Stephen Saddow - Academia.edu (original) (raw)
Papers by Stephen Saddow
physica status solidi (b), 2001
ABSTRACT
Journal of Biosensors & Bioelectronics, 2018
ECS Transactions, 2016
The intracortical neural interface (INI) could be a key component of brain machine interfaces (BM... more The intracortical neural interface (INI) could be a key component of brain machine interfaces (BMI), devices which offer the possibility of restored physiological neurological functionality for patients suffering from severe trauma to the central or peripheral nervous system. Unfortunately the main components of the INI, microelectrodes, have not shown appropriate long-term reliability due to multiple biological, material, and mechanical issues. Silicon carbide (SiC) is a semiconductor that is completely chemically inert within the physiological environment and can be micromachined using the same methods as with Si microdevices. We are proposing that a SiC material system may provide the improved longevity and reliability for INI devices. The design, fabrication, and preliminary electrical and electrochemical testing of an all-SiC prototype microelectrode array based on 4H-SiC, with an amorphous silicon carbide (a-SiC) insulator, is described. The fabrication of the planar microelec...
Journal of Applied Physics, 1995
The optoelectronic properties of high-resistivity p-type hexagonal silicon carbide (6H-SiC) have ... more The optoelectronic properties of high-resistivity p-type hexagonal silicon carbide (6H-SiC) have been investigated using lateral photoconductive switches. Both photovoltaic and photoconductive effects are reported, measured at 337 nm, which is above the 6H-SiC absorption edge. These photoconductive switches have been fabricated with dark resistances of up to 1 MΩ; photoconductive switching efficiencies of more than 80% have been achieved. In addition, these devices displayed a high-speed photovoltaic response to nanosecond laser excitations in the ultraviolet spectral region; in particular, the observed photovoltaic response pulse width can be shorter than the exciting laser pulse width. This subnanosecond photovoltaic response has been modeled and good qualitative agreement with experiment has been obtained.
Micromachines
In recent years, several new applications of SiC (both 4H and 3C polytypes) have been proposed in... more In recent years, several new applications of SiC (both 4H and 3C polytypes) have been proposed in different papers. In this review, several of these emerging applications have been reported to show the development status, the main problems to be solved and the outlooks for these new devices. The use of SiC for high temperature applications in space, high temperature CMOS, high radiation hard detectors, new optical devices, high frequency MEMS, new devices with integrated 2D materials and biosensors have been extensively reviewed in this paper. The development of these new applications, at least for the 4H-SiC ones, has been favored by the strong improvement in SiC technology and in the material quality and price, due to the increasing market for power devices. However, at the same time, these new applications need the development of new processes and the improvement of material properties (high temperature packages, channel mobility and threshold voltage instability improvement, thi...
Chemistry of Materials, 2021
X-ray-activated near-infrared luminescent nanoparticles are considered as new alternative optical... more X-ray-activated near-infrared luminescent nanoparticles are considered as new alternative optical probes due to being free of autofluorescence, while both their excitation and emission possess a high penetration efficacy in vivo. Herein, we report silicon carbide quantum dot sensitization of trivalent chromium-doped zinc gallate nanoparticles with enhanced nearinfrared emission upon X-ray and UV−vis light excitation. We have found that a ZnGa 2 O 4 shell is formed around the SiC nanoparticles during seeded hydrothermal growth, and SiC increases the emission efficiency up to 1 order of magnitude due to band alignment that channels the excited electrons to the chromium ion.
![Research paper thumbnail of Erratum: “Valence and conduction band offsets at beryllium oxide interfaces with silicon carbide and III-V nitrides” [J. Vac. Sci. Technol. B 37, 041206 (2019)]](https://attachments.academia-assets.com/113855070/thumbnails/1.jpg)
](Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 2020
Growth-induced temperature changes during transition metal nitride epitaxy on transparent SiC sub... more Growth-induced temperature changes during transition metal nitride epitaxy on transparent SiC substrates
Scientific reports, Jan 8, 2018
The role of GABAergic neurotransmission on epileptogenesis has been the subject of speculation ac... more The role of GABAergic neurotransmission on epileptogenesis has been the subject of speculation according to different approaches. However, it is a very complex task to specifically consider the action of the GABAa neurotransmitter, which, in its dependence on the intracellular level of Cl, can change its effect from inhibitory to excitatory. We have developed a computational model that represents the dentate gyrus and is composed of three different populations of neurons (granule cells, interneurons and mossy cells) that are mutually interconnected. The interconnections of the neurons were based on compensation theory with Hebbian and anti-Hebbian rules. The model also incorporates non-synaptic mechanisms to control the ionic homeostasis and was able to reproduce ictal discharges. The goal of the work was to investigate the hypothesis that the observed aberrant sprouting is promoted by GABAa excitatory action. Conjointly with the abnormal sprouting of the mossy fibres, the simulatio...
