Pijun Liu

Collision of hydrogen atom with single-walled carbon nanotube: Adsorption, insertion, and healing

Interaction of hydrogen atom with (5, 5) single-walled carbon nanotube (SWNT) has been studied over the collision energy range from 1 to 30 eV using a molecular dynamics simulation method. In the energy interval of 1–3 eV, the hydrogen atom can be chemisorbed on the outer wall of the SWNT, provided the impact point is near a vertex carbon atom of a hexagon. The lowest incident energy needed for a hydrogen atom to pass through a hexagon ring on the SWNT is estimated to be 14 eV. Hydrogen atoms that enter into the SWNT would either be encapsulated in it to form endohedral H@tube complex, or escape out of it. The hole on the sidewall of the nanotube induced by the collision of hydrogen atom can be healed after relaxation for several picoseconds.

Radiation damage and annealing behavior of 2.0 MeV 160Er+ implanted silicon

Abstract Radiation damage and annealing behavior of Si (100) implanted with 2 MeV Er + ions with various doses have been investigated using Rutherford backscattering spectrometry and channelling (RBS/C) technique. The damage profile of silicon substrate induced by 2.0 MeV E + , at a dose of 1×10 14 ions cm −2 was extracted using the multiple-scattering dechannelling model of Feldman, and the result is in good agreement with the TRIM96 calculation. The experimental results show that the annealing behavior of 2.0 MeV Er + implanted into silicon is strongly influenced by the implantation dose and annealing temperature. For the samples with dose of 5×10 14 ions cm −2 and more, an abnormal annealing behavior was found and a qualitative explanation has been given.

Range distribution and electronic stopping powers for fluorine ions in -implanted potassium titanyl phosphate and LiNbO3

Abstract Range distributions and electronic stopping cross-sections for fluorine ions in 19 F + -implanted potassium titanyl phosphate (KTP) and LiNbO3 in an energy range of 50–330 keV were measured by using the 19 F(p,αγ)16O resonant nuclear reaction at ER=872.1 keV. A proper convolution calculation method was used to extract the true distribution of fluorine from the experimental excitation yield curves. The electronic stopping powers were derived by fitting the projected range distributions simulated by using TRIM/XLL code to the experimentally measured range distributions. The experimental range distribution parameters, Rp and ΔRp, and the electronic stopping cross-sections were compared with those obtained from different Monte Carlo simulation computer codes.

Electronic stopping powers for fluorine ions in 19F+-implanted tin-oxide films prepared by APCVD

Abstract Electronic stopping powers for 50–180 keV 19F ions in tin-oxide films were obtained by range measurement. Depth profiles of 19F in tin-oxide films were measured by using the 19F(p,αγ)16O resonant nuclear reaction at ER=872.1 keV. A proper convolution calculation method was used to extract the true distribution of fluorine from the experimental excitation yield curves. The electronic stopping powers were derived through fitting the projected range distributions, simulated by using the TRIM/XLL code, to the experimentally measured range distributions. It is shown that the electronic stopping cross-sections obtained in this work agree well with those calculated by using TRIM90 and can be well described by the four-parameter formulae. But they are systematically larger than the results obtained from the TRIM98 code.

The importance of electronic exchange-correlation in non-self-consistent frozen density approximation

The effects of different treatments for the exchange-correlation energy on the accuracy of non-self-consistent frozen density approximation (FDA) are discussed. Local spin density approximation (LSDA) and non-local spin density approximation (NLSDA) are employed, respectively. Corresponding results obtained by using full-self-consistent density functional theory (DFT) are also given for the purpose of comparison. Explicit calculations for hydrogen bonds, covalent bonds and ionic bonds indicate that, comparing with LSDA, NLSDA can improve the accuracy of FDA as well as that of DFT. This improvement attributed to the refinements in the treatment for the electronic exchange-correlation energy may help to extend the application of FDA.

