Search

The diffusion of indium atoms in silicon-dioxide films previously implanted with arsenic ions with different energies is studied in relation to the temperature of postimplantation annealing. It is established that the diffusion properties of indium depend on the presence of arsenic atoms in the film and their energy. An increase in the As content in the region of the average projective range of In+ ions prevents the diffusion of In towards the SiO2 film surface at high annealing temperatures and stimulates the diffusion of In deep into the film in the form of a monovalent interstitial site. The experimentally observed effects are interpreted on the assumption of the formation of In–As pairs in neighboring substitutional positions in the SiO2 matrix. [ABSTRACT FROM AUTHOR]

By means of Rutherford backscattering spectrometry, electron microscopy, and energy-dispersive X-ray spectroscopy, the distribution and interaction of In and As atoms implanted into thermally grown SiO2 films to concentrations of about 1.5 at % are studied in relation to the temperature of subsequent annealing in nitrogen vapors in the range of T = 800–1100°C. It is found that annealing at T = 800–900°C results in the segregation of As atoms at a depth corresponding to the As+-ion range and in the formation of As nanoclusters that serve as sinks for In atoms. An increase in the annealing temperature to 1100°C yields the segregation of In atoms at the surface of SiO2 with the simultaneous enhanced diffusion of As atoms. The corresponding diffusion coefficient is DAs = 3.2 × 10–14 cm2 s–1. [ABSTRACT FROM AUTHOR]

The ion-beam synthesis of InSb nanocrystals in the buried SiO layer of a silicon-on-insulator structure is investigated. The distributions of In and Sb atoms after annealing at a temperature of T = 500-1100°C are studied. It is established that the redistribution of implanted atoms is unsteadily dependent on the annealing temperature. The formation of InSb nanocrystals occurs at Ta ≥ 800°C near the Si/SiO interface and at a depth corresponding to the mean paths R. Analysis of the profiles of implanted atoms and of the structure and depth distribution of nanocrystals formed allows an inference regarding the two-stage character of formation of the InSb phase. In the initial stage, antimony precipitates are formed; further the precipitates serve as nuclei for indium and antimony to flow to them. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we use large area light pulse induced melting of deposited thin silicon films on oxidised silicon wafers to prepare coarse grained dendritic crystal structures. The results show that the addition of carbon prevents the agglomeration of the molten silicon films and largely influences the crystallisation process. The low solubility of carbon in liquid silicon and its effect on the silicon melting temperature induces a distinctive lateral dendritic grain growth. XTEM, SEM, AFM and ToF-SIMS investigations have been performed to study the crystallisation process and to characterise the resulting film structure. [Copyright &y& Elsevier]

Abstract: 3C-SiC nanocrystallites were epitaxially formed on a single crystalline Si surface covered by a 150nm thick SiO2 capping layer after low dose carbon implantation and subsequent high temperature annealing in CO atmosphere. Carbon implantation is used to introduce nucleation sites by forming silicon–carbon clusters at the SiO2/Si interface facilitating the growth of 3C-SiC nanocrystallites. [Copyright &y& Elsevier]

Abstract: Growth of InSb nanocrystals at the Si/SiO2 bonding interface of silicon-on-insulator (SOI) structures has been studied as a function of the annealing temperature. SOI structures with the ion implanted regions above and below the bonding interface were produced as a result of the hydrogen transfer of the Sb+ ion implanted silicon layer from first silicon substrate to the In+ ion implanted SiO2 layer thermally-grown on the second silicon substrate. Rutherford backscattering spectrometry and high-resolution transmission electron microscopy (XTEM) were used to study the properties of the prepared structures. Up-hill diffusion of In and Sb atoms from the implantation regions toward the bonding interface as well as subsequent interface-mediated growth of InSb nanocrystals were observed as the annealing temperature achieved 1100°C. The strain minimizing orientations of the Si and InSb lattice heteropairs were obtained from XTEM analysis of the grown nanocrystals. [Copyright &y& Elsevier]

Abstract: Nanometer-thick silicon-germanium-on-insulator (SGOI) structures have been produced by the implantation of Ge+ ions into thermally grown SiO2 layer and subsequent hydrogen transfer of silicon film on the Ge+ ion implanted substrate. The intermediate nanometer-thick Ge layer has been formed as a result of the germanium atom segregation at the Si/SiO2 bonding interface during annealing at temperatures 800–1100 оС. From a thermodynamic analysis of Si/Ge/SiO2 system, it has been suggested that the growth of the epitaxial Ge layer is provided by the formation of a molten layer at the Si/SiO2 interface due to the Ge accumulation. The effect of germanium on the hole mobility in modulation-doped heterostructures grown over the 3–20nm thick SGOI layers was studied. An increase in the Hall hole mobility in SGOI-based structures by a factor of 3–5 was obtained in comparison with that in respective Ge-free SOI structures. [Copyright &y& Elsevier]