Materials Science and Engineering: C, 2017
Goal: Nanowires are promising biomaterials in multiple clinical applications. The goal of this st... more Goal: Nanowires are promising biomaterials in multiple clinical applications. The goal of this study was to investigate the cytotoxicity of carbon-doped silica nanowires (SiO x C y NWs) on a fibroblastic cell line in vitro. Materials and methods: SiO x C y NWs were grown on Si substrates by CVD process. Murine L929 fibroblasts were cultured in complete DMEM and indirect and direct cytotoxicity tests were performed in agreement with ISO 19003-5, by quantitating cell viability at MTT and chemiluminescent assay. Cell cultures were investigated at Scanning Electron Microscope (SEM) and immunocytochemistry to observe their morphology and investigate cell-NWs interactions. Furthermore, hemocompatibility with Platelet-rich Plasma was assayed at SEM and by ELISA assay. Results: SiOxCy NWs proved biocompatible and did not impair cell proliferation at contact assays. L929 were able to attach on NWs and proliferate. Most interestingly, L929 reorganised the NW scaffold by displacing the nanostructure and creating tunnels within the NW network. NWs moreover did not impair platelet activation and behaved similarly to flat SiO 2. Conclusions: Our data show that SiOxCy NWs did not release cytotoxic species and acted as a viable and adaptable scaffold for fibroblastic cells, thus representing a promising platform for implantable devices.
Materials Science Forum, 2016
Silicon carbide is a well-known wide-band gap semiconductor traditionally used in power electroni... more Silicon carbide is a well-known wide-band gap semiconductor traditionally used in power electronics and solid-state lighting due to its extremely low intrinsic carrier concentration and high thermal conductivity. What is only recently being discovered is that it possesses excellent compatibility within the biological world. Since publication of the first edition of Silicon Carbide Biotechnology: A Biocompatible Semiconductor for Advanced Biomedical Devices and Applications five years ago [1], significant progress has been made on numerous research and development fronts. In this paper three very promising developments are briefly highlighted – progress towards the realization of a continuous glucose monitoring system, implantable neural interfaces made from free-standing 3C-SiC, and a custom-made low-power ‘wireless capable’ four channel neural recording chip for brain-machine interface applications.
2014 IEEE 9th Nanotechnology Materials and Devices Conference (NMDC), 2014
Silicon carbide (SiC) has long been known as a robust semiconductor with superior properties to s... more Silicon carbide (SiC) has long been known as a robust semiconductor with superior properties to silicon for electronic applications. The cubic form of SiC, known as 3C-SiC, has been researched for non-electronic applications, such as MEMS and biosensors. In particular, our group has demonstrated that 3C-SiC is one of the few semiconductor materials that possesses both bio- and hemacompatibility, thus opening up a plethora of applications for this material. We have pioneered several biomedical devices using 3C-SiC grown on Si substrates, and recently have been investigating the use of this novel material for both biosensor and neural prosthetic applications. Research to develop suitable biosensors, mainly via surface functionalization of 3C-SiC surfaces, has shown that 3C-SiC can be functionalized in much the same was as Si. We review nearly a decade of activity in 3C-SiC on Si biotechnology, with particular emphasis on the most promising applications: surface functionalization, in-vivo glucose sensing and biomedical implants for connecting the human nervous system to advanced prosthetics.