Defect formation and annealing behavior of Si implanted by high-energy 166Er ions

Abstract Si crystals were implanted at room temperature with 2.0 MeV 166 Er + ion doses of 5×1012, 1×1014, 5×1014, 1×1015 and 2.5×10 15 ions / cm 2 . Conventional furnace thermal annealings were carried out in the temperature range from 600°C to 1150°C. The radiation damage and annealing behavior were investigated using the Rutherford backscattering spectrometry and channeling (RBS/C) technique. Doses above 5×10 14 ions / cm 2 were found to produce amorphous layers. The experimental results show that the annealing behavior of 2.0 MeV Er+ implanted into silicon is strongly influenced by the implantation dose and annealing temperature. For the samples with dose of 5×10 14 ions / cm 2 and more, an abnormal annealing behavior was found and a qualitative explanation has been given. For the sample implanted with dose of 2.5×10 15 ions / cm 2 , a substantial Er outdiffusion has been investigated. Er outdiffusion increases with annealing temperature, Er depth distribution changes from an initially unimodal Gaussian form to a bimodal distribution with a build up of Er concentration near the surface.

Monte Carlo study of the polarization and depolarization properties of order–disorder ferroelectrics

Abstract The spontaneous polarization and depolarization in order–disorder ferroelectrics are studied using a Monte Carlo computer simulation method. Our study has been developed in a framework of the transverse field Ising model with the nearest-neighbor interaction. Two effects of tunneling frequency and external electrical field on the polarization and depolarization are taken into consideration. From our simulation results, the polarization of order–disorder ferroelectrics decreases significantly with the increase in tunneling frequency. The remnant polarization and the saturation coercive force of these ferroelectrics are also calculated, and a good agreement with previous theoretical and experimental results is obtained.

Implanted dopant and associated damage profile in MeV 166Er+ implanted silicon

Abstract The dopant and associated damage profiles in 2 MeV Er + ion-implanted (100)Si were investigated using Rutherford backscattering spectroscopy and channelling (RBS/C) technology. A convolution program was used to extract the concentration distributions of Er from the measured RBS spectra. While the values of the projected range R p obtained from the experiments agree well with those from TRIM96 simulations, the values of projected range straggling Δ R p from the experiments are systematically larger than those from the simulations by a factor of 18%. The damage profile in the silicon substrate induced by 2.0 MeV Er + at a dose of 1×10 14 ions/cm 2 was extracted using the multiple-scattering dechannelling model of Feldman, and the result is in good agreement with the TRIM96 calculation.

An investigation of range distribution parameters for bismuth ion-implantation in silver gallium disulphur

Abstract Range distributions for bismuth ions implanted in AgGaS 2 in an energy range of 80–300 keV were investigated by using 2.1 MeV He 2+ Rutherford backscattering spectrometry (RBS). A convolution calculation method was used to extract the true distributions of bismuth from the measured RBS spectra. The range distribution parameters, R p and Δ R p , were obtained and compared with that obtained from Monte Carlo simulation. The experimental R p values agree with the Monte Carlo simulation values very well, but the experimental Δ R p values are systematically larger than those from the theoretical simulation.

Damage profiles and damage annealing behavior in Al0.168Ga0.348In0.484P/GaAs implanted with 200 keV Zn+ ions

Abstract Damage profiles and the associated annealing behavior in Al 0.168 Ga 0.348 In 0.484 P/GaAs samples implanted with 200 keV Zn + ions were investigated by using Rutherford backscattering spectrometry and channeling (RBS/C) technique. A computer code was used to extract quantitative damage profiles from the RBS/C spectra. The measured damage profiles are compared with those obtained from TRIM98 computer simulation code, and a good agreement between the measurements and the TRIM98 simulations was observed. The annealing behavior of the damage induced in the AlGaInP/GaAs samples was studied and compared with that induced in GaP bulk crystal substrates under the same implantation and annealing conditions. The result shows that the structure of the radiation damage induced in the quaternary III–V compound, AlGaInP, is more complicated than that in the binary III–V compound, GaP.