Effect Of Ion Bombardment Research Articles

Effects of ion bombardment on a two-dimensional target: Atomistic simulations of graphene irradiation

Using atomistic computer simulations based on analytical potential and density-functional theory models, we study effects of ion irradiation on graphene. We identify the types and concentrations of defects which appear in graphene under impacts of various ions with energies ranging from tens of electron volts to mega-electron volts. For two-dimensional targets, defects beyond single and double vacancies are formed via in-plane recoils. We demonstrate that the conventional approach based on binary-collision approximation and stochastic algorithms developed for bulk solids cannot be applied to graphene and other low-dimensional systems. Finally, taking into account the gas-holding capacity of graphene, we suggest the use of graphene as the ultimate membrane for ion-beam analysis of gases and other volatile systems which cannot be put in the high vacuum required for the operation of ion beams.

Effect of ion bombardment on the field emission property of tetrapod ZnO

The influences of ion bombardment on the field emission performance of tetrapod ZnO nanostructures are reported. As the scanning electron microscopy images and photoluminescence spectrum show, the tips of the field emitters are destroyed and the surface state of the field emitters is also changed after the ion bombardment. The ion bombardment has a considerable effect on the field emission properties of the tetrapod ZnO field emitters. After Ar+ ion bombardment with the energy of 3 keV and the ion current of 0.05 μA for 30 min, the turn-on field increases about 63% and the threshold field increases about 77%, respectively. There are two main reasons for the variation in field-emission property: (1) the decrement of the field enhancement factor β, which is caused by the variation in morphology of field emitter; (2) the increment of work function φ, which is caused by the changed concentration of the surface oxygen vacancy.

Role of polymer structure and ceiling temperature in polymer roughening and degradation during plasma processing: a beam system study of P4MS and PαMS

The degradation and roughening of polymers during plasma processing are important for the understanding of patterning of critical dimension features for both current and future lithographic techniques. Recently, the role of plasma-generated VUV photons in both the roughening and smoothing of current generation 193 nm photoresist (PR) has been investigated. However, a general understanding of the importance of polymer chemistry and structure on the degradation and roughening of polymers during plasma processing, which could be useful for polymer selection for next generation lithography, is currently lacking. Through the use of a beam system approach, the effects of ion bombardment and VUV radiation during plasma processing are investigated for two polymers with the same composition but different structure: poly(4-methyl styrene) (P4MS) and poly(α-methyl styrene) (PαMS). PαMS degrades under VUV radiation when heated above room temperature while P4MS is stable up to 70 °C, the maximum temperature studied. Both polymers undergo a drastic reduction in ion sputter yield at an ion fluence of 1 × 1016 ions cm−2, associated with the formation of a highly modified near-surface region. Almost no surface roughness is generated after VUV radiation, with moderate surface roughness formed on PαMS after ion bombardment at 70 °C. In contrast, extreme levels of surface roughness (∼10 nm rms) are observed for PαMS after simultaneous exposure to VUV photons and ion bombardment at 70 °C. Similarities to the synergistic roughening of current generation 193 nm PR under simultaneous VUV photons and ion bombardment are discussed.

Fabrication of Carbon Nanowalls using Plasma-enhanced Chemical Vapor Deposition

We have proposed a novel plasma processing, i.e., radical-controlled processing using radical injection technique, and demonstrated the formation of carbon nanowalls (CNWs) using fluorocarbon plasma-enhanced chemical vapor deposition assisted by hydrogen atom injection. CNWs can be described as the two-dimensional graphite nanostructures with edges, which are composed of the stacks of plane graphene sheets standing almost vertically on the substrate, forming wall structure with high aspect ratio. Growth mechanism of CNWs was discussed on the basis of density measurements of important radicals in the plasma. Moreover, CNWs were formed by using the multi-beams of fluorocarbon radicals, hydrogen atoms and ions, and the effect of ion bombardment on the nucleation of CNWs was investigated.

イオン衝撃が薄膜特性に及ぼす影響

This study examined the effect of argon ion bombardment on the internal stress of a nickel film. As a means of expressing the effect of ion bombardment, we propose an ion bombardment parameter based on the momentum of the ions. The magnitude of the ion momentum determined from the plasma potential was not dependent on the sputter power. With the increase in sputter power, the increase in the impingement frequency of nickel atoms onto the substrate was greater than the increase in the impingement frequency of Ar+ ions. It has become evident that the ratio of impingement argon ions to nickel particles onto the substrate mainly affects the variation in the ion bombardment parameter in relation to the sputter power. Thus, it has been demonstrated that the internal stress of a nickel film can be predicted using the ion bombardment parameter.

