Simulation of boron nitride sputtering process and its comparisonwith experimental data

In the paper, TRIM and TRIDYN simulation codes were used to simulate the sputtering processes of boron nitride (BN) films during bombardment of ions. The TRIM and TRIDYN codes are applicable to the simulation of sputtering processes of different target materials with amorphous and polycrystalline structure. The results of the simulations are compared with experimental data. The sputtering experiments of polycrystalline hexagonal BN (h-BN) and cubic BN (c-BN) films were performed in a Commonwealth Scientific Corporation (CSC) 38-cm ion beam source device. The comparison of calculated and experimental results indicated that a) the experimental sputtering yields of h-BN and c-BN films bombarded with Ar⁺ ions versus the angle of incidence are in reasonable agreement with the calculated results; b) the sputtering yields of h-BN and c-BN bombarded with Ar⁺ are nearly of the same values versus the angle of incidence-preferential sputtering of h-BN was not found; c) the calculated sputtering. Yields of BN as a function of Ar⁺ ion energy are very sensitive to values of the surface binding energy (SEE); and d) surface binding energy between 2 and 3 eV for BN appears to be reasonable for the simulation of sputtering process of h-BN and c-BN films     

Ion sputtering rates of W-, Ti- and Cr-carbides studied at different Ar ion incidence angles

To study the ion sputtering rates of W-, Ti- and Cr-carbides, trilayer structures comprising C-graphite (59 nm)/WC (50 nm)/W (38 nm), C-graphite (56 nm)/TiC (40 nm)/Ti (34 nm) and C-graphite (46 nm)/C₃C₂ (60 nm)/Cr (69 nm) with a tolerance ±2% were sputter deposited onto smooth silicon substrates. Their precise structural and compositional characterization by transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) revealed that the WC and Cr₃C₂ layers were amorphous, while the TiC layer had a polycrystalline structure. The ion sputtering rates of all three carbides, amorphous carbon and polycrystalline Cr, Ti and W layers were determined by means of Auger electron spectroscopy depth profiling as a function of the angle of incidence of two symmetrically inclined 1 keV Ar⁺ ion beams in the range between 22° and 82°. The sputtering rates were calculated from the known thicknesses of the layers and the sputtering times necessary to remove the individual layers. It was found that the sputtering rates of carbides, C-graphite and metals were strongly angle dependent. For the carbides in the range between 36° and 62° the highest ion sputtering rate was found for Cr₃C₂ and the lowest for TiC, while the values of the sputtering rates for WC were intermediate. The normalized sputtering yields calculated from the experimentally obtained data for all three carbides followed the trend of theoretical results obtained by calculation of the transport of ions in solids by the SRIM code. The sputtering yields are also presented in terms of atoms/ion. Our experimental data for two ion incidence angles of 22° and 49° and reported values of other authors for C-graphite and metals are mainly inside the estimated error of about ±20%. The influence of the ion-induced surface topography on the measured sputtering yields was estimated from the atomic force microscope (AFM) measurements at the intermediate points of the corresponding layers on the crater walls formed during depth profiling.     

Sodium halide sputtering by H+, He+, Ar+ ions

Sputtering experiments were performed with 70 to 300 keV H⁺, He⁺ and Ar⁺ ions impinging on KC1, KBr and Kl. The alkali halide samples are prepared as polycrystalline layers of about 2500 Å thickness, deposited on carbon-aluminium backings. During the ion bombardment the targets are kept at elevated temperatures between 50 and 300°C, in order to study the temperature dependence of sputtering. During the irradiation the removal of halogen and sodium is simultaneously observed by Rutherford backscattering.

The present results are (i) preferential sputtering of the halogen atoms, (ii) temperature dependent sputtering yields with 0.2 eV activation energy, (iii) sputtering yields proportional to the electronic stopping power, rather than the nuclear stopping power, and (iv) sputtering yields orders of magnitude higher than estimated by elastic collision cascade theories. These findings can be interpreted by a Pooley process with subsequent migration of the interstitial halogen atom to the surface.     

Anisotropic angular distribution of sputtered atoms

The sputtering yield angular distributions have been calculated on the basis of the ion energy dependence of total sputtering yields for Ni and Mo targets bombarded by low-energy Hg⁺ ions. The calculated curves show excellent agreement with the corresponding Wehner's experimental results of sputtering yield angular distributions. This fact clearly demonstrates the intrinsic relation between the ion energy dependence of total sputtering yields and the sputtering yield angular distribution. This intrinsic relation had been ignored in Yamamura's papers [Yamamura, Y. (1982). Theory of sputtering and comparison to experimental data, Nucl. Instr. and Meth., 194, 515–522; Yamamura, Y. (1981). Contribution of anisotropic velocity distribution of recoil atoms to sputtering yields and angular distributions of sputtered atoms, Rad. Eff., 55, 49–55.] due to some obvious mistakes.     

