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Elucidating the interaction between magnetic moments and itinerant carriers is an important step to spintronic applications. Here, we investigate magnetic and transport properties in d0 ferromagnetic SiC single crystals prepared by postimplantation pulsed laser annealing. Magnetic moments are contributed by the p states of carbon atoms, but their magnetic circular dichroism is different from that in semi-insulating SiC samples. The anomalous Hall effect and negative magnetoresistance indicate the influence of d0 spin order on free carriers. The ferromagnetism is relatively weak in N-implanted SiC compared with that in Al-implanted SiC after annealing. The results suggest that d0 magnetic moments and itinerant carriers can interact with each other, which will facilitate the development of SiC spintronic devices with d0 ferromagnetism.

Results show that the phase formation in the implantation process of aluminum into silicon carbide occurs at an aluminum concentration above 10 at. %. Data reveal that phase transformation changes the material properties of the alumina/silicon carbide system.

The influence of high dose ion irradiation through amorphous surface layers in single crystalline 6H-SiC at elevated temperatures was analyzed. Quantification for irradiation at 500 degrees Celsius was conduced on material swelling, subsequent densification and surface erosion. Ion beam induced recrystallization was examined in the temperature range from 300-1300 degrees Celsius. The findings indicate that perfect epitaxial regrowth in (0001)-oriented 6H-SiC cannot be achieved by ion irradiation at elevated temperatures.

Step height measurements, optical microscopy and x-ray diffraction analysis were use to systematically examine the annealing behavior of amorphous silicon carbide (SiC) layers created by the implantation of Si MeV into 6H-SiC. The findings revealed two annealing stages. The first stage is between 200 degrees and 700 degrees centigrade, at which period the amorphous layer densificates after five minutes. The second stage is at temperatures beyond 700 degrees centigrade and is characterized by the combined defect annealing and recrystallization.

The ion fluence and temperature dependence of the amorphization process in silicon carbide induced by irradiation has been investigated using in situ laser reflectometry and ex situ Rutherford backscattering spectrometry. The amorphization fluence relies weakly on temperature below 300 K, and strongly above 300 K. A higher ion fluence for the amorphization of silicon carbide is needed at very low temperatures compared to silicon.

A study was conducted on the kinetics of ion-beam-induced interfacial amorphization (IBIIA) in silicon. This process is different from bulk amorphization in terms of the critical energy density approach and the evolution of the roughness of the amorphous/crystalline interface during ion irradiation. The findings indicate that the temperature dependence of IBIIA can be characterized by three regimes: athermal ion-beam-induced defect generation, thermally activated recombination of defects and athermal transport of defects towards the amorphous/crystalline interface.

Digital signage is an emerging new communication technology. Digital signage system reduces the environmental costs associated with traditional printed signage. It is used to display the dynamic content (e.g., audio, video, announcements, webpages) using Internet of Things (IoT). It uses Raspberry pi a small credit card sized computer to store locally and process the information and also reduce the production cost. In order to update the information the content management software is developed using free open source software. The used programming technologies are WAMP server, Html Abstraction Markup Language (HAML), My structured Query Language (MySQL) database and Python. This proposed system is used to display the required information to the students in college campus and where the real time information is needed (e.g., Universities, Hospitals, Railway Station, Corporate buildings, malls, subways). Moreover the digital signage system is flexible and dynamic compared with printable signage system. [ABSTRACT FROM AUTHOR]

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]

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 electrical properties of heavily Al doped single and nanocrystalline 4H–SiC layers on semi-insulating 4H–SiC substrate, prepared by multienergy, high-fluence Al implantation and subsequent furnace annealing, are investigated by sheet resistance and Hall effect measurements. Ion beam induced crystallization is used to prepare the nanocrystalline SiC layers. The doping levels are chosen around the solid solubility limit of 2×1020 cm-3 in the range from 5×1019 to 1.5×1021 cm-3. The comparison of the results shows that heavily Al doped single crystalline SiC layers have superior conduction properties. The lowest resistivities measured at room temperature are 0.08 and 0.8 Ω cm for the single crystalline and nanocrystalline samples, respectively. Recent results on enhanced Al acceptor activation in nanocrystalline SiC cannot be confirmed. There is an upper limit for the hole concentration in the nanocrystalline samples independent of the Al supersaturation level in the as-implanted state due to outdiffusion of Al in excess to the solid solubility limit during annealing. In contrast to the nanocrystalline SiC layers the as-implanted Al profile in single crystalline material remains stable after annealing even for concentrations above the solid solubility limit. Therefore, in single crystalline material efficient impurity band conduction due to strongly interacting acceptors can be achieved in the range of supersaturation. For lower doping levels impurity band conduction is more effective in nanocrystalline SiC. [ABSTRACT FROM AUTHOR]

