Control of the proton beam charge and energy in a laser-driven double-layer target was numerically investigated. Generally the proton beam charge is determined by the areal density σ=. nl of the second layer, while the accelerating field is governed by the substrate thickness L. From a series of one-dimensional particle-in-cell simulations over a broad range of σ and L, it was confirmed that those two control parameters do not interfere significantly, indicating the beam charge and energy can be separately controlled. We suggest self-assembly monolayers technique be used for the fabrication of the areal density of the second layer. ⓒ 2015 Elsevier B.V