Transport And Range Of Ions In Matter Research Articles

A novel self-aligned double patterning integrated with Ga+ focused ion beam milling for silicon nanowire definition

Self-aligned double (SADP) or quadruple (SAQP) patternings have been used to obtain sub-resolution lithographies (sub-10 nm). For this purpose, usually, these patternings are integrated with 193 nm immersion (193iL), extreme ultra-violet (EUVL) and electron beam (EBL) lithographies. In this work, SADPs are integrated with Ga+ Focused Ion Beam (FIB) milling, which is a novel alternative to traditional 193iL, EUVL and EBL, mainly for prototyping of nanodevices. Furthermore, the FIB milling is a maskless process, thus being more flexible than EBL and cheaper than EUVL. The FIB milling was carried out on the a-Si:H/Al (deposited on Si substrate) to pattern the parallel Al nanowires (AlNWs), which are used as mandrel in our SADP. The a-Si:H layer, used as spacer in our SADP, also is an effective barrier against the Ga+ ion bombardment directly on Al surface, avoiding damages on the AlNW mandrel. Thus, after FIB milling, SADP and plasma etch steps, Silicon Nano-Wires (SiNWs), with dimensions (extracted by Scaning Electron Microscopy (SEM)) of fin width and pitch of 35 nm and 170 nm, respectively, were obtained. This is an excellent result, similar to obtained by SADP methods integrated with traditional lithographies. Therefore, our SADP with FIB milling is a flexible alternative to obtain SiNWs for 3D nanostructure technologies prototypes. Furthermore, a last important result, extracted from energy dispersive x-ray spectroscopy (EDS) spectrum, is the Ga peak absence, indicating that no trace of gallium (for an EDS detection limit of 1%) could be detected into SiNWs. This result agrees the TRIM (Transport and Range of Ions in Matter) simulation of gallium ion implantation in a-Si:H/Al structure.

Surface modification by metal ion implantation forming metallic nanoparticles in an insulating matrix

There is special interest in the incorporation of metallic nanoparticles in a surrounding dielectric matrix for obtaining composites with desirable characteristics such as for surface plasmon resonance, which can be used in photonics and sensing, and controlled surface electrical conductivity. We have investigated nanocomposites produced by metal ion implantation into insulating substrates, where the implanted metal self-assembles into nanoparticles. The nanoparticles nucleate near the maximum of the implantation depth profile (projected range), which can be estimated by computer simulation using the TRIDYN code. TRIDYN is a Monte Carlo simulation program based on the TRIM (Transport and Range of Ions in Matter) code that takes into account compositional changes in the substrate due to two factors: previously implanted dopant atoms, and sputtering of the substrate surface. Our study show that the nanoparticles form a bidimentional array buried a few nanometers below the substrate surface. We have studied Au/PMMA (polymethylmethacrylate), Pt/PMMA, Ti/alumina and Au/alumina systems. Transmission electron microscopy of the implanted samples show that metallic nanoparticles form in the insulating matrix. These nanocomposites have been characterized by measuring the resistivity of the composite layer as a function of the implantation dose. The experimental results are compared with a model based on percolation theory, in which electron transport through the composite is explained by conduction through a random resistor network formed by the metallic nanoparticles. Excellent agreement is found between the experimental results and the predictions of the theory. We conclude in that the conductivity process is due only to percolation (when the conducting elements are in geometric contact) and that the contribution from tunneling conduction is negligible.

AES and EELS tools associated to TRIM simulation methods to study nanostructures on III-V semiconductor surfaces

At low energy (300 eV), the Ar+ ions bombardment lead to the formation of small nanodots on the InP and the InSb surface compounds. We used the Auger electron spectroscopy (AES) and electron energy loss spectroscopy (EELS) to detect the presence of these features. However, these techniques alone do not allow us to determine with accuracy their disturbed dimension related to the height and periodicity. For this reason, we combine these spectroscopy methods with the TRIM (transport and range of ions in matter), SRIM (Stopping and Range of Ion in Matter) and Sigmund simulation methods to show the mechanism of interaction between the argon ions and the III-V compounds cited above and determine the dimension of disturbed areas as a function of Ar+ energy during 30 min.

AES, EELS and TRIM simulation method study of InP(100) subjected to Ar+, He+and H+ions bombardment.

