Impact of UV Irradiation on Thermally Grown 4H-SiC MOS Devices

2012 ◽  
Vol 717-720 ◽  
pp. 765-768 ◽  
Author(s):  
Daisuke Ikeguchi ◽  
Takashi Kirino ◽  
Shuhei Mitani ◽  
Yuki Nakano ◽  
Takashi Nakamura ◽  
...  
Keyword(s):  
Uv Irradiation ◽  
Uv Light ◽  
Irradiation Time ◽  
Marked Change ◽  
Intrinsic Property ◽  
State Density ◽  
Oxide Semiconductor ◽  
Mos Capacitors ◽  
The Impact ◽  
Thermally Grown

The impact of ultraviolet (UV) light irradiation on thermally grown SiO2/4H-SiC structures was investigated by characterizing the 4H-SiC metal-oxide-semiconductor (MOS) capacitors fabricated with and without UV irradiation onto the oxide layers. The UV irradiation was found to significantly increase a hysteresis in capacitance-voltage (C-V) characteristics and cause a positive flatband voltage (VFB) shift, suggesting the generation of oxide charges and traps. Since the values of C-V hysteresis and VFB shift depend on the UV irradiation time, the electrical defects were considered to be induced during UV irradiation. In contrast, UV irradiation caused no marked change for the reference Si-MOS capacitors, indicating that the generation of UV-induced electrical defects was an intrinsic property of thermally grown SiO2/SiC structures. A detailed characterization of SiC-MOS capacitors with terraced SiO2 layers revealed that the UV-induced defects were located near the SiO2/SiC interface. The interfacial fixed charge density (QOX) was estimated to be 1.7×1012 cm-2 for the sample with UV irradiation, while that of the sample without UV irradiation was 1.0×1012 cm-2. Also, a slight increase was found in interface state density (Dit) due to UV irradiation. These results imply that the UV-induced defect generation correlates with residual carbon impurities at the SiO2/SiC interface.

Novel Approach for Improving Interface Quality of 4H-SiC MOS Devices with UV Irradiation and Subsequent Thermal Annealing

2013 ◽  
Vol 740-742 ◽  
pp. 741-744 ◽  
Author(s):  
Heiji Watanabe ◽  
Daisuke Ikeguchi ◽  
Takashi Kirino ◽  
Shuhei Mitani ◽  
Yuki Nakano ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Thermal Annealing ◽  
Uv Irradiation ◽  
Uv Light ◽  
Interface State ◽  
State Density ◽  
Mos Devices ◽  
Novel Approach ◽  
Subsequent Thermal Annealing ◽  
Thermally Grown

We report on the harmful impact of ultraviolet (UV) light irradiation on thermally grown SiO2/4H-SiC(0001) structures and its use in subsequent thermal annealing for improving electrical properties of SiC-MOS devices. As we previously reported [1], significant UV-induced damage, such as positive flatband voltage shift and hysteresis in capacitance-voltage curves as well as increased interface state density, was observed for SiC-MOS devices with thermally grown oxides. Interestingly, the subsequent annealing of damaged SiO2/SiC samples resulted in superior electrical properties to those for untreated (fresh) devices. These findings imply that UV irradiation of the SiO2/SiC structure is effective for eliciting pre-existing carbon-related defects and transforming them into a simple configuration that can be easily passivated by thermal treatment.

Effect of Interfacial Localization of Phosphorus on Electrical Properties and Reliability of 4H-SiC MOS Devices

2013 ◽  
Vol 740-742 ◽  
pp. 695-698 ◽  
Author(s):  
Tsuyoshi Akagi ◽  
Hiroshi Yano ◽  
Tomoaki Hatayama ◽  
Takashi Fuyuki
Keyword(s):  
Interface State ◽  
State Density ◽  
Oxide Semiconductor ◽  
Conduction Band Edge ◽  
Mos Capacitors ◽  
Mos Devices ◽  
Device Properties ◽  
Phosphorus Doped ◽  
Post Deposition ◽  
Mos Device

Metal-oxide-semiconductor (MOS) capacitors with phosphorus localized near the SiO2/SiC interface were fabricated on 4H-SiC by direct POCl3treatment followed by SiO2deposition. Post-deposition annealing (PDA) temperature affected MOS device properties and phosphorus distribution in the oxide. The sample with PDA at 800 °C showed narrow phosphorus-doped oxide region, resulting in low interface state density near the conduction band edge and small flatband voltage shift after FN injection. The interfacial localization of phosphorus improved both interface properties and reliability of 4H-SiC MOS devices.

