Dimitre Karpuzov

• PhD, DSc
• Project Manager at University of Alberta

Depth profiling of NbxO/W multilayered samples was carried out using O2+, Cs+ or Ar+ beams of different energies (2 keV, 1 keV and 0.5 keV). The obtained depth profiles showed that sputtering with O2+ or Ar+ beams can reveal the distribution of light elements, while sputtering with Cs+ cannot show correctly their distribution if lower energy of 0.5...

A facile method, Graphene Oxide (GO) modified electrochemically pre-anodized screen-printed carbon electrodes (SPCEs), was developed for the determination of nicotinamide adenine dinucleotide (NADH) in neutral aqueous solution. Compared with the bare SPCEs and the reduced Graphene Oxide (rGO) modified SPCEs (rGO/SPCEs), the GO/SPCEs exhibit greatly...

Time reference was introduced in the TRIM computer simulation code without changing the "event-driven" logic of the program. The code was applied to model the atomic collision cascades and sputtering of amorphous copper targets caused by bombardment of keV ions of different masses (Be, Ne, Ar, Cu, Xe, Au). Time-dependent characteristics of ion-indu...

A two-dimensional classical dynamics model for calculating the reflection coefficient of keV-ion beams backscattered from a crystal surface at glancing incidence is presented. The target is considered as consisting of one or two layers of atomic strings. A string potential of cylindrical symmetry was constructed by using the well-known "universal"...

The scattering of Ar, Ne, and He ions from the Cu {100} face has been investigated by a digital computer technique; only binary elastic collisions of ions with the lattice atoms have been considered; the angular and energy distribution at various directions of incidence are discussed. The scattering by surface atomic chains and its contribution to...

The 2D-dopant and defect distributions resulting from 80 keV ion implantation of As+ ions into Si through a high-edge mask are presented. The distributions are obtained by means of an efficient computer procedure using the results of Monte Carlo simulation. Two versions of the computer code TRIM are used. The 2D-target atom redistribution is obtain...

Irradiation by ion beams, used alone or combined with electron beams/X-rays, is in the basis of most vacuum techniques for surface analysis of materials. The ion bombardment effects in solids are however still hard to predict and consequently the ion beam techniques are less quantitative than others. Lack of proper description of some mechanisms an...

It is shown that inelastic losses included in calculations ofenergy spectra of ions reflected from the crystal surface result in worse resolution of the peaks related to quasisingle and multiple scattering. The great inelastic losses, for small sliding angles could explain the nonmonotonic appearance of two peaks when the ion beam is parallel to th...

Ion reflection based on a two-target-atom model is considered. In this approximation simple estimates of the angular distribution for small sliding angles are obtained (with or without thermal vibrations of atoms). The energy spectra in this case are also discussed. [Russian Text Ignored].

Thin metallic layers of Cu, Cr, or Ag were deposited on Si substrates and then sputtered as in a standard depth profiling mode. The etching was completed by using 1–5 keV Ar+ beam, scanned over the surface. The composition of the exposed etched surface was monitored by X-ray photoelectron spectroscopy (XPS) or Auger electron spectroscopy (AES). Whe...

This work is devoted to the secondary ion mass spectroscopic application in the studies of ink layering on paper. Optical methods are often unreliable in the identification of ink layering on substrates. We demonstrated the power of time-of-flight secondary ion mass spectroscopy (ToF-SIMS) by measuring the secondary ion mass spectra of handwriting...

We report self-organized metal nanopatterns on Si substrates produced by ion beam etching. We have deposited thin layers of metal such as Cu or Ag on Si substrates and then etched the deposited layers by a 1–5 keV Ar+ ion beam at room temperature. At the stage when the metal-Si interface is reached, we have observed networks of metal clusters on th...

Experimental and simulated energy distributions of Ga+ and In+ secondary ions produced by 4 keV Ne+, Ar+ and Kr+ bombardment of the AIIIBV semiconductors (GaP, GaAs, GaSb, InP, InAs and InSb) are reported. The measurements were carried out for a wide range of initial energy (up to 1000 eV) in a small solid angle along the surface normal, without ap...

Thin films containing iron silicides are prepared by two methods. The first one consists in depositing a-Si:H:Fe thin films by magnetron co-sputtering followed by rapid thermal annealing (RTA). The second one is ion implantation of Fe in a-Si:H thin films and RTA treatment. The samples are characterized by Fourier transform infrared spectroscopy (F...

