CEMS study on aluminium implanted iron

Up to now a great deal of investigations in ion beam mixing of iron-aluminium layers are known. However, the easier way to produce such layers by direct implantation of aluminium ions in iron is less studied. In the present work aluminium implanted iron layers are studied. Iron samples were implanted with aluminium ions at 50, 100, and 200 keV, respectively, with doses between 5×10¹⁶ and 5×10¹⁷ cm⁻². Independent of energy, at doses up to 2×10¹⁷ cm⁻², besides alpha iron further magnetic fractions with a Fe₃Al-like structure are formed while at a dose of 5×10¹⁷ cm⁻² amorphous nonmagnetic components are formed.     

CEMS study of a nitrogen implanted CrNi 18.9 steel

Conversion electron Mössbauer spectroscopy (CEMS) has been used to study a commercial X10CrNiTi 18.9 steel implanted with varying nitrogen doses and at varying implantation temperatures. At low nitrogen doses the fcc γ-phase transformed to the bcc structure. With increasing implantation dosages we have observed the precipitation of Fe-nitrides and a reverse (α→γ) transformation. High implantation temperatures lowered the nitrogen content of the Fe-nitrides and favoured the formation of Cr-nitrides.     

CEMS study of defect annealing in Fe implanted AlN

An AlN thin film grown on sapphire substrate was implanted with 45 keV ⁵⁷Fe and ⁵⁶Fe ions at several energies to achieve a homogeneous concentration profile of approximately 2.6 at.%. in the AlN film. Conversion electron Mössbauer Spectroscopy data were collected after annealing the sample up to 900 °C. The spectra were fitted with three components, a single line attributed to small Fe clusters, and two quadrupole split doublets attributed to Fe substituting Al in the wurtzite AlN lattice and to Fe located in implantation induced lattice damage. The damage component shows significant decrease on annealing up to 900 °C, accompanied by corresponding increases in the singlet component and the substitutional Fe.     

Deep levels of iron implanted inn-type silicon

Results of an investigation of 19 organic dyes pumped by a 1.7 MW discharge-pumped XeCl excimer laser are reported. The dye-laser emission covered a wide wavelength range from 340 nm to 710 nm.P-terphenyl shows efficient laser action. The highest energy conversion efficiency exceeds 40% in visible region. In comparison with 250 kW nitrogen laser pumping, higher efficiencies are obtained for most of these dyes in the same dye-laser configuration.     

CEMS of Sb+ implanted stainless steels

Martensitic transformations have been analysed in a series of antimony implanted austenitic stainless steels using CEMS. The implanted samples contain about 70 vols martensite, which is considerably more than can be formed conventionally by plastic deformation or cooling below the martensite start temperature. CEM spectra from implantation induced martensite and from martensite formed in conventional processes are virtually identical. In both cases the hyperfine field is ≈ 25T.     

Ellipsometric study of tellurium implanted silicon

Abstract

Ellipsometric parameters as a function of the dose (D = 2.10¹³ ? 2.10¹⁵ ions cm^?2) and annealing temperature have been measured on the silicon implanted with 30 keV Te ions. Obtained information on lattice disorder are to a great extent comparable with those of other methods, e.g. backscattering technique. Moreover optical constants of a damage surface layer may be estimated.     

CEMS study on iron film oxidized in various oxygen pressures

In order to prepare the Fe_1?xO film, Fe metals evaporated on sapphire substrate were oxidized in the furnace for 2 hours at 800°C. The pressure of oxygen between 10^?14 and 10^?19 atm. was controlled by changing the flow rates of CO₂ and H₂ gases. After the oxidation, the conversion Mössbauer spectra for the samples were measured by a He+10%CH₄ proportional counter. It was found that at this temperature the usually accepted Fe_1?xO was not made for 2 hours, but the unknown oxidation state of Fe was formed at the oxygen pressure of 10^?16.5 alm.. Its isomer shift relative to α-Fe and quadrupole splitting are 0.92 mm/sec and 1.71 mm/sec. The normal Fe_1?xO was formed at the oxygen pressure of 10^?16.5 atm. when the oxidation time was extended to 6.5 hours, in addition to Fe₃O₄.     

X-ray reflectivity study of hydrogen implanted silicon

The X-ray reflectivity (XRR) technique was used to study monocrystalline silicon samples implanted with H₂ ions at an energy of 31 keV and to the dose of 2 × 10¹⁶ hydrogen atoms/cm². All samples were subsequently isochronally annealed in vacuum at different temperatures in the range from 100 to 900 °C. Although the hydrogen depth distribution was expected to be smooth initially, fringes in the XRR spectra were observed already in the implanted but not annealed sample, revealing the presence of a well-defined film-like structure. Annealing enhances the film top to bottom interface correlation due to structural relaxation, resulting in the appearance of fringes in the larger angular range, already at low annealing temperatures. The thickness of the film decreases slowly up to 350 °C where substantial changes in the roughness are observed, probably due to the onset of larger clusters formation. Further annealing at higher temperatures restores the high correlation of the film interfaces, while the thickness decreases with the temperature more rapidly.     