Systematic features of endotaxial growth of intermediate germanium layers at the bonding interface in the silicon-on-insulator structure consisting of buried SiO2 layer implanted with Ge+ ions are studied in relation to the annealing temperature. On the basis of the results for high-resolution electron microscopy and thermodynamic analysis of the Si/Ge/SiO2 system it is assumed that the endotaxial growth of the Ge layer occurs via formation of a melt due to enhanced segregation and accumulation of Ge at the Si/SiO2 interface. Effect of germanium at the bonding interface on the Hall mobility of holes in silicon layers with nanometer-scale thickness is studied. It is found that the structures including the top silicon layer with the thickness 3–20 nm and incorporating germanium feature the hole mobility that exceeds by a factor of 2–3 the hole mobility in corresponding Ge-free silicon-on-insulator structures. [ABSTRACT FROM AUTHOR]

The properties of germanium implanted into the SiO2 layers in the vicinity of the bonding interface of silicon-on-insulator structures are studied. It is shown that, under conditions of high-temperature (1100°C) annealing, germanium nanocrystals are not formed, while the implanted Ge atoms segregate at the Si/SiO2 bonding interface. It is established that, in this case, Ge atoms are found at sites that are coherent with the lattice of the top silicon layer. In this situation, the main type of traps is the positive-charge traps; their effect is interpreted in the context of an increase in the surface-state density due to the formation of weaker Ge-O bonds. It is found that the slope of the drain-gate characteristics of the back MIS transistors increases; this increase is attributed to an increased mobility of holes due to the contribution of an intermediate germanium layer formed at the Si/SiO2 interface. [ABSTRACT FROM AUTHOR]

A series of experimental and theoretical investigations has been initiated for 6H-SiC samples sequentially implanted with high doses of N[sup +](65 keV) + N[sup +](120 keV) + Al[sub +](100 keV) + Al[sub +](160 keV) ions at temperatures between 200 and 800°C. Nitrogen and carbon distribution profiles are measured by ERD and structural defect distributions are measured by Rutherford backscattering with channeling. A comparison between the experimental data and the results of computer simulation yields a physical model to describe the relaxation processes of the implanted SiC structure, where the entire implanted volume is divided into regions of different depth, having different guiding kinetics mechanisms. [ABSTRACT FROM AUTHOR]

Systematic evolution of the 400 nm electroluminescence (EL) with increasing flash lamp annealing (FLA) temperature from 800 to 1100 °C in an Er-doped Ge-rich metal-oxide semiconductor structure is presented. No significant change in the 1535 nm Er EL is observed with increasing FLA temperature. Enhancement of the 400 nm EL decay time with rising FLA temperature is found to be associated with recrystallization of the damaged Ge clusters in the absence of Ge outdiffusion. The 400 nm EL quenching with continuous charge injection process is also discussed within the device operation time. [ABSTRACT FROM AUTHOR]

High quality 3C-SiC nanocrystallites were epitaxially formed on (100) Si wafers covered by a 150 nm thick SiO2 capping layer after low dose carbon implantation and high temperature annealing in CO atmosphere. Carbon implantation is used to introduce nucleation sites by forming silicon-carbon clusters at the SiO2/Si interface acting as nucleation sites for the growth of 3C-SiC nanocrystallites. The formation of the nucleation clusters as well as the morphology, the size, and the density of the nanocrystals were systematically studied by conventional and high resolution transmission electron microscopy. The nanocrystallites were developed following two different modes of growth: The first develops facets along the <100> crystallographic direction giving tetragonal grains and the second facets along the <110> direction resulting in elongated nanocrystallites. The formation mechanism of the nanocrystallites and the strain related with them are also discussed. [ABSTRACT FROM AUTHOR]

The impact of rapid thermal annealing (RTA) in producing samples by sequential implantation of Si and Er ions into a 200 nm SiO2 layer combined with different annealing cycles as well as the corresponding room-temperature visible and infrared photoluminescence (PL) have been studied. The Er-related PL intensity at 1533 nm for the samples prepared by implanting Si with subsequent annealing, followed by Er implantation, and final annealing (type I) was found to be stronger than the one produced similarly but without the first annealing step (type II). In fact, the 1533 nm peak intensity in the optimized RTA processed sample is comparable to the PL yield of the furnace-annealed sample. Moreover, the excitation wavelength (405 nm) was found to be suitable for exciting the Si=O related point defects in the SiO2 layer and can provide a PL band with a maximum at ∼580 nm. While this band was further intensified in the presence of Si nanocrystals (Si NCs), it became weaker by introducing additional Er3+ ions with a concomitant rise of the 1533 nm Er PL, confirming the visible range pumping of Er3+. The detailed spectral analyses suggest that the 580 nm band is the result of the excitation/deexcitation mechanism in molecule such as states in the Si=O or the Si=O state mediated recombination of carriers in Si NCs according to the model proposed by [Wolkin et al., Phys. Rev. Lett. 82, 197 (1999)]. The samples were further characterized by transmission electron microscopy and Fourier-transform infrared spectroscopy. The time-resolved PL measurements and a modeling by rate equations were also performed to determine and justify the energy migration mechanism from Si NC to the neighboring Er3+. [ABSTRACT FROM AUTHOR]

