Ion Beam Induced Epitaxial Crystallization Research Articles

Activation energies for light ions in ion beam induced epitaxial crystallization

Activation energies of ion beam induced epitaxial crystallization (IBIEC) of Si have been measured for B, C and O ions at 0.7 or 3 MeV at temperatures 150–400°C. An activation energy for B was measured to be 0.26 eV in the range 250–400°C. This value was smaller than those for heavier ions Ge (0.28 eV) and Au (0.37 eV). Activation energies for B, C and O ions in the range of 150–400°C were found to be temperature dependent, where activation energies separately calculated for two temperature regimes varied from 0.18 to 0.37 eV. Results suggest that the ion beam induced epitaxial crystallization cannot be characterized by a single activation energy and several types of defect are involved in crystal growth.

Epitaxial crystallization during 600 °C furnace annealing of amorphous Si layer deposited by low-pressure chemical-vapor-deposition and irradiated with 1-MeV Xe ions

The amorphous Si layers deposited by low-pressure chemical vapor deposition on (100)-crystal-Si substrates and subjected to Xe-ion-beam irradiation are crystallized epitaxially in a layer-by-layer fashion to the surface during 600 °C furnace annealing. Layer-by-layer crystallization can be accomplished by irradiating the layers with a 1-MeV Xe-ion-beam for a 2×1015/cm2 dose at 310 °C prior to furnace annealing. In all cases during furnace annealing that amorphous Si layers are polycrystallized or are grown vertically in isolated epitaxial-columnar-structures and then grown laterally into the amorphous region surrounding each column, the ion-beam-induced epitaxial crystallization (IBIEC) method epitaxially crystallizes them in a layer-by-layer fashion. This is because O atoms that were at the initial interface and that prevented layer-by-layer crystallization or columnar-epitaxial-growth diffuse remarkably because of irradiation. This diffusion decreases the peak concentration and facilitates layer-by-layer crystallization. O atoms at the interface are also diffused by irradiation with 80-keV P, 100-keV As, and 150-keV As ions. This diffusion results in the columnar growth during 600–800 °C furnace annealing. Whether layer-by-layer growth or columnar growth occurs during the furnace annealing depends on the peak concentration of oxygen at the interface. Direct evidence is shown that O diffusion is enhanced by the amount of inelastic electronic scattering of incident ion beam under the same elastic nuclear scattering conditions. The rates of IBIEC and of epitaxial crystallization during furnace annealing after 1-MeV Xe-ion-beam irradiation for a 2×1015/cm2 dose are affected by the amount of oxygen in the amorphous layer. The rate of layer-by-layer IBIEC using a 1-MeV Xe-ion-beam is nearly twice as high for a sample heated in the deposition furnace after evacuation as it is for a sample heated before evacuation. This difference is due to the smaller amount of oxygen in the amorphous Si layer of the former sample.

Monte Carlo simulation of ion beam-assisted solid phase epitaxy

We have developed a computer simulation of ion beam-induced epitaxial crystallisation (IBIEC) based on the familiar kink-and-ledge model which describes thermally activated solid phase epitaxy. In the latter, kinks are assumed to form (via thermal activation) on ledges. Here, we assume that the deposited ion energy induces kink formation on the terraces as well as on the ledges. We then derive, with minimal restrictions on the growth laws, the interface morphology evolution. The latter is correlated to the growth speed, and an interpretation of the IBIEC temperature dependence is proposed. The power laws which characterise the simulated interface evolution are those of the Kardar-Parisi-Zhang universality class.

Ion beam modification of Si/SiC/Si layer systems

Buried, homogeneous silicon carbide (SiC) layers were formed in (100) and (111) silicon by ion beam synthesis (IBS). In order to study the ion beam induced epitaxial crystallization (IBIEC) of buried SiC layers, the carbide layers were amorphized by irradiation with 2 MeV Si 2+ ions at 300 K, followed by solid-phase epitaxial regrowth of surrounding amorphized silicon layers. IBIEC experiments were performed at 320° and 600°C using a 800 keV Si + beam. It is shown by transmission electron microscopy and electron diffraction that IBIEC works well on buried SiC layers and results in epitaxial recrystallization at considerably lower target temperatures than necessary for thermal annealing. The IBIEC process starts from both SiC/Si interfaces and may be accompanied by heterogeneous nucleation of poly-SiC as well as interfacial layer-by-layer amorphization, depending on irradiation conditions. The structure of the recrystallized regions in dependence of dose, dose rate, temperature and crystal orientation is described in detail.

