AES investigations of Ar+ ion retention in Si during Ar sputtering

Argon retention in silicon has been studied by AES in the energy range between 1 and 15 keV at bombardment fluences up to ∼10¹⁸ ions/cm². AES data of implanted argon in silicon near the surface region, as obtained during sputtering, can be interpreted qualitatively by a simple model of ion collection. Discrepancies between calculated and measured saturation values of collected argon ions indicate that during implantation at high fluences addition surface effects become important and that the simple model of ion collection has to account for this. Quantitative AES correlated with RBS indicates pronounced concentration gradients of argon in silicon near surface regions.     

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.     

The influence of argon ion bombardment on the electrical and optical properties of clean silicon surfaces

The effect of low energy noble gas ion bombardment on the electrical and optical properties of Si(211) surfaces has been investigated by surface conductivity and field effect measurements, ellipsometry and AES. With this combination of techniques, information is obtained concerning the electrical properties, the chemical composition and the damage of the surface layer. Upon ion bombardment in the energy range of 500–2000 eV, ellipsometry shows the formation of a damaged surface layer with optical properties close to those of an evaporated amorphous silicon film. In order to measure the conductivity changes as sensitive as possible, nearly intrinsic silicon crystals were used. For the clean, 5200 Ω cm Si(211) surface, bombarded only with a mass-analyzed argon ion beam, a small increase in conductivity is found to occur after a small ion dose (saturation after 5 × 10¹⁴ ions cm^?2 while after 5 × 10¹³ ions cm^?2 already half of the increase has occurred). The effect was found to be independent of ion energy between 500 and 2000 eV. As the field effect signal did not change after this treatment, it is concluded that the surface state density in the neighbourhood of the Fermi level shows a slight decrease.     

ISS measurement of surface composition of AuCu alloys by simultaneous ion bombardments with Ar+ and He + ions

Surface composition of Au-Cu(43 at%) alloy under 1.5–5 keV argon ion bombardment has been investigated by ion scattering spectroscopy (ISS). In this experiment, we adopted a specific technique to use mixed He⁺ and Ar⁺ ions as primary beam in order to perform sputtering (Ar⁺) and ISS measurement (He⁺) simultaneously. The outermost atom layer of Au-Cu alloys under Ar⁺ ion bombardment is Au-rich leading to the conclusion that Ar⁺ ion bombardment of AuCu alloys causes the preferential sputtering of Cu atoms, resulting in a Au-rich outermost atom layer and a depletion layer of Au atoms beneath the outermost atom layer due to ion-beam-enhanced surface segregation. This result explains the experimental results obtained by AES as well.     

Investigations on the effect of argon ion bombardment on the structural and optical properties of crystalline gallium antimonide

The effects of bombardment of 250 keV argon ions in n-type GaSb at fluences 2×10¹⁵ and 5×10¹⁵ ions cm^?2 were investigated by high-resolution X-ray diffraction (HRXRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). HRXRD studies revealed the presence of radiation-damaged layer (strained) peak in addition to the substrate peak. The variation in the lattice constant indicates the strain in the bombarded region. The out-of-plane (?_⊥) and in-plane strains (?_|) determined from the profiles of several symmetric and asymmetric Bragg reflections, respectively, were found to change with the ion fluence. Simulations of XRD patterns using dynamical theory of X-ray scattering (single-layer model) for the damaged layer yielded good fits to the recorded profiles. FTIR transmission studies showed that the optical density (α·d) of GaSb bombarded with different fluences increases near the band edge with increase in ion fluence, indicating the increase in the defect concentration. The density of the defects in the samples bombarded with different fluences was in the range of 3.20×10²¹–3.80×10²¹ cm^?3. The tailing energy estimated from the transmission spectra was found to change from 12.0 to 58.0 meV with increasing ion fluences, indicating the decrease of crystallinity at higher fluences. SEM micrographs showed the swelling of the bombarded surface of about 0.33 μm for the fluence of 2×10¹⁵ ions cm^?2, which increased to 0.57 μm for the fluence of 5×10¹⁵ ions cm^?2.     

