fabricate ultrathin MoP single crystals. Then, we study the second harmonic generation (SHG) of 2D MoP for the first time due to its intrinsic non-centrosymmetric structure. Our study provides an new approach to synthesize and explore other 2D TMPs for future applications.

二维（2D）过渡金属磷化物（TMP）预计具有许多新颖的性质和各种应用。作为TMPs家族的一员，磷化钼（MoP）表现出许多特殊的理化性质。然而，由于缺乏可靠的制造方法，没有报道高质量2D MoP单晶的合成，这限制了2D MoP的探索。在这里，我们报告了液态金属通过以下途径生长出厚度低至10 nm的高质量超薄MoP单晶：化学气相沉积（CVD）。液体Ga的光滑表面被认为是用于生产2D MoP单晶的合适生长衬底。Mo源由于高表面能而向Ga表面扩散，与磷源发生反应，从而制造出超薄的MoP单晶。然后，由于其固有的非中心对称结构，我们首次研究了二维MoP的二次谐波生成（SHG）。我们的研究提供了一种合成和探索其他2D TMP的新方法，以供将来应用。