Search

We review older and more recent work concerning modification of thin films during irradiation with heavy ions in the electronic energy deposition regime: loss of H2 and N2 from the bulk of several thin film materials, electronic sputtering of SiO2 and oxygen diffusion across an interface in SiO2. [Copyright &y& Elsevier]

The stopping powers in silicon of heavy ions, with atomic numbers ranging from 4 to 29, have been determined using a time-of-flight elastic recoil detection analysis (TOF ERDA) set-up. In transmission geometry, the energy loss of heavy elastic recoils in the self-supporting silicon foil of known thickness is measured over a continuous range of recoil energies using time-of-flight (TOF) spectrometry. By essentially calibrating the Si detector for each channel over the measured energy region using the TOF spectrometer, an uncertainty of less than 4% is achieved. The stopping powers are parameterized using a sixth order polynomial and compared with the limited experimental data in the literature. In the energy regimes where experimental data exist, the present data exhibit good agreement with most data. Stopping powers predicted by SRIM (the stopping and range of ions in matter) are in reasonable agreement with much of the experimental data, and SRIM-2003 predictions are in somewhat better agreement than SRIM-2000. There are, however, still some discrepancies between SRIM predictions and the experimental data. [Copyright &y& Elsevier]

In order to understand electronic sputtering phenomenon, a systematic study is performed by bombarding fullerene (C60) thin films deposited on Si and glass substrates with Au and Ag ions of different energies. The incident ion velocity, charge state and substrate dependent electronic sputtering yield (sputtered atoms/ion) of C is measured on-line by elastic recoil detection analysis (ERDA) technique in the three different sets of studies. The salient features observed in these experiments are that the yield is quite high (∼103 atoms/ion and above), which is influenced by the above-mentioned three physical parameters. Slower ion having same electronic energy deposition (Se) as compared to its high velocity counterpart erodes more. C60 films deposited on more insulating substrate (electrically and thermally: glass) shows higher sputtering yield as compared to those deposited on Si substrate. However, no charge state effect was observed in the electronic sputtering yield within the detection limit of the set up. [Copyright &y& Elsevier]

Using nitrogen plasma immersion ion implantation into Mo, the nitride phase formation and nitrogen diffusion behavior were investigated in the temperature range from 330 to 580 °C. In all cases, the formation of a new phase (beside the Mo substrate) was observed with X-ray diffraction. Good agreement of this phase with powder diffraction files of cubic Mo2N was found, albeit the exclusion of a slightly distorted tetragonal modification was not unequivocal due to the low signal intensity. Elastic recoil detection analysis indicated a surface nitrogen concentration of 35–40 at.%. The thickness of this surface layer was always larger than the projected range, as calculated with TRIM, and it increased with longer process time or higher temperature. In addition to this diffusion process, the formation of a deep tail of nitrogen into the bulk Mo was observed, starting near a temperature of approximately 500 °C. [Copyright &y& Elsevier]

The influence of bending stress on the hydrogen behaviour in titanium was investigated by elastic recoil detection analysis with a heavy ion microbeam (micro ERDA) and X-ray diffraction (XRD). The samples were made by hydrogen ion implantation into polished pure titanium sheets. Three-dimensional hydrogen distributions were obtained by scanning the microbeam over the sample using the depth information of ERDA. Inhomogeneous hydrogen distributions in the titanium were observed which vary with the depth. With mechanical bending of the samples the inhomogeneities increased in varied grade. The surface hydrogen loaded by surface polishing is stable, whereas the implanted hydrogen located inside of the sample is mobile under bending. These different hydrogen behaviours are relevant to the chemical states of hydrogen. Different titanium hydrides are formed by the different loading methods. An relatively unknown titanium-dihydride phase (TiH2(x)) with a tetragonal texture was identified by XRD in the depth region of implanted hydrogen. It is less stable than the normal titanium-dihydride phase (TiH2(δ)) observed in the surface region. The change of hydrogen distribution is related to the dehydrogenation of the TiH2(x) and TiH(γ) under bending. [Copyright &y& Elsevier]

