Defects formation in the dual B+ and N+ ions implanted silicon

Silicon wafers were implanted with 40 keV B⁺ ions (to doses of 1.2×10¹⁴ or 1.2×10¹⁵ cm^–2) and 50 or 100 keV N⁺ ions (to doses from 1.2×10¹⁴ to 1.2×10¹⁵ cm^–2). After implantations, the samples were furnace annealed at temperatures from 100 to 450 °C. The depth profiles of the radiation damages before and after annealing were obtained from random and channeled RBS spectra using standard procedures. Two damaged regions with different annealing behaviour were found for the silicon implanted with boron ions. Present investigations show that surface disordered layer conserves at the annealing temperatures up to 450 °C. The influence of preliminary boron implantation on the concentration of radiation defects created in subsequent nitrogen implantation was studied. It was shown that the annealing behaviour of the dual implanted silicon layers depends on the nitrogen implantation dose.The authors would like to thank the members of the INP accelerator staff for the help during the experiments. The work of two authors (V.H. and J.K.) was partially supported by the Internal Grant Agency of Academy of Science of Czech Republic under grant No. 14805.     

Blue-cathodoluminescent layers synthesis by high-dose N, C and B SiO2 implantation

Thermal silicon oxide layers have been implanted at 600 °C with N⁺+C⁺, N⁺+B⁺ and N⁺+C⁺+B⁺ ions. Two different implantation doses have been chosen in order to introduce peak concentrations at the projected range comparable to the SiO₂ density. Some pieces of the samples have been annealed in conventional furnace at 1200 °C for 3 h. After annealing, cathodoluminescence measurements show in all cases a main broad band centered at 460 nm (2.7 eV). High doses of C implantation give rise to an intensity attenuation. Phases formed in the oxides have been investigated by Fourier transform infrared spectroscopy before and after annealing. The spectra suggest that N incorporates as BN and probably as a ternary BCN phase in the triply implanted samples, while C seems to bond mainly with B. Boron is also bonded to O in B-O-Si configuration. Depth structure and quantitative composition of the films were deduced from fittings of the spectroscopic ellipsometry measurements.     

Luminescence and structure of nanosized inclusions formed in SiO2 layers under double implantation of silicon and carbon ions

Luminescent and structural characteristics of SiO₂ layers exposed to double implantation by Si⁺ and C⁺ ions in order to synthesize nanosized silicon carbide inclusions have been investigated by the photoluminescence, electron spin resonance, transmission electron microscopy, and electron spectroscopy methods. It is shown that the irradiation of SiO₂ layers containing preliminary synthesized silicon nanocrystals by carbon ions is accompanied by quenching the nanocrystal-related photoluminescence at 700–750 nm and by the enhancement of light emission from oxygen-deficient centers in oxide in the range of 350–700 nm. Subsequent annealing at 1000 or 1100°C results in the healing of defects and, correspondingly, in the weakening of the related photoluminescence peaks and also recovers in part the photoluminescence of silicon nanocrystals if the carbon dose is less than the silicon dose and results in the intensive white luminescence if the carbon and silicon doses are equal. This luminescence is characterized by three bands at ～400, ～500, and ～625 nm, which are related to the SiC, C, and Si phase inclusions, respectively. The presence of these phases has been confirmed by electron spectroscopy, the carbon precipitates have the sp ³ bond hybridization. The nanosized amorphous inclusions in the Si⁺ + C⁺ implanted and annealed SiO₂ layer have been revealed by high-resolution transmission electron microscopy.     

Sequence of structural-phase states during implantation of C+, N+, and Si+ ions into molybdenum

The sequence of structural-phase changes in the surface layer of molybdenum during pulsed implantation of N⁺, C⁺, and Si⁺ ions has been studied. At radiation doses 5·10¹⁶ cm^–2 we detected qualitatively similar structural-phase transformations with the formation of highly dispersed secondary-phase particles (nitrides, carbides, and silicides), dislocations, point defects, and clusters of defects. At radiation doses (1–2)·10¹⁷ cm^–2 implantation of C⁺ and Si⁺ ions causes amorphization of the surface layer; nitrogen implantation is accompanied by the formation of continuous layers of the nitride phase on the surface.Siberian Physicotechnical Institute at the V. D. Kuznetsov State University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 3–9, February, 1994.     