Molecular dynamics simulations for amorphous/crystalline Si interface: Amorphization and crystallization induced by simple defects

Molecular dynamics calculations have been performed to simulate ion-beam-induced epitaxial crystallization (IBIEC) and interfacial amorphization (IBIIA) at an amorphous/crystalline (a/c) Si interface based on the ordinary Langevin equation employing the Tersoff potential for Si. Half part of the c-Si lattice composed of 216 atoms was amorphized by accumulating divacancy and di-interstitial (D-D) pairs and a/c interfaces were formed. Simple defects such as single vacancies and divacancies were introduced at the a/c interfaces and atomistic simulations were carried out. Neither IBIEC nor IBIIA were observed by introducing only vacancy-type defects. On the other hand, a D-D pair was found to give rise to both amorphization and crystallization. These results suggest that IBIEC and IBIIA can be described as a bond-switching process between the 6-member and 5- or 7-member rings which can be induced by a D-D pair formation at the a/c interface.

Ion-beam-induced epitaxial crystallization (IBIEC) and solid phase epitaxial growth (SPEG) of Si 1− xC x layers in Si fabricated by C ion implantation

Amorphous Si 1− x C x layers in Si(100) (0.013 ≤ x ≤ 0.032 at peak concentration) formed by 35 keV 12C implantation were crystallized by solid phase epitaxial growth (SPEG) up to 850°C and by ion-beam-induced epitaxial crystallization (IBIEC) with 400 keV Ar or Ge ions at 300–400°C. SPEG process has induced the epitaxial growth up to the surface for samples with x ≤ 0.019 and IBIEC process has induced that for samples with x ≤ 0.025. Rutherford backscattering spectrometry (RBS) measurements have revealed a direct scattering peak due to extended defects around the depth of peak C concentration both in SPEG-grown samples ( x = 0.019) and IBIEC-grown sample ( x = 0.025). X-ray diffraction (XRD) has shown a growth with smaller tensile strain in both SPEG- and IBIEC-grown samples than in fully strained layers. Photoluminescence (PL) measurements at 2 K have shown a strong I 1 line emission in IBIEC-grown samples, which can be attributed to vacancy clustering. The local configuration of defects around C atoms in the IBIEC-grown samples is thought to be an origin of the smaller tensile strain.

Erbium doping of Si via ion-beam-induced epitaxial crystallization: another route to room-temperature photoluminescence

Si was doped with Er by combining Er ion implantation with ion-beam-induced epitaxial crystallization (IBIEC) at 320 °C and rapid thermal post-annealing at 980 °C. The structural evolution and the Er lattice site occupation during and after this treatment were studied via high-resolution electron microscopy (HREM) and Rutherford backscattering channelling (RBS/C). We obtain approximately 3×10 20 Er cm −3 (about 40% of the implanted dose) in well-defined lattice sites. Photoluminescence (PL) occurs at room temperature. The effect of oxygen co-doping was studied by comparing the PL and lattice locations of Er in Czochralski (CZ), epitaxial, and oxygen-implanted epitaxial hosts.

Photoluminescence studies of epitaxial Si 1− xGe x and Si 1− x−yGe xC y layers on Si formed by ion beam synthesis

Low temperature (2 K) photoluminescence (PL) properties of epitaxial Si 1− x Ge x and Si 1− x−y Ge x C y layers on Si ( x = 0.13 and y = 0.014 at peak concentration) formed by ion beam synthesis (IBS) have been investigated. Samples were prepared by a high-dose Ge with/without C ion implantation (I 2) at room temperature and by subsequent three different crystallization techniques: (i) furnace annealing (FA) process up to 840°C, (ii) ion beam-induced epitaxial crystallization (IBIEC) process with 400 keV Ge or Ar ions at 300–350°C, and (iii) IBIEC process followed by FA process up to 640°C (IBIEC + FA). Although FA-grown Si 1− x−y Ge x C y samples showed G-line (C sSi iC s complex) emission at 0.969 eV, IBIEC-grown samples presented a sharp I 1 non-phonon emission at 1.0193 eV. This indicates that C atoms agglomeration is dominant for FA-grown samples, while a creation of trigonal tetravacancy cluster is dominant for IBIEC-grown samples. On the other hand, (IBIEC with Ge ions + FA)-grown Si 1− x−y Ge x C y samples showed neither G-line nor I 1-related emissions, which indicates that good crystalline Si 1− x−y Ge x C y layers without C agglomeration were formed by this process. In contrast, (IBIEC with Ar ions + FA)-grown samples exhibited novel successive PL vibronic sidebands at 0.98–1.03 eV. From their excitation power dependence measurements, they were found to be associated with exciton bound to defects levels created by Ar + bombardment.

