因此，我正在尝试重新创建下面附加的图像。我已经完成了大部分结构，但我不知道如何使用阴影在右侧图上创建形状。我还想能够更改阴影的颜色，例如浅灰色或深灰色。我该怎么做？
\documentclass[tikz,border=3mm]{standalone}
\usepackage{tikz}
\usepackage{amsmath} %Note I do not know what other packages are necessary since I have my own package that already has everything I need in it.
\begin{document}
\begin{tikzpicture}
\draw[Latex-Latex,thick] (0,5.5) node[above]{$E$/eV} -- (0,0) -- (4,0) -- (4,5.5);
\draw[thick,-Latex] (4.5,5.5) -- (4.5,0) -- (8.5,0);
\draw[thick] (0,-0.1) node[below]{0} -- (0,0.1);
\draw (2,-0.1) node[below]{$k$};
\draw[thick] (4,-0.1) node[below]{$\frac{\pi}{a}$} -- (4,0.1);
\draw (6.5,-0.1) node[below]{\textsc{dos}, $N(E)$};
\draw[dotted,thick] (0,4) -- (8.5,4) node[right]{$E_F$};
\draw[thick] (0,0.25) ..controls +(0:2.5) and +(180:1.5).. (4,1.5)
node[pos=0.75,inner sep=0pt](s){};
\draw[thick] (0,3.4) ..controls +(0:3) and +(180:1.5).. (4,3.65)
node[pos=0.75,inner sep=0pt](px){};
\draw[thick] (0,3.5) ..controls +(0:3.0) and +(180:1.5).. (4,3.75)
node[pos=0.75,inner sep=0pt](py){};
\draw[thick] (0,4.5) ..controls +(0:3) and +(180:1.5).. (4,3)
node[pos=0.75,inner sep=0pt](pz){};
\node[xshift=-2em] at (s) {$2s$};
\node[] at (0.8,3.1) {$2p_x$, $2p_y$};
\node[] at (0.4,4.8) {$2p_z$};
\end{tikzpicture}
\end{document}
图像：
另一个：