Boron electrical activation in dual B+ + N+ + and B+ + Ar+ ion-implanted silicon

Silicon wafers were implanted with 40 keV B⁺ ions and then with 50 keV N⁺ or 100 keV Ar+ ions to doses from 1.2 x 1014 to 1.2 x 1015 cm^–2. The implanted samples were studied using the Hall effect and standard van der Pauw methods. The dependences of the sheet resistivity and the sheet concentration of charge carriers on the annealing temperature in the range from 700 to 1300 K were obtained. Models describing the influence of additional implantation of nitrogen and argon ions on the process of boron electrical activation during annealing are proposed.     

MeV Al+ and Al2+ ions implantation in Si(100): surface roughness and defects in the bulk

This paper deals with the implantation of high-energy (1.0–3.0 MeV) atomic and molecular Al⁺ ions in Si(100) to a fluence of 5×10¹⁴ Al atoms/cm² at room temperature. The molecular effect, i.e. the increase of the displacement yield compared with the sum of the atomic yields, and the damage formation as well as defect behaviour after annealing have been investigated. A detailed experimental study has been made of the evolution of extended secondary defects which form during thermal anneals of Al⁺ or Al₂ ⁺ irradiated silicon. The samples have been examined using combined Rutherford backscattering and channeling experiments together with transmission electron microscopy observations. The surface structure of the implanted wafers has been measured by atomic force microscopy. The results for the implantation-induced roughness at the Si surface, resulting from Al⁺ or Al₂ ⁺ irradiation at the same energy/atom, total atomic fluence, flux rate, and irradiation temperature, are presented and discussed. Received: 19 August 1999 / Accepted: 20 October 1999 / Published online: 23 February 2000     

Synthesis of nano-sized SiC precipitates in Si by simultaneous dual-beam implantation of C+ and Si+ ions

Nanometer-sized SiC precipitates were synthesized in situ in Si by simultaneous implantation of two ion beams of C⁺ and Si⁺ ions. The results of simultaneous dual-beam implantation are compared with those of sequential dual-beam ion implantation and of single-beam C⁺ ion implantation. Remarkable differences are observed regarding the content and the crystal quality of SiC precipitates as well as the defect structure of the Si substrate. The SiC precipitation during dual-beam synthesis is found to depend on the ion energy of the second beam and on the implantation mode, simultaneous or sequential. For suitable implantation conditions, simultaneous dual-beam synthesis can improve the in situ SiC formation in comparison to the single-beam synthesis. A higher density of SiC precipitates with better crystal quality was observed, whereas their size was not changed. The second ion beam enables a shift in the dynamic equilibrium of constructive and destructive processes for SiC formation. A model is proposed assuming that SiC precipitation preferentially proceeds in regions with vacancy defects. The implantation process itself creates vacancy-dominated and also interstitial-dominated regions. The balance of the local point-defect composition is shifted under the second ion beam. In this way, the conditions for SiC precipitation can be modified. Received: 18 February 2002 / Accepted: 17 May 2002 / Published online: 17 December 2002 RID="*" ID="*"Corresponding author. Fax: +49-351/260-3411, E-mail: koegler@fz-rossendorf.de     

Release of a diamond-like film on a nickel surface irradiated simultaneously with carbon ions and electrons

Nickel samples at temperatures of 300–1000°C have been irradiated simultaneously with 10-to 30-keV C⁺ ions and 1-to 5-keV electrons. The release of implanted carbon atoms on the surface of a sample with the formation of a transparent carbon film with the prevailing sp ³ hybridization has been observed. The thickness of the film is several tens of nanometers. The formation of films is attributed to the acceleration of the formation of carbon structures in samples irradiated by accelerated electrons.     

Quantum chemical study of the properties of an SiO<Subscript>2</Subscript>/Si(100) interface implanted with boron ions

Quantum-chemical calculations of the properties of a B⁺ ion-implanted SiO₂/Si(100) interface are presented. Dependencies of the total energy of a B⁺ ion cluster system on the location of B⁺ ions in oxygen and silicon vacancies are calculated, along with the geometric and electronic characteristics of the equilibrium cluster states with implanted boron ions.     