Flash lamp annealing in the millisecond regime of heteroepitaxial silicon carbide on silicon structures involves melting the silicon below the SiC layer, but the deep faceted nature of the liquid-solid interface leads to unacceptable surface roughness. This paper describes a method of controlling melting by implanting a high dose of carbon at a controlled depth below the Si/SiC interface, which significantly alters the melting characteristics of the silicon. This technology has also been applied to SiC and Si multilayer heterostructures. Results confirm the effectiveness of this approach for increasing surface uniformity, making liquid phase processing compatible with standard device fabrication techniques. A thermal model has also been developed to describe this process and results indicate that the theoretical work is consistent with the experimental evidence. The model is a valuable tool for predicting the onset of melting, maximum temperatures, and process windows for controlled liquid phase epitaxy. [ABSTRACT FROM AUTHOR]

This paper describes the development of a thermal model for flash lamp processing of 3C-SiC on silicon substrates in the millisecond regime, the FLASiC process. The model is a numerical solution of the enthalpy equation, using a modified implicit Crank-Nicholson scheme to combine accurate prediction of melt depths with reasonable computation times. The model has been calibrated against experiments and then used to compute the temperature distribution in the wafer during annealing. The results show the time and extent of melting as a function of layer thickness, wafer preheat temperature, and pulse intensity and duration. The kinetics of melting and regrowth have also been considered. [ABSTRACT FROM AUTHOR]

Using combined microstructural and electroluminescence (EL) investigations of the Er-doped Ge-rich SiO2 layers, it is established that the Ge-related oxygen-deficiency centers (GeODCs), which are associated with the 407 nm light emission, are situated at the Ge nanocrystal/SiO2 interface. Electrically driven energy transfer from the Er3+ to GeODCs causes an increase in the 407 nm EL intensity. It reaches a maximum before quenching with increasing Er concentration due to the crystalline-to-amorphous transition of Ge nanocrystals. Ge concentration dependent quenching of the maximum EL intensity and the peak shifting toward higher Er concentration are discussed in terms of the reduction of the surface-to-volume ratio with increasing nanocrystal size. [ABSTRACT FROM AUTHOR]

The crystallization of silicon-on-insulator films, implanted with high doses of hydrogen ions, upon annealing with millisecond pulses is studied. Immediately after hydrogen-ion implantation, the formation of a three-phase structure composed of silicon nanocrystals, amorphous silicon, and hydrogen bubbles is detected. It is shown that the nanocrystalline structure of the films is retained upon pulsed annealing at temperatures of up to ∼1000°C. As the temperature of the millisecond annealing is increased, the nanocrystal dimensions increase from 2 to 5 nm and the fraction of the nanocrystalline phase increases to ∼70%. From an analysis of the activation energy of crystal phase growth, it is inferred that the process of the crystallization of silicon films with a high (∼50 at %) hydrogen content is limited by atomic-hydrogen diffusion. [ABSTRACT FROM AUTHOR]

Abstract: Thin polycrystalline silicon films are attractive for the fabrication of active matrix liquid crystal displays. We propose the use of flash lamp annealing to crystallize amorphous silicon layers on glass substrates as a low-cost manufacturing route. In this process, amorphous silicon can be crystallized both by solid phase crystallization (SPC) and in the super lateral growth (SLG) regime. We present a thermal model which incorporates the phase transitions during annealing and we have shown that predictions from the model are in good agreement with experimental observations. In addition, the model is a valuable aid to optimizing the process conditions. [Copyright &y& Elsevier]

Abstract: The use of 3C-SiC wafers for device fabrication has been restricted by the high defect density in the substrates. Flash lamp annealing (the FLASiC process) has been shown to reduce the defect density in 3C-SiC by at least an order of magnitude. This process involves melting a layer of silicon in contact with the 3C-SiC layer on a time scale of milliseconds and the subsequent regrowth of the SiC layer by liquid phase epitaxy. This paper shows how the transport of carbon in the liquid silicon is determined by the structure of the starting substrate and process conditions. The movement of carbon controls the dissolution and regrowth of the SiC and determines the morphology of the regrown film. [Copyright &y& Elsevier]

The influence of SiO2 and SiNx cover layers on the dopant distribution as well as microstructure of high fluence Ga implanted Si after thermal processing is investigated. The annealing temperature determines the layer microstructure and the cover layers influence the obtained Ga profile. Rapid thermal annealing at temperatures up to 750°C leads to a polycrystalline layer structure containing amorphous Ga-rich precipitates. Already after a short 20?ms flash lamp annealing, a Ga-rich interface layer is observed for implantation through the cover layers. This effect can partly be suppressed by annealing temperatures of at least 900°C. However, in this case, Ga accumulates in larger, cone-like precipitates without disturbing the surrounding Si lattice parameters. Such a Ga-rich crystalline Si phase does not exist in the equilibrium phase diagram according to which the Ga solubility in Si is less than 0.1 at. %. The Ga-rich areas are capped with SiOx grown during annealing which only can be avoided by the usage of SiNx cover layers. [ABSTRACT FROM AUTHOR]

