How can I shift ymin to zero when values are near to zero?

Question

How can I shift ymin to zero when values are near to zero? I also try ymin=0 command but it does not work.

\begin{figure}[h]
\centering
\begin{tikzpicture}
\begin{axis}[
ybar, ymax=4,
enlargelimits=0.15,
legend style={at={(0.5,-0.20)},
anchor=north,legend columns=-1},
ylabel={Surface Roughness (nm)},
xlabel={Substrate},
symbolic x coords={Glass,Silicon,PEN},
xtick=data,
nodes near coords,
nodes near coords align={vertical},
]
\addplot [fill= white] coordinates {(Glass,2.4) (Silicon,1.1) (PEN,1.8)};
\addplot [fill = black] coordinates  {(Glass,1.1) (Silicon,0.2) (PEN,1.0)};

\legend{Profilometer,AFM}
\end{axis}
\end{tikzpicture} 
\caption{Substrate Vs IBD Surface Roughness(Avg)}
\label{Subvibd}
\end{figure}

Answer 1

Removing enlargelimits=0.15 and introducing ymin=0 again, would make the y-axis start from 0.