Search

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.