(100)-oriented silicon substrates were implanted with 50keV Te+ or Pb+ ions at room temperature with doses varied in the range 1×1015 to 1×1018cm−2. Formation of ion beam-assisted Te and Pb nanocrystals in the layer amorphised by the implantation has been established. The accumulation of impurities, sputtering and formation of high-dose implantatio...

The ejection of energetic particles during steady-state ion surface bombardment has been investigated by means of a dynamic computer simulation as well as in a secondary ion mass spectrometry (SIMS)/low-energy ion scattering from surfaces (LEIS) experiment. The emphasis of this comparative study is on the mass dependence of high-energy tails in spu...

Depth and lateral-spread distributions of defects generated by 0.5-5 keV argon beam in crystalline nickel has been determined by using the computer simulation program MARLOWE. Over the whole energy range, vacancies are well separated from the interstitials and the formation of depleted zones is clearly indicated. Densities of defects and deposited...

Clusters of independently tailored areal density and size distribution were grown on semiconductor surfaces by molecular beam epitaxy and were used subsequently as masks for selective ion beam modification. Field emission scanning electron microscopy shows sharp interfaces between the amorphous area exposed to ion beams and areas of crystalline sil...

Aluminium nitride thin films were deposited by reactive d.c. magnetron sputtering on various substrates. The analytical tools used to characterise the aluminium nitride thin films were electron beam diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray analysis and polarised infrared reflection. From these techniques the structure,...

The effects of the ambient atmosphere in the annealing chamber on the electrical and structural characteristics of Zn-implanted III-V compound semiconductors, processed by low-power pulsed-laser annealing are presented. The samples were analyzed using several complementary experimental techniques: Reflection high-energy electron diffraction, Ruther...

The effect of 12 MeV electron irradiation of p-type Si-SiO2 structures is studied by Deep Level Transient Spectroscopy (DLTS) measurements. The DLTS spectra of non-irradiated samples exhibit one peak only corresponding to a deep level located in the forbidden gap at 0.56 eV above the valence band edge of the Si matrix. Four additional, shallower le...

Thin films of AlN were deposited at a total gas pressure of 7×10−4mbar and a nitrogen partial presure of 9×10−5mbar by reactive d.c. magnetron sputtering. Low-carbon steel 08KP, Si (100) wafers and monocrystal KCl were used as substrates. Electron microprobe analysis (EMA), X-ray photoelectron spectroscopy (XPS), polarised infra-red reflection and...

structures implanted with 50-keV boron ions is studied by deep-level transient spectroscopy (DLTS) measurements. The DLTS spectra of ion-implanted samples exhibit one peak which corresponds to adeep level located in the forbidden gap of the silicon matrix at Ec-0.40eV below the conducting band edge. New additional shallower levels are found in the...

The effect of 12 MeV electron irradiation of p-type Si-SiO2 structures is studied by Deep Level Transient Spectroscopy (DLTS) measurements. The DLTS spectra of non-irradiated samples exhibit one peak only corresponding to a deep level located in the forbidden gap at 0.56 eV above the valence band edge of the Si matrix. Four additional, shallower le...

Low-power pulsed-laser annealing was applied to Zn+-implanted InP samples. In order to avoid surface oxidation during the treatment, the laser irradiation was carried out in inert ambient of nitrogen at different pressures. The analytical techniques used include Rutherford backscattering spectroscopy, reflection high energy electron diffraction, an...

Reflection high-energy electron diffraction (RHEED) and X-ray photoelectron spectroscopy (XPS) were used to demonstrate the effects of Zn+-ion implantation and subsequent low-power pulsed laser annealing (LPPLA) on the crystallinity and the P/In ratio near the surface of InP. The influence of ion-beam effects during depth profiling by a 1 to 5 keV...

The structure of (100) silicon implanted with Zn⁺ ions at an energy of 50 keV was studied. The ion doses were varied from 1×10¹⁵ to 1×10¹⁷ cm^-2 and the beam current density was 10 μA cm^-2. The analytical techniques employed for sample characterization included cross‐sectional transmission elect...

