Theoretical investigation about secondary deposition of thin-film formation by molecular dynamics simulation
The thin-film growth has been confirmed to be assembled by an enormous number of clusters in experiments of CVD. Sequence of clusters’ depositions proceeds to form the thin-film in short time as gas fluids through surface of substrate. Such growth mechanism has been mainly investigated on the basis of experiment. Due to immense cost of the experimental equipment and low level of current measurement technology, the comprehension about authentic effect of formation condition on properties of nanomaterial is limited in qualitative manner. Three quantitative items: flatness of primary deposition, adhesion between cluster and substrate, and degree of epitaxial growth were proposed to evaluate the property of thin-film. In this simulation, three different cluster sizes of 203, 653, and 1563 atoms with different velocities (0, 10, 100, 1000, and 3000 m/s) were deposited on a Cu(0 0 1) substrate whose temperatures were set between 300 and 1000 K. Four clusters and one cluster were used in primary deposition and secondary deposition, respectively. To increase initial velocity not only enhanced the speed of epitaxial growth, adhesion between clusters and substrate, but also increased the degree of epitaxy for primary deposition and secondary deposition. Exfoliation pattern of thin-film was profoundly dependent on initial velocity through comparison between adhesion of primary and secondary deposition. Moreover, the epitaxial growth became well as the temperature of substrate was raised, and the degree of epitaxy of small cluster was larger than that of larger cluster, no matter of primary and secondary deposition.
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