ECS Transactions, 2014
Silicon carbide (SiC) has long been known as a robust semiconductor with superior properties to s... more Silicon carbide (SiC) has long been known as a robust semiconductor with superior properties to silicon for electronic applications. The cubic form of SiC, known as 3C-SiC, has been researched for non-electronic applications, such as MEMS and biosensors. In particular, our group has demonstrated that 3C-SiC is one of the few semiconductor materials that possesses both bio- and hemacompatibility, thus opening up a plethora of applications for this material. We have pioneered several biomedical devices using 3C-SiC grown on Si substrates, and recently have been investigating the use of this novel material for both continuous glucose monitoring and neural prosthetic applications. We will review nearly a decade of activity in this regard, with particular emphasis on the most promising applications: in vivo continuous glucose monitoring and biomedical implants for connecting the human nervous system to advanced prosthetics.
Materials Science Forum, 2000
ABSTRACT
Materials Science Forum, 2010
SiC is a candidate material for micro-and nano-electromechanical systems (MEMS and NEMS). In orde... more SiC is a candidate material for micro-and nano-electromechanical systems (MEMS and NEMS). In order to understand the impact that the growth rate has on the residual stress of CVD-grown 3C-SiC hetero-epitaxial films on Si substrates, growth experiments were performed and the resulting stress was evaluated. Film growth was performed using a two-step growth process with propane and silane as the C and Si precursors in hydrogen carrier gas. The film thickness was held constant at ~2.5 µm independent of the growth rate so as to allow for direct films comparison as a function of the growth rate. Supported by profilometry, Raman and XRD analysis, this study shows that the growth rate is a fundamental parameter for low-defect and low-stress hetero-epitaxial growth process of 3C-SiC on Si substrates. XRD (rocking curve analysis) and Raman spectroscopy show that the crystal quality of the films increases with decreasing growth rate. From curvature measurements, the average residual stress within the layer using the modified Stoney's equation was calculated. The results show that the films are under compressive stress and the calculated residual stress also increases with growth rate, from-0.78 GPa to-1.11 GPa for 3C-SiC films grown at 2.45 and 4 µm/h, respectively.
Silicon Carbide and Related Materials 2011, Pts 1 and 2, 2012
SiC is a candidate material for micro-and nano-electromechanical systems (MEMS and NEMS). In orde... more SiC is a candidate material for micro-and nano-electromechanical systems (MEMS and NEMS). In order to understand the impact that the growth rate has on the residual stress of CVDgrown 3C-SiC hetero-epitaxial films on Si substrates, growth experiments were performed and the resulting stress was evaluated. The film thickness was held constant at ~2.5 µm independent of the growth rate so as to allow for direct comparison of films as a function of the growth rate. Supported by profilometry, Raman and micro-machined free-standing structures, this study shows that the growth rate is a fundamental parameter for the low-defect and the low-stress hetero-epitaxial growth process of 3C-SiC on Si substrates.
Materials Science Forum, 2009
We have developed a high-quality growth process for 3C-SiC on on-axis (111)Si substrates with the... more We have developed a high-quality growth process for 3C-SiC on on-axis (111)Si substrates with the ultimate goal to demonstrate high quality and yield electronic and MEMS devices. A single-side polished 50 mm (111)Si wafer was loaded into a hot-wall SiC CVD reactor for growth. The 3C-SiC process was performed in two stages: carbonization in propane and hydrogen at 1135°C and 400 Torr followed by growth at 1380°C and 100 Torr. X-ray diffraction rocking curve analysis of the 3C-SiC(222) peak indicates a FWHM value of 219 arcsec. This is a very interesting result given that the film thickness was only 2 µm, thus indicating that the grown film is of very high quality compared with published literature values. X-ray polar figure mapping was performed and it was observed that the micro twin content was below the detection limit. Therefore TEM characterization was performed in plan view to allow assessment of the stacking fault density as well as confirmation of the very low micro twin con...
Technology & Innovation, 2011
Solid-State Electronics, 2001
6H-SiC lateral double implanted metal oxide semiconductor ®eld eect transistors have been fabrica... more 6H-SiC lateral double implanted metal oxide semiconductor ®eld eect transistors have been fabricated on four p-type wafers with p-type epitaxial layers doped with Al at 2±7 Â 10 16 cm À3. Each of the wafers received two nitrogen implants of heavy and light doses for drain/source and drift regions, respectively. The wafers had the implants activated at 1600°C in an Ar ambient (one wafer) or a silane overpressure ambient (three wafers). The subsequent characterization con®rmed a much smoother surface for the silane-annealed wafers, with step bunching reduced from 25 nm peak steps with periodicity of 1 lm to undetectable steps. Near optimal breakdown voltages of 600 V were obtained for a 9 lm drift region length devices, and threshold voltage ranged from 9 to 12 V. Average values for eective channel mobility l eff were in the range 35.2±44.1 cm 2 /V s for the three silane-annealed wafers, and 30.0 cm 2 /V s for the argonannealed wafer.
