Energy Loss Of Hydrogen Ions Research Articles

Molecular dynamics simulation of silicon vacancy defects in silicon carbide by hydrogen ion implantation and subsequent annealing

Silicon vacancy defects in 4H-SiC are promising candidates for quantum technology. However, the fabrication of controlled atomistic defects in 4H-SiC is still a challenge. In this work, we used molecular dynamics (MD) simulations to study the mechanism of the evolution of silicon vacancy defects and damage during hydrogen ion implantation and subsequent annealing. By considering the electronic energy loss of hydrogen ions, the distribution of implanted hydrogen ions, and the atomic-scale mechanism of silicon vacancy defects and damage can be described more accurately. The results can observe the changing trend of silicon vacancy defects with the complete structure during the entire implantation and annealing process, and it is found that the local temperature generated by hydrogen ion implantation may affect the fluctuation of silicon vacancy defects. Besides, the yield of silicon vacancy defects can be improved by optimizing annealing conditions, and there is an optimal annealing temperature.

Electronic stopping power of hydrogen in HfO2 at the stopping maximum and below

Electronic energy loss of hydrogen ions in HfO2 was investigated in a wide energy range in the medium and low energy ion scattering regime. Experiments by Time-Of-Flight Medium-Energy Ion Scattering (TOF-MEIS) with proton and deuteron projectiles were performed in backscattering geometry for nm-films of HfO2 on Si with an ultrathin SiO2 interface layer prepared by ALD. At energies around the stopping maximum excellent agreement is found with earlier results from Behar et al. (2009) [45] and theoretical predictions. Towards lower energies discrepancies between experiment and calculations increase slightly. The low energy data exhibits excellent velocity proportionality and indicates the absence of clear effects due to distinct electronic states. Thus, no apparent velocity threshold can be extrapolated from the experiments within the uncertainty of present data. The magnitude of the energy loss is discussed in terms of a free-electron model and compared with the expected electron densities from plasmon frequencies.

Electronic stopping power of hydrogen in KCl at the stopping maximum and at very low energies

The electronic energy loss of hydrogen ions in KCl was investigated in a wide energy range. Thin films of KCl were evaporated on an Au/Si substrate. Rutherford Backscattering Spectrometry (RBS) was performed with protons and deuterons at energies from 30 to 400 keV/nucleon. At lower energies experiments were performed by Time-Of-Flight Low energy ion scattering (TOF-LEIS) again with proton and deuteron projectiles. Experimental results are compared to calculated/tabulated values for the electronic energy loss. Whereas at energies beyond the stopping maximum very good agreement is found, at lower ion energies discrepancies between experiment and calculations increase. At very low ion velocities the extrapolated stopping cross section ε predicts vanishing electronic energy loss at energies below 100 eV/nucleon.

Apparent Velocity Threshold in the Electronic Stopping of Slow Hydrogen Ions in LiF

The electronic energy loss of hydrogen ions (protons and deuterons) in thin supported films of LiF has been studied in backscattering geometry for specific energies from 700 eV/u to 700 keV/u, using Rutherford backscattering spectroscopy and time-of-flight low-energy ion scattering spectroscopy. For specific energies below 8 keV/u, our data confirm velocity proportionality for the stopping cross section epsilon (like in a metal) down to 3.8 keV/u, as observed previously for protons and antiprotons despite the large band gap (14 eV) of LiF. Below 3.8 keV/u, the present results indicate an apparent velocity threshold at about 0.1 a.u. for the onset of electronic stopping.

Contribution of valence electrons to the electronic energy loss of hydrogen ions in oxides

Based upon measured electronic stopping cross sections for protons of some solid oxygen compounds (H 2O-ice, SiO 2, Al 2O 3 and LiNbO 3) in the overall energy range 10–700 keV we investigate the contribution of valence electrons to the stopping process. We use first Born approximation calculations to subtract the core contribution of the constituents from the measured data. The result may be interpreted as that part of the electronic stopping cross section which is due to the valence electrons, ε val. It is proportional to the number of valence electrons but turns out to be quite insensitive to the detailed properties of the valence states like band gap, ionizity or band structure. This finding is corroborated by the fact that for energies above 100 keV, even ε val of the oxides coincides with ε val of oxygen gas, provided the different number of valence electrons is taken into account.

Investigation of the electronic energy loss of hydrogen ions in H 2O: influence of the state of aggregation

The gas-solid difference (phase effect) of the electronic stopping cross section (SCS) is investigated for hydrogen projectiles in H 2O at energies near the stopping maximum. We find experimentally, that at low ion velocities the SCS of the gas is considerably higher than that of the solid (up to 15%). This result is discussed in terms of differences between the valence states of H 2O vapor and of ice and in terms of the projectile inelastic processes.