It is generally believed that the 1.5 μm Er luminescence is enhanced by transferring energy from Si nanocrystals to the nearest Er3+ ions in Er-doped Si-rich SiO2 layers during optical pumping. Here, the influence of Ge nanocrystals instead of excess Si in the same environment is studied using electroluminescence technique on metal-oxide-semiconductor structures. An increase of the 400 nm electroluminescence intensity with a concomitant reduction of the Er-related emission is observed. This is explained in the light of an inverse energy transfer process from Er3+ to the Ge-related oxygen-deficiency centers. [ABSTRACT FROM AUTHOR]

The effect of rare-earth clustering in dielectric media on the electroluminescence (EL) intensity, the charge trapping and the EL quenching was investigated using the example of Tb and Eu-implanted SiO2 layers. It was shown that the increase in the REOX cluster size induced by an increase in the furnace annealing temperature resulted in an increase in the concentration of electron traps with capture cross sections from 2×10-15 to 2×10-18 cm2. This is probably associated with an increase in the concentration of oxygen deficiency centers as well as with strained and dangling bonds in the SiO2 matrix which leads to an enhanced scattering of hot electrons and a decrease in the excitation cross section of the main EL lines of RE3+ ions. For the main EL lines of Tb3+ and Eu3+ ions the relation of the EL quenching to negative and positive charge generation in the SiO2 was considered. It was demonstrated that in case of REOX nanoclusters with small sizes (up to 5 nm) the EL quenching process can mainly be explained by a defect shell model which suggests the formation of negatively charged defect shells around the nanoclusters leading to a Coulomb repulsion of hot electrons and a suppression of the RE3+ excitation. At high levels of the injected charge (more than 2×1020 e/cm2) a second stage of the EL quenching was observed which was contributed to a positive charge accumulation in the SiO2 at a distance beyond the tunneling distance from the SiO2[Single_Bond]Si interface. In case of Eu-implanted SiO2 the quenching of the main EL line of Eu3+ is mostly correlated with positive charge trapping in the bulk of the dielectric. A model of EL quenching of the main Eu3+ line is proposed. [ABSTRACT FROM AUTHOR]

Heavily p-type doped Ge layers were fabricated by 100 keV Ga implantation and subsequent flash lamp annealing for 3 ms in the temperature range between 700 and 900 °C. For comparison, some samples were annealed in a rapid thermal processor for 60 s. Ga fluences of 2×1015, 6×1015, and 2×1016 cm-2 were chosen in order to achieve Ga peak concentrations ranging from values slightly below the equilibrium solid solubility limit of 4.9×1020 cm-3 up to 3.5×1021 cm-3 which corresponds to a maximum Ga content of about 8 at. %. The structure of the doped layer and the Ga distribution were investigated by Rutherford backscattering spectrometry in combination with ion channeling, cross-sectional electron microscopy, and secondary ion mass spectrometry. Temperature dependent Hall effect measurements were carried out in order to determine the electrical properties of the Ga-doped Ge layers. It is shown that by flash lamp annealing Ga diffusion into the bulk can be completely avoided and the Ga loss by outdiffusion from the surface is reduced. The lowest sheet resistance of 36 Ω/sq. was achieved for the medium Ga concentration annealed at 900 °C. The best Ga activation values are 73%, 60%, and 24% for the three Ga fluences under investigation. The Ga activation is correlated with the layer regrowth. Incomplete epitaxial regrowth as observed in some samples leads to lower activation. [ABSTRACT FROM AUTHOR]

The anomalous wear-out phenomena of Eu-implanted metal-oxide-semiconductor devices were investigated. It will be shown that in contrast to other rare earth elements the electroluminescence (EL) intensity of Eu-implanted SiO2 layers can rise under constant current injection before the known EL quenching will start. Under certain circumstances, this rise may amount up to two orders of magnitude. The EL behavior will be correlated with the microstructural and electrical properties of the devices. Transmission electron microscopy and Rutherford backscattering spectroscopy were applied to trace the development of Eu/Eu oxide clusters and the diffusion of Eu to the interfaces of the gate oxide layer. The hydrogen profile within the SiO2–SiON interface region was determined by nuclear reaction analysis. Current-voltage characteristics, EL decay times, and the progression of the voltage and the EL spectrum with increasing charge injection were measured to study charge and trapping phenomena in the oxide layer to reveal details of the EL excitation mechanism. A first qualitative model for the anomalous life time behavior is proposed. [ABSTRACT FROM AUTHOR]

Using combined electroluminescence (EL) and photoluminescence (PL) studies we establish that the energy transfer process from the Er3+ to the Ge-related oxygen-deficiency centers (GeODCs) plays the key role in enhancing the 404 nm EL intensity in Ge-rich SiO2. Er doping induced structural modification does not appear to be relevant, which is deduced from the 404 nm PL quenching with increasing Er concentration, implying a gradual loss of GeODCs. In contrast to PL, the 404 nm EL intensity increases by 0.3% Er doping followed by a gradual decrease in intensity for higher Er concentrations, which is described in terms of a competition between the energy transfer process and the gradual segregation of Er due to the destruction of GeODCs with Er doping. This fact is further discussed in the light of ab initio molecular orbital calculations. [ABSTRACT FROM AUTHOR]