In this paper the authors investigate the effect of implantation temperature on the structural properties of diamond implanted with high fluences of Si between 5.3×1017 Si cm-2 and 1×1018 Si cm-2. In order to reduce radiation-induced damage and to enhance SiC formation the implantations were performed at elevated temperatures in the range from 900 to 1200 °C. Subsequently, all samples were annealed for 10 min at 1500 °C in a rf-heated furnace. X-ray diffraction revealed the formation of cubic SiC nanocrystallites in a buried layer inside the implanted diamond. The implantation-induced damage was assessed by analyzing graphitization of the surface-near layer using Raman spectroscopy. With increasing Si fluence the implantation-induced damage rises and the nearly perfect alignment of the formed SiC crystallites within the host diamond lattice deteriorates. However, raising the implantation temperature from 900 to 1000 °C reduces the damage in the diamond and increases the amount, size, and epitaxial alignment of the crystalline SiC precipitates. Further increase of the implantation temperature gives no improvement in the quality of the SiC-rich layer. Instead, the damaged diamond converts into graphite and the formation of SiC crystallites is obstructed. [ABSTRACT FROM AUTHOR]

Epitaxial SiC nanocrystals are fabricated by high-fluence Si implantation into natural diamond at elevated temperatures between 760 and 1100 °C. Fluences under investigation range from 4.5 to 6.2×1017 Si cm-2. This implantation scheme yields a buried layer rich of epitaxially aligned SiC nanocrystals within slightly damaged diamond. The generation of a small fraction of graphitic sp2 bonds of up to 15% in the diamond host matrix cannot be avoided. Unintentional coimplantation with nitrogen results in a very high doping level of more than 1021 cm-3. Resistivity and Hall measurements in van der Pauw geometry reveal a high, thermally stable n-type conductivity with electron concentrations exceeding 1020 cm-3 and mobilities higher than 2 cm2 /V s. It is supposed that both the SiC regions as well as the diamond matrix exhibit n-type conductivity and that the electron transport occurs across the low-resistivity SiC nanograins. In the SiC nanocrystals the electrons originate from nitrogen donors whereas in diamond defects are responsible for the electron conductivity. The formation of disordered graphite, which leads to low electron mobility, is substantially reduced by the SiC formation. [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]

The sheet resistance and structural properties of high-fluence Si-implanted diamond were investigated. In order to minimize the radiation damage and to facilitate SiC formation the implantation was performed at 900°C. All samples were subsequently annealed in a rf-heated furnace at 1500°C for 10 min in order to remove defects and thermally unstable phases. X-ray diffraction, infrared absorption spectrometry, and high-resolution cross-sectional transmission electron microscopy revealed the formation of a buried layer inside the implanted diamond, which contains SiC nanocrystallites. These SiC nanocrystals have a cubic structure and are nearly perfectly aligned with the diamond lattice. Raman spectroscopy was applied to analyze radiation-damage-induced graphitization in dependence on the implantation conditions. The sheet resistance of the samples was measured as function of temperature by four point probe technique in van-der-Pauw geometry. The decrease of the sheet resistance with increasing ion fluence unambiguously shows the influence of implantation-induced damage. The behavior of the sheet resistance can strongly be modified by additional nitrogen implantation. The resulting higher conductivity is interpreted as partial incorporation of the nitrogen donor into the SiC nanocrystals. However, when the Si fluence exceeds a critical value of 5.3×10[SUP17]Si[SUP+]cm[SUP-2] at 900°C the diamond is irreversibly damaged and defect related conductivity dominates. [ABSTRACT FROM AUTHOR]

Focuses on a study which examined amorphization of 6H-SiC with germanium ions at room temperature and subsequent ion-beam-induced epitaxial crystallization (IBIEC) with silicon ions. Significance of SiC to the semiconductor industry; Experimental results; Results and discussion.