Deep levels of iron implanted in n -type silicon

N-type silicon was implanted with iron at 300keV. Deep-level measurements were performed after annealing pprocesses at various temperatures between 500 and 1100°C. Various levels were observed but no electrical active centers were detectable in the upper half of the forbidden band of Si after 800°C annealing.     

Photoluminescence and structural defects in silicon layers implanted by iron ions

The photoluminescence spectra of silicon samples implanted by ⁵⁶Fe⁺ ions [energy, 170 keV; dose, 1×10¹⁶, (2–4)×10¹⁷ cm^?2] and annealed at temperatures of 800, 900, and 1000°C are measured. The structure of the samples at each stage of treatment is investigated using transmission electron microscopy (TEM). It is found that the phase formation and morphology of crystalline iron disilicide precipitates depend on the dose of iron ions and the annealing temperature. A comparison of the dependences of the intensity and spectral distribution of the photoluminescence on the measurement temperature, annealing temperature, and morphology of the FeSi₂ phase revealed the dislocation nature of photoluminescence.     

CEMS and DCEMS investigations of Al-implanted iron

-Fe surfaces were implanted with a nominal dose of 5×10¹⁷ Al ions/cm² at 50 keV and a current density of about 3.7 A/cm². Samples of different shapes and thicknesses have been used in order to test the influence of heat flow from specimen to target holder during implantation. Integral and energy differential (depth-selective)⁵⁷Fe conversion electron Mössbauer spectroscopy (CEMS and DCEMS) were employed. The spectra indicated a magnetic phase characterised by a broad hyperfine field distributionP(B _hf), a non-magnetic phase, and -Fe. The relative intensity of the non-magnetic phase was enhanced if the thermal contact during implantation became worse. An energy dependence of DCEM spectra in the L-electron range was observed. Model calculations using L-electron weight functions and experimental concentration profiles obtained by secondary neutral mass spectroscopy (SNMS) yielded fair agreement between calculated and experimental phase signals. The results demonstrate that the non-magnetic Fe-Al alloy phase with high Al concentration is located closer to the surface than the magnetic alloy phase, which extends to much larger depth than expected.     

Epitaxial growth of silicon on silicon implanted with iron ions and optical properties of resulting structures

The method of ultrahigh-vacuum low-temperature (T = 850°C) purification of silicon single crystals having the (100) and (111) orientation and implanted with low-energy (E = 40 keV) iron ions with various doses (Φ = 10¹⁵?1.8×10¹⁷ cm^?2) and subjected to pulsed ion treatment (PIT) in a silicon atom flow has been tested successfully. The formation of semiconducting iron disilicide (β-FeSi₂) near the surface after PIT is confirmed for a Si(100) sample implanted with the highest dose of iron ions. The possibility of obtaining atomically smooth and reconstructed silicon surfaces is demonstrated. Smooth epitaxial silicon films with a roughness on the order of 1 nm and a thickness of up to 1.7 μm are grown on samples with an implantation dose of up to 10¹⁶ cm^?2. Optical properties of the samples before and after the growth of silicon layers are studied; the results indicate high quality of the grown layers and the absence of iron disilicide on their surface.     

Magnetic resonance of metallic nanoparticles in vitreous silicon dioxide implanted with iron ions

Silica glasses exposed to steady-state and pulsed irradiation with Fe⁺ ions are studied using magnetic resonance. The irradiation doses used in experiments are equal to 1 × 10¹⁵, 1 × 10¹⁶, and 1 × 10¹⁷ cm^?2. It is found that, under both steady-state and pulsed irradiation conditions, glass samples exposed at a dose of 1 × 10¹⁷ cm^?2 exhibit a broadband orientation-dependent signal. The shape of inclusions is evaluated under the assumption that the observed spectrum is caused by the ferromagnetic resonance induced in a new phase of metallic iron.     