Journal of Materials Research, 2012
In this article, the biofunctionalization of 6H-SiC (0001) surfaces via self-assembled monolayers... more In this article, the biofunctionalization of 6H-SiC (0001) surfaces via self-assembled monolayers (SAMs) has been studied as a means to modify the in vitro biocompatibility of this semiconductor substrate with H4 (human neuroglioma) and PC12 (rat pheochromocytoma) cells. Silanization with aminopropyldiethoxymethylsilane (APDEMS) and aminopropyltriethoxysilane (APTES), which provided moderately hydrophilic surfaces, and alkylation with 1-octadecene that produced hydrophobic surfaces were used to control the 6H-SiC surface chemistry and evaluate changes in cell viability and morphology due to these surface modifications. The morphology of the cells was evaluated with atomic force microscopy. In addition, 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide (MTT) assays were used to quantitatively evaluate the cell viability on the SAM-modified surfaces. In all cases, the cell proliferation was observed to improve with respect to untreated 6H-SiC surfaces, with up to a 2x increase in viability on the 1-octadecene-modified surfaces, up to 6x increase with APDEMS-modified surfaces, and up to 8x increase with APTES-modified surfaces. This proves the potential of SiC as a substrate for medical devices given the possibility to tailor its surface chemistry for specific applications.
IEEE Transactions on Microwave Theory and Techniques, 1995
An optoelectronic attenuator suitable for the optical control of microwave-integrated circuits is... more An optoelectronic attenuator suitable for the optical control of microwave-integrated circuits is presented. High-speed photoconductive switches are embedded in planar microwave transmission lines fabricated on both semi-insulating GaAs and high-resistivity silicon substrates, and a fiber pigtailed semiconductor laser diode is used to control the microwave signal level on these high-speed lines. Forty-five dB of microwave attenuation was demonstrated with a
physica status solidi (b), 2001
ABSTRACT
Journal of Biosensors & Bioelectronics, 2018
ECS Transactions, 2016
The intracortical neural interface (INI) could be a key component of brain machine interfaces (BM... more The intracortical neural interface (INI) could be a key component of brain machine interfaces (BMI), devices which offer the possibility of restored physiological neurological functionality for patients suffering from severe trauma to the central or peripheral nervous system. Unfortunately the main components of the INI, microelectrodes, have not shown appropriate long-term reliability due to multiple biological, material, and mechanical issues. Silicon carbide (SiC) is a semiconductor that is completely chemically inert within the physiological environment and can be micromachined using the same methods as with Si microdevices. We are proposing that a SiC material system may provide the improved longevity and reliability for INI devices. The design, fabrication, and preliminary electrical and electrochemical testing of an all-SiC prototype microelectrode array based on 4H-SiC, with an amorphous silicon carbide (a-SiC) insulator, is described. The fabrication of the planar microelec...
Journal of Applied Physics, 1995
The optoelectronic properties of high-resistivity p-type hexagonal silicon carbide (6H-SiC) have ... more The optoelectronic properties of high-resistivity p-type hexagonal silicon carbide (6H-SiC) have been investigated using lateral photoconductive switches. Both photovoltaic and photoconductive effects are reported, measured at 337 nm, which is above the 6H-SiC absorption edge. These photoconductive switches have been fabricated with dark resistances of up to 1 MΩ; photoconductive switching efficiencies of more than 80% have been achieved. In addition, these devices displayed a high-speed photovoltaic response to nanosecond laser excitations in the ultraviolet spectral region; in particular, the observed photovoltaic response pulse width can be shorter than the exciting laser pulse width. This subnanosecond photovoltaic response has been modeled and good qualitative agreement with experiment has been obtained.