Microstructure and composition of TiC/a-C:H nanocomposite thin films deposited by a hybrid IPVD/PECVD process

Titanium containing amorphous carbon (TiC/a-C:H) films were deposited by a hybrid IPVD/PECVD (Ionized Physical Vapor Deposition/Plasma Enhanced Chemical Vapor Deposition) process combining titanium target magnetron sputtering and PECVD in an Ar–CH 4 plasma. Films with various carbon contents have been deposited by variation of the composition of the Ar–CH 4 plasma mixture. The films were characterized by XPS, EDX, XRD and TEM. The film characterization was focused on the effect of the argon ion bombardment on the surface composition measured by in situ XPS. This ion erosion allows enhancing the XPS signal coming from the TiC crystallites on the surface. The evolution of the microstructure as a function of carbon content in the films was studied. A transition from percolated TiC nanocrystallites with a preferential (111) crystalline orientation to isolated nanocrystallites TiC embedded in amorphous carbon was observed with an increasing carbon content in the films. This evolution was coupled with the variation of the electrical resistivity, measured by a four probe method.

An ion momentum as a novel parameter for the preparation of the magnetostrictive thin film

The Sm–Fe system known as Giant magnetostrictive (GM) thin films was prepared by d.c. magnetron sputtering process. The present study has shown the importance of the energetic incidence ions onto the depositing film surface for the magnetostrictive properties. The effect of ion bombardment on the magnetostrictive characteristics of GM films was quantitatively discussed. The new parameter, ion momentum, was proposed for the design of GM films.

Mechanisms involved in HBr and Ar cure plasma treatments applied to 193 nm photoresists

In this article, we have performed detailed investigations of the 193 nm photoresist transformations after exposure to the so-called HBr and Ar plasma cure treatments using various characterization techniques (x-ray photoelectron spectroscopy, Fourier transformed infrared, Raman analyses, and ellipsometry). By using windows with different cutoff wavelengths patched on the photoresist film, the role of the plasma vacuum ultraviolet (VUV) light on the resist modifications is clearly outlined and distinguished from the role of radicals and ions from the plasma. The analyses reveal that both plasma cure treatments induce severe surface and bulk chemical modifications of the resist films. The synergistic effects of low energetic ion bombardment and VUV plasma light lead to surface graphitization or cross-linking (on the order of 10 nm), while the plasma VUV light (110–210 nm) is clearly identified as being responsible for ester and lactone group removal from the resist bulk. As the resist modification depth depends strongly on the wavelength penetration into the material, it is found that HBr plasma cure that emits near 160–170 nm can chemically modify the photoresist through its entire thickness (240 nm), while the impact of Ar plasmas emitting near 100 nm is more limited. In the case of HBr cure treatment, Raman and ellipsometry analyses reveal the formation of sp2 carbon atoms in the resist bulk, certainly thanks to hydrogen diffusion through the resist film assisted by the VUV plasma light.

Size-dependent effect of ion bombardment on Au nanoparticles on top of various substrates: Thermodynamically dominated capillary forces versus sputtering

Hexagonally ordered arrays of Au nanoparticles exhibiting narrow size distributions were prepared on top of Si wafers with either a thin native oxide or a thick thermally oxidized layer as well as on top of crystalline (0001)-oriented sapphire substrates. Subsequent irradiation of these nanoparticles by 200 keV ${\text{Ar}}^{+}$ and ${\text{Xe}}^{+}$, respectively, in combination with transmission electron microscopy analysis (TEM) corroborated the previously reported phenomenon of bombardment-induced burrowing of metallic nanoparticles into ${\text{SiO}}_{x}$ while conserving their spherical shape [X. Hu et al., J. Appl. Phys. 92, 3995 (2002)]. Performing the ion irradiations on particle ensembles of different radii ${R}_{0}$ $(1.3\text{ }\text{nm}\ensuremath{\le}{R}_{0}\ensuremath{\le}5.3\text{ }\text{nm})$ and determining the burrowing effect by atomic force microscopy combined with TEM provide sufficient statistics to allow a quantitative description of this effect. In addition to the thermodynamic driving forces necessary for the burrowing effect, sputtering of the nanoparticles due to the ion bombardment has to be included to arrive at an excellent theoretical description of the experimental data. The magnitude of sputtering can be quantified for the Au/sapphire system, where the burrowing effect is found to be completely suppressed. In that case, the theoretical description can even be improved by assuming a size-dependent sputtering coefficient for the Au nanoparticles. Combining this type of sputtering with the thermodynamically driven burrowing effect delivers a consistent model for all ion bombarded Au nanoparticles on top of ${\text{SiO}}_{x}$. Specifically, the residual heights of the ${\text{Ar}}^{+}$- or ${\text{Xe}}^{+}$-induced burrowing of Au nanoparticles can be scaled on top of each other if plotted versus the average displacements per target atom rather than versus the applied ion fluences.

