No abstract

Sn eutectic melt was undercooled and spontaneously solidified in the encasement of a glass flux. Structure morphologies of the sample surface as well as inside the sample were systematically examined, and a critical undercooling of 130 K was clearly revealed for the alloy. Below the critical undercooling, coupled lamellar eutectics (a-Ni and b-Ni 3 Sn) dendritically grow in the undercooled melt. Beyond the critical undercooling, a-Ni dendrites first form during the early recalescence. b-Ni 3 Sn nucleates uniformly in the remaining liquid and then separately grows with a-Ni. Solidification of the remaining liquid into lamellar eutectics only occurs at the places in the sample surface layer where the space between the a-Ni dendrite arms is large enough. The finding that all the solidification structures at undercooling above 20 K comprise anomalous eutectics indicates that both coupled eutectic growth and decoupled dendritic growth in the rapid solidification can result in the anomalous eutectic formation. The results also indicate that it is feasible to measure the crystal growth velocity by observation of the recalescence front when undercooling exceeds 50 K for this alloy.

The nondestructive and clean transfer of 2D‐layered materials from growth onto target substrates is a key step in their practical applications. Some nonetching transfer methods are developed to avoid contaminations from chemical etchants, while the influences of other transfer media, such as the commonly used water, are rarely explored. Herein, a one‐step polymer‐free transfer of monolayer MoS2 from glass onto a graphite substrate by using only ultrapure water as the working medium is reported. Based on room‐temperature observations, it is revealed that the MoS2–graphite interface is not atomically flat due to the trapping of water clusters, and even extended ultrahigh‐vacuum annealing processes cannot easily remove the trapped water. More interestingly, the intensive scanning tunneling microscopy/spectroscopy investigations show that the interfacial water can be converted into an insulating layer by sample cooling down to ≈78 K, leading to a weakened interfacial interaction of MoS2/graphite and a more intrinsic bandgap of MoS2. This work hereby provides fundamental insights into the effect of wet‐transfer‐induced water intercalation on the structural and electronic properties of 2D‐layered materials, which should inspire the development of more clean transfer routes for achieving improved device performances.