We report on large negative and positive magnetoresistance in inhomogeneous, insulating Si:Ga films belowa critical temperature of about 7 K. The magnetoresistance effect exceeds 300%at temperatures below3Kand fields of 8T. The comparison of the transport properties of superconducting samples with that of insulating ones reveals that the large magnetoresistance is associated with the appearance of local superconductivity. A simple phenomenological model based on localized Cooper pairs and hopping quasiparticles is able to describe the temperature and magnetic field dependence of the sheet resistance of such films. [ABSTRACT FROM AUTHOR]

The results of epitaxial crystallization of Si by mega-electron-volt heavy-ion-beam irradiation can be understood based on the 'point defect diffusion model.' The inelastic electronic scattering effects need not be determined in explaining the decrease in the normalized crystallization rate with increasing nuclear deposited energy.

Silicon films with Ga-rich nanoprecipitates are superconductors or insulators in dependence on their normal state resistance. Even in the insulating state of the film superconducting nanoprecipitates exist below the critical temperature of 7 K and determine its complex transport behavior. In this range sometimes large, random resistance jumps appear that are accompanied by little temperature changes. The resistance fluctuates between a well-defined low-resistance value and a broader band of higher resistances. Jumps to higher resistance are associated with a temperature decrease and vice versa. We present experimental results on these fluctuations and suppose a first order phase transition in the film as probable origin. [ABSTRACT FROM AUTHOR]

Ge films with a mean Ga content of about 8 and 1 at.% hole concentration can be fabricated by ion implantation and subsequent flash-lamp annealing. The Ge:Ga films become superconducting below critical temperatures in the range between 1 and 2 K depending on the film resistance. The change in the macroscopic transport properties during step-wise surface etching can be described by a homogeneously doped layer model. However, the Ga distribution is extremely heterogeneous on the nanoscale. Atom-probe tomography analyses reveal the presence of Ga-rich precipitates with Ga clusters of up to 10 000 atoms. Since no percolating Ga clusters exist, it can be supposed that the heavy doping of Ge enables a coherent superconducting state via the proximity effect. [ABSTRACT FROM AUTHOR]

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]

Superconducting layers in silicon and germanium are fabricated via gallium implantation through a thin SiO2 cover layer and subsequent rapid thermal annealing. Gallium accumulation at the SiO2/Si and SiO2/Ge interfaces is observed but no pure gallium phases were found. In both cases superconducting transition occurs around 6-7 K which can be attributed to the metallic conducting, gallium rich interface layer. However, the superconducting as well as the normal-state transport properties in gallium overdoped silicon or germanium are different. [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]

We report new experimental results on how superconductivity in gallium-doped germanium (Ge:Ga) is influenced by hole concentration and microstructure. Ion implantation and subsequent flash-lamp annealing at various temperatures have been utilized to prepare highly p-doped thin films consisting of nanocrystalline and epitaxially grown sublayers with Ga-peak concentrations of up to 8 at. %. Successive structural investigations were carried out by means of Rutherford-backscattering spectrometry in combination with ion channeling, secondary-ion-mass spectrometry, and high-resolution cross-sectional transmission electron microscopy. Hole densities of 1.8·1020 to 5.3·1020 cm-3 (0.4 to 1.2 at. %) were estimated via Hall-effect measurements revealing that only a fraction of the incorporated gallium has been activated electrically to generate free charge carriers. The coincidence of a sufficiently high hole and Ga concentration is required for the formation of a superconducting condensate. Our data reflect a critical hole concentration of around 0.4 at. %. Higher concentrations lead to an increase of Tc from 0.24 to 0.43 K as characterized by electrical-transport measurements. A short mean-free path indicates superconductivity in the dirty limit. In addition, small critical-current densities of max. 20 kA/m2 point to a large impact of the microstructure. [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]