Oxidation of iron studied by PAC and CEMS

A metallic Fe specimen, implanted with ¹¹¹In, was oxidized and subsequently annealed in a high vacuum for PAC spectroscopy. This treatment gave rise to a huge PAC signal. The magnitude of the hyperfine field was found to be one third of that in metallic Fe. CEMS on an enriched Fe foil given exactly the same treatment has revealed that a maghemite phase (γ-Fe₂O₃) is formed right after the oxidation treatment and a magnetite phase (Fe₃O₄) after the vacuum annealing. ¹¹¹In in the magnetite phase was found to give rise to a PAC signal with large amplitude. PAC spectroscopy in an external magnetic field has revealed that the site of ¹¹¹In is the tetrahedral site of the magnetite with the hyperfine field of +12 T, which is in excellent agreement with those in the ferrites. The present method of oxidation of metallic Fe with nuclear probes in it is quite useful for the study of oxidation processes. Also, it provides us with a simple means to prepare ferrite specimens incorporated with nuclear probes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Nitrogen implanted in iron: AES and Pes study

AES and PES studies of nitrogen in iron implanted with molecular nitrogen ions having an energy of 120 keV and doses on the order of 10¹⁷ N-atoms/cm² were performed. Measuring nitrogen concentration depth profiles, a remarkable accumulation of nitrogen near surface was found besides the ordinary concentration maximum at the depth of mean projected range R_p of nitrogen ions. In addition to strong nitride bonding state a weakly bonded nitrogen was also observed. It manifested itself by time-dependent changes in spectra and by a distinct value of N 1s binding energy. The reasons for the concept of weakly bonded nitrogen, probably of molecular form, are discussed.     

A CEMS investigation of57Fe+Al implanted in Al foil

⁵⁷Fe implanted and post Al implanted in aluminum foil have been performed at low energy of 27keV and the CEMS shows the formation of intermetallic compounds FeAlσ and Fe₂Alσ during the ion bombardment. The results are discussed with the enhanced diffusion by energetic ion bombardment.     

Quantitative determination of fayalite layers on iron by CEMS

In the processing of silicon iron (Fe-3%) Si), so-called ‘fayalite layers’ are formed. By CEMS, they were found to consist of an outer Fe³⁺-oxide layer and an inner Fe₂SiO₄ (fayalite) layer. Sometimes an additional wüstite contribution was found. Thef-factor of fayalite was determined experimentally (f _fayalite/f _α-Fe=0.47±0.04) and, by use of it, the thicknesses of the layers on some silicon iron samples could be calculated from CEMS data.     

Thermal evolution of high dose Fe implanted Si(100) at 623 K: A CEMS study

Hyperfine interactions associated to the phases produced by 623 K Fe implantation into Si(100) and by subsequent thermal treatments at temperatures up to 1273 K have been studied by conversion electron Mössbauer spectroscopy. The results suggest that in the as implanted sample the short range order around the ⁵⁷Fe probes is \beta-FeSi₂-like. This phase orders with a thermal treatment at 773 K. A preferential orientation of the electric field gradient was detected from the relative height of the quadrupole interaction components. It was found that the transition to the high temperature phase \alpha-FeSi₂ occurred at least 50 K below the reported value.     

DPAC study of radiation damage in178W recoil implanted silicon

The annealing behaviour of radiation damage in¹⁷⁸W recoil implanted n-type Si is studied from 295 to 641 K by the differential perturbed angular correlation method (DPAC), using¹⁷⁸Hf as probe nuclei for the first time. Preliminary results suggest that oxygen-vacancy (O-V) pairs are observed, which give rise to a quadrupole interaction characterized by |V _zz|=5.41×10¹⁸ V/cm² (v _Q=2550 MHz). The probe nuclei also experience an electric field gradient (EFG) due to distant defects.     

Channeling study of boron implanted silicon: Liquid nitrogen temperature implantation

Silicon samples have been boron implanted at 150 keV at liquid nitrogen temperature to a dose of 3.6 × 10¹⁵/cm². This dose rendered the implanted layer amorphous as viewed by helium ion backscattering. Four kinds of room temperature measurements were made on the same set of samples as a function of the isochronal annealing temperature. The measurements made were the determination of the substitutional boron content by the channeling technique using the B¹¹(p, α) nuclear reaction, observation of the disorder by helium ion backscattering, determination of the carrier concentration by van der Pauw Hall measurements, and the sheet resistivity by four point probe measurements. These measurements are compared with results from samples implanted at room temperature. The carrier concentration correlates well with the substitutional boron content for both room temperature and liquid nitrogen temperature implantations. Following annealing temperatures in the 600 to 800°C range, a much larger percentage of the boron lies on substitutional lattice sites, and therefore the carrier concentration is larger, if the implantation is done at liquid nitrogen temperature rather than at room temperature. Following liquid nitrogen temperature implantation, reverse annealing is observed from 600 to 800°C in the substitutional boron content, carrier concentration and sheet resistivity. The boron is more than 90 per cent substitutional after annealing to 1100°C for both the room temperature and liquid nitrogen temperature implantations. The low temperature implantation produced a buried amorphous layer, and this layer was observed to regrow from both the surface and substrate sides at approximately equal rates.