X-ray photoelectron spectroscopy-based valence band spectra of passive films on titanium

Titanium (Ti) is always covered by thin passive films. Thus, valence band (VB) spectra, obtained using X-ray photoelectron spectroscopy (XPS), are superpositions of the VB spectra of passive films and that of the metallic Ti substrate. In this study, to obtain the VB spectra only of passive films, angular resolution (for eliminating the substrate Ti contribution) and argon ion sputtering (for removing passive films) were used along with XPS. The passive film on Ti was determined to consist of a very thin TiO₂layer with small amounts of Ti₂O₃, TiO, hydroxyl groups, and water with a thickness of 5.9 nm. The VB spectra of Ti were deconvoluted into four peak components: a peak at ~1 eV, attributed to the Ti metal substrate; a broad peak in the 3–10 eV range, mainly attributed to O 2p (~6 eV) and O 2p-Ti 3d hybridized states (~8 eV), owing to the π (non-bonding) and σ (bonding) orbitals in the passive oxide film; and a peak at ~13 eV, attributed to the 3σ orbital of O 2p as OH⁻or H₂O. The VB region spectrum between approximately 3 and 14 eV from Ti is originating from the passive film on Ti. In particular, characterization of VB spectrum obtained with a takeoff angle of less than 24° is effective to obtain VB spectrum only from the passive film on Ti. The property as n-type semiconductor of the passive film on Ti is probably higher than that of rutile TiO₂ceramics.     

Low-energy electron and X-ray degradation of biomedical plasma-fluoropolymer

Plasma-deposited thin films of fluoropolymer on metallic substrates were degraded by low-energy (1-100 eV) electrons and X-ray irradiation to simulate irradiation conditions of implanted coated stents in the human body during diagnostic procedures using high energy radiation. The desorption of anions and cations from the surface of the films induced by 1-100 eV electrons was recorded by mass spectrometry. The electron energy dependence of the emission of F⁻ exhibited a resonant peak at 12.9 ± 0.4 eV, showing the formation of a transient excited anion and a monotonic rise at higher energies, associated to dipolar dissociation. In the positive ion mode, the fragments F⁺, CF⁺, CF₂⁺, CF₃⁺, C₃F₃⁺, C₂F₄⁺ and C₂F₅⁺ were observed. Emission thresholds were measured and laid above 25 eV. The shape of the cation emission curves versus electron energy showed no resonant process. X-ray degradation was studied by X-ray photoelectron spectroscopy for different exposure times. Loss of fluorine in -CF₂ groups was observed and damage mechanisms were proposed.     

Low energy ion bombardment of Ti and TiNx films

The influence of low energy ion bombardment on TiN_x film growth and film properties was investigated. The discharge was characterized using Langmuir probe technique as well as energy resolved mass spectrometry with a plasma monitor (Hiden HAL 301 S/EQP). The deposited films were investigated by means of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Increasing the N₂ gas flow as well as increasing the negative substrate voltage at constant gas flow effect an increase of the N/Ti ratio in the films determined by XPS. The influence of the energy flux to the surface due to ion bombardment was mainly recognized in the substructure of the films. In addition, pure Ti films were modified by nitrogen ion bombardment after deposition using an ion gun. An increase of the N/Ti ratio was observed with increasing ion energy. Finally saturation is reached.     

Structural and electronic properties of HfO2 films on Si through H2O2 wet oxidation with improved thermal stability

The thermal stability and material properties of HfO₂ thin films on Si substrates with and without H₂O₂ wet chemical oxidation were investigated. The HfO₂ samples were deposited through plasma-enhanced atomic layer deposition and subjected to thermal annealing. They were then examined using X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, reflection electron energy loss spectroscopy, and conductive atomic force microscopy. For the Si substrate without H₂O₂ wet chemical oxidation, a native oxide (~1.8 nm) was formed on the substrate before HfO₂ deposition. After the annealing process at 600°C, the band gap (E_g) of the HfO₂ films increased from 6.0 to 6.2 eV due to the diffusion of Si into HfO₂. Furthermore, the conduction and valence band offsets (ΔE_c and ΔE_v, respectively) between HfO₂ and Si changed from 1.02 to 1.42 and 3.86 to 3.66 eV, respectively. After the H₂O₂ wet oxidation of the Si substrate, a 1.5-nm chemical oxide was formed instead of a native oxide. The band offset and E_g values of HfO₂ were similar before and after 600°C annealing (ΔE_v = 3.86 eV, ΔE_c = 1.02 eV, and E_g = 6.0 eV), implying the high thermal stability of the HfO₂ films. Accordingly, wet oxidation not only prevents diffusion from chemical oxide but also markedly improves the oxide leakage current, which is useful for developing highly efficient and thermally stable HfO₂ gate oxides in Si-based integrated circuit devices.     

