Kinetic Energy Of Incident Ions Research Articles

Atomic simulations of effect on thermal conductivity of ion-irradiated graphene

It is an effective approach to manipulate the physical properties of graphene by defects produced by ion irradiation. In this work, we first simulate the process of ions bombardment on graphene by molecular dynamics, present the relationship between the probability of defects occurrence and the kinetic energy of incident ions. Whereafter we calculate the thermal conductivity of graphene suffering from ions irradiation by non-equilibrium molecular dynamics simulation. It is found that the thermal conductivity of graphene is remarkably suppressed by ions irradiation due to the generation of defects such as adatoms and vacancies. The underlying influence of irradiation dose and kinetic energy of incident ions on the thermal conductivity of graphene is well interpreted by the probability of defects occurrence. Our findings are helpful for understanding and tuning the thermal conductivity of graphene by defect engineering.

Single-Ion Deconvolution of Mass Peak Overlaps for Atom Probe Microscopy.

Due to the intrinsic evaporation properties of the material studied, insufficient mass-resolving power and lack of knowledge of the kinetic energy of incident ions, peaks in the atom probe mass-to-charge spectrum can overlap and result in incorrect composition measurements. Contributions to these peak overlaps can be deconvoluted globally, by simply examining adjacent peaks combined with knowledge of natural isotopic abundances. However, this strategy does not account for the fact that the relative contributions to this convoluted signal can often vary significantly in different regions of the analysis volume; e.g., across interfaces and within clusters. Some progress has been made with spatially localized deconvolution in cases where the discrete microstructural regions can be easily identified within the reconstruction, but this means no further point cloud analyses are possible. Hence, we present an ion-by-ion methodology where the identity of each ion, normally obscured by peak overlap, is resolved by examining the isotopic abundance of their immediate surroundings. The resulting peak-deconvoluted data are a point cloud and can be analyzed with any existing tools. We present two detailed case studies and discussion of the limitations of this new technique.

Effect of Co+ implantation on structural and optical properties in single-crystal TiO2

Ion implantation technique is used for doping Co+ to single crystal TiO2(001). The implanted energies and the fluences of Co+ are 40keV and 11016cm-2; 80 keV and 51015, 11016, 51016, 11017cm-2; 120 keV and 11016cm-2, respectively. And then, the structural and the optical properties of all samples are characterized by using X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), UV - Vis diffuse reflectance spectroscopy (UV-Vis DRS), and these impurities in implanted samples are also analyzed. From the XRD spectra of implanted samples we observe that the greater damage is caused with the increase of the kinetic energy of incident ions. UV - Vis diffuse reflectance spectroscopy measurement shows that the absorbance of visible band is enhanced in all the implanted samples, and the optical band gap decreases with implanted ion fluence increasing from 51015cm-2 to 51016cm-2.

<i>In-Situ</i> Optical Reflection Measurement of a Si(100) Surface under Hydrogen Ion Irradiation

Ion implantation (ion irradiation) is a powerful technique for modifying the near-surface properties of functional materials such as micro- and nano-crystals, alloys, semiconductors and electron devices. However, the kinetic energy of incident ions introduces lattice damage through electron excitation and atomic displacement, sometimes resulting in undesirable modification of the near-surface properties. In addition, the production of displaced atoms of which number is usually much larger than the number of the implanted ions makes the behavior of the implanted ions very complex. The behavior and effect of hydrogen implanted in silicon are of considerable technological importance, because hydrogen interact with defect and/or impurities in silicon, thereby modifying the electrical properties of the semiconductors. 1) Although hydrogen in crystal silicon has been investigated extensively, and various configuration of hydrogen have been reported on the basis of infrared 2,3) and Raman spectroscopy, 4,5) the dynamic change in the electronic structure of silicon under H þ irradiation is still not understood well. Therefore, in order to understand the properties of hydrogen implanted silicon, in-situ analysis of electronic structure with fine depth resolution is very important. In the present study, we have applied the optical reflection technique to study the chemical effects of irradiated hydrogen on the electronic structure of the surface silicon. 2. Experimental

Stress generation mechanisms in carbon thin films grown by ion-beam deposition

A three-dimensional molecular dynamics (MD) simulation is performed to study the stress generation mechanisms in carbon thin films grown by ion-beam deposition. The relationship between the kinetic energy of incident ions and the steady-state film stress is established. Examination of the atomic stress and film microstructures reveals that the grown films contain a significant fraction of vacancies, contradicting the presumption of the subplantation model. By taking into account both interstitials and vacancies, an analytical model is developed, in which the formation of the compressive stress is attributed to competing mechanisms between generation and recovery of the defects. This model can satisfactorily explain the numerical observation in which compressive stress prevails in films in the presence of vacancies. The present study provides useful insights into tailoring residual stress to control thin film curvature in microelectromechanical systems (MEMS) by ion-beam machining.

An anomalous decrease in the scattered N2+-ion yield from Al(111)

The incident-energy dependence and the angular distribution of the scattered N2+-ion yield from an Al(111) surface were measured in the incident-energy range 10-150 eV. A sudden decrease in the incident-energy dependence of the energy dissipating N2+-ion yield was observed in the 45 degrees specular scattering geometry. The observed result is closely correlated with the normal component of the kinetic energy of incident ions. The authors propose a possible mechanism in which the sudden decrease appears as a result of the N2+ dissociation induced by the translational-to-internal-energy transfer.