Electronic interactions of medium-energy ions in hafnium dioxide

Abstract

In this article, the electronic interaction of medium-energy ions with hafnium dioxide is studied. Stopping cross sections for He ions in the energy range from 30 to 160 keV have been measured in backscattering experiments from thin films of HfO 2 on Si using time-of-flight medium-energy ion scattering. The observed energy loss for helium ions is found to be high compared to expectations from earlier results for hydrogen in HfO 2 , a result which indicates a contribution from energy-loss processes that is different from direct excitation of electron-hole pairs in close collisions. Furthermore, data exhibit a significant deviation from velocity proportionality. A discussion of the results, together with data from studies for H and He in SiO 2 , show characteristic differences which are traced back to different electronic structures of the target materials and their influence on the charge-exchange channels that are active in the interaction with helium. Charge exchange, in turn, via shifted mean-charge states, will influence the observed ionization along the ion track. The results can furthermore serve as reference values for ion-beam-based depth profiling at medium and low ion energies.

Electronic excitation of transition metal nitrides by light ions with keV energies

“…for He ions is significantly higher than in N 2 , by up to a factor of two for low energies, in clear contrast to expectations from a naïve atomistic model. A similar discrepancy between data for protons and He has been observed for other target materials with vastly different electronic structures [23,74,75]. On the same line, also DFT-based predictions for the same electron gas density as employed to model our data for protons (magenta line in figure 5) underestimate the energy loss of He ions.…”

Electronic Stopping of Slow Protons in Oxides: Scaling Properties

“…In fact, in oxides AxO1-x, the SCS is proportional to the atomic fraction of oxygen, 1-x, while detailed electronic properties such as band gap energy or valence electron density are not relevant. At higher ion velocities, such a behavior has been observed for Al2O3, SiO2 and H2O ice [44] as well as for HfO2 versus SiO2 [28] and traced back to an O 2p 6 configuration as if in oxides the ionic character of the local bonds would prevail. At low ion velocities, however, details of the density of states (DOS) might be highly relevant, since even the subtle differences between specific metals have clear impact on the observed Se, e.g., for Au and Pt [10,11].…”

“…HfO2 thin films were deposited on SiO2/Si by atomic layer deposition [28]; VO2 thin films were sputter deposited on Si and subsequently thermally oxidized [29]. The annealed VO2 films were checked for the first-order phase transition by optical transmission (near infrared) while cycling forward and backward through TC.…”

“…HfO2 thin films were deposited on SiO2/Si by atomic layer deposition [28]; VO2 thin films were sputter deposited on Si and subsequently thermally oxidized [29]. The annealed VO2…”

Round‐robin test of medium‐energy ion scattering for quantitative depth profiling of ultrathin HfO2/SiO2/Si films

“…16 It can be determined with the transmission method by measuring the energy reduction before and after passing through the thin film 17 or the backscattering peak height 18 or width. 19,20 The published electronic stopping data have been collected [21][22][23][24][25][26][27][28][29][30][31][32][33] and made available to the public in the International Atomic Energy Agency (IAEA) website by Paul. 34 Ziegler, Biersack, and Littmark (ZBL) created a semiempirical database by integrating vast amounts of experimental data, which has now evolved into the SRIM 6 program.…”