Effect of the electropolymerisation conditions on the electrochemical, morphological and structural properties of PEDOTh films

Poly(3,4-ethylenedioxythiophene) (PEDOTh) films were deposited on platinum electrodes by consecutive potential scanning from acetonitrile solutions with 50 mM EDOTh. The effect of the supporting electrolyte used during electropolymerisation, namely LiClO₄, TBAClO₄ and TBAPF₆, in the redox behaviour, surface morphology and degree of crystallinity of the films has been investigated by cyclic voltammetry, X-ray diffraction analysis and scanning electron microscopy, respectively. The use of LiClO₄ leads to a higher electropolymerisation efficiency and an increase of electroactivity and crystallinity of the polymers. This electrolyte promotes the formation of a more compact morphology with clusters of different sizes. The film porosity increases when Li⁺ is substituted by a larger cation, TBA⁺. The PEDOTh layer obtained with as counter ion is more porous than the obtained with and presents a fibrillar aspect. The influence of the scan rate was also studied for films obtained in TBAClO₄, and high electropolymerisation efficiency and an increase of crystallinity were observed for a low scan rate. PEDOTh films with different number of growing cycles were obtained in LiClO₄, pointing their redox behaviour to structural rearrangement during thickening; the thicker film presents higher structural organization. It was possible to prepare films in different conditions, but with the same electroactivity, showing the same structural arrangement.     

Fe-doped and Mn-doped titanium dioxide thin films

Thin films of TiO₂ doped with Fe and Mn were deposited on F-doped SnO₂-coated glass by spin coating. Dopant concentrations of 3–7 wt% (metal basis) were used. The structural, chemical, and optical characteristics of the films were investigated. Laser Raman microspectroscopy and glancing angle X-ray diffraction data showed that the films consisted of the anatase polymorph of TiO₂. X-ray photoelectron spectroscopy data indicated the presence of Fe³⁺, Mn⁴⁺, and Mn³⁺ in the doped films, as predicted by calculated thermodynamic stability diagrams, and the occurrence of atomic disorder and associated structural distortion. Ultraviolet–visible spectrophotometry data showed that the optical indirect band gap of the films decreased significantly with increasing dopant levels, from 3.36 eV (undoped) to 2.95 eV (7 wt% Fe) and 2.90 eV (7 wt% Mn). These improvements are attributed to single (Fe) or multiple (Mn) shallow electron/hole trapping sites associated with the dopant ions.     

Effect of EMIMBF4 ionic liquid addition on the structure and ionic conductivity of LiBF4-complexed PVdF-HFP polymer electrolyte films

New polymer electrolyte films of lithium tetrafluoroborate (LiBF₄)-complexed poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) embedded with different quantities of 1-ethyl-3methylimidazolium tetrafluoroborate (EMIMBF₄) ionic liquid were prepared by solution casting. The prepared films were characterized using various techniques: X-ray diffraction, scanning electron microscopy, impedance spectroscopy and electrochemical measurements. The pure PVdF-HFP possessed a semi-crystalline structure and its amorphicity increased with the addition of LiBF₄ salt and EMIMBF₄ ionic liquid. The size and interconnection of pores in the films were enhanced by EMIMBF₄. Impedance measurements indicated that the room-temperature ionic conductivity of the films increased with increasing EMIMBF₄ concentration until 15 wt.%, being up to 0.202 × 10⁻⁴ S cm⁻¹, and then decreased with further increasing EMIMBF₄ concentration. In addition, the temperature-dependent ionic conductivity of the polymer electrolyte films followed an Arrhenius relation and the 15 wt.% EMIMBF₄-incorporated gel polymer electrolyte film exhibited a low activation energy for ionic conduction, being about 0.28 eV. Finally, the electrochemical stability window of the 85PVdF-HFP:15LiBF₄+15 EMIMBF₄ gel polymer electrolyte films was evaluated as approximately 4.4 V, which is a promising value for ion battery applications.     