Processing and Characterization of MOS Capacitors Fabricated on 2°-Off Axis 4H-SiC Epilayers

2016 ◽  
Vol 858 ◽  
pp. 663-666
Author(s):  
Marilena Vivona ◽  
Patrick Fiorenza ◽  
Tomasz Sledziewski ◽  
Alexandra Gkanatsiou ◽  
Michael Krieger ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Interface State ◽  
State Density ◽  
Metal Oxide Semiconductor ◽  
Interface State Density ◽  
Device Fabrication ◽  
Oxide Semiconductor ◽  
Mos Capacitors ◽  
Oxide Breakdown

In this work, the electrical properties of SiO2/SiC interfaces onto a 2°-off axis 4H-SiC layer were studied and validated through the processing and characterization of metal-oxide-semiconductor (MOS) capacitors. The electrical analyses on the MOS capacitors gave an interface state density in the low 1×1012 eV-1cm-2 range, which results comparable to the standard 4°-off-axis 4H-SiC, currently used for device fabrication. From Fowler-Nordheim analysis and breakdown measurements, a barrier height of 2.9 eV and an oxide breakdown of 10.3 MV/cm were determined. The results demonstrate the maturity of the 2°-off axis material and pave the way for the fabrication of 4H-SiC MOSFET devices on this misorientation angle.

Passivation and Generation of States at P-Implanted Thermally Grown and Deposited N-Type 4H-SiC/SiO2 Interfaces

2016 ◽  
Vol 858 ◽  
pp. 697-700 ◽  
Author(s):  
Tomasz Sledziewski ◽  
Heiko B. Weber ◽  
Michael Krieger
Keyword(s):  
Electrical Properties ◽  
Response Time ◽  
Side Effect ◽  
Oxide Semiconductor ◽  
Epitaxial Layers ◽  
Interface Traps ◽  
Semiconductor Interface ◽  
Mos Capacitors ◽  
Thermally Grown Oxides ◽  
Thermally Grown

In this work the effect of phosphorus on the electrical properties of n-type 4H-SiC MOS capacitors is studied. Phosphorus ions are implanted into the epitaxial layers prior to the deposition of SiO2 by PECVD, in shallow depths and at concentrations at the oxide-semiconductor interface in the range of (5 x 1017…1 x 1019) cm-3. Those samples are compared with 31P-implanted 4H-SiC MOS capacitors with thermally grown oxides, which were primarily investigated in the previous work of the authors. It is shown that independently of the oxide technology phosphorus may lead to decrease of the density of interface traps, whose response time to the AC voltage is longer than 1 µs. The side-effect of the implantation of phosphorus is generation of the very fast interface states, which are able to follow the frequencies over 1 MHz.

Degradation of PVDF-based composite membrane and its impacts on membrane intrinsic and separation properties

2016 ◽  
Vol 36 (3) ◽  
pp. 261-268 ◽  
Author(s):  
Mei Jiun Lee ◽  
Chi Siang Ong ◽  
Woei Jye Lau ◽  
Be Cheer Ng ◽  
Ahmad Fauzi Ismail ◽  
...  
Keyword(s):  
Uv Irradiation ◽  
Exposure Time ◽  
Composite Membrane ◽  
Polyvinylidene Fluoride ◽  
Uv Light ◽  
Irradiation Time ◽  
Uv Exposure ◽  
Polymeric Membrane ◽  
Permeate Flux ◽  
Wastewater Treatment Process

Abstract In this work, an attempt was made to evaluate the effects of ultraviolet (UV) irradiation period on the intrinsic and separation properties of composite membrane composed of organic polyvinylidene fluoride and inorganic titanium dioxide (TiO2) nanoparticles by exposing the membrane to UV-A light for up to 250 h. The changes on membrane structural morphologies and chemical characteristics upon UV exposure were studied by field-emission scanning electron microscope and Fourier transform infrared, respectively. It was observed that some cracks and fractures were formed on the membrane outer surface when it was exposed to 120-h UV light. Further increase in UV irradiation time to 250 h had caused membrane structure to collapse, turning it into powder form. Filtration experiments showed that the permeate flux of irradiated membrane was significantly increased from 10.89 L/m2 h to 21.84 L/m2 h (>100% flux increment) while oil rejection decreased with increasing UV exposure time from 0 h to 120 h. Furthermore, the mechanical strength and thermal stability of irradiated membrane were also reported to decrease with increasing UV exposure time, suggesting the negative impacts of UV light on the membrane overall stability. This research is of particular importance to evaluate the suitability and sustainability of polymeric membrane, which is widely considered as the host for photocatalyts and used for wastewater treatment process under UV irradiation.

scholarly journals Tailoring the Nonlinear Optical Response of Some Graphene Derivatives by Ultraviolet (UV) Irradiation

Nanomaterials ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 152
Author(s):  
Aristeidis Stathis ◽  
Zoi Bouza ◽  
Ioannis Papadakis ◽  
Stelios Couris
Keyword(s):  
Uv Irradiation ◽  
Nonlinear Optical ◽  
Irradiation Time ◽  
Optical Response ◽  
Nonlinear Optical Response ◽