The dependence of the size distribution of the pulsed laser deposited micron sized particles from the laser fluence and its influence to the thickness of the deposited layer

摘要

During the pulsed laser deposition of Teflon the thin layer is built up by particles with dimensions from molecular to micrometer range deposited onto the substrate surface. With the knowledge of the size distribution of the deposited particles we used a model for simulating and predicting the growth of the thin film. An ArF excimer laser was used to deposit Teflon particles on the surface of a Silicon wafer under real PLD conditions. The target was pre-ablated by 1000 pulses, the pressure in the PLD chamber was 2 × 10~(-5) Torr and the substrate temperature was 250 ℃. The number of the particulates deposited by 10 laser pulses and their size distribution were determined by atomic force (AFM) and optical microscopes. Based on the AFM images the relation between the dimensions and volume of the investigated grains was also determined. At 3.2 J/ cm~2 laser fluence the size distribution of the particulates with dimensions above 500 nm could be well described with a first order exponential decay function having 2.38 μm decay constant. Below 100 nm the number of deposited Teflon grains increased by several orders of magnitude, however, their contribution to the total volume of the transferred material was found to be only about 2%. The results of the numerical simulations of the thin film growth were in good agreement with our previous PLD experiments. The minimum number of the pulses required to obtain a contiguous layer and its thickness could also be estimated.