X-ray photoelectron spectroscopy study of neodymium niobate and tantalate precursors and thin films

Neodymium niobate NdNbO₄ (NNO) and tantalate NdTaO₄ (NTO) thin films (~100 nm) were prepared by sol-gel/spin-coating process on Al₂O₃ substrate with LaNbO₄/PbZrO₃ interlayer and annealing at 1000°C. Surface chemistry was investigated by X-ray photoelectron spectroscopy (XPS). The core-level XPS studies of sol-gel NNO and NTO were performed for the first time. The binding energy differences Δ(O―Nb) and Δ(O―Ta) were used to characterize average energies of Nb―O bonding in NNO (322.9 eV) and Ta―O bonding in NTO (504.2 eV). The XPS demonstrated single valence state of Nd (Nd³⁺) in precursors. Nd concentration (at. %) decreases from 22% in precursors to 7% in films considering the substrate contains C, Al, Si, Pb, and Zr elements (37%) at Nb or Ta (5%) and O (51%). The X-ray diffraction analyses verified formation of the monoclinic (M-NdNbO₄ or M′-NdTaO₄), orthorhombic (O-NdNbO₄) and tetragonal (T-NdTaO₄) phases in precursors and films. Single valence state of Nd³⁺ was confirmed in these films designed for the application in environmental electrolytic thin film devices.     

Enhanced photoluminescence properties of Gd (x-1) Sr x O: CdO nanocores and their study of optical,structural, and morphological characteristics

Synthesis of Gd doped Sr_x O: CdO (x = 1.4, 1.6, 1.8) nanostructures (NS) was achieved through the coprecipitation method by using CTAB (cetyl trimethyl ammonium bromide) with the purpose to investigate the effect of Gd doping on the optical, structural, morphological, and photoluminescence properties at room temperature. Mixed phase of tetragonal crystal structure verified via X-ray diffraction technique, no structural variation was observed except lattice distortion. Size of the crystallites (D), morphology studied by SEM (scanning electron microscopy) analysis, nanoparticles (NPs) crystalized roughly flake-like morphology with homogeneous particle distribution centered at ~ 78 nm, ~56 nm, ~65 nm, ~88 nm for pure and Gd _(x-1) doped Sr _xO: CdO nanostructure, respectively. Fourier transform infrared spectroscopic investigation (FTIR) revealed the presence of Gd–O–Gd, Cd–O, Sr–O, and OH peaks appeared at ~1321 cm ^?1, ~1550 cm ^?1, ~1400 cm ^?1–3300 cm ^?1 with small variation in vibration modes due to Gd doping. Optical absorptivity observed in the range of 325 nm–359 nm (redshifted) with absorption edges at 346 nm, 364 nm, and 380 nm for Gd _(x-1) doped Sr _xO: CdO nanostructure, respectively. This redshift on the bandgap was discussed in terms of new band levels below conduction band. The energy gap was calculated using Kubelka-Munk theory and was found to be in the range of 3.22 eV–2.61 eV. X-ray photoelectron spectroscopy (XPS) performed to determine chemical composition and binding energies of Gd 3d _3/2, Sr 3d _3/2, and Cd 3d _3/2, O1s, and C1s observed at 150.8 eV, 141.6 eV, 411.0 eV, 530.4 eV, and 285.6 eV indicating Gd⁺³ ion replaces Sr⁺² in all concentrations. Our results showed that Gd-doped Sr _xO: CdO nanoparticles exhibited enhanced photoluminescence (PL) properties in contrast to the pure Gd₂O₃ with Gd⁺³ randomly incorporated into crystal structure, probably in tetrahedral sites. The composition of Gd _0.6 doped Sr _x O: CdO NS exhibited photoluminescent emission spectra, peaks centered at 433 ± 3 nm, 449 ± 3 nm, and 469 ± 2 nm (λ _excitation = 318 nm) and for Gd _0.8 doped Sr _x O: CdO nanostructure showed broad emission peak at 412 ± 2 nm to 433 ± 2 nm (λ _excitation = 380 nm), which indicates a reduction in defects with an increase in Gd doping. The transitions can be ascertained with shielding of 4f shells of Gd ⁺³ ions by 6s, 5d shells by the interaction of other Gd ⁺³ ions.     

