Nanotribological properties of 2-D MoS_2 on different substrates made by atomic layer deposition (ALD)

摘要

The friction influence of 2-D molybdenum disulfide (MoS2) films deposited on different substrates (Si, SiO2 and Al2O3) by atomic layer deposition (ALD) has been investigated. All of the three substrates showed a trend of decreasing friction with increasing number of layers of MoS2, but the friction leveled off for more than 6 layers samples. Comparing these 2-D MoS2 films with each other, MoS2 on the Al2O3 possesses the lowest friction, while MoS2 on the Si possesses the highest one, owing to effect of substrate on the specific self-limiting reaction in ALD process. At the same time, the friction of the monolayer MoS2 is strongest affected by sulfur deficient. As the number of layers increases, the influence of the substrate on the friction of MoS2 can be approximately characterized by the work of adhesion. Greater work of adhesion corresponds to a higher friction force. When the thickness is more than 6 layers, the substrate effect disappears gradually. Moreover, the friction of 2-D MoS2 could be controlled near linearly by changing plasma treatment time within the range from 1 to 20 s, which suggests a possible way for the friction control of 2-D MoS2 on different substrate quasi-qualitatively or even qualitatively.