MATLAB: Publication Quality Matlab Plot

graph

I am writing a research paper. But the Matlab graph are of very low resolution, in the sense that when it is copy pasted into MS Word, the colored lines are not properly visible.What should I do to make the graph clear? Example for the following program, I need to plot high resolution plot
 sys = tf([1],[1 4 5])
sys2 = tf([1],[1 4.1 5.1])
step(sys)
hold on
step(sys2)
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