Luminescence effects of ion-beam bombardment of CdTe surfaces

In the present work, we report the effect of low-energy ion bombardment on CdTe surfaces. The effect is revealed by FESEM images and photoluminescence (PL) measurements carried out before and after irradiation of CdTe polycrystals by means of an ion-beam sputtering (IBS) system. An important improvement in the luminescence of CdTe was observed in the irradiated areas, related to defect-free surfaces.

Ion bombardment of Poly-Allyl-Diglycol-Carbonate (CR-39)

Ion bombardment is thought to have great potential for improving the optical properties of polymeric materials. In this paper, Poly-Allyl-Diglycol-Carbonate (CR-39) polymer samples were bombarded with 320 keV Ar and 130 keV He ions, at different ion fluences. Effects of ion bombardment on the optical properties of CR-39 have been investigated using UV–vis spectrophotometer and photoluminescence (PL) spectroscopy. UV–vis spectra of irradiated samples reveal that the optical band gap decreases with increasing the ion fluence for both Ar and He ions. The width of the tail of localized states in the band gap ( E u) was evaluated using the Urbach edge method. The decrease in the PL intensity with the increase in the ion fluence was observed. This decrease is attributed to ion bombardment induced defects and clusters in the CR-39 which serves as non-radiative centers.

MeV Si ions bombardment effects on the thermoelectric properties of nano-layers of nanoclusters of Ag in SiO 2 host

We prepared 50 periodic nano-layers of SiO 2/Ag x SiO 2(1 − x) with Au layer deposited on both sides as metal contacts. The deposited multi-layer films have a periodic structure consisting of alternating layers where each layer is 10 nm thick. The purpose of this research is to generate nano-layers of nanocrystals of Ag with SiO 2 as host and as buffer layer using a combination of co-deposition and MeV ion bombardment taking advantage of energy deposited in the MeV ion track to nucleate nanoclusters. Our previous work showed that these nanoclusters have crystallinity similar to the bulk material. Nanocrystals of Ag in silica produce an optical absorption band at about 420 nm. Due to the interaction of nanocrystals between sequential nanolayers there is widening of the absorption band. The electrical and thermal properties of the layered structures were studied before and after 5 MeV Si ions bombardment at various fluences to form nanocrystals in layers of SiO 2 containing few percent of Ag. Rutherford Backscattering Spectrometry (RBS) was used to monitor the stoichiometry before and after MeV bombardments.

MeV Si ions bombardment effects on the thermoelectric properties of Co0.1SbxGey thin films

We have grown three different monolayer Co0.1SbxGey (x=2,4,11 and y=15,7,15) thin films on silica substrates with varying thickness between 100 and 200nm using electron beam deposition. The high-energy (in the order of 5MeV) Si ion bombardments have been performed on samples with varying fluencies of 1×1012, 1×1013, 1×1014 and 1×1015ions/cm2. The thermopower, electrical and thermal conductivity measurements were carried out before and after the bombardment on samples to calculate the figure of merit, ZT. The Si ions bombardment caused changes on the thermoelectric properties of films. The fluence and temperature dependence of cross plane thermoelectric parameters were also reported. Rutherford backscattering spectrometry (RBS) was used to analyze the elemental composition of the deposited materials and to determine the layer thickness of each film.

Ion beam modification of chitosan and cellulose membranes for simulation of ion bombardment of plant cell envelope

Ion beam biotechnology has been developed for induction of DNA transfer into biological cells. To separately investigate effects of ion interaction with plant cell envelope for understanding relevant mechanisms, this study used chitosan and cellulose membranes to simulate the cell envelope and characterize behavior of the membranes modified by ion beam. Chitosan and cellulose membranes were bombarded with argon and nitrogen ion beams at energy of 15–25keV to fluencies in orders of 1015ion/cm2. Modifications of the membrane surface morphology, contact angle and electric characteristics were investigated. Results showed that subjected to ion bombardment, the membrane surface was roughened, the contact angle of the membrane surface was varied, the membrane impedance was decreased and the conductance and capacitance were increased. These modifications explain effects of ion bombardment of plant cell envelope on induction of DNA transfer.