A flash lamp has been used to uniformly anneal large wafers with diameters approaching 100 mm. The equipment applies a pulse, with duration of 3–20 ms, resulting in large transient thermal gradients in the wafer. In this paper, we present separate models of the thermal reaction of this process and its effect upon the mechanical behavior, in order to predict stresses and shape changes, and to capture practical phenomenon. We further use the model to follow changes in the expected response consequent on altering process conditions, such as preheating and pulse duration, as well as exploring important issues associated with scaling to large wafer sizes. This work presents an initial description of the thermomechanical response of wafers to flash lamp annealing in the millisecond time regime and is therefore fundamental to the use of this technique in the fabrication of semiconductor devices. [ABSTRACT FROM AUTHOR]

Al supersaturated SiC layers (5×1020 Al cm-3) were produced by multienergy, high-dose ion implantation into 6H- and 4H-SiC. Several implantation schemes with varying implantation sequence and temperature were investigated. In dependence on the implantation conditions damaged single-crystalline, amorphous, or nanocrystalline layers were formed. The layer morphology and Al distribution in the as-implanted state as well as structural changes and related Al redistribution after high-temperature annealing (1500–1700 °C) were characterized by cross-sectional transmission electron microscopy, Rutherford backscattering spectrometry in combination with ion channeling, atomic force microscopy, and secondary-ion mass spectrometry. Remarkable Al redistribution effects have been found after annealing of Al supersaturated SiC. During high-temperature annealing Al atoms in excess to the solid solubility (2×1020 Al cm-3) tend to precipitate in single-crystalline SiC whereas they diffuse out in amorphous or nanocrystalline SiC. Redistribution of Al with concentration below the solid solubility is governed by transient enhanced diffusion which can be controlled by the annealing scheme. Amorphization of SiC is advantageous in the case of Al doping to levels higher than the solid solubility because it prevents Al precipitation during annealing and helps to form boxlike Al profiles with smooth plateau and abrupt edge. [ABSTRACT FROM AUTHOR]

Ge/Si quantum dot (QD) structures doped with Mn have been tested by the EPR method to find the optimal conditions for formation of the diluted magnetic semiconductor (DMS) phase inside QDs. The effect of Mn doping has been studied for two series of samples: series A with QDs grown at 450°C and varied Mn concentration and series B with QDs grown at different temperature with Mn concentration x = 0.02. Several effects of modification of the EPR spectra due to Mn presence in the samples have been obtained. These effects are related to (i) strain reduction due to Ge—Si intermixing, (ii) QD enlargement and change in QD shape, (iii) presence of an additional magnetic field produced by Mn atoms incorporated in QDs. The data obtained allow us to understand the reasons for irreproducibility of the results available in the literature on the creation of magnetic Ge1 − xMnx quantum dots. [ABSTRACT FROM AUTHOR]

Using X-ray absorption near edge structure spectroscopy, extended X-ray absorption fine structure spectroscopy, atomic force microscopy, and Rutherford backscattering spectroscopy, the features of the microstructure and elemental composition of Si/GeMn magnetic systems obtained by molecular beam epitaxy and containing quantum dots are studied. Intense mixing of Ge and Si atoms is found in all samples. The degree of mixing (diffusion) correlates with the conditions of synthesis of Si/GeMn samples. For these systems, direct contacts of germanium atoms with manganese atoms are characterized and the presence of interstitial manganese with tetrahedral coordination and substitution of manganese for germanium and silicon in the lattice sites is found. The presence of stoichiometric phases Ge8Mn11, Ge3Mn5 is not detected. The correlations of the Ge, Si, and Mn coordination numbers in the Ge environment are determined both with the Mn flux value (evaporator temperature) and with the temperature at which quantum dots are grown, as well as with other synthesis conditions. The manganese concentration in the samples is determined. [ABSTRACT FROM AUTHOR]

The furnace and flash-lamp annealing (FLA) temperature dependent variation in the room temperature 1.53 μm Er photoluminescence (PL) from Er-doped Ge-rich SiO2 layers is investigated. The appearance of the 1.53 μm Er PL is discussed in the framework of the phonon-assisted fluorescent resonant energy transfer from Ge-related luminescence-centers (LCs) to the Er3+. Detailed analyses suggest that in case of FLA the decrease in the 1.53 μm Er PL intensity is governed by the temperature dependent recrystallization of Ge nanoclusters, while for furnace-annealing it is associated with the reduction in the LC-Er3+ coupling due to Ge out-diffusion and the formation of Er-rich clusters with increasing temperature. [ABSTRACT FROM AUTHOR]