Molecular adsorption and the chemistry of plasma-deposited thin organic films: Deposition of oligomers of ethylene glycol

Weakly ionized, radio-frequency, glow-discharge plasmas formed from methyl ether or the vapors of a series of dimethyl oligo(ethylene glycol) precursors (general formula: H-(CH₂OCH₂)_n-H;n=1 to 4) were used to deposit organic thin films on polytetrafluoroethylene. X-ray photoelecton spectroscopy (XPS) and static secondary ion mass spectrometry (SIMS) of the thin films were used to infer the importance of adsorption of molecular species from the plasma onto the surface of the growing, organic film during deposition. Films were prepared by plasma deposition of each precursor at similar deposition conditions (i.e., equal plasma power (W), precursor flow rate (F), and deposition duration), and at conditions such that the specific energy (energy/mass) of the discharge (assumed to be constrained byW/FM, whereM=molecular weight of the precursor) was constant. At constantW/FM conditions, two levels of plasma power (and, hence, twoFM levels) and three substrate temperatures were examined. By controlling the energy of the discharge (W/FM) and the substrate temperature, these experiments enabled the study of effects of the size and the vapor pressure of the precursor on the film chemistry. The atomic % of oxygen in the film surface, estimated by XPS, and the intensity of theC-O peak in the XPS C_ls spectra of the films, were used as indicators of the degree of incorporation of precursor moieties into the plasma-deposited films. Analysis of films by SIMS suggested that these two measures obtained from XPS were good indicators of the degree of retention in the deposited films of functional groups from the precursors. The XPS and SIMS data suggest that adsorption of intact precursor molecules or fragments of precursor molecules during deposition can have a significant effect on film chemistry. Plasma deposition of low vapor pressure precursors provides a convenient way of producing thin films with predictable chemistry and a high level of retention of functional groups from the precursor.     

Effect of Ion Energy on Structure and Composition of Cathodic Arc Deposited Alumina Thin Films

The effect of energy supplied to the growing alumina film on the composition and structure has been investigated by varying substrate temperature and substrate bias potential. The constitution and composition were studied by X-ray diffraction and elastic recoil detection analysis, respectively. Increasing the substrate bias potential from −50 to −100 V caused the amorphous or weakly crystalline films to evolve into stoichiometric, crystalline films with a mixture of the α- and γ-phase above 700 ^oC, and γ-phase dominated films at temperatures as low as 200 ^oC. All films had a grain size of <10 nm. The combined constitution and grain size data is consistent with previous work stating that γ-alumina is thermodynamically stable at grain sizes <12 nm [McHale et al., Science 277, 788 (1997)]. In order to correlate phase formation with synthesis conditions, the plasma chemistry and ion energy distributions were measured at synthesis conditions. These results indicate that for a substrate bias potential of −50 V, ion energies in excess of 100 eV are attained, both from a high energy tail and the accelerated ions with charge >1. These results are of importance for an increased understanding of the evolution of film composition and microstructure, also providing a pathway to γ-alumina growth at temperatures as low as 200 ^o C.     

To Study the Effect of Nanoparticle TiO2 on Sodium (Na+) – Ion Conducting Solid Polymer Electrolyte System: [80PEO:20NaPF6]

To study the effect of nanofiller particle TiO₂ on sodium (Na⁺) – ion conducting solid polymer electrolyte (SPE) film: [80PEO:20NaPF₆] and nanocomposite polymer electrolyte (NCPE): [80PEO:20NaPF₆] + xTiO₂, where x = 1–9 wt. (%) have been prepared. SPE film composition: [80PEO:20NaPF₆] selects as Ist-phase host and nano-sized (<100 nm) filler materials TiO₂ as IInd-phase dispersoid. Both SPE and NCPE films have been prepared by the hot-press technique. Filler particle-dependent conductivity study reveals the NCPE system: [80PEO:20NaPF₆] + 8TiO₂ as the highest conducting composition with σ_rt − 3.53 × 10⁻⁶ S cm⁻¹, which is approximately one order of magnitude higher than the SPE optimum conducting composition (OCC) (σ_rt) ≈ 7.78 × 10⁻⁷ S cm⁻¹. Ion transport properties for both SPE and NCPE system have been evaluated in terms of ionic conductivity (σ) and total ionic (t_ion)/cationic (t₊) transference numbers using combined AC/DC techniques in order to evaluate its usefulness in all-solid-state battery applications. Structural/thermal properties have been characterized using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques. A cyclic voltammetry (CV) study has been performed in SPE and NCPE OCC film to evaluate the electrochemical performance for battery application.     