The 2D-dopant and defect distributions resulting from 80 keV ion implantation of As+ ions into Si through a high-edge mask are presented. The distributions are obtained by means of an efficient computer procedure using the results of Monte Carlo simulation. Two versions of the computer code TRIM are used. The 2D-target atom redistribution is obtain...

A method based on a thermocouple detector measuring simultaneously the total flux of energetic particles and the portion of the charged particles is proposed and studied. These data allow the neutral fraction of the ion beam to be easily calculated and the fraction is determined for different values of the working gas pressure in Ar and SF6. The re...

The composition and structure of an InP{100} surface in both the (1 × 1) and the reconstructed (4 × 2) phases, prepared by ion bombardment and annealing, have been examined by time-of-flight scattering and recoiling spectrometry (TOF-SARS) and low-energy electron diffraction (LEED) . Time-of-flight spectra of scattered and recoiled neutrals plus io...

A modified version of the Monte-Carlo computer code TRIM is used to study the scattering of energetic ions from random surfaces. Angular and energy distributions of scattered particles are obtained for the ‘rough surface’ model. It is shown that the position and the magnitude of the peaks in the energy distributions of ions for a given scattering a...

It has been recently established that the crystallinity of ion-implanted GaAs samples can be restored by using a low-power pulsed-laser annealing (LPPLA) technique. In this paper we report an improvement of carrier activation achieved after low-temperature processing (added to LPPLA) at temperatures low enough to avoid substantial losses of As. By...

The surface and subsurface compositional changes of Cu-Ni alloys with different stoichiometries were studied in situ using 5 keV Ar ion sputtering and X-ray photoelectron spectroscopy. The altered layer formed at room temperature exhibits enrichment of Cu-atoms at the surface due to segregation phenomena and diffusion. The size of the effect depend...

The azimuthal anisotropy of 3 keV Ar+ ions scattered from a Ni(111) single crystal surface at relatively large angle (theta = 40°) is investigated. Shadowing mode (incidence angle, alpha = 5° measured from the surface) was used. Correlation between the azimuthal anisotropy and the energy distribution of the scattered ions is observed both experimen...

Time was introduced in the well-known TRIM code without changing the “event-driven” logic of the program. This modified TRIM code was used to simulate the slowing-down process of fast Cu ions in amorphous Cu targets. Distributions of the radial range and slowing-down time of the ions together with other time-dependent characteristics of the process...

Data on the effects of 140 keV Zn+ implanation of (100)GaAs and the consequent low-power pulsed laser annealing (LPPLA) on the composition of the surface layers are presented. The implantation does was 1014 cm −2 and the sample temperature was kept at 110 ± 10°C. THE LPPLA was carried out by 10–30 pulses of a Q-switched ruby laser (λ = 694.3 nm, τ...

The composition of the cutermost surface layers of polycrystalline CuBe alloys has been investigated by Auger electron spectroscopy (AES). Relative changes in the surface composition under Ar+ ion bombardment at different fluences up to the steady-state conditions have been monitored by AES in ultrahigh vacuum. The experimental results are compared...

Wafers of (100) GaAs have been implanted with 140 keV Zn+ ions at off-channeling direction up to a fluence of 1×1014 cm-2. The target temperature was kept at 110+/-10°C. The defect clusters and the damage depth distributions were investigated by planar and cross-sectional high-resolution transmission electron microscopy (HRTEM and XHRTEM) and were...

This work is part of a series of investigations started a few years ago to study high fluence ion beam effects. Experimental and computer techniques are applied here to the implantation of 40 keV As+ in (111) Si samples at doses ranging from 1 × 1016 to 2 × 1017 cm-2. The experimental evolution of the profile was analyzed by 2 MeV RBS spectroscopy....

Depth profiling of 200 Å Al thin films on Si substrates is performed experimentally using oxygen in the ion beam source or in the analysis chamber. These depth profiles are also obtained by dynamic Monte Carlo simulation. In addition to the simulation of the ballistic cascade development, the computer code also includes additional chemically guided...

The secondary ion yields from Nb(100) and Nb(111) crystals bombarded with 3–7 keV Ar ions at various azimuthal and polar angles of incidence are measured. The reductions of the sputtering yields due to channeling along the major planar and axial channels of the crystals are separated. The effect is found to depend on the channel orientation relativ...