The rate of removal of material from SiO2 as a result of heavy ion irradiation, with energies in which energy loss via excitation and ionization of the solid predominates, depends strongly on the stopping power and angle of incidence of the incoming ions. There appears to be a threshold stopping power for SiO2 of 500 eV/(1015 at/cm2) (or 3.5 keV/nm). This electronic sputter yield has been found to reach values as large as 104 atoms/incoming ion for 66 MeV Ag ions at an angle of incidence of 7° with the plane of the surface. Strikingly, the electronic sputter yield is very small for thin SiO2 layers of a thickness ⩽1 nm when grown on c-Si, but it is appreciable for such layers deposited on the insulator silicon nitride.The data are discussed in the light of existing models for electronic sputtering invoking also models for potential sputtering of SiO2 by low-energy, highly charged ions. [Copyright &y& Elsevier]

Elastic recoil detection analysis has been used to study the interaction between soda-lime glass substrates and a-Si:H films. It has been established that H and Na ions penetrate from the near-surface region of the substrate into the deposited film. The results have shown that the influence of the substrate on the properties of a-Si:H can be strongly reduced by glass surface modification using the processes of ion exchange and ion extraction. [Copyright &y& Elsevier]

The influence of oxygen exposure on three chemically different poly para-phenylene vinylene (PPV) derivatives used in polymeric light emitting devices (PLEDs) has been investigated. During device preparation, PPV layers have been exposed to oxygen either in the dark or during the irradiation with visible light, before the cathode was applied. Device efficiency was studied by electrical and optical characterisation and correlated to oxygen depth profiles measured with Elastic Recoil Detection Analysis (ERDA).Treatment with oxygen during light exposure leads to a decrease in current, light output and efficiency. It was found that two different PPV derivatives show the same current and light output reduction with different oxygen uptake. This behaviour is explained in terms of a different chemical structure and the number of structural defects (tolane-bisbenzyl moieties (TBBs)) incorporated. For two PPV derivatives treated with oxygen in the dark a reduction in current and light output was found, while the efficiency was unchanged. Another PPV derivative, however, shows a shift in the on-set voltage of the light output accompanied by an increased oxygen level at the PPV/Ca interface. It is concluded that after exposure in the dark, oxygen is incorporated in the PPV by Van der Waals interaction. During evaporation of the cathodes, oxygen will diffuse to the cathode and will be gettered by the calcium, which results in the formation of an electron injection barrier. [Copyright &y& Elsevier]

Films of CNx/Si, TiNx/AISI 304 and AlOx/Si were analyzed with 7Li ions from 4.0 to 4.5 MeV and an experimental arrangement that, through detection of scattered projectiles and recoils by a single detector, allows quantification of H, light elements and heavier ones. A discussion is presented of the capabilities of Rutherford backscattering spectrometry (RBS) and conventional elastic recoil detection analysis (ERDA) compared to elastic forward analysis. [Copyright &y& Elsevier]

Retention of He implanted into W single crystals and the He irradiation effects on H behavior were studied by ion beam analysis techniques. During implantation of 4He+ with 2–10 keV at 295 K, an accumulation of H started in the He implanted layer when the retained He concentration saturated. For the crystal irradiated by 10 keV He+ at 820 K, a remarkable increase of H was found in the He saturated layer, after stopping the implantation and cooling down the crystal below 400 K. Though blisters and exfoliation were observed for the surface irradiated at 820 K, less lattice disorder was found in the implanted layer and the thermal release of H occurred at lower temperature, in comparison with the crystal implanted at 295 K. [Copyright &y& Elsevier]

The present work reports the dependence of electronic sputtering on thickness of fullerene film. The energetic ions of 200 MeV Au15+ are taken from NSC Pelletron at New Delhi and the Tandem accelerator at Munich. On-line elastic recoil detection analysis (ERDA) with ΔE–E telescope detector is used to determine the electronic sputtering yield. We observed systematic decrease in sputtering yield of carbon with increase in film (C60/silicon) thickness. [Copyright &y& Elsevier]