Ion beam induced epitaxial crystallization of SrTiO 3

The epitaxial crystallization of amorphous SrTiO 3 on single crystal SrTiO 3 (100) has been induced by ion irradiation at temperature range of 70–230°C. Rutherford backscattering spectrometry and ion channeling were used to evaluate the crystallization. The contribution of thermally induced solid phase epitaxial crystallization (SPEC) is negligible at temperatures used in the present experiments. The crystallization is attributed to ion beam induced epitaxial crystallization (IBIEC), and is characterized by an activation energy of 0.2 eV. This value is about 1 5 relative to that of solid phase epitaxial crystallization (SPEC). As to the dependence of IBIEC on impurities, a retarded IBIEC has been observed in Nb-doped SrTiO 3.

Design of Functional Inorganic Materials by Ion Beams. Ion Beam Induced Epitaxial Crystallization of Inorganic Materials.

IBIEC (Ion Beam Induced Epitaxial Crystallization) is one of the methods of SPEC (Solid Phase Epitaxial Crystallization) and is characterized by its low temperature crystallization and low thermal activation energy relative to thermally induced SPEC. IBIEC has been investigated for many years from the view of interest in its mechanism concerned with ion-solid interaction and application to a low temperature SPEC process particularly in Si. Recently, this technique has been tried to apply to many different kinds of materials such as compound semiconductors (GaAs, BP, InP and GeSi), carbide (SiC), silicides (NiSi2 and CoSi2) and even oxides (Al2O3 and SrTiO3). In this article, the authors reviewed the features, proposed mechanisms and application of IBIEC to Si and other materials with the existing state of affairs.

Crystallization of SiSn and SiSnC layers in Si by solid phase epitaxy and ion-beam-induced epitaxy

For the synthesis of novel group-IV semiconductors, crystalline growth of amorphous Si 1− x Sn x and Si 1− x−y Sn x C y layers in Si formed by Sn and C ion implantation has been investigated with solid phase epitaxial growth (SPEG) and ion-beam-induced epitaxial crystallization (IBIEC). Si(100) wafers were implanted at RT with 110 keV or 270 keV 120Sn ions to a dose up to x = 0.03 at peak concentration and 17 keV or 35 keV 12C ions up to y = 0.025 at peak concentration. SPEG experiments at 750°C have shown epitaxial crystallization of the strained alloy layer in the Si 1−x Sn x Si sampl ( x = 0.03) and strain-compensated layer in the Si 1−x−y Sn x C y Si sample with medium C concentration ( x = 0.03 and y = 0.019). IBIEC experiments performed with 400 keV Ar ions at 350°C have also induced epitaxial crystallization for the Si 1−x Sn x Si sample ( x = 0.025), whereas those of Si 1− x−y Sn x C y ( x = 0.025 and y = 0.014) have shown a collapse of epitaxial growth. Photoluminescence (PL) from SPEG-grown Si 1− x Sn x and Si 1− x−y Sn x C y samples has shown neither prominent I 1 nor G peaks. Present results have revealed features in crystalline growth properties, in both techniques, for the non-thermal equilibrium fabrication of these new alloy semiconductors.