A dynamic Monte Carlo program developed for the simulation of high-fluence effects in ion bombardment of multicomponent targets is described. The program includes a code for modelling the chemically guided motion of the slowed down primaries and recoils. Examples of the application of the simulation program to Ar+ sputtering of CdHgTe and SiO2, O+...

It has been shown [Todorov and Fossum, J Vac Sci Technol, B6, 466 (1988)] that ultra-thin (d ≈ 50 Å) oxide films can be grown on silicon surfaces at reduced substrate temperatures using oxygen-containing low energy ion beams (E < 200 eV). The oxide film evolution with increasing fluence can be explained by a general model based on the competing pro...

Mesa structures and thin membranes are obtained by means of wet anisotropic etching using the etch-stop effect of nitrogen-implanted silicon. Dynamic Monte Carlo simulation is applied to calculate the implanted nitrogen profile. The use in sensor technology of nitrogen ion implantation in silicon with doses as low as 5×1016 cm−2 is described.

Self-limiting growth of ultrathin (~ 40 Å) oxide films on silicon surfaces has been performed using oxygen-containing low energy ion beams (E ≈ 100 eV) at reduced substrate temperatures. The observed weak dependence of the steady-state thickness on substrate temperature testifies the nonthermal nature of the oxidation process. A model based on the...

GaAs crystals were implanted with 140 keV Zn ions at random incidence and a dose of 1014 cm-2. Annealing by a low-power pulsed laser was used to recover the radiation damage. The samples were analysed by RHEED and RBS techniques. The effect of the annealing on the recovery of structure defects in GaAs is reported.

Depth distributions of displaced atoms for boron and arsenic implanted (111) silicon have been studied both by RBS channeling measurements and by a Monte Carlo simulation technique. The experiments and calculations are compared for ion energies of 80 and 160 keV and different doses. The computer code based on TRIM depth distributions takes into acc...

Low‐power annealing by a pulsed laser is used to recover the structure of low‐dose implanted (100) GaAs crystals. Reflection high‐energy electron diffraction with variable glancing incidence is employed to detect the structural changes at different depths in the specimens. The depth dependence of the damage is studied in more detail by Rutherford b...

GaAs 100 wafers were implanted and later annealed by using three different techniques: furnace thermal annealing (FTA), flash lamp (RTA) and low-power laser annealing (LPLA). The resulting modifications of the structure were studied by RHEED. The RHEED pattern analysis indicates that: (a) A well annealed structure is observed after thermal treatmen...

Semi-insulating Cr-doped (100) GaAs was implanted with Bi+ with energy 40 keV at room temperature in a 7 ° off-axis direction. The implanted dose was varied between 2 × 1015 cm-2 and 1 × 1016 cm-2. The profile evolution was studied experimentally by RBS measurements and theoretically by a new dynamic computer code. It is based on sputtering yield v...

The binary-collision approximation (BCA) based on the MARLOWE computer code is used to simulate the energy and angular distributions of atoms sputtered from a Rh(111) crystal surface exposed to ion bombardment. The influence of the depth-of-origin and replacement collisions on these distributions is discussed. The results are compared to the molecu...

A secondary ion mass spectrometer with high energy, angle and mass resolution is used to study the energy and angular distributions of ions sputtered from molybdenum (110) surface under 4 keV argon beam bombardment. The sputtering at different beam orientations is also simulated by the MARLOWE computer code. The sputtering yields, in addition to th...

Thin 15 nm bilayers of antimony on silicon, or a thin 10 Å antimony marker layer buried in a matrix of silicon, were irradiated with 10 keV Ar+ at room temperature with fluences in the range from 5 × 1014 to 3 × 1016 ions cm-2 Sputtering of the antimony film during ion irradiation was compensated for by simultaneous controlled deposition (dynamic m...

Samples of (100), (111) and (110) oriented Ge-crystals were implanted with 40 keV Te+ ions at fluences between 5 × 1013 and 5 × 1014 cm-2. The beam alignment during the implantation was alpha = 0 ° or within 6 to 7° from the surface normal. The disorder depth profiles were analysed by using conventional and high depth resolution RBS channeling of 2...

Thin polyimide films deposited on silicon or metal covered glass-ceramic substrates were exposed to ion bombardment at different fluences ranging from 1 × 1012 to 1.5 × 1016 cm-2. The XPS technique was used to study the polymer stoichiometry of the near surface layers (~ 75 Å) before and after the bombardment. The results show that the stoichiometr...