The mean stopping power of He, Be, C and Al in carbon has been studied in a continuous energy ranging from ∼100 to 800 keV per nucleon using a modified time of flight-energy elastic recoil detection analysis set-up. In order to eliminate the calibration problems of Si detectors associated with heavy ions, the time of flight section was used to measure recoil energy both before entering and after passing through the stopping foil. Consequently, the energy dependence of the stopping power was achieved with high precision. The effect of the foil thickness on the mean stopping power was investigated by tilting the stopping foil at different angles to the incoming particles to increase the effective foil thickness up to ∼22%. The stopping curves obtained at different tilting angles show a similar energy dependence with scattering less than ∼0.8% from each other, and no obvious thickness dependence is observed. Both the stopping power and the energy dependence are in good agreement with the literature data. Comparing with semi-empirical SRIM prediction, considerable discrepancies up to 6%, 10% and 8% in stopping values for Be, C and Al, respectively, are observed. [Copyright &y& Elsevier]

Hydrogen impregnation is one of the main sources of contamination in AlN thin films obtained by atomic layer deposition method (ALD) as many studies report. Such impurities can be potentially detrimental to mechanical and electrical properties of the material. In this study methods belonging to ion-beam analysis (IBA) group, namely: elastic recoil detection analysis (ERDA), nuclear reaction analysis (NRA) and secondary-ion mass spectrometry (SIMS) were utilized to examine AlN thin films obtained by plasma-enhanced atomic layer deposition (PE-ALD) with use of trimethylaluminium (TMA) and N 2 +H 2 gas mixture as precursors. Several depositions of AlN layers were carried out with different values of N 2 +H 2 flux intensity (20, 100, 150 sccm) and TMA pulse (0.06, 0.12, 0.15 s) in order to investigate whether such alterations would produce any effect on the resulting films. Data obtained within the scope of this study suggest that AlN grown by PE-ALD exhibit rather low amounts of hydrogen impurities, especially when compared to thermal ALD. Furthermore, the effect of high-temperature treatment in N 2 atmosphere was studied and was found out to produce a positive effect on the chemical composition of AlN films. • AlN thin films were deposited by PE-ALD using trimethylaluminium (TMA) and N 2 +H 2 gas mixture. • The films were analyzed by IBA methods: SIMS, NRA and ERDA. • The hydrogen was quantified for all samples. • The IBA methods also revealed oxidization of the films, which is alleviated by high-temperature annealing in N 2 atmosphere. [ABSTRACT FROM AUTHOR]

• 40 keV C ions implanted into 110, 190 and 240-nm-thick SiO 2 caps on Si at 600°C • C depth-profile after 1250°C annealing by detection of recoiled C from inside SiO 2 • C peak-shift of ~50 nm toward the SiO2/Si interface • C: ~100% was in the 240 nm SiO 2 -cap but ~20% migrates to form 5-nm SiC at interface • C are diluted in SiO 2 ; driven-force to the interface with ~50 nm of capture range C+ ions at 40 keV were implanted up to 2.8 × 1017 cm−2 into SiO 2 /Si(001) structures (samples kept at 600°C) with SiO 2 thicknesses of 110, 190 and 240 nm. They were subsequently annealed at 1250°C under a flux of 99% Ar and 1% O 2. Afterwards, we measured by Elastic Recoil Detection Analysis (ERDA) the C concentration along the whole SiO 2 until the Si side nearby the SiO 2 /Si interface. We could probe C-recoiled within a narrow depth-window of about 35 nm, thus a combined procedure of ERDA and sequential etching steps of the SiO 2 cap was performed. After each etching step, which removed ~ 30 nm of the oxide, we calculated a normalized result, both in extension and in intensity (in relation to a standard sample). The C distribution profile for the 110 nm case is consistent with the SRIM (The Stopping and Range of Ions in Matter) simulation of implanted C into a SiO 2 (110-nm)/SiC(55-nm)/Si(bulk) structure. For the 190 nm one, the measured C shows a shift of ~ 40 nm towards SiO 2 /Si interface and a systematic concentration-increase from about the middle of the cap layer up to the SiO 2 /Si interface. However, according to SRIM simulation, the C concentration was supposed to decrease when approaching the interface. For the 240 nm SiO 2 -cap, it shows a peak-shift of ~ 50 nm towards the SiO 2 /Si interface in relation to the simulation. Our results indicate that the SiO 2 /Si interface efficiently attracts C within a capture range of about 50 nm from the interface. This C peak-shift in the SiO 2 towards the SiO 2 /Si interface, is only consistent with diffusion models based on C dissolved in SiO 2 , forming bonds with Si or O, or even C-C complexes, but not with SiC precipitation in it. [ABSTRACT FROM AUTHOR]