Three new coordination complexes of cobalt(III), manganese(II), and copper(II) with N,N,O-donor hydrazone ligands: syntheses and structural characterizations

Three new coordination complexes, 2{[Co(L¹)₂]ClO₄} · 0.5CH₃OH (1), [Mn(L²)₂] (2), and [Cu(HL²)(L²)]ClO₄ · 2H₂O (3) have been synthesized from two tridentate N,N,O-donor hydrazone ligands HL¹, 2-acetylpyridine-salicyloylhydrazone, and HL², 2-benzoylpyridine-salicyloylhydrazone, respectively and thoroughly characterized by elemental analysis, FT-IR, UV–Vis, electrochemical, and room temperature magnetic susceptibility measurements. Structures of the complexes have been unequivocally established by single crystal X-ray diffraction technique. Structural analysis reveals that 1 consists of two chemically similar but crystallographically independent cationic [Co(L¹)₂]⁺ units and 2 consists of a neutral [Mn(L²)₂] molecule while 3 consists of a cationic [Cu(HL²)(L²)]⁺ unit. Metal ions display distorted octahedral geometry in 1 and 2 while in 3 it shows a distorted square pyramidal geometry. Ligand conformations around the metal ions are stabilized by the presence of intra-ligand hydrogen bonding in all the complexes. Structure of 3 reveals that a perchlorate ion linked to the complex by hydrogen bonding via a water molecule.     

Separation of uranium from solid (U,Pu, Ag) oxide analytical waste: effect of batch size and nitric acid molarity

This work presents the investigation of some commercially available and commonly used Si₃N₄ foils prepared with LPCVD technique. The density and the stoichiometry of these films were determined by Rutherford backscattering spectroscopy and profilometry, while the study of impurities was achieved with particle induced X-ray emission method. It was found that the density of the studied Si₃N₄ films is significantly less (~2.71 g cm^?3), while the stoichiometry is close to the values of the bulk material. The results were verified by measuring the ion energy loss through the films by scanning transmission ion microscopy.     

Preparation and photoelectric properties of mesoporous ZnO films

Mesoporous ZnO films doped with Ti⁴⁺ (M-ZnO) have been prepared by doping process and sol–gel method. The films have mesoporous structures and consist of nano-crystalline phase, as evidenced from small angle X-ray diffraction and high resolution transmission electron microscopy. The wide angle X-ray diffraction of M-ZnO films confirms that M-ZnO has hexagonal wurtzite structure and ternary ZnTiO₃ phases. Ultraviolet–visible transmittance spectra, absorbance spectra and energy gaps of the films were measured. The Eg of M-ZnO is 3.25 eV. Photoluminescence intensity of M-ZnO centered at 380 nm increases obviously with the excitation power, which is due to the doping process and enhanced emission efficiency. M-ZnO thin films display a positive photovoltaic effect compared to mesoporous TiO₂ (M-TiO₂) films.     

The effect of different substrate temperatures on the structure and luminescence properties of Y2O3:Bi3+ thin films

Y₂O₃:Bi³⁺ phosphor thin films were prepared by pulsed laser deposition in the presence of oxygen (O₂) gas. The microstructure and photoluminescence (PL) of these films were found to be highly dependent on the substrate temperature. X-ray diffraction analysis showed that the Y₂O₃:Bi³⁺ films transformed from amorphous to cubic and monoclinic phases when the substrate temperature was increased up to 600 °C. At the higher substrate temperature of 600 °C, the cubic phase became dominant. The crystallinity of the thin films, therefore, increased with increasing substrate temperatures. Surface morphology results obtained by atomic force microscopy showed a decrease in the surface roughness with an increase in substrate temperature. The increase in the PL intensities was attributed to the crystallinity improvement and surface roughness decrease. The main PL emission peak position of the thin films prepared at substrate temperatures of 450 °C and 600 °C showed a shift to shorter wavelengths of 460 and 480 nm respectively, if compared to the main PL peak position of the powder at 495 nm. The shift was attributed to a different Bi³⁺ ion environment in the monoclinic and cubic phases.     