Many theoretical works deal with recoil mixing of thin or thick Layers on a substrate [1,2,3,4]. These studies were carried out within the assumption of isotropic angular distribution of the moving low-energy cascade atoms. This is true if E ” Eo, where E is the initial energy of the primary ions and Eo amounts to between 10 and 100 eV [5]. In this...

Lattice disordering has been studied both experimentally by RBS-channelling measurements and theoretically by a Monte Carlo calculation technique. Single-crystal (100) silicon has been phosphorus implanted with an energy of 60 keV at room temperature in a 7° off-axis direction. The implanted doses varied between 5 x 1014 and 4 x 1015 cm−2. Channell...

Cross-sectional high resolution transmission electron microscopy has been used to obtain direct information on the in-depth radiation damage distribution of weakly damaged GaAs by Si-ion implantation. A comparison is made between the experimental data and the calculated (using TRIM computer simulations) deposited energy by nuclear stopping for the...

The role of channeling on the degree of the disorder induced by ion implantation of crystalline Ge is studied by using TEM and high resolution RBS supported by MARLOWE computer simulations. Direct information on the damage depth profile is also obtained by cross-sectional high resolution transmission electron microscopy (XHRTEM). The atomic structu...

Sputtering of copper, nickel and alumium polycrystalline targets by 40 keV Ar+ ions is simulated by a NIARLOWE-based computer code. Angle-of-incidence dependence of sputtering yields and depth-of-origin distributions are calculated. The angular distributions and energy spectra of sputtered particles are similar to those found earlier for low-energy...

Serial implantation of, probably high fluence, different ion species into a common substrate may be a useful method of generating materials standards for surface analytical techniques. Such a method may, however, suffer from atomic relocation processes within and from the substrate resulting from ballistic and diffusion processes and sputtering. In...

Thin (10 nm) films of Sb on LT AN BR 100 RT AN BR silicon have been irradiated with 10 kev Ar** plus at room temperature to fluences in the range 5 multiplied by 10**1**4-3 multiplied by 10**1**6 ions cm** minus **2. Sputtering of the thin Sb film during ion irradiation has been compensated for by simultaneous controlled deposition using a techniqu...

By using computer simulation technique for monitoring the slowing down of bismuth, arsenic, and titanium ions of 40 keV energy in amorphous silicon, the evolution of surface concentration and depth profile with dose accumulation is considered. Mean ranges in a wide interval of dimensionless energy are also estimated and compared with available expe...

Both MARLOWE-based computer simulation and transport theory have been used to evaluate the depth distributions of ion range and damage in InP assuming diatomic or monoatomic (Ge-substituted) targets. Results indicate that the mean depth and straggling in both distributions are higher for the diatomic target but deviations are less than 10–15% for t...

Direct observation of radiation damage induced by heavy ion implantation in crystalline germanium by means of high-resolution electron microscopy is reported. The dark-field lattice imaging mode is used, under conditions suitable for object like imaging. Conventional TEM is used for estimating the efficiency of creating visibly damaged regions.Heav...

Transmission sputtering of thin (up to 300 Å) gold films bombarded by 10 to 20 keV Ar ions is simulated by using the MARLOWE computer code. The energy spectra, angle of ejection and depth of origin distributions of ejected particles are presented. The results indicate that even for a thin film the cascading of the recoils is sufficient to produce a...

The impact parameter dependence of inelastic energy loss, based on a revised Firsov model, is calculated for collisions of Cu, Ne, Ar, Kr and Xe projectile ions with Cu atoms by assuming a Biersack-Ziegler interatomic potential. The results compare favourably with similar estimates for a Moliere potential and an exponential decrease of which the cl...

In a technique known as dynamic recoil mixing, a film of constant mass of a particular material can be maintained on a substrate while it is being bombarded by energetic ions. The technique has been applied to study recoil implantation of gold into silicon. Rutherford back-scattering and chemical etch methods have been used to determine the transmi...

Range distributions in inhomogeneous binary targets have been investigated both theoretically and experimentally. Silicon single crystal targets [(111) orientation] were implanted with 40 keV Pb+ ions to fluences in the range from 5 × 1014 to 7.5 × 1016 cm-2 prior to bombardment with 80 keV Kr+ ions to a fluence of 5 × 1015 cm-2. The samples were a...