Micromachines
In recent years, several new applications of SiC (both 4H and 3C polytypes) have been proposed in... more In recent years, several new applications of SiC (both 4H and 3C polytypes) have been proposed in different papers. In this review, several of these emerging applications have been reported to show the development status, the main problems to be solved and the outlooks for these new devices. The use of SiC for high temperature applications in space, high temperature CMOS, high radiation hard detectors, new optical devices, high frequency MEMS, new devices with integrated 2D materials and biosensors have been extensively reviewed in this paper. The development of these new applications, at least for the 4H-SiC ones, has been favored by the strong improvement in SiC technology and in the material quality and price, due to the increasing market for power devices. However, at the same time, these new applications need the development of new processes and the improvement of material properties (high temperature packages, channel mobility and threshold voltage instability improvement, thi...
Chemistry of Materials, 2021
X-ray-activated near-infrared luminescent nanoparticles are considered as new alternative optical... more X-ray-activated near-infrared luminescent nanoparticles are considered as new alternative optical probes due to being free of autofluorescence, while both their excitation and emission possess a high penetration efficacy in vivo. Herein, we report silicon carbide quantum dot sensitization of trivalent chromium-doped zinc gallate nanoparticles with enhanced nearinfrared emission upon X-ray and UV−vis light excitation. We have found that a ZnGa 2 O 4 shell is formed around the SiC nanoparticles during seeded hydrothermal growth, and SiC increases the emission efficiency up to 1 order of magnitude due to band alignment that channels the excited electrons to the chromium ion.
Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 2020
Growth-induced temperature changes during transition metal nitride epitaxy on transparent SiC sub... more Growth-induced temperature changes during transition metal nitride epitaxy on transparent SiC substrates
Scientific reports, Jan 8, 2018
The role of GABAergic neurotransmission on epileptogenesis has been the subject of speculation ac... more The role of GABAergic neurotransmission on epileptogenesis has been the subject of speculation according to different approaches. However, it is a very complex task to specifically consider the action of the GABAa neurotransmitter, which, in its dependence on the intracellular level of Cl, can change its effect from inhibitory to excitatory. We have developed a computational model that represents the dentate gyrus and is composed of three different populations of neurons (granule cells, interneurons and mossy cells) that are mutually interconnected. The interconnections of the neurons were based on compensation theory with Hebbian and anti-Hebbian rules. The model also incorporates non-synaptic mechanisms to control the ionic homeostasis and was able to reproduce ictal discharges. The goal of the work was to investigate the hypothesis that the observed aberrant sprouting is promoted by GABAa excitatory action. Conjointly with the abnormal sprouting of the mossy fibres, the simulatio...
Materials Science and Engineering: C, 2017
Goal: Nanowires are promising biomaterials in multiple clinical applications. The goal of this st... more Goal: Nanowires are promising biomaterials in multiple clinical applications. The goal of this study was to investigate the cytotoxicity of carbon-doped silica nanowires (SiO x C y NWs) on a fibroblastic cell line in vitro. Materials and methods: SiO x C y NWs were grown on Si substrates by CVD process. Murine L929 fibroblasts were cultured in complete DMEM and indirect and direct cytotoxicity tests were performed in agreement with ISO 19003-5, by quantitating cell viability at MTT and chemiluminescent assay. Cell cultures were investigated at Scanning Electron Microscope (SEM) and immunocytochemistry to observe their morphology and investigate cell-NWs interactions. Furthermore, hemocompatibility with Platelet-rich Plasma was assayed at SEM and by ELISA assay. Results: SiOxCy NWs proved biocompatible and did not impair cell proliferation at contact assays. L929 were able to attach on NWs and proliferate. Most interestingly, L929 reorganised the NW scaffold by displacing the nanostructure and creating tunnels within the NW network. NWs moreover did not impair platelet activation and behaved similarly to flat SiO 2. Conclusions: Our data show that SiOxCy NWs did not release cytotoxic species and acted as a viable and adaptable scaffold for fibroblastic cells, thus representing a promising platform for implantable devices.