Effect of swift heavy ion irradiation on the physical properties of CuIn(S0.4Se0.6)2 alloy thin films prepared by solution growth technique

Alloy thin films of CuIn(S_0.4Se_0.6)₂ material were deposited using the solution growth technique. The various deposition parameters such as pH of solution, time, concentration of ions and temperature have been optimized for the device grade thin films. The as-deposited films were annealed in a rapid thermal annealing (RTA) system at 450 °C in air for 5 min and subjected to high-energy Ag ion irradiations. Ag ion irradiation has been performed with an energy of 100 MeV at a fluency of 5×10¹² ions/cm² on the thin film. The changes in optical and electrical properties that occurred before and after post-deposition treatments in CuIn(S_0.4Se_0.6)₂ thin films were studied using X-ray diffraction (XRD) and AFM; increase in crystallinity was observed after annealing and irradiation. In addition, structural damages were observed in irradiated thin films. After annealing and irradiation, the surface roughness was seen to be increased. Decrease in resistivity was observed, which is consistent with the optical energy band gap. The results are explained by considering the high energy deposited due to the electronic energy loss upon irradiation, which modified the properties of the material.     

Influence of Mn incorporation on the structural and optical properties of sol gel derived ZnO film

Undoped and manganese doped ZnO (ZnO:Mn) films were prepared by sol gel method using spin coating technique. The effect of Mn incorporation on the structural and optical properties of the ZnO film has been investigated. The crystalline structure and orientation of the films have been investigated by using their X-ray diffraction spectra. The films exhibit a polycrystalline structure. Mn incorporation led to substantial changes in the structural characteristics of the ZnO film. The scanning electron microscopy (SEM) images of the films showed that the surface morphology of the ZnO film was affected by the Mn incorporation. The transparency of the ZnO film decreased with the Mn incorporation. The optical band gap and Urbach energy values of the ZnO and ZnO:Mn films were found to be 3.22, 3.19 eV and 0.10, 0.23 eV, respectively. The optical constants of these films, such as refractive index, extinction coefficient and optical dielectric constants were determined using transmittance and reflectance spectra. The refractive index dispersion curve of the films obeys the single oscillator model with dispersion parameters. The oscillator energy, E _o , and dispersion energy, E _d, of the films were determined 5.30 and 16.26 eV for ZnO film and 5.80 and 12.14 eV for ZnO:Mn film, respectively.     

Electrochemical deposition and characterization of SnS thin films

Thin films of SnS were cathodically deposited onto stainless steel substrates from bath containing 0.025 M SnSO₄, 0.25 M KSCN and 0.25 M Na₂SO₄. The mechanism of electrochemical co-deposition of tin and sulphur was investigated by cyclic voltammetry. Analysis of the chronoamperometric current–time transients suggested that, in the potential range −560 to −590 mV vs saturated calomel electrode, the electrodeposition of SnS involved progressive nucleation model. However, at a potential −600 mV, the electrodeposition involved instantaneous nucleation model. The deposits have been characterized by scanning electron microscopy, X-ray diffraction and optical measurements. SnS films were found to be polycrystalline with an optical energy gap of 1.38 eV.     

Hydrogen Plasmas Processing of Graphene Surfaces

To assist the development of plasma processes to pattern graphene in a controlled way, interactions between hydrogen plasma species (H, H⁺, H₂ ⁺) and various types of graphene surfaces (monolayer, nanoribbons, multilayer) are investigated using atomic-scale simulations. It is shown that only “hot” H particles (i.e., with a kinetic energy greater than ~0.4 eV at 300 K) can adsorb on the basal plane of surface-clean graphene while adsorption is barrierless on free edges or vacancies. Surface reaction probabilities (reflection, adsorption, penetration) are found to strongly vary with the incident species energy, which allows to determine specific energy ranges (or process windows) for different types of H₂ plasma treatment: lateral etching of graphene nanoribbons (GNRs), cleaning of graphene surfaces or vertical etching of multilayer graphene (MLG) stacks. Molecular dynamics simulations of GNRs trimming in downstream H₂ plasmas allow to understand the mechanism which governs the anisotropic etching of ribbons and explains the absence of line-edge roughness on their edges. Interactions between low-energy (5–25 eV) H _x ⁺ (x = 1, 2) ions with MLG are also investigated. Ion-induced damage (hydrogenation of successive graphene sheets, creation of vacancies) and etching of the MLG stack are found to vary with the ion energy, the ion fluence and the ion composition.