Polycrystalline targets of Al, Ni and Cu were bombarded with a 40 keV argon ion beam and the angle of incidence dependence of photon yields measured. The collision processes involved were simulated using the MARLOWE computer code to obtain both the sputtering yields and the normal-velocity (V⊥) distributions. The results are discussed in terms of e...

Three distinct peaks are observed in scattering of 4 keV Ar+ from rows on the Mg(0001) surface. Computer simulation work indicates that the central peak is due to “zig-zag” collision sequences, in which the ions scatter between neighbouring surface atomic rows. The implications of these observations for neutralization lifetime estimation are discus...

Germanium targets were bombarded with 100 keV Ar ions. Steps were formed on the surface by shadow masking and the change in the profile during further bombardment without the mask was determined by scanning electron micsroscopy. A step by step iteration computer technique was used to simulate the development of these profiles.Experimental data on t...

The depth distribution of species implanted to high fluences can be distorted by collision processes such as atomic mixing and range perturbation resulting from stopping power modifications. In the present work, theoretical and computer simulation treatments have been used to study high-fluence depth-profile modification.In the preliminary investig...

Very low energy helium ions have been injected into Ni (100) single crystal substrates previously implanted with argon ions of higher controlled energy and fluence, and the subsequent evolution of the atoms during thermal annealing have been observed mass spectrometrically. Studies of the helium evolution spectra were obtained for different argon i...

The spatial distribution of defects in Ti, TiN and W targets induced by bombardment with different rare-gas ions in the keV energy range is studied, following WSS theory. The damage rate near the surface is compared with the residual gas sorption efficiency measured by other authors, revealing a non-monotonic dependence on the ion/target atoms mass...

Inelastic energy-loss in a single collisionT e and related stopping cross-sectionT e based on the Firsov model are evaluated for different screening functions in the elastic interaction potentials. Various approximations ofT e andS e for keV-ions in solids are discussed.

A generalized eddy-viscosity function νT, is introduced in order to express the Reynolds stress in an incompressible dusty gas as a linear combination of the Kronecker and rate-of-strain tensors. On the basis of Saffman's dusty-gas model a transport equation for the eddy viscosity is derived from the general turbulence energy equations, thereby int...

Experimental and detailed, three-dimensional computer simulation studies of the scattering of low energy argon ions incident at grazing angles onto a nickel single crystal have shown that under certain, well defined conditions, surface hyperchannelling dominates the reflection process. The applicability of simple computer simulation models to the s...

Features of ion scattering for small angles of incidence, up to about 10° from the surface, have been examined for 6 keV Ar ions in a plane of incidence parallel to the (001) direction in the nickel (110) surface. Ions scattered between the surface layer atoms, either above the surface, or slightly below the surface in the semi-channel make a signi...

Comparison of experimental energy spectra with computer simulation results demonstrates the possibility of distinguishing between several groups of ions, the trajectories of which are spatially separated during the scattering process. The separation resolved is less than a lattice unit and could be used in surface study.

Computer simulation of the reflection of a keV ion beam from a single crystal is carried out for different target temperatures. Ar ions bombarding obliquely a Cu lattice with 2 keV, and a Ni crystal with 30 keV energy are considered. The potentials used are of Born-Mayer (Ae−r/b) and Firsov (Br−2) type respectively. Uncorrelated thermal vibrations...

The regimes of high conversion efficiency of cascade triplers of optical radiation are theoretically investigated. A conversion efficiency of 100% for plane waves can be reached. Analytical expressions for the wave amplitudes in this case are given. The conversion efficiencies for a laser beam with Gaussian distribution of the amplitude in space an...

The motion of 200 keV B ions in the [111] direction in a silicon single crystal has been investigated using a computer simulation method. Profiles of the depth distribution of implanted ions for both an ideal crystal and a crystal with thermal vibrations have been obtained. A study of the defect distribution has been carried out.

The reflection of argon ions with an energy of 50 to 500 eV from a copper single crystal is simulated on a digital computer. Three models are used to describe the interaction of the projectiles with the crystal: 1. the ion interacts in each moment only with the nearest crystal atom, 2. the ion interacts with all atoms of some microcrystallite whose...