Auger Electron Spectroscopy (AES) and Electron Energy Loss Spectroscopy (EELS) have been performed in order to investigate the InP(100) surface subjected to ions bombardment. The InP(100) surface is always contaminated by carbon and oxygen revealed by C-KLL and O-KLL AES spectra recorded just after introduction of the sample in the UHV spectrometer chamber. The usually cleaning process of the surface is the bombardment by argon ions. However, even at low energy of ions beam (300 eV) indium clusters and phosphorus vacancies are usually formed on the surface. The aim of our study is to compare the behaviour of the surface when submitted to He+ or H+ ions bombardment. The helium ions accelerated at 500V voltage and for 45 mn allow removing contaminants but induces damaged and no stoichiometric surface. The proton ions were accelerated at low energy of 500 eV to bombard the InP surface at room temperature. The proton ions broke the In-P chemical bonds to induce the formation of In metal islands. Such a chemical reactivity between hydrogen and phosphorus led to form chemical species such as PH and PH3, which desorbed from the surface. The chemical susceptibly and the small size of H+ advantaged their diffusion into bulk. Since the experimental methods alone were not able to give us with accuracy the disturbed depth of the target by these ions. We associate to the AES and EELS spectroscopies, the TRIM (Transport and Range of Ions in Matter) simulation method in order to show the mechanism of interaction between Ar+, He+ or H+ ions and InP and determine the disturbed depth of the target by argon, helium or proton ions.

Investigation by AES, EELS and TRIM Simulation Method of InP(100) Subjected to He<sup>+</sup> and H<sup>+</sup> Ions Bombardment

Auger Electron Spectroscopy (AES) and Electron Energy Loss Spectroscopy (EELS) have been performed in order to investigate the InP(100) surface subjected to ions bombardment. The InP(100) surface is always contaminated by carbon and oxygen revealed by C-KLL and O-KLL AES spectra recorded just after introduction of the sample in the UHV spectrometer chamber. The usually cleaning process of the surface is the bombardment by argon ions. However, even at low energy of ions beam (300 eV) indium clusters and phosphorus vacancies are usually formed on the surface. The aim of our study is to compare the behaviour of the surface when submitted to He+ or H+ ions bombardment. The helium ions accelerated at 500 V voltage and for 45 mn allow removing contaminants but induces damaged and no stoichiometric surface. The proton ions were accelerated at low energy of 500 eV to bombard the InP surface at room temperature. The proton ions broke the In-P chemical bonds to induce the formation of In metal islands. Such a chemical reactivity between hydrogen and phosphorus led to form chemical species such as PH and PH3, which desorbed from the surface. The chemical susceptibly and the small size of H+ advantaged their diffusion into bulk. Since the experimental methods alone were not able to give us with accuracy the disturbed depth of the target by these ions. We associate to the AES and EELS spectroscopies, the TRIM (Transport and Range of Ions in Matter) simulation method in order to show the mechanism of interaction between Ar+, He+ or H+ ions and InP and determine the disturbed depth of the target by argon, helium or proton ions.

Investigation by EELS and TRIM simulation method of the interaction of Ar + and N + ions with the InP compound

In this study, the EELS results revealed the great sensitivity of InP compound submitted to Ar + or N + ions at low energy. The preliminary treatment of InP by the Ar + ions was useful as part of the cleaning process of the surface. Further argon ions bombardment on cleaned InP led however to breaking of chemical bonds In–P, with desorption of phosphorus atoms and appearance of In metal distributed on InP. The damaged InP by Ar + ions, constituted the diphase (In; InP) system of depth of about 30 Å, involving a superficial roughness. The In metal proportion on such a system was determined by a calculation method based on the experimental EELS spectra of pure In and InP. We submitted the heated and no heated system (In; InP) to nitrogen ions bombardment. The nitrogen reacted with the In metal to compensate the phosphorus vacancies so that InN species were formed. The heating of (In; InP) system at 450 °C, allowed the surface reconstruction with elimination of defects due to the structure and the roughness. The temperature also caused the coalescence of In metal towards the surface. Because of the physical stability of the interface of heated (In; InP) system, the nitrogen reacted with the outmost layers of In metal to form a homogeneous layer of InN of thickness estimated at 20 Å. We associated to the EELS the TRIM (Transport and Range of Ions in Matter) simulation method in order to show the mechanism of interaction Ar + or N + ions-InP and determine the disturbed depth as a function of the energy. The EELS alone was not able to give us with accuracy the disturbed depth of the target by these ions.

AES, EELS and TRIM investigation of InSb and InP compounds subjected to Ar + ions bombardment

The interaction of ions with matter plays an important role in the treatment of material surfaces. In this paper we study the effect of argon ion bombardment on the InSb surface in comparison with the InP one. The Ar + ions, accelerated at low energy (300 eV) lead to compositional and structural changes in InP and InSb compounds. The InP surface is more sensitive to Ar + ions than that of InSb. These results are directly inferred from the qualitative Auger electron spectra (AES) and electron energy loss spectroscopy (EELS) analysis. However, these techniques alone do not allow us to determine with accuracy the disturbed depth in Ar + ions of InP and InSb compounds. For this reason, we combine AES and EELS with the simulation method TRIM (transport and range of ions in matter) to show the mechanism of interaction between the ions and the InP or InSb and hence determine the disturbed depth as a function of Ar + energy.