Ion bombardment-induced charge state effects CaO single crystals: F+ and F centers

The effects of heavy-and light-ion bombardment on defect formation in CaO have been investigated by UV-absorption spectroscopy and volume measurements. While 500 keV Ar or Ca implantation produces only F⁺ centers, 240 keVH produces both F⁺ and F centers at a F⁺ to F ratio of 5.6 to 1. On the other hand, when an argon implanted sample is subsequently bombarded with hydrogen, about 30% of the F⁺ centers anneal during 1 ×10¹⁴ H/cm²; at higher H fluences, new F⁺ and F centers are produced. An effect of energy partition between ionization and nuclear/atomic collision processes for the incident ions on the charge state of the resulting defect is thus clearly demonstrated.

The formation and annealing of these defects are accompanied by volume changes in the ion implanted surface layer which can be monitored in sltu with a cantilever beam technique. The measurements show volume expansion of the order of 1.5% following 10¹⁶ 500 keV Ar implantation; subsequent implantation of 10¹⁸ 240 keV H compacts the previously expanded material by 25 %. These results are in qualitative agreement with the optical data and seem to indicate that volume changes are associated with the formation and annealing of F⁺ centers.     

Formation of cubic silicon carbide layers on silicon under the action of continuous and pulsed carbon ion beams

The structure and infrared absorption of cubic silicon carbide (β-SiC) layers produced by the continuous high-dose implantation of carbon ions (C⁺) into silicon (E=40 keV and D=5×10¹⁷ cm⁻²), followed by the processing of the implanted layers with a high-power nanosecond pulsed ion beam (C⁺, τ=50 ns, E=300 keV, and W=1.0–1.5 J/cm²), are investigated. Transmission electron microscopy and electron diffraction data indicate the formation of a coarse-grained polycrystalline β-SiC layer with grain sizes of up to 100 nm. A characteristic feature of such a layer is the dendritic surface morphology, which is explained by crystallization from the melt supercooled well below the melting point of β-SiC.     

Nitrogen centers in GaP produced by hot implantation

Backscattering yields of 1.5 MeV?He⁺ ions and low temperature photoluminescence (PL) spectra were measured in GaP crystals implanted with 200 keV?N⁺ ions as functions of ion-dose, temperature during implantation and annealing temperature after implantation. Backscattering results indicate that hot implantation at 500°C greatly reduces radiation damage. The PL intensities of NN lines become maximum in the sample implanted with N⁺ ions of 3 × 10¹⁴cm^?2 at 500°C, and annealed at 1000°C for 1 hr with aluminum glass. The PL intensity is comparable to that of the nitrogen-doped sample during liquid phase epitaxy which is widely accepted as the best method of introducing nitrogen into GaP crystals. In the case of 500°C—hot implantation, the radiation damage produced during implantation is annealed out at 700 ~ 800°C and the implanted nitrogen substitutes for the phosphorous sites after annealing at 900 ~ 1000°C. Some kinds of defects or strains remain around the NN centers even in implanted samples with a maximum PL efficiency. These defects or strains don't seem to reduce the PL efficiency. In the case of room temperature implantation, PL efficiency decreases to one-hundredth or one-thousandth due to the formation of the non-crystalline state compared with hot implantation.     

Local magnetic order in silicon implanted with high-energy ions

A room-temperature local magnetic order has been detected in silicon implanted with high-energy Kr⁺ and Xe⁺ ions. The evidence of the presence of the local magnetic order are the electron magnetic resonance lines with g-factor values of about 2.2 and 3.4, the hysteresis of the resonance magnetic field values of these lines, the anisotropy characteristic of ferromagnets, and the broadening. The ordering effect is retained after the annealing of samples at temperatures of no higher than 1270 K.     

Compound synthesis in TiO2 implanted with Rubidium

Rubidium ions, with energy in the range 0.1 MeV, 2.0 MeV have been implanted in TiO₂ single crystals at RT and LNT.

Defects induced by implantation have been studied by optical spectroscopy, X-ray diffraction, RBS, TEM and electrical conductivity.