Surface disorder in c-Si induced by swift heavy ions

The disorders induced in crystalline silicon (c-Si) through the process of electronic energy loss in the swift heavy ion irradiation were investigated. A number of silicon <1 0 0> samples were irradiated with 65 MeV oxygen ions at different fluences, 1×10¹³ to 1.5×10¹⁴ ions/cm², and characterized by the Raman spectroscopy, the optical reflectivity, the X-ray reflectivity, the atomic force microscopy (AFM) and the X-ray diffraction (XRD) techniques. The intensity, redshift, phonon coherence length and asymmetric broadening associated with the Raman peaks reveal that stressed and disordered lattice zones are produced in the surface region of the irradiated silicon. The average crystallite size, obtained by analyzing Raman spectrum with the phonon confinement model, was very large in the virgin silicon but decreased to<100 nm dimension in the ion irradiated silicon. The results of the X-ray reflectivity, AFM and optical reflectivity of 200–700 nm radiation indicate that the roughness of the silicon surface has enhanced substantially after ion irradiation. The diffusion of oxygen in silicon surface during ion irradiation is evident from the oscillation in the X-ray reflectivity spectrum and the sharp decrease in the reflectivity of 200–400 nm radiation. The rise in temperature, estimated from the heat spike model, was high enough to melt the local silicon surface. The results of XRD indicate that lattice defects have been induced and a new plane <2 1 1> has been formed in the silicon <1 0 0>after ion irradiation. The results of the present study show that the energy deposited in crystalline silicon through the process of electronic energy loss ～0.944 keV/nm per ion is sufficient to induce disorders of appreciable magnitude in the silicon surface even at a fluence of ～10¹³ ions/cm².     

Auger electron spectroscopy (AES) studies of argon ion induced desorption of carbon from tantalum

AES studies of argon ion induced desorption of carbon from tantalum were performed. The carbon adlayer was allowed to adsorb from a well characterized residual gas atmosphere, that was unvarying within 20%. The argon ions impact on the surface at an angle of 60° from the surface normal with energies between 0.2 to 1.0 keV. The total desorption cross section values measured under these conditions are 0.07–1.1 × 10^?15 cm².     

Laser induced ion emission from wide bandgap materials

At fluences well below the threshold for plasma formation, we have characterized the direct desorption of atomic ions from fused silica surfaces during 157 nm irradiation by time-resolved mass spectroscopy. The principal ions are Si⁺ and O⁺. The emission intensities are dramatically increased by treatments that increase the density of surface defects. Molecular dynamics simulations of the silica surface suggest that silicon ions bound at surface oxygen vacancies (analogous to E′ centers) provide suitable configurations for the emission of Si⁺. We propose that emission is best understood in terms of a hybrid mechanism involving both antibonding chemical forces (Menzel-Gomer-Redhead model) and repulsive electrostatic forces on the adsorbed ion after laser excitation of the underlying defect.     

Effects of silicon negative ion implantation in semi-insulating gallium arsenide

ABSTRACT

In the present work, effects of silicon negative ion implantation into semi-insulating gallium arsenide (GaAs) samples with fluences varying between 1?×?10¹⁵ and 4?×?10¹⁷?ions?cm^?2 at 100?keV have been described. Atomic force microscopic images obtained from samples implanted with fluence up to 1?×?10¹⁷?ion?cm^?2 showed the formation of GaAs clusters on the surface of the sample. The shape, size and density of these clusters were found to depend on ion fluence. Whereas sample implanted at higher fluence of 4?×?10¹⁷?ions?cm^?2 showed bump of arbitrary shapes due to cumulative effect of multiple silicon ion impact with GaAs on the same place. GXRD study revealed formation of silicon crystallites in the gallium arsenide sample after implantation. The silicon crystallite size estimated from the full width at half maxima of silicon (111) XRD peak using Debye-Scherrer formula was found to vary between 1.72 and 1.87?nm with respect to ion fluence. Hall measurement revealed the formation of n-type layer in gallium arsenide samples. The current–voltage measurement of the sample implanted with different fluences exhibited the diode like behavior.     

Impurity redistribution in Pb implanted and annealed silicon

Reordering of 〈111〉 silicon, implanted with Pb ions at energies >100 keV and fluences ～5 × 10¹⁵ cm^?2 is accompanied by substantial impurity indiffusion in addition to pronounced outdiffusion and accumulation at the near surface region.     