The systematic features of the formation of Ge nanocrystals in SiO thin films implanted with Ge ions and then subjected to high-temperature annealing (1130°C) are studied in relation to hydrostatic pressure. It is established that annealing at atmospheric pressure is accompanied by the diffusion of Ge atoms from the implantation region to the Si substrate and does not induce the formation of Ge nanocrystals. An increase in pressure during annealing yields a deceleration in the diffusion of germanium into silicon and is accompanied by the formation of twinned lamellae at the Si/SiO interface (at pressures of ~10 bar) or by the nucleation and growth of Ge nanocrystals (at pressures of ~10 bar) in the SiO film. The results are discussed on the basis of the concept of a change in the activation volume of the formation and migration of point defects under conditions of compression. [ABSTRACT FROM AUTHOR]

The electronic transport properties of insulating Si:Ga films with superconducting, Ga-rich nanoprecipitates are investigated in dependence on temperature, current, and magnetic field. The large negative magnetoresistance, observed below the critical temperature can be explained by Cooper pair breaking and subsequent tunneling of the fermionic quasiparticles. Localization due to quantum interferences of bosons or fermions, as recently discussed, seems not to be the reason for the insulating state and the large magnetoresistance. Cooper pair tunneling is blocked by the high Coulomb barrier. The quasiparticles can overcome the barrier by inelastic cotunneling that results in nonlinear current-voltage characteristics and negative electroresistance. Since the experimental results obtained for the Si:Ga film resemble that of many other films with superconducting nanoprecipitates the conclusions drawn here could be quite general. [ABSTRACT FROM AUTHOR]

An electroluminescent device utilizing a heterostructure of amorphous terbium doped carbon-rich SiOx (a - SiOx : C : Tb) on silicon has been developed. The a - SiOx : C : Tb active layer was formed by RF magnetron sputtering of a - SiO1-x : Cx : H(:Tb) film followed by high-temperature oxidation. It was shown that, depending on the polarity of the applied voltage, the electroluminescence is either green or white, which can be attributed to different mechanisms of current transport through the oxide film -- space charge limited bipolar double injection current for green electroluminescence and trap assisted tunneling or Fowler-Nordheim tunneling for white electroluminescence. [ABSTRACT FROM AUTHOR]

Abstract: The integration of III–V semiconductor material within silicon technology is crucial for performance of advanced electronic devices. This paper presents the investigations of microstructural and opto-electronic properties of GaAs quantum dots (QDs) formed in silicon by means of sequential ion implantation and flash lamp annealing (FLA). Formation of crystalline GaAs QDs with well-defined crystal orientation and conductivity type was confirmed by high resolution transmission electron microscopy and μ-Raman spectroscopy. The influence of the post implantation millisecond-range annealing on the evolution of the nanoparticles size, shape, crystallographic orientation and doping type of GaAs QDs is discussed. [Copyright &y& Elsevier]

Si films sputter deposited on thermally oxidized Si are enriched with Ga by ion implantation through a SiO2 capping layer. The morphology and the electrical transport properties of these films are investigated after rapid thermal annealing. Amorphous, Ga-rich nanoinclusions are embedded in a nanocrystalline Si matrix. The metallic nanoinclusions become superconducting below 7 K. They form a random network of junctions to heavily doped Si crystallites. Small modifications of the junction properties, e.g. by annealing or current pulses, can dramatically change the electronic transport in the film. Ga-rich Si films show a wealth of low-temperature transport phenomena, which have been known until now only from granular metals or high-temperature superconductors: superconductor-insulator transition, quasi-reentrant superconductivity and current-controlled sheet resistance. The possibility to prepare and modify Ga-rich Si films with microelectronics-compatible technology makes them interesting for both fundamental research on transport phenomena in nanostructured, disordered superconductors as well as for the integration of superconducting circuits into Si devices. [ABSTRACT FROM AUTHOR]

Heavily Ga implanted Si nanolayers covered with a thin SiO2 layer exhibit a superconductor-insulator transition in dependence on annealing conditions. The transition characteristics resemble those of ultrathin quench-condensed metal films although the implanted layer differs clearly in composition, width, and nanostructure. This implies a general physical mechanism for the superconductor-insulator transition in thin, disordered layers which is supposed to be a quantum phase transition between dual states-the superconducting and the superinsulating one. There is a resistance criterion for the phase transition closely associated with a critical hole concentration. [ABSTRACT FROM AUTHOR]

Superconducting Ga-rich layers in Ge are fabricated by Ga implantation through a thin Si02 cover layer. After annealing in a certain temperature window, Ga accumulation at the SiC/Ge interface is observed. However, no Ga-containing crystalline phases are identified. Thus it is suggested that the volatile Ga is stabilized in an amorphous mixture of all elements available at the interface. Electrical transport measurements reveal p-type metallic conductivity and superconducting transition. The superconducting properties of the samples with high Ga concentration at the interface change dramatically with etching the amorphous surface layer. A critical temperature of 6 K is measured before, whereas after etching it drops below 1 K. Therefore, one can conclude that the superconducting transport is based on two different layers: a Ga-rich amorphous phase at the interface and a heavily Ga-doped Ge layer. Finally, the comparison of the transport properties of Ga-rich Ge with those of Si demonstrates distinct differences between the interface layers and even the deeper-lying doped regions. [ABSTRACT FROM AUTHOR]