High energy Si ions bombardment effects on the properties of nano-layers of SiO2/SiO2 + Ag

We grew 50 periodic SiO2/SiO2+Ag multi-layers by electron beam deposition technique. The co-deposited SiO2+Ag layers are 7.26nm, SiO2 buffer layers are 4nm, and total thickness of film was determined as 563nm. We measured the thickness of the layers using in situ thickness monitoring during deposition, and optical interferometry afterwards. The concentration and distribution of Ag in SiO2 were determined using Rutherford backscattering spectrometry (RBS). In order to calculate the dimensionless figure of merit, ZT, the electrical conductivity, thermal conductivity and the Seebeck coefficient of the layered structure were measured at room temperature before and after bombardment with 5MeV Si ions. The energy of the Si ions was chosen such that the ions are stopped deep inside the silicon substrate and only electronic energy due to ionization is deposited in the layered structure. Optical absorption (OA) spectra were taken in the range 200–900nm to monitor the Ag nanocluster formation in the thin layers.

Influence of ion-beam bombardment on the optical properties of LDPE polymer blends

Ion beams have been found to be widely applicable in improving the structure and physical properties of polymers. In this paper, the effect of ion bombardment on the optical properties of low density polyethylene (LDPE)/styrene butadiene rubber (SBR) blend (LDPE/SBR) was studied. Polymer samples were bombarded with 130 keV He and 320 keV Ar ions to fluencies ranging from 1 × 1013 to 2 × 1016 ions cm−2. The pristine and ion beam bombarded samples were investigated using ultraviolet–visible (UV–Vis) spectrophotometry. The optical band gap (Eg) was decreased from ∼2.3 to ∼1.22 eV for the pristine sample and those samples bombarded with He and Ar ions at the highest fluence. The change in the optical gap indicates the presence of a gradual phase transition for the polymer blends. With increasing ion fluence, a decrease in both the energy gap and the activation energy was observed. The number of carbon atoms (N) in a formed cluster is found to be directly proportional to ion fluence and is determined according to the modified Tauc equation.

High-quality epitaxial Si growth at low temperatures by atmospheric pressure plasma CVD

We have studied the epitaxial Si growth on 4-inch-(001) Si wafers by atmospheric pressure plasma chemical vapor deposition (AP-PCVD) using a porous-carbon electrode. Defect-free growth of epitaxial Si is confirmed in the temperature range 470–570 °C by transmission electron microscopy. High minority carrier generation lifetime (2.0 ms) is observed in the Si film grown at 570 °C with a rate of 0.35 μm/min. In situ H 2 AP-plasma cleaning of the substrate surface is effective for eliminating O and C concentration peaks at the film/substrate interface. Effects of plasma heating and ion bombardment of the growing-film surface have been discussed.

Effect of ion bombardment on the optical properties of LDPE/EPDM polymer blends

Ion bombardment is a suitable tool to improve the physical properties of polymers. In the present study, the effect of ion bombardment on the optical properties of low density polyethylene (LDPE)/Ethylene propylene diene monomer (EPDM) blend (LDPE/EPDM) was studied. Polymer samples was bombarded with 130 keV He and 320 keV Ar ions at fluencie s levels ranging from 1 × 10 13 to 2 × 10 16 ions/cm 2. The untreated and ion beam bombarded samples were investigated using ultraviolet-visible (UV-Vis) spectrophotometry. The optical band gap ( E g), was decreased from ∼2.9 eV for the pristine sample down to 1.7 eV for the samples bombarded with He and Ar ions at the highest fluences. Change in the optical gap indicates the presence of a gradual phase transition for the polymer blends. Activation energy has been investigated as a function of the ion fluences. With increasing ion fluence, a decrease in both the energy gap and the activation energy was observed. The number of carbon atoms ( N) in a formed cluster is determined according to the modified Tauc's equation.

Ion bombardment effects on ZnO nanowires during plasma treatment

We present the effects of ion bombardment on ZnO nanowires caused by their exposure to an Ar inductively coupled plasma. The conductivity of the individual ZnO nanowire was increased in up to 3 orders of magnitude due to increase in both carrier concentration and mobility, with a substantial negative shift in the threshold gate voltage also being observed. The drastic changes in the electrical properties were attributed to the decrease in species adsorbed on the surface, as well as to the increase in oxygen vacancies near the surface caused by ion bombardment.

Influence of RF Bias on the Deposition of CrN Studied by OES

Chromium nitride coatings were synthesized by DC magnetron sputtering techniques. Optical emission spectroscopy (OES) was applied to investigate the role of the different level RF substrate biases. The results show that the main chemical reaction process occurred on substrate surface and OES signal ratio I(N 2 )/I(Cr) can be used to predict the composition evolution. Ion bombardment effects were identified, especially in the range from 60 V to 100 V, they provide benefits to make coating denser and improve mechanical properties.