Materials Science Forum, 2016
Silicon carbide is a well-known wide-band gap semiconductor traditionally used in power electroni... more Silicon carbide is a well-known wide-band gap semiconductor traditionally used in power electronics and solid-state lighting due to its extremely low intrinsic carrier concentration and high thermal conductivity. What is only recently being discovered is that it possesses excellent compatibility within the biological world. Since publication of the first edition of Silicon Carbide Biotechnology: A Biocompatible Semiconductor for Advanced Biomedical Devices and Applications five years ago [1], significant progress has been made on numerous research and development fronts. In this paper three very promising developments are briefly highlighted – progress towards the realization of a continuous glucose monitoring system, implantable neural interfaces made from free-standing 3C-SiC, and a custom-made low-power ‘wireless capable’ four channel neural recording chip for brain-machine interface applications.
2014 IEEE 9th Nanotechnology Materials and Devices Conference (NMDC), 2014
Silicon carbide (SiC) has long been known as a robust semiconductor with superior properties to s... more Silicon carbide (SiC) has long been known as a robust semiconductor with superior properties to silicon for electronic applications. The cubic form of SiC, known as 3C-SiC, has been researched for non-electronic applications, such as MEMS and biosensors. In particular, our group has demonstrated that 3C-SiC is one of the few semiconductor materials that possesses both bio- and hemacompatibility, thus opening up a plethora of applications for this material. We have pioneered several biomedical devices using 3C-SiC grown on Si substrates, and recently have been investigating the use of this novel material for both biosensor and neural prosthetic applications. Research to develop suitable biosensors, mainly via surface functionalization of 3C-SiC surfaces, has shown that 3C-SiC can be functionalized in much the same was as Si. We review nearly a decade of activity in 3C-SiC on Si biotechnology, with particular emphasis on the most promising applications: surface functionalization, in-vivo glucose sensing and biomedical implants for connecting the human nervous system to advanced prosthetics.
ECS Transactions, 2014
Silicon carbide (SiC) has long been known as a robust semiconductor with superior properties to s... more Silicon carbide (SiC) has long been known as a robust semiconductor with superior properties to silicon for electronic applications. The cubic form of SiC, known as 3C-SiC, has been researched for non-electronic applications, such as MEMS and biosensors. In particular, our group has demonstrated that 3C-SiC is one of the few semiconductor materials that possesses both bio- and hemacompatibility, thus opening up a plethora of applications for this material. We have pioneered several biomedical devices using 3C-SiC grown on Si substrates, and recently have been investigating the use of this novel material for both continuous glucose monitoring and neural prosthetic applications. We will review nearly a decade of activity in this regard, with particular emphasis on the most promising applications: in vivo continuous glucose monitoring and biomedical implants for connecting the human nervous system to advanced prosthetics.
Materials Science Forum, 2000
ABSTRACT
Materials Science Forum, 2010
SiC is a candidate material for micro-and nano-electromechanical systems (MEMS and NEMS). In orde... more SiC is a candidate material for micro-and nano-electromechanical systems (MEMS and NEMS). In order to understand the impact that the growth rate has on the residual stress of CVD-grown 3C-SiC hetero-epitaxial films on Si substrates, growth experiments were performed and the resulting stress was evaluated. Film growth was performed using a two-step growth process with propane and silane as the C and Si precursors in hydrogen carrier gas. The film thickness was held constant at ~2.5 µm independent of the growth rate so as to allow for direct films comparison as a function of the growth rate. Supported by profilometry, Raman and XRD analysis, this study shows that the growth rate is a fundamental parameter for low-defect and low-stress hetero-epitaxial growth process of 3C-SiC on Si substrates. XRD (rocking curve analysis) and Raman spectroscopy show that the crystal quality of the films increases with decreasing growth rate. From curvature measurements, the average residual stress within the layer using the modified Stoney's equation was calculated. The results show that the films are under compressive stress and the calculated residual stress also increases with growth rate, from-0.78 GPa to-1.11 GPa for 3C-SiC films grown at 2.45 and 4 µm/h, respectively.
Silicon Carbide and Related Materials 2011, Pts 1 and 2, 2012
SiC is a candidate material for micro-and nano-electromechanical systems (MEMS and NEMS). In orde... more SiC is a candidate material for micro-and nano-electromechanical systems (MEMS and NEMS). In order to understand the impact that the growth rate has on the residual stress of CVDgrown 3C-SiC hetero-epitaxial films on Si substrates, growth experiments were performed and the resulting stress was evaluated. The film thickness was held constant at ~2.5 µm independent of the growth rate so as to allow for direct comparison of films as a function of the growth rate. Supported by profilometry, Raman and micro-machined free-standing structures, this study shows that the growth rate is a fundamental parameter for the low-defect and the low-stress hetero-epitaxial growth process of 3C-SiC on Si substrates.
