Time-of-flight mass spectrometry of particle emission during irradiation with slow, highly charged ions

Abstract

We describe a setup for the analysis of secondary ions and neutrals emitted from solid surfaces and two-dimensional materials during irradiation with highly charged ions. The ultra-high-vacuum setup consists of an electron beam ion source to produce bunches of ions with various charge states q (e.g. Xe 1+ -Xe 46+ ) and thus potential energies, a deceleration/acceleration section to tune the kinetic energy of the ions in the range of 5 keV to 20 x q keV, a sample stage for laser-cleaning and positioning of freestanding as well as supported samples, a pulsed excimer laser for postionization of sputtered neutrals, and a reflectron type time-of-flight mass spectrometer enabling us to analyze mass and velocity distributions of the emitted particles. With our setup, contributions from potential and kinetic energy deposition can be studied independently of each other. Charge dependent experiments conducted at a constant kinetic energy show a clear threshold for the emission of secondary ions from SrTiO 3 . Data taken with the same projectile charge state, but at a different kinetic energy, reveals a difference in the ratio of emitted particles from MoS 2 . In addition, first results are presented, demonstrating how velocity distributions can be measured with the new setup.

Model for Nanopore Formation in Two-Dimensional Materials by Impact of Highly Charged Ions

“…Furthermore, atoms are accelerated predominantly in the plane of the layer which transfers a considerable fraction of their kinetic energy on nearby atoms, thus “heating” the lattice (Figure a). A different heating mechanism (strong electron–phonon coupling not present in our model) has been proposed recently to explain the velocity distribution of Mo atoms released from MoS 2 supported on Au and SiO 2 . In the threshold region in our study (shaded area in Figure ) only a few atoms are sputtered (positive energies in Figure b) with small kinetic energies leaving behind atoms still bound in the crystal lattice (at negative energies) but with one or two neighboring atoms missing with binding energies of around −0.3 and −0.15 au, respectively.…”

Velocity distributions of particles sputtered from supported two-dimensional MoS2 during highly charged ion irradiation

“…The potential parameters were obtained by first-principles simulations, where ε denotes the interaction strength, σ is the zero-crossing distance of the potential with the minimum being at r min = 2 1/6 σ , and r c defines the cut-off radius. been described in detail elsewhere [19], and here we will only briefly summarize its main capabilities. Our ultrahigh vacuum setup is based on a reflectron type time-of-flight mass spectrometer, designed to analyze secondary particles emitted during ion irradiation.…”

“…To select and modify the beam parameters (see supporting information for detailed beam characterization) a bending sector magnet and a deceleration section described in Ref. [19] have been used. Due to ion irradiation sputtered sample particles are postionized by an Excimer laser (ExciStar XS by Coherent) with a wavelength of 157 nm.…”

Вероятность Ионизации Атомов, Распыленных При Бомбардировке Поверхности Металлов Одно- И Многозарядными Ионами

“…Такая возможность возникает при бомбардировке металлов многозарядными ионами (МЗИ). Недавно было установлено, что по сравнению с однозарядными ионами взаимодействие МЗИ с поверхностью металлов приводит к существенному увеличению интенсивности выхода распыленных атомных ионов [7,8] и возбужденных атомов [9]. Эти результаты свидетельствуют о возможности повышения чувствительности, а следовательно, и информативности методов диагностики поверхности при использовании МЗИ в качестве зондирующих пучков.…”