Ion beam induced amorphization and recrystallization of Si/SiC/Si layer systems

Epitaxial, buried silicon carbide (SiC) layers have been fabricated in (100) and (111) silicon by ion beam synthesis (IBS). In order to study the ion beam induced epitaxial crystallization (IBIEC) of buried SiC layers, the resulting Si/SiC/Si layer systems were amorphized using 2 MeV Si 2+ ion irradiation at 300 K. An unexpected high critical dose for the amorphization of the buried layers is observed. Buried, amorphous SiC layers were irradiated with 800 keV Si + ions at 320 and 600°C, respectively, in order to achieve ion beam induced epitaxial crystallisation. It is demonstrated that IBIEC works well on buried layers and results in epitaxial recrystallization at considerably lower target temperatures than necessary for thermal annealing. The IBIEC process starts from both SiC/Si interfaces and may be accompanied by heterogenous nucleation of poly-SiC as well as interfacial layer-by-layer amorphization, depending on irradiation conditions. The structure of the recrystallized regions in dependence of dose, dose rate, temperature and crystal orientation is presented by means of TEM investigations.

Radiation damage and annealing behaviour of Ge +-implanted SiC

In recent years, single-crystal SiC has become an important electronic material due to its excellent physical and chemical properties. The present paper reports a study of the defect reduction and recrysallisation during annealing of Ge +-implanted 6H-SiC. Implants have been performed at 200 keV with doses of 1 × 10 14 and 1 × 10 15 cm −2. Furnace annealing has been carried out at temperatures of 500, 950 and 1500°C. Three analytical techniques including Rutherford backscattering spectrometry in conjunction with channelling (RBS/C), positron annihilation spectroscopy (PAS) and cross-sectional transmission electron microscopy (XTEM) have been employed for sample characterisation. It has been shown that damage removal is more complicated than in ion-implanted Si. The recrystallisation of amorphised SiC layers has been found to be unsatisfactory for temperatures up to 1500°C. The use of ion-beam-induced epitaxial crystallisation (IBIEC) has been more successful as lattice regrowth, although still imperfect, has been observed to occur at a temperature as low as 500°C.

Reply to ‘‘Comment on ‘Evidence of enhanced epitaxial crystallization at low temperature by inelastic electronic scattering of mega-electron-volt heavy-ion-beam irradiation’ ’’ [J. Appl. Phys. 80, 4235 (1996)

Enhanced epitaxial crystallization by mega-electron-volt (MeV) heavy-ion-beam irradiation cannot be explained only by the diffusion-limited model. The validity of data showing the absence of dose rate effect on MeV ion-beam-induced epitaxial crystallization (IBIEC) rate is examined in relation to the self-ion-beam annealing effect in MeV As+-ion-beam irradiation in the crystalline Si substrate. The reliability of the experimental results showing the critical thickness dependence in the diffusion-limited model is discussed in detail. It is pointed out that there is room to question the existence of critical thickness. Two guidelines for constructing an accurate IBIEC model are proposed.

Surface modification of the poly(ethyleneterephthalate) foil by reactive ion beam bombardment

Poly(ethyleneterephthalate) foils have been subjected to the action of oxygen ion beams in order to investigate induced surface modifications vs beam parameters (ion energy and fluence). The ion beam-plasma system was characterised by mass spectrometry and the resulting modifications of the polymer surface were analysed by transmission electron microscopy, IR and X-ray photoelectron spectrometry. It is pointed out that a so-called ion beam induced epitaxial crystallization (IBIEC) process takes place for PET samples treated with oxygen ions with relative low energy. The mechanism is mainly controlled by the ratio between the fluence of fast atomic and molecular oxygen ions. This ratio determines the probability for the yielding of the polymer chains with critical dimensions and also the rates for the dynamic defect annealing and the defect production.

Synthesis of metastable group-IV alloy semiconductors by ion implantation and ion-beam-induced epitaxial crystallization

In order to synthesize metastable group-IV binary alloy semiconductor thin films on Si, Si(100) substrates were implanted with 17 keV C ions forSi/ 1−yC ySi and alternatively with 110 keV Sn ions forSi/ 1−zSn zSi. Subsequent ion-beam-induced epitaxial crystallization (IBIEC) with 400 keV Ar ions at 300–400°C has induced a good epitaxial growth up to the surface both forSi/ 1−yC ySi (y=0.014 at peak concentration) and forSi/ 1−zSn zSi (z=0.029 at peak concentration). X-ray diffraction measurements have shown a growth ofSi/ 1−yC ySi with smaller tensile strain than forSi/ 1−yC ySi grown by solid phase epitaxial growth (SPEG) up to 650°C. Photoluminescence measurements have revealed properties of defect related to I 1(Ar) line and G line emissions for IBIEC-grownSi/ 1−yC ySi samples. IBIEC has induced an incomplete crystalline growth and a loss of implanted Sn atoms forSi/ 1−zSn zSi (z=0.086 at peak concentration).

