Investigation of the exit charge state distribution of highly charged ions transmitted through 2D materials

2D materials exhibit unique electronic and optical properties due to surface and quantum confinement effects [1]. To tailor the properties of 2D materials for a specific application ion beams may be used for implantation of foreign atoms or to deliberately introduce defects. The impact of energetic particles on a solid surface can result in a strong excitation of the electronic system, which leads to damage formation [2]. Highly charged ions (HCIs) provide a large amount of potential energy stored due to the ionization of dozens of electrons. With their high charge state q less or equal than Z they resemble a moving point charge creating a strong electric field in its vicinity. Freestanding 2D materials serve as ultimately thin solid targets for classical beam foil experiments giving insights not only into the charge exchange dynamics of the ions but also into the electronic response of a solid target to an ultrafast (fs) strong electric field pulse [3,4,5]. A large electron current density is present upon ion impact on a 2D material and thus surprisingly short neutralization times of only a few femtoseconds were determined by measuring the exit charge for different energies of incident slow HCIs on single layer graphene [3,4]. Here we extend our investigations to other 2D materials beyond graphene, namely MoS2 and hBN. They exhibit different structural and electronic properties, which have an influence on the neutralization process. Charge state distributions are recorded by utilization of a setup composed of deflector plates and a microchannel plate, which allows the measurement of low charge states and even neutralized ions. [1] W. Choi et al., Materials Today 20 (3) (2017). [2] F. Aumayr et al., J. Phys.: Condens. Matter. 23 (2011) 393001. [3] E. Gruber et al., Nat. Commun. 7, 13948 (2016). [4] R. A. Wilhelm et al., Phys. Rev. Lett. 119, 103401 (2017). [5] R. A. Wilhelm et al., Phys. Rev. Lett. 112, 153201 (2014).