Abstract: Recently, superconductivity has been found in heavily boron-doped diamond prepared by high temperature/high pressure synthesis or chemical vapour deposition. An alternative doping method of technological relevance is ion implantation. It is an open question whether superconductivity can also be obtained in boron-implanted diamond. Here we report on the transport and magnetic properties of high dose (2.3×1016–1.7×1017 cm−2) boron-implanted natural IIa diamond samples doped at elevated temperature of 900 °C and subsequently annealed at 1500 °C and 1700 °C. For comparison implantation at room temperature was also carried out. The samples were further characterized by Raman and infrared spectroscopy. No superconductivity could be detected in the samples at temperatures down to 40 mK. We discuss the possible origin for the absence of superconductivity. [Copyright &y& Elsevier]

Phosphorus implantation (30 keV, 3×1015 cm-2) into preamorphized Ge and subsequent rapid thermal or flash lamp annealing is investigated. During annealing a significant P diffusion in amorphous Ge is not observed. However, the fast solid phase epitaxial regrowth causes a rapid redistribution of P. After completion of the regrowth and at temperatures above 500 °C, a concentration-dependent diffusion of P in crystalline Ge takes place and leads to considerable loss of P toward the surface. An appreciable influence of implantation defects on the diffusion coefficient of P is not detected. For 60 s rapid thermal annealing at 600 °C and for 20 ms flash lamp annealing at 900 °C, the junction depth and the sheet resistance vary between 140 and 200 nm and between 50 and 100 Ω, respectively, and the maximum electrical activation of P is about 3–7×1019 cm-3. [ABSTRACT FROM AUTHOR]

Cubic SiC is implanted with carbon ions at 600, 900, 1100 and 1200 °C. X-ray diffraction and transmission electron microscopy revealed the influence of implantation temperature and dose rate on the formation of graphite and diamond precipitates, respectively. The high dose carbon implantation at 600 °C yields graphite already in a textured form. Spherical diamond grains, which are always epitaxial to the SiC, are found in samples implanted at 900 °C or higher. Increasing the dose rate leads to formation of graphite instead of diamond at 900 °C as well. Hence, a critical temperature for diamond evolution exists, which depends on dose rate. Size and shape of the formed diamond precipitates is not influenced by dose rate within the investigated range. Increasing the fluence results in bigger diamond nanocrystals, which are bordered by facets. [Copyright &y& Elsevier]

Nanocrystals of silicon carbide were synthesized inside natural diamond using high dose silicon implantation. In order to retain the diamond structure implantation was done at 900 °C. The samples were subsequently annealed in an rf-heated furnace at 1500 °C for 10 min. X-Ray diffraction (XRD), IR absorption spectrometry and high-resolution cross-sectional transmission electron microscopy (HRTEM) are used to investigate formation and structure of SiC nanocrystallites in the implanted diamond. Raman spectroscopy contributed to trace implantation-induced destruction of the diamond. A first characterization of the electrical properties of the implanted and annealed samples is done by four-point probe measurements. The results indicate a highly conductive, buried layer inside the diamond. This layer contains cubic SiC nanocrystals, which are perfectly aligned with the diamond lattice. However, when fluence exceeds a critical value of 5.3×1017 Si+ cm−2, the diamond is irreversibly damaged and defect conduction type dominates. [Copyright &y& Elsevier]

Ion-beam-induced crystallization was used to transform amorphized, heavily Al doped SiC layers to nanocrystalline material. The morphology of the as-implanted and the annealed layers was studied by XTEM. The electrical properties were analyzed by sheet resistance and Hall measurements and compared with crystalline reference samples. A high-temperature annealing step is necessary to activate the implanted Al acceptor atoms. During annealing the mean grain size of the nanocrystals grow from 3 to 35 nm. The Al doped, nanocrystalline SiC has a much lower sheet resistance than the crystalline reference samples. It was found that this is due to the enhanced hole concentration which could be explained by a higher solid solubility of Al in the nanocrystalline SiC. [Copyright &y& Elsevier]