Materials Science Forum, 2009
We have developed a high-quality growth process for 3C-SiC on on-axis (111)Si substrates with the... more We have developed a high-quality growth process for 3C-SiC on on-axis (111)Si substrates with the ultimate goal to demonstrate high quality and yield electronic and MEMS devices. A single-side polished 50 mm (111)Si wafer was loaded into a hot-wall SiC CVD reactor for growth. The 3C-SiC process was performed in two stages: carbonization in propane and hydrogen at 1135°C and 400 Torr followed by growth at 1380°C and 100 Torr. X-ray diffraction rocking curve analysis of the 3C-SiC(222) peak indicates a FWHM value of 219 arcsec. This is a very interesting result given that the film thickness was only 2 µm, thus indicating that the grown film is of very high quality compared with published literature values. X-ray polar figure mapping was performed and it was observed that the micro twin content was below the detection limit. Therefore TEM characterization was performed in plan view to allow assessment of the stacking fault density as well as confirmation of the very low micro twin con...
Technology & Innovation, 2011
Solid-State Electronics, 2001
6H-SiC lateral double implanted metal oxide semiconductor ®eld eect transistors have been fabrica... more 6H-SiC lateral double implanted metal oxide semiconductor ®eld eect transistors have been fabricated on four p-type wafers with p-type epitaxial layers doped with Al at 2±7 Â 10 16 cm À3. Each of the wafers received two nitrogen implants of heavy and light doses for drain/source and drift regions, respectively. The wafers had the implants activated at 1600°C in an Ar ambient (one wafer) or a silane overpressure ambient (three wafers). The subsequent characterization con®rmed a much smoother surface for the silane-annealed wafers, with step bunching reduced from 25 nm peak steps with periodicity of 1 lm to undetectable steps. Near optimal breakdown voltages of 600 V were obtained for a 9 lm drift region length devices, and threshold voltage ranged from 9 to 12 V. Average values for eective channel mobility l eff were in the range 35.2±44.1 cm 2 /V s for the three silane-annealed wafers, and 30.0 cm 2 /V s for the argonannealed wafer.
Journal of Materials Research, 2012
In this article, the biofunctionalization of 6H-SiC (0001) surfaces via self-assembled monolayers... more In this article, the biofunctionalization of 6H-SiC (0001) surfaces via self-assembled monolayers (SAMs) has been studied as a means to modify the in vitro biocompatibility of this semiconductor substrate with H4 (human neuroglioma) and PC12 (rat pheochromocytoma) cells. Silanization with aminopropyldiethoxymethylsilane (APDEMS) and aminopropyltriethoxysilane (APTES), which provided moderately hydrophilic surfaces, and alkylation with 1-octadecene that produced hydrophobic surfaces were used to control the 6H-SiC surface chemistry and evaluate changes in cell viability and morphology due to these surface modifications. The morphology of the cells was evaluated with atomic force microscopy. In addition, 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide (MTT) assays were used to quantitatively evaluate the cell viability on the SAM-modified surfaces. In all cases, the cell proliferation was observed to improve with respect to untreated 6H-SiC surfaces, with up to a 2x increase in viability on the 1-octadecene-modified surfaces, up to 6x increase with APDEMS-modified surfaces, and up to 8x increase with APTES-modified surfaces. This proves the potential of SiC as a substrate for medical devices given the possibility to tailor its surface chemistry for specific applications.
IEEE Transactions on Microwave Theory and Techniques, 1995
An optoelectronic attenuator suitable for the optical control of microwave-integrated circuits is... more An optoelectronic attenuator suitable for the optical control of microwave-integrated circuits is presented. High-speed photoconductive switches are embedded in planar microwave transmission lines fabricated on both semi-insulating GaAs and high-resistivity silicon substrates, and a fiber pigtailed semiconductor laser diode is used to control the microwave signal level on these high-speed lines. Forty-five dB of microwave attenuation was demonstrated with a