D. Karpuzov

Dynamic Monte-Carlo simulation of compositional change and atomic redistribution in multicomponent targets under ion bombardment

Abstract 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 SiO 2 , O + implantation into Si and Ar + sputtering of Al/Si with concurrent adsorption of O 2 are presented and compared with experimental results.

Reactively DC magnetron sputtered thin AlN films studied by X-ray photoelectron spectroscopy and polarised infrared reflection

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, microstructure, chemical state, percentage content of the elements and IR properties of the films were observed and the formation of the AlN compound was confirmed.

Iron silicide formed in a-Si:Fe thin films by magnetron co-sputtering and ion implantation

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 (FTIR), X-ray photoelectron spectroscopy (XPS), Rutherford back-scattering (RBS). FTIR spectra show absorption bands typical for β-FeSi 2 at 263, 293, 308, 345 and 425 cm -1 . It is shown that the optimal concentration of Fe in the co-sputtered films to obtain β-FeSi 2 is 35-40% and the optimal RTA temperature is 900°C. XPS spectra show that β-FeSi 2 is formed in as-deposited and annealed co-sputtered a-Si:H:Fe and implanted a-Si:H thin films.

Ability of reflection high energy electron diffraction (RHEED) to observe structural modifications in ion-implanted and annealed GaAs

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 treatment in furnace at 850 °C for 30 min; (b) the particular RTA employed leads to some texturing, but is not sufficient to provide good structural effects; (c) best annealing under our conditions is obtained by the LPLA technique, especially for low ion doses (less than 1013 cm−2); (d) variable-glancing-angle RHEED is an effective and convenient method to investigate the ion induced disorder in crystals at small depths.

High‐dose phenomena in zinc‐implanted silicon crystals

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 electron microscopy and x‐ray energy dispersion analysis. The energy deposition of the ion beam was calculated by using computer simulation codes. For the two lower doses of 1×1015 and 1×1016 a crystalline‐to‐amorphous transformation was observed in the implanted layer and this was correlated with the thermal history of the implants and the attendant changes in morphology. In contrast, an amorphous‐to‐crystalline transition was found to occur at higher doses, namely 5×1016 and 1×1017, where the formation of a complex, structured layer consisting of an amorphous phase mixed with crystalline grains of Zn and partly recrystallized Si was identified together with other specific structural features. Detailed characterization ...

Low energy ion beam oxidation of silicon surfaces: ballistics, diffusion and chemistry

Abstract Self-limiting growth of ultrathin (~ 40 A) 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 competing processes of shallow implantation and sputtering is applied to describe the growth of the oxide films. Dynamic computer simulation is used to investigate the role of collision-cascade and chemically guided atomic transport.

Electrical characterization of defects induced by 12 MeV electrons in p—type Si-SiO2 structures

Abstract 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 levels are found in the spectra after bombardment with high-energy electrons, whereas the peak intensity is dependent on the irradiation dose. The corresponding activation energy of the created defects, as well as the density of the traps and the electron-capture cross sections are evaluated.

Angle and energy distributions of sputtered particles from molybdenum (110) surfaces

Abstract 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 the angular distribution of sputtered particles are assessed as a function of a given angle and energy.

Low‐power pulsed‐laser annealing of implanted GaAs

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 backscattering analysis. The annealing results depend on the irradiation conditions. A laser energy window below the melting threshold is found within which the structure can be restored to about as high degree of crystallinity as the virgin one, without any visible surface damage. A simple theoretical estimate shows that the temperature rise of the material is far below the melting threshold. This rise is too short in time to cause substantial dopant diffusion; however, it can enhance well the point‐defect mobility.

Time evolution of ion slowing-down in amorphous solids

Abstract 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 were obtained at different projectile energies. A comparison was made with the results obtained by Robinson using the time-dependent MAR-LOWE computer code [Phys. Rev. B 40 (1989) 10717].