Damage formation in Ge during Ar and He implantation at 15 K

Ar⁺ and He⁺ ions were implanted into Ge samples with (1 0 0), (1 1 0), (1 1 1) and (1 1 2) orientations at 15 K with fluences ranging from 1×10¹¹ to 1×10¹⁴ cm⁻² for the Ar⁺ ions and fluences ranging from 1×10¹² to 6×10¹⁵ cm⁻² for the He⁺ ions. The Rutherford backscattering (RBS) technique in the channelling orientation was used to study the damage built-up in situ. Implantation and RBS measurements were performed without changing the target temperature. The samples were mounted on a four axis goniometer cooled by a close cycle He cryostat. The implantations were performed with the surface being tilt 7° off the ion beam direction to prevent channelling effects. After each 300 keV Ar⁺ and 40 keV He⁺ implantation, RBS analysis was performed with 1.4 MeV He⁺ ions.For both the implantation ions, there is about no difference between the values found for the damage efficiency per ion for the four different orientations. This together with the high value (around 5 times higher than that found in Si), gives rise to the assumption of amorphous pocket formation per incident ion, i.e. direct impact amorphization, already at low implantation fluences. At higher fluences, when collision cascades overlap, there is a growth of the already amorphized regions.     

The influence of incidence angle on disorder production in Cl and Ar ion implanted Si

Abstract

Cl and Ar ions have been implanted, at 30 keV and at various incidence angles, into Si substrates maintained at room temperature during implantation. Implantation induced Si disorder was measured using RBS channelling. The effects upon disorder of various incidence angles were studied over a fluence range of 10¹²-6·10¹⁵ ions·cm^?2

The results show that, at low fluences Cl and Ar ion implantations generate a bimodal disorder-depth profile, whilst at higher fluences measurements of amorphised layer thickness as a function of ion incidence angle allow values of the standard deviation of the disorder profile parallel and transverse to the ion beam direction for each ion to be obtained with good agreement to theoretical predictions. The disorder-fluence behaviour under these conditions is ion species independent.     

Effect of ion irradiation on the thermoluminescence properties of K2Ca2(SO4)3 phosphor

This paper presents the thermoluminescence (TL) studies of ion-irradiated potassium–calcium mixed sulfate phosphor. The sample was prepared by the solid-state diffusion method. The X-ray diffraction study of the prepared sample suggests an orthorhombic structure with an average particle size of 0.16 μ m. The samples were irradiated with 1.2 MeV argon ions at fluences varying between 10¹¹ and 10¹⁵ ions/cm². The argon ions penetrate to a depth of 1.93 μ m and lose their energy mainly via electronic stopping. Due to ion irradiation, a large number of defects such as oxygen vacancies, radicals and color centers are formed in the sample. TL glow curves were recorded for each of the ion fluences. A linear increase in the intensity of TL glow peaks was found with an increase in the ion dose from 72 kGy to 720 MGy. The kinetic parameters associated with the prominent glow peaks were calculated using glow curve deconvolution, different glow curve shapes and sample heating rate methods.     

硫在镍(100)表面偏析动力学研究

本文使用AES-LEED联合装置研究了650—800℃温度范围内硫在镍(100)表面上的偏析动力学。结果表明,在较短退火时间内硫的表面浓度正比于退火时间的平方根,与McLean的动力学模型是一致的。扩散系数与温度的关系为D(cm²/s)=5×10^-3exp(-44600/RT)。硫偏析在镍(100)表面达到饱和值,LEED观察指出形成了硫的c(2×2)结构。深度剖面分析,硫/镍俄歇峰高比随氩离子剥离时间指数降低。 关键词：     

Reflectivity modification of polymethylmethacrylate by silicon ion implantation

The effect of silicon ion implantation on the optical reflection of bulk polymethylmethacrylate (PMMA) was examined in the visible and near UV. A low-energy (30 and 50 keV) Si⁺ beam at fluences in the range from 10¹³ to 10¹⁷ cm⁻² was used for ion implantation of PMMA. The results show that a significant enhancement of the reflectivity from Si⁺-implanted PMMA occurs at appropriate implantation energy and fluence. The structural modifications of PMMA by the silicon ion implantation were characterized by means of photoluminescence and Raman spectroscopy. Formation of hydrogenated amorphous carbon (HAC) layer beneath the surface of the samples was established and the corresponding HAC domain size was estimated.     