Microstructural characterisation of carbon implanted austenitic stainless steel

Low carbon (316L) austenitic stainless steel has been implanted with carbon ions with a fluence of 5 × 10 17 C ions/cm 2 using an ion energy of 75 keV. The effect of carbon ion implantation on the microstructure of the austenitic steel has been examined in cross-section using transmission electron microscopy (TEM) both before and after implantation, and the implantation data correlated with a computer based simulation, TRIM (Transport and Range of Ions in Matter). It has been found that the high-fluence carbon ion implantation modified the microstructure of the steel, as demonstrated by the presence of two amorphous layers separated by a layer of expanded austenite.

A microstructural and mechanical study on the effects of carbon ion implantation on zirconia-toughened-alumina

Biomedical grade (>99.97% purity) alumina, zirconia and zirconia-toughened-alumina (ZTA) have been implanted with carbon ions at a dose of 5 × 1017 C ions/cm2 using an ion energy of 75 keV. The near-surface hardness of these bioceramics was examined using a load partial-unload indentation technique, both before and after implantation. The surfaces of the bioceramics have also been examined in cross-section using transmission electron microscopy (TEM) both before and after implantation and the implantation data correlated with a computer based simulation, TRIM (Transport and Range of Ions in Matter). The grinding and polishing treatment used prior to the implantation treatment has been found to have a strong influence on the surface microstructures for all three ceramics, although more significant modifications are brought about by carbon ion implantation. A comparison was made between the near-surface hardness of the unimplanted and carbon ion implanted surfaces of these bioceramics with relation to the modified microstructure. TEM examination of the implanted surfaces has demonstrated the formation of a sub-surface amorphous layer in all three materials as well as other microstructural modifications, such as microcracking and an increase in the near-surface dislocation density, that are characteristic of ion damage. The hardness data reveals that carbon ion implantation tends to decrease the surface hardness of alumina and zirconia with increasing ion dose, with a significant decrease occurring at the immediate near surface for both materials.

Evaluation of the ion bombardment energy on silicon dioxide films deposited from O[sub 2]/TEOS plasmas on Si and unstrained Si[sub 0.83]Ge[sub 0.17]/Si substrates

Silicon dioxide films are deposited on Si and unstrained Si0.83Ge0.17 from O2/tetraethylorthosilicate plasmas in a helicon reactor operated at low pressure (2 mTorr). The effect of the negative dc self-bias voltage (0 to −200 V) on the film properties is investigated. X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry measurements have been performed on ultrathin (∼5 nm) films to gain better insight into the quality of the dielectric/semiconductor interface. We observed that the ion bombardment energy is responsible for the amorphization of the substrate, which is in agreement with the TRIM (transport and range of ions in matter) simulation results. In the case of SiGe samples, a GeO2 phase is detected in the XPS spectra which increases with the applied bias. Changes on the vibrational properties are observed on thick films (500 nm) while refractive index and p-etch measurements are only slightly sensitive to the voltage applied to the substrate. Complementary electrical measurements have been carried out on metal–oxide–semiconductor capacitors. For films deposited on Si substrates, C–V measurements indicated a degradation of the electrical properties with increasing energy of the impinging ions. The results obtained on SiGe samples exhibit typical negative fixed charges in the oxide with a rather low density of interface states (Dit∼5×1011 cm−2 eV−1).

CO2 Formation over a Catalytic Surface Containing Free Oxygen in the Subsurface Monolayers

In this work, we developed Monte Carlo simulations to understand the transient experiments on CO 2 formation at the oxygen-rich ruthenium surface observed in recent experiments [A. Bottcher et al., J. Phys. Chem. B 193, 6267 (1999)]. We modeled this very complex system by a semi-infinite cubic lattice, the catalyst having been represented by the (001) free surface, and the typical profile shapes obtained by employing the TRIM (Transport and Range of Ions in Matter). When the surface is exposed to a constant flux of CO molecules we observe the formation of CO 2 due to the Langmuir-Hinshelwood process. The number of active sites over the surface is taken proportional to the number of monolayers of oxygen deposited due to the sputtering mechanism. Increasing the temperature, the active sites on the free surface become more mobile, and the subsurface oxygen atoms migrate to surface through diffusion. We show that desorption of CO molecules from the surface is very important at higher temperatures. Even taking high values for the diffusion of active sites and subsurface oxygen, a small desorption rate of CO leads the surface to become quickly poisoned by these molecules, therefore blocking the diffusion of oxygen atoms towards the topmost layer.