Ga-rich layers in Si were fabricated by 80 keV Ga implantation through a 30 nm SiO2 cover layer and subsequent rapid thermal annealing for 60 s in a temperature range between 500 °C and 1000 °C. Fluences of 2x1016 cm-2 and 4x1016 cm-2, leading to Ga peak concentrations of 8 at. % and 16 at. %, are chosen. Residual damage in the implanted layers and the Ga distribution were investigated by Rutherford-backscattering spectrometry in combination with ion channeling, cross-sectional electron microscopy, and x-ray photoelectron spectroscopy. Temperature-dependent Hall-effect measurements were carried out in order to determine the electrical properties of the implanted layers. It is shown that annealing at temperatures up to 800 °C leads to the formation of polycrystalline layers containing random distributed amorphous clusters. At the Si/SiO2 interface a dense and narrow band of Ga-rich clusters is observed. For 4 x 1016 cm-2 the amount of mobile Ga is higher than for 2x1016 cm-2 and an increase of the cluster density at the Si/SiO2 interface was found. Due to the higher cluster density for 4x1016 cm-2 this interface layer can become superconducting below 7 K with critical fields exceeding 9 T at optimized annealing conditions. Critical currents are above 1 kA/cm² and therefore this seems to be a possible material system for future microelectronic applications. After annealing at 900 °C and above, the implanted layers are single crystalline and no amorphous precipitates were detected. [ABSTRACT FROM AUTHOR]

Using scanning transmission electron microscopy and aberration-corrected high-resolution transmission electron microscopy the existence of Er around Ge nanocrystals (NCs) is established. In fact, Ge NCs with Er-rich graded interfaces are proposed experimentally and validated by theoretical modeling using a supercell structure that consists of compounds determined by x-ray diffraction. The local electronic structure of the proposed interface geometry is found to be in accordance with the hypothesis behind the inverse energy transfer process from the Er3+ to Ge related oxygen-deficiency centers. [ABSTRACT FROM AUTHOR]

Abstract: Flash-lamp annealing (FLA) on a millisecond time scale has been shown to be a promising tool in the preparation of high-quality semiconducting materials. The process imposes time varying through-thickness temperature profiles on the substrates being processed, and consequently thermal stresses. A combined thermal and optical model has been developed to predict the substrate temperature distribution and this model has been linked to a structural model to compute stresses and deflections. The paper shows how these models can be used to explore process conditions in flash lamp annealing, with particular regard to the annealing of ion implants in silicon and the crystallization of amorphous silicon layers on glass substrates. [Copyright &y& Elsevier]

Abstract: Ion implantation-induced damage depth profiles of 450keV Al+ ion-implanted 6H-SiC were studied using RBS/C technique for implantations along channeling direction and non-channeling direction with fluence of 3.4×1015 cm−2. Bevelling method of sample preparation was used to get access to the deeper situated layers over the whole damaged region and below. To determine damage degree at the specific depth of the bevelled sample, RBS/C technique combined with a 3MeV Li2+ ion beam of size of about 30μm×30μm was utilized (micro-RBS/C). The micro-RBS/C method combined with the bevelling technique gave us a possibility to probe deeper reaching damage regions than in the case of conventional RBS/C investigations. It also utilizes a near-surface part of backscattered spectra, which is slightly influenced by damage created by probing ions and a random fraction of probing beam. Additionally, there is no need to perform energy calibration of detector for backscattered particles. Due to much smaller sample area hit by probing ions of micro-beam, the required fluence, comparable to that at conventional RBS/C measurements is obtained at much lower charge. Negligibly small effect of bevelling-induced mechanical damage has been observed in this study. The obtained results by micro-RBS/C method validate the results of computer simulations (Crystal-TRIM software). [Copyright &y& Elsevier]

Abstract: The paper gives an overview of our recent work in the field of thermal processing of advanced semiconductor structures by millisecond flash lamp annealing (FLA). Topics covered include ultra-shallow junction (USJ) formation and heteroepitaxial growth of improved quality thin films of cubic silicon carbide (3C-SiC). The latter is a new development, which opens up promising 3C-SiC growth possibilities and may lead to wider application of FLA. The so-called FLASiC process (Flash LAmp Supported Deposition of SiC) is based on a new type of nanoscale liquid-phase epitaxy at the SiC/Si interface resulting in the formation of a thin, low-defect density seed layer of SiC onto which thicker epitaxial SiC layers can be grown. [Copyright &y& Elsevier]