Abstract: The knowledge and amount of stopping power measurements available for heavy ions is much smaller than for H and He, with negative consequences for the accuracy of interpolative calculational schemes such as SRIM. We have used a bulk method, previously developed by us and applied successfully to other systems, to determine experimentally the stopping power of C in Si between 0.3 and 14.9MeV. This is particularly useful for heavy ion elastic recoil detection analysis, given that Si is one of the most commonly analysed materials, and C is a light element whose quantitative determination is ideally made with HI-ERDA. Obtained results are compared with SRIM and MSTAR as well as with other available data. [Copyright &y& Elsevier]

Abstract: The continuing development of depth profiling with MeV ion beam methods with depth resolutions in the nanometre, and even sub-nanometre, regime implies the resolved depth become comparable with the interatomic spacing. To investigate how short-range ordering influences depth profiles at these resolutions, we have employed a mathematical modelling approach. The radial, and depth distribution, functions were calculated for (100) surface, random and amorphous Si structures at 300K produced using molecular dynamics simulations with the EDIP quasi-empirical potential. The results showed that short-range ordering lead to reduction of the scattering yield below the deep asymptotic level within about half a interatomic distance which will give a perturbation of the scattering yield for Rutherford Backscattering Spectrometry (RBS) and glancing incidence Elastic Recoil Detection Analysis (ERDA) geometries. [Copyright &y& Elsevier]

Abstract: In this work we have studied the individual a-Si and a-Ge hydrogenated layers prepared by RF sputtering on Si (100) substrates using Ar and H2 gas mixture. The absolute value of atomic content of the H was determined by Elastic Recoil Detection Analysis (ERDA) with 1.6 MeV 4He+ beam. The dynamics of the out diffusion was investigated by annealing in high purity (99.999%) argon atmosphere at 350 °C for several hours. It was clearly shown that hydrogen can diffuse out faster from Ge film than from the Si one during annealing of the samples. [Copyright &y& Elsevier]

Thermoelectric properties of ScN thin films grown by reactive magnetron sputtering on Al2O3(0001) wafers are reported. X-ray diffraction and elastic recoil detection analyses show that the composition of the films is close to stoichiometry with trace amounts (∼1 at. % in total) of C, O, and F. We found that the ScN thin-film exhibits a rather low electrical resistivity of ∼2.94 μΩm, while its Seebeck coefficient is approximately ∼-86 μV/K at 800 K, yielding a power factor of ∼2.5 × 10-3 W/mK2. This value is anomalously high for common transition-metal nitrides. [ABSTRACT FROM AUTHOR]

Abstract: We report here loss of H monitored by on-line elastic recoil detection analysis (ERDA) technique from passivated Hg1− x Cd x Te (MCT) wafers due to irradiation by 80MeV Ni9+, 120MeV Au15+ and 200MeV Ag10+. The loss of H is more in case of the wafer irradiated by Ag ions as compared to other two because of higher electronic energy loss (S e). For same S e value, H loss is more in case of the wafer having x =0.29 as compared to the one having x =0.204. This is due to higher band gap of the former as compared to the later, which is an important data for proper use of these materials as IR detector in intense radiation zone. These results are explained on the basis of thermal spike model of ion–solid interaction. [Copyright &y& Elsevier]

Abstract: Large erosion (∼1.1×104 atoms/ion) of H from hydrogenated MCT wafers is observed due to the bombardment with 80MeV Ni9+ ions. The initial H areal concentration and hydrogen depletion rate is monitored by elastic recoil detection analysis. The ion-damaged zones from where depletion of H takes place have been calculated from fluence-dependent hydrogen areal content analysis. The results are explained on the basis of the thermal spike model of ion–solid interaction. [Copyright &y& Elsevier]