On the reflection coefficient of keV heavy-ion beams from solid targets

Measurements of the reflected fractions of sodium, potassium, and krypton ions impinging on polycrystalline silver and gold and amorphous germanium targets have been made at medium keV energies. The reflected fraction depends strongly on mass ratio and weakly on energy. Previous calculations of ion reflection (based on random slowing-down by elastic collisions in an infinite medium) have been extended. Corrections to the calculated values due to electronic stopping and surface effects have been estimated. Agreement between measurements and calculations is satisfactory.     

Energieverlustmessungen mit 60 keV Elektronen an amorphem und polykristallinem Selen und Tellur und Bestimmung optischer Konstanten

The energy loss functions Im—(1/?) of amorphous and polycrystalline Selenium and Tellurium are determined from energy loss spectra of 60 keV electrons in the energy range up to 30 eV. The optical constants ?₁ and ?₂ are calculated from the energy loss function by Kramers Kronig analysis. The energy difference in the position of the volume plasma loss of amorphous and polycrystalline foils is compared with the calculated change in free electron plasma energy resulting from density change. Characteristic structure dependence of the optical constants are found to be similar for Selenium and Tellurium. They are discussed in terms of the results of band structure calculations.     

The influence of channelling on the sputtering yield of polycrystalline copper

Abstract A simple model is proposed to test the applicability of Sigmund's theory to polycrystalline copper targets. A fixed amount of fortuitous chan = nelling is allowed in the target and the sputtering coefficient is calculated by using a combination of single crystal sputtering theory and Sigmund's for= mula. The results indicate that the effect of channelling is to shift the sputtering maximum to higher energy values than predicted by the amorphous target theory. Furthermore, the form of the sputtering yield-energy curves deviate significantly from the Sigmund sputtering curve.     

MONTE CARLO STUDIES OF RADIATION DAMAGE INDUCED BY FUSION:DYNAMIC SIMULATION OF SPUTTERING

In this paper, the sputtering caused by fusion of ⁴He particles in the first wall materials is investigated by using the dynamic Monte Carlo simulation, which is based on the binary collision approximation. The dependences of sputtering yields on the incident energy and angle, as well as the comparisons of results calculated using the Monte Carlo methed with results from experiments, are discussed. Energy spectrum and angular distributions of sputtered species, the depth of origin of the sputtered particles as well as range distributions of incident ions are given. From a comparison between the related experimental data and the calculated results with static and dynamic simulation it has been found that a better agreement is obtained for dynamic simulation.     

合金三元和四元系无定形靶中离子射程研究

本文应用Vagard定律,由二元系投影射程R_p的线性组合计算合金三元或四元系R_p。计算的H⁺→GaAlAs,InAs,InGaAs,Be⁺→GaInSb和InAsSb,以及B⁺→Cd_0.2Hg_0.8Te多元系合金靶的R_p,与文献报道的实测值或计算值甚为符合。此外,还计算了H⁺→GaInAsP,GaAlAsSb和 关键词：     

Experiments on the sputtering of neutral Cu2 dimers from Cu by Ar+ ions (60–300 eV)

A planar polycrystalline copper target was bombarded normally by Ar⁺ ions with energies ranging from 60 to 300 eV. in the source of a mass spectrometer. The neutral particles sputtered normally from the target were post-ionized and analyzed in the mass spectrometer. A thermionically sustained, magnetically confined low pressure arc plasma was used to supply the bombarding ions, and for post-ionization of the neutral sputtered species. It was found that the relative yields of the sputtered neutral post-ionized Cu₂ dimers are linearly proportional to S², where S is the total sputtering yield for Ar⁺ -Cu. The results support the recombination model for the formation of neutral dimers in sputtering.     

Sputtering of A 3 B 5 materials (GaP, GaAs, GaSb, InP, and InSb) by 2-to 14-keV N 2 + ions

Investigations of the general characteristics and distinctive features of sputtering of A ³ B ⁵ materials (GaP, GaAs, GaSb, InP and InSb) under bombardment with N ₂ ⁺ ions have been carried out. From the experimental data, dependences of the sputtering yield of these materials on the incidence angle and ion energy have been obtained and the surface relief patterns produced by target etching have been studied. It has been shown that the dependence on energy of the sputtering yield for GaP, GaAs, and InP can be adequately described by the Haffa-Switkovski formula for binary materials and Yudin’s approximation for elemental targets. Sputtering of GaSb and InSb proceeds in the surface layer recrystallization mode, and the sputtering yield agrees with calculations based on Onderlinden’s model. From a comparison of the experimental and calculated dependences, the surface bonding energies have been determined.     

Semiempirical calculation of the fine-structure parameters for np 5 n′p configurations

The fine-structure parameters are calculated semiempirically in the intermediate coupling scheme for the np ⁵ n′p configurations of rare gas atoms and a number of ions. The calculation is based on the two-electron matrix of the energy operator, which takes into account, along with the electrostatic interaction, all magnetic interactions. Diagonalizing the energy matrix with the calculated values of the fine-structure parameters yields energy values exactly coinciding with the experimental data, as well as the coupling coefficients and the gyromagnetic ratios. The results obtained are compared with the available literature data.     