Photoluminescence (PL) from CdS nanoclusters formed in the matrix of a Langmuir–Blodgett film and from the same clusters with the matrix removed has been studied. The PL spectrum of clusters in the matrix has the form of a broad band (full width at half-maximum (FWHM) ∼0.6 eV) peaked at 2.4 eV. After removing the matrix with hexane, the PL spectrum consists of a high-energy band at 2.9 eV (FWHM ∼0.2 eV) and two low-energy bands at 2.4 and 2.0 eV (FWHM ∼0.5 eV). The high-energy band is attributed to exciton recombination in the nanoclusters, and the bands at 2.4 and 2.0 eV, to recombination via levels related to defects in the bulk of the matrix and at the nanocluster–matrix interface, respectively. © 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The influence of hydrostatic compression on the implantation-induced synthesis of Ge nanocrystals in SiO[sub 2] host was studied. It is found that high-temperature annealing under pressure leads to retardation of Ge diffusion in SiO[sub 2]. It is shown that unstressed Ge nanocrystals are formed as a result of conventional annealing (under atmospheric pressure). Annealing under pressure is accompanied by formation of hydrostatically stressed Ge nanocrystals. The stress in Ge nanocrystals was determined from optical-phonon frequencies in the Raman spectra. The shift of Raman resonance energy (E[sub l], E[sub 1] + Δ[sub l]) corresponds to the quantization of the ground-state energy for a two-dimensional exciton at the critical point M[sub 1] of germanium. It is ascertained that a photoluminescence band peaked at 520 nm is observed only in the spectra of the films which contain stressed Ge nanocrystals. [ABSTRACT FROM AUTHOR]

6H-SiC samples were amorphised by multiple Al implantations at room temperature, in order to study the annealing process. The paper deals with the influence of specific annealing conditions, such as furnace atmosphere and heating rate, on SiC reordering and Al profile. Below a certain deposited nuclear energy, solid phase epitaxy is possible and leads to recrystallisation under precise conditions (high heating rate, silicon partial pressure prescribed). Above it, material etching and dopant losses are observed, even though annealing has proven to be efficient for avoiding surface impairment (due to a specific cleaning process). [Copyright &y& Elsevier]

Abstract. The lattice damage of silicon produced by ion implantation at extremely high current density of 0.8 A/cm[sup 2] (2.5 x 10[sup 18] cm[sup -2] s[sup -1]) was investigated. In a focused ion beam system, implantation was carried out with 70 kev Co ions, fluences of 1.2 x l0[sup 16]cm[sup -2] and 6.7 x 10[sup 15]cm[sup -2] into Si (111) at room temperature and elevated temperatures between 355 Celsius and 400 Celsius. Radiation damage measurements were performed by Rutherford backscattering/channeling spectroscopy and micro-Raman analysis. The radiation damage was studied as a function of pixel dwell-time and implantation temperature. The critical temperature for amorphization increases with current density. Although the fluence of the focused ion implantation was constant, crystalline layers were obtained for short and amorphous layers for long pixel dwell-times. The critical dwell-time of crystalline/amorphous transition increases with implantation temperature. From the results a typical time for deflect annealing of 10[sup-5] s at 400 Celsius and an activation energy of (2.5 +/- 0.6) eV were deduced. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL), Raman scattering, and the Rutherford backscattering of α-particles were used to study the formation of the centers of radiative-recombination emission in the visible region of the spectrum on annealing of the SiO[sub 2] layers implanted with Ge ions. It was found that the Ge-containing centers were formed in the as-implanted layers, whereas the stages of increase and decrease in the intensities of PL bands were observed following an increase in the annealing temperature to 800°C. The diffusion-related redistribution of Ge atoms was observed only when the annealing temperatures were as high as 1000°C and was accompanied by formation of Ge nanocrystals. However, this did not give rise to intense PL as distinct from the case of Si-enriched SiO[sub 2] layers subjected to the same treatment. It is assumed that, prior to the onset of Ge diffusion, the formation of PL centers occurs via completion of direct bonds between the neighboring excess atoms, which gives rise to the dominant violet PL band (similar to the PL of O vacancies in SiO[sub 2]) and a low-intensity long-wavelength emission from various Ge-containing complexes. The subsequent formation of centers of PL with λ[sub m] ∼ 570 nm as a result of anneals at temperatures below 800°C is explained by agglomeration of bonded Ge atoms with formation of compact nanocrystalline precipitates. The absence of intense PL following the high-temperature anneals is believed to be caused by irregularities in the interfaces between the formed Ge nanocrystals and the SiO[sub 2] matrix. [ABSTRACT FROM AUTHOR]

We report on superconducting properties of gallium-enriched silicon layers in commercial (100) oriented silicon wafers. Ion implantation and subsequent rapid thermal annealing have been applied for realizing gallium precipitation beneath a silicon-dioxide cover layer. Depending on the preparation parameters, we observe a sharp drop to zero resistance at 7 K. The critical-field anisotropy proofs the thin-film character of superconductivity. In addition, out-of-plane critical fields of above 9 T and critical current densities exceeding 2 kA/cm2 promote these structures to be possible playgrounds for future microelectronic technology. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) spectroscopy of hydrogen-doped indium oxide (IO) tubular nanostructures shows presence of paramagnetic oxygen vacancies (VO) at room temperature. For temperatures below 80 K, the EPR spectra exhibit two distinct split resonances correspond to S=12 hydrogen electron spin. Interestingly, presence of hydrogen EPR resonances is accompanied by absence of EPR signal of VO, which is restored above 80 K with the concomitant disappearance of signature resonances from hydrogen. The temperature dependent donor and passivation behavior of hydrogen has been directly observed in metal oxide. This could provide valuable explanations of various VO induced controversial properties of IO nanostructures. [ABSTRACT FROM AUTHOR]