During implantation, the implanted samples are blue colored after irradiation. This coloration is due to an optical absorption band localized at 900 nm which corresponds to optical transition of intrinsic defects identified as Ti³⁺. These defects are induced by a chemical reaction between the implanted ions and the oxygen of the lattice as in the case of D⁺, H⁺, Li⁺, Na⁺ and K⁺ implanted in rutile.^1-3

The synthesis of a new phase in heavily implanted rutile is exhibited by using a thermal treatment and by combining techniques such as RBS, TEM and X-ray diffraction at glancing angle in the temperature range 300°C-700°C.

This compound does not correspond to metallic precipitates of rubidium which are observed in MgO implanted with Rb ions.

Planar defects have been observed in the implanted area. A correlation is exhibited between these defects and the precipitates of the new phase. From X-ray diffraction measurements and TEM observations, the composition of the synthetized compound is likely Rb₂TiO₃.     

The enhancement of the anodization of ion implanted silicon and its novel application

The enhancement of the anodization of silicon due to ion implantation is observed to be significant in the case of heavy ion implant with doses more than 10¹⁴ ions/cm². The studies indicate that the chemical effect caused by the implanted ions is smaller, but the lattice defects introduced by the implantation play an important role in the enhancement of the oxidation rate. A novel application of this effect to investigate the depth profile of damage in heavy implanted silicon is shown.     

Experimental studies of complex crater formation under cluster implantation of solids

The results of a systematic study of surface defect formation after energetic Ar_n⁺ (n = 12, 22, 32, 54) and Xe_n⁺ (n = 4, 16) cluster ion implantation into silicon and sapphire are presented. Implantation energies vary from 3 to 18 keV/ion. Two cases of comparative studies are carried out: the same cluster species are implanted into two different substrates, i.e. Ar_n⁺ cluster ions into silicon and sapphire and two different cluster species Ar_n⁺ and Xe_n⁺ are implanted into the same kind of substrate (silicon). Atomic force, scanning electron and transmission electron microscopies (AFM, SEM and TEM) are used to study the implanted samples. The analysis reveals the formation of two types of surface erosion defects: simple and complex (with centrally positioned hillock) craters. It is found that the ratio of simple to complex crater formation as well as the hillock dimensions depend strongly on the cluster species, size and impact energy as well as on the type of substrate material. Qualitative models describing the two comparative cases of cluster implantation, the case of different cluster species and the case of different substrate materials, are proposed.     

TEM analysis of the influence of dose on damage behavior in MeV Au2+-implanted silicon

Extended lattice damage created by implantation of 3.6 MeV Au²⁺ ions has been investigated using transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS). Systematic observations of damage for Au²⁺ ions implanted with varying doses into silicon are explained in terms of a model. The origin of two distinct bands of extended defects is explained in terms of annealing of the central region of implant-damage, during the course of the implantation. Two distinct bands of Au precipitates are observed in high-dose implanted samples. This observation is explained as being the result, in part, of segregation of gold in front of a recrystallizing front, and in part, of gettering of dopant-atoms to nodes in a dislocation network. The network arises as a result of dynamic annealing of damaged crystalline silicon.     

Superconducting properties and structural phase transformation of Nb2N induced by C+ - and N+-implantation

Thin films of h.c.p. Nb₂N implanted uniformly wilh 25 at.% C⁺ or N⁺ ions were found to transform into the f.c.c. Bl structure; film surface temperatures did not exceed 200°C. The resistive superconducting transition sharpened markedly and T_c was found to increase after implantation, presumably due to the structural change. X-Ray diffraction measurements were used to determine crystal structure and lattice parameters. A possible mechanism for the transformation is discussed.     

57Fe conversion electron Mössbauer spectrometric study of boron and carbon ion implanted irons

Amorphous layers produced at the surface of iron by B⁺ and C⁺ implantation (50 kV, 1×10¹⁸ ions cm⁻²) were analyzed by CEMS. The CEM spectrum of B⁺ implanted layer was composed of broad doublet and sextet. Spread hyperfine field distribution, P(H), indicates the formation of extremely disordered FeB layer. Annealing at 400°C brought about precipitation of FeB, which was converted to Fe₂B by annealing at 500°C. The P(H) for C⁺ implanted iron was resolved to 3 subpeaks with H values of 11.0, 18.0 and 22.5 T. The amorphous FeC phase was strongly correlated to crystalline Fe₅C₂ and Fe₂C, which precipitated at 300°C and were transformed into Fe₃C at 500°C. The amorphous layer disappeared by annealing at 600°C.