Ar+ and Xe+ velocities near the presheath-sheath boundary in an Ar/Xe discharge

The velocities of Ar+ and Xe+ ions near the presheath-sheath boundary in an Ar/Xe discharge are studied by particle-in-cell Monte Carlo simulation. For a pure argon discharge the argon ion has almost the same velocity profile as it does in the mixture of argon and xenon. Similarly, for a xenon discharge the xenon ion has almost the same velocity profile as it does in the mixture of argon and xenon. The ion speed at the sheath-presheath boundary is the same for an ion in a pure argon or xenon discharge and for the same ion in a mixture of argon and xenon. We conclude that, in our simulation, each ion reaches its own Bohm speed at the presheath-sheath interface.     

Preferential sputtering of TIC under keV Ar+ ion bombardment: Simultaneous sputtering-ISS measurement with He+ and Ar+ ions

The composition change of the outermost atom layer of TiC(110) under ion bombardment with 1.5–3 keV He⁺ and He⁺ + Ar⁺ ions has been measured by ion scattering spectroscopy with He⁺ ions at different sample temperatures. It has been found that the preferential sputtering of C atoms takes place for both the He⁺ and Ar⁺ ion bombardment, however the preferred sputtering is more pronounced for Ar⁺ ions than for He⁺ ions. The ion bombardment with He⁺ ions at elevated sample temperatures hardly results in any change in surface composition below ～800°C, while Ar⁺ ion bombardment results in C enrichment for elevated temperatures as reported so far.     

INFRARED EMISSION FROM Si IMPLANTED WITH HIGH Er CONCENTRATION

Erbium-doped silicon has been fabricated by ion implantation performed on a metal vapour vacuum arc ion source. After rapid thermal annealing (RTA), 1.54μm photoluminescence was observed at 77K. Rutherford backscattering spectrum indicated that Er ions are mainly distributed near the surface of the samples, and Er concentration exceeded 10²¹cm^-3. Needle nanometre crystalline silicon (nc-Si) was formed on the substrate surface. Band edge emission spectrum at 10K verified that the minority carrier lifetime increased upon RTA. The photocarrier mediated processes enabled energy transferring from nc-Si (or c-Si) to the Er³⁺ ions and resulted in light emission of 1.54μm.     

AES analysis of nitridation of Si(100) by 2–10 keV N+2 ion beams

Ion beam nitridation of Si(100) as a function of N⁺₂ ion energy in the range of 2–10 keV has been investigated by in-situ Auger electron spectroscopy (AES) analysis and Ar⁺ depth profiling. The AES measurements show that the nitride films formed by 4–10 keV N⁺₂ ion bombardment are relatively uniform and have a composition of near stoichiometric silicon nitride (Si₃N₄), but that formed by 2 keV N⁺₂ ion bombardment is N-rich on the film surface. Formation of the surface N-rich film by 2 keV N⁺₂ ion bombardment can be attributed to radiation-enhanced diffusion of interstitial N atoms and a lower self-sputtering yield. AES depth profile measurements indicate that the thicknesses of nitride films appear to increase with ion energy in the range from 2 to 10 keV and the rate of increase of film thickness is most rapid in the 4–10 keV range. The nitridation reaction process which differs from that of low-energy (< 1 keV) N⁺₂ ion bombardment is explained in terms of ion implantation, physical sputtering, chemical reaction and radiation-enhanced diffusion of interstitial N atoms.     

Surface modifications of ultra-thin gold films by swift heavy ion irradiation

Gold films of thickness 10 and 20 nm grown on float glass substrate by thermal evaporation technique were irradiated with 107 MeV Ag⁸⁺ and 58 MeV Ni⁵⁺ ions at different fluences and characterized by Grazing Incidence X-ray Diffraction (GIXRD) and Atomic Force Microscopy (AFM). The pristine films were continuous and no island structures were found even at these small thicknesses. The surface roughness estimated from AFM data did not show either monotonic increase or decrease with ion fluences. Instead, it increased at low fluences and decreased at high fluences for 20 nm thick film. In the 10 nm film roughness first increased with ion fluence, then decreased and again increased at higher fluences. The pattern of variation, however, was identical for Ni and Ag beams. Both the beams led to the formation of cracks on the film surface at intermediate fluences. The observed ion-irradiation induced thickness dependent topographic modification is explained by the spatial confinement of the energy deposited by ions in the reduced dimension of the films.