Epitaxial crystallization and nucleation during MeV-ion beam processing of amorphous GaAs surface layers

〈100〉-GaAs wafers were preamorphized in a thin surface layer using 50 keV 14N +-ions. Ion beam induced epitaxial crystallization (IBIEC) and interfacial amorphization (IBIIA) were studied as a function of the target temperature using MeV Ar +- or Kr +-ions. Backscattering experiments and electron microscopy show that the IBIEC process is stopped above a critical irradiation temperature due to enhanced ion beam induced nucleation and growth of crystallites. At a fixed dose an optimum irradiation temperature for IBIEC was found, at which the recrystallized layer thickness has a maximum and crystallite formation is negligible. This offers the possibility to crystallize much larger thicknesses than ≈65 nm which stands for the maximum value reported up to now.

Ion beam assisted recrystallization of [formula omitted] structures

The analysis of ion beam induced epitaxial crystallization (IBIEC) of SiC Si structures obtained by high dose C ion implantation into amorphous Si (preamorphized by Ge ion implantation) has been performed by FTIR, Raman scattering, TEM and RBS measurements. The data obtained show the formation of an amorphous SiC layer on the amorphous Si at successive Ge and C ion implantations in crystalline Si. During IBIEC processing, the Si amorphous region below the implanted layer recrystallizes epitaxially. However, in the carbon implanted layer polynucleation occurs, forming a nanocrystalline SiC layer. The epitaxial crystallization stops when the recrystallization front reaches the carbon implantation tail. Finally, Raman measurements show the presence of some residual amorphous phase, likely related to the surface and intergrain regions.

Evidence of enhanced epitaxial crystallization at low temperature by inelastic electronic scattering of mega-electron-volt heavy-ion-beam irradiation

The inelastic electronic scattering of 84Kr at energies of 0.5–5 MeV and 131,132Xe ions at energies of 1–5 MeV is directly confirmed to play a role in the ion-beam-induced epitaxial crystallization (IBIEC) of amorphous Si layers on crystalline Si substrates at 310–450 °C. The crystallization rate per unit vacancy (normalized crystallization rate) created by the elastic nuclear scattering of the incident ion beam at the amorphous–crystalline (a/c) interface is increased 40%–50% by increasing the inelastic electronic scattering three- to fourfold while maintaining the same elastic nuclear scattering conditions at the a/c interface. This normalized crystallization rate also increases with the inelastic electronic scattering at the a/c interface. However, the percentage of increase falls to about 20% as the absolute value of the inelastic electronic energy loss at the a/c interface decreases to below about 20 keV/ion/(20 nm) or as the number of vacancies created at the a/c interface increases to more than 250/ion/(20 nm). At 310–450 °C the activation energy for IBIEC induced by Kr or Xe irradiation is 0.5–0.6 eV. This value slightly larger than the 0.2–0.3 eV reported for temperatures below 300 °C reflects the thermally activated solid-phase epitaxy. The mechanism of this enhanced crystallization by inelastic electronic scattering is discussed qualitatively.

Ion beam-induced interfacial growth in Si and silicides

We review the mechanisms and consequences of ion beam-induced epitaxial crystallization (IBIEC) in the transition metal- or rare earth-implanted aSi cSi systems, as determined from in situ transmission electron microscopy (TEM) during irradiation, combined with channeling, high resolution TEM and optical measurements. IBIEC experiments on nm-size crystals confirm previously measured low values of interface roughness in IBIEC. We have performed interfacial growth simulations which indicate that the IBIEC process is, in fact, interface roughness-limited. They also suggest that interfacial growth processes are similar in several respects to surface growth processes, and that they largely determine (i) the growth habit of silicide precipitation, which is dominated by the interfacial energy, (ii) the possibility of trapping a large fraction of the impurities in non-equilibrium sites, leading to significant supersaturation. A consequence of this effect is to allow incorporation of large (over 300-fold supersaturation) Er concentrations in the substitutional sites of the Si lattice, leading to room-temperature photoluminescence (without any oxygen co-implantation). Evidence of a new, thermally induced instability in interfacial growth is presented: it displays both intermittency and very high growth rates, and is strongly affected by ion irradiation.