Stability of subatomic carbon films on metal surfaces against low-energy gas ion bombardment

The earlier developed original experimental technique for measuring and analyzing the parameters of low-frequency fluctuations of the field-emission current in metal film systems is used to measure the sputtering yield Y _f of carbon films (with a coverage Θ ranging from 1 to 4) applied on Fe, Nb, Ta, and U substrates. The value of Y _f is calculated by an expression derived within a theoretical model developed. The sputtering ratios were measured for the case when the carbon films are sputtered by H⁺ and He⁺ ions with an energy E _i between 2 and 10 keV. With Θ fixed, the energy dependences of Y _f are obtained for each of the ions. In addition, for each of the ions, the Θ dependences of Y _f are found for several values of E _i. In all the cases, the measured values of Y _f far exceed those for pure carbon. With another original technique that combines field-ion microscopy (FIM) and precise measurement of current and/or luminous properties of local regions in FIM images, the energy thresholds E _th of sputtering carbon films applied on the metal surfaces are found. The energy distributions of Y _f in the near-threshold energy range for various Θ are obtained.     

Study of the sputtering of adsorbates by low energy ions (O on Ni)

Sputtering or ion impact desorption of adsorbed layers has been studied by low energy ion scattering and model calculations. For adsorption of a monolayer or less (e.g. oxygen on nickel) the desorption by ions can be readily observed by He⁺ ion scattering from the development of the adsorbate and substrate signal as a function of time. Desorption cross sections for Ne⁺ and He⁺ ions in the energy range from 500 eV to 1600 eV are given. These results are compared with the model calculations and the influence of various parameters can be studied by this comparison. The contribution of different processes to the sputtering mechanism is discussed.     

Determination of the negative ion yield of copper sputtered by cesium ions

Abstract

This paper describes the determination of secondary ion yields for negative ions obtained by bombardment of copper by cesium ions. Stable and reproducible surface conditions are reached by high rate sodium deposition simultaneously with sputtering. An optimum thickness of sodium corresponding to about one monolayer is found. Total negative ion yields K ^? _Σ are measured by a double modulation technique. Individual negative ion yields K ^? _i are then found by mass spectrometrically determining the various negative ion intensities, the sum of which relates linearly to K ^? _Σ. This method is based on the assumption of an equal angular and energy distribution of all sputtered negative ions. Data are given for K^? _Σ and K ^? _Cu and K^? _O. The dependence of K ^? _i on primary ion energy (500 to 2500 eV) is similar to ordinary sputtering which points to the same basic mechanism in both cases.     

Sputtering of Cu atoms by Ar ions

Sputtering of Cu single-crystal, polycrystal and amorphous targets by 5 keV Ar ions has been studied by the binary collision lattice simulation code Cosipo. The sputtering yields, angular distributions, energy distributions and the space distributions of the original positions of the sputtered Cu atoms have been calculated. The results are discussed within the framework of cascade generations and surface structure.     

Growth and properties of Ti-Cu films with respect to plasma parameters in dual-magnetron sputtering discharges

Properties of different methods of magnetron sputtering (dc-MS, dual-MS and dual-HiPIMS) are studied and compared with respect to intermetallic Ti-Cu film formation. The quality and features of thin films are strongly influenced by the energy of incoming particles. The ion velocity distribution functions (IVDFs) were measured by time-resolved retarding field analyzer (RFA) in the substrate position. Thin films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD) and X-ray reflectometry (XR). Properties and crystallography of Ti-Cu films are discussed as a function of ion energy which is affected by the mode of sputtering. It was found that IVDFs measured in pulsed discharges exhibit double-peak distribution. The IVDFs reach the maximum at ion energies about  ~8 eV. The ion saturated current is highest in dual-HiPIMS discharge (~5 μA/cm²) and is mostly represented by Cu⁺ and Ar⁺ ions. The mode of sputtering influences chemical composition and film formation. The copper forms polycrystalline fcc-phase while much smaller Ti particles enwraps the copper crystallites or are part of a solid solution.     

Incident angle dependence of electronic desorption and sputtering by energetic ions

It is shown that deviations of the dependence of sputtering yield on the incident angle, θ, from the standard (cos θ)⁻¹ dependence can be indicative of a depth dependence in the net energy deposition in the surface region. Information about the sputter ejection mechanism is shown to be obtained only secondarily. We give expressions that allow one to relate the measured dependence of the yields on angle of incidence to the dependence of energy deposition on depth. This is used to analyze results for condensed gas sputtering and heavy ion desorption of organic molecular ions. This analysis indicates that the spatial distribution of excitations produced by the secondary electrons is important in determining these yields. This is also confirmed by observed differences in the yields for transmission and back-sputtering which is a closely related effect.