It was reported that massive scalar fields can form bound states around Kerr black holes (Herdeiro and Radu, Phys. Rev. Lett. 112:221101, 2014). These bound states are called scalar clouds; they have a real frequency ω=mΩH\documentclass[12pt]{minimal}
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\begin{document}$$\omega =m\Omega _\mathrm{H}$$\end{document}, where m\documentclass[12pt]{minimal}
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\begin{document}$$m$$\end{document} is the azimuthal index and ΩH\documentclass[12pt]{minimal}
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\begin{document}$$\Omega _\mathrm{H}$$\end{document} is the horizon angular velocity of Kerr black hole. In this paper, we study scalar clouds in a spherically symmetric background, i.e. charged stringy black holes, with the mirror-like boundary condition. These bound states satisfy the superradiant critical frequency condition ω=qΦH\documentclass[12pt]{minimal}
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\begin{document}$$\omega =q\Phi _\mathrm{H}$$\end{document} for a charged scalar field, where q\documentclass[12pt]{minimal}
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\begin{document}$$q$$\end{document} is the charge of the scalar field, and ΦH\documentclass[12pt]{minimal}
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\begin{document}$$\Phi _\mathrm{H}$$\end{document} is the horizon’s electrostatic potential. We show that, for the specific set of black hole and scalar field parameters, the clouds are only possible for specific mirror locations rm\documentclass[12pt]{minimal}
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\begin{document}$$r_\mathrm{m}$$\end{document}. It is shown that analytical results of the mirror location rm\documentclass[12pt]{minimal}
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\begin{document}$$r_\mathrm{m}$$\end{document} for the clouds perfectly coincide with numerical results in the qQ≪1\documentclass[12pt]{minimal}
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\begin{document}$$qQ\ll 1$$\end{document} regime. We also show that the scalar clouds are also possible when the mirror locations are close to the horizon. Finally, we provide an analytical calculation of the specific mirror locations rm\documentclass[12pt]{minimal}
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\begin{document}$$r_\mathrm{m}$$\end{document} for the scalar clouds in the qQ≫1\documentclass[12pt]{minimal}
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\begin{document}$$qQ\gg 1$$\end{document} regime.