Abstract: Structural analysis was performed on the 55 kinds of diamond-like carbon (DLC) films. The ratio of sp2 hybridized carbon in the film, sp2/(sp2 + sp3) ratio, was determined by the carbon K-edge near-edge X-ray absorption fine structure (NEXAFS) spectroscopy using synchrotron radiation in the soft X-ray region. In addition, hydrogen content in the DLC film was determined by elastic recoil detection analysis (ERDA) using an electrostatic accelerator. Furthermore, the density of the DLC film was measured by X-ray reflectivity method. Analyzed DLC films were divided broadly into four groups. Group 1 was characterized by high density, low sp2/(sp2 + sp3) ratio and low H content. Group 2 was characterized by low density, high sp2/(sp2 + sp3) ratio and low H content. Group 3 was characterized by medium density, and medium sp2/(sp2 + sp3) ratio and relative high H content. Most samples in the present study were belonging to this group. Group 4 was characterized by low sp2/(sp2 + sp3) ratio in spite of low density. H contents of samples in this group were relatively high. [Copyright &y& Elsevier]

The effect of soft X-ray irradiation on hydrogenated silicon-containing diamond-like carbon (Si-DLC) films intended for outer space applications was investigated by using synchrotron radiation (SR). We found that the reduction in film thickness was about 60 nm after 1600 mA·h SR exposure, whereas there was little change in their elemental composition. The reduction in volume was attributable to photoetching caused by SR, unlike the desorption of hydrogen in the case of exposure of hydrogenated DLC (H-DLC) film to soft X-rays. The ratio of the sp2 hybridization carbon and sp3 hybridization carbon in the hydrogenated Si-DLC films, sp2/(sp2 + sp3) ratio, increased rapidly from ~0.2 to ~0.5 for SR doses of less than 20 mA·h. SR exposure significantly changed the local structure of carbon atoms near the surface of the hydrogenated Si-DLC film. The rate of volume reduction in the irradiated hydrogenated Si-DLC film was 80 times less than that of the H-DLC film. Doping DLC film with Si thus suppresses the volume reduction caused by exposure to soft X-rays. [ABSTRACT FROM AUTHOR]

• Impurity concentrations of ALD grown HfO 2 films were determined using ERDA. • The GPC correlates with the H impurity level and the layer thickness uniformity. • GIXRD was used to determine the crystal structure, crystal size and crystallinity. • Spots arising in the HfO 2 topography coincide with the onset of crystallisation. Hafnium oxide was deposited from tetrakis(dimethylamino)hafnium (TDMAHf) and water by atomic layer deposition (ALD) on heated 4 ″ Si wafers covered with native oxide in the temperature range from 100 ° C to 350 ° C. Optimized self-limiting ALD reaction and smallest hydrogen impurity level have been realized for a substrate temperature of 300 ° C. The stoichiometry of deposited films and hydrogen impurity level were measured by elastic recoil detection analysis. The hafnium to oxygen ratio showed the expected 1:2 value. Besides hydrogen, no other impurities could be detected. Furthermore, a strong correlation between the growth rate per cycle (GPC), film uniformity and level of hydrogen impurities was observed. In addition, the characterization of the crystal structure showed the appearance of some crystallites in an amorphous matrix already for a growth temperature of 250 ° C and a pure crystalline layer at a growth temperature of 350 ° C. The increased crystallinity with increasing growth temperature was attributed to a higher seed concentration and a nearly constant crystal size. [ABSTRACT FROM AUTHOR]

Carbon films prepared by plasma assisted chemical vapor deposition were doped by laser active ion Er3+. The characterisation of the layers was performed using Rutherford backscattering spectrometry and elastic recoil detection analysis. Optical properties of the waveguides were measured at 660 nm wave length using standard prism spectroscopy. The correlation between the layer composition and the content of incorporated erbium and layer optical properties shows very interesting aspects [SPIE 4281, San Jose (2001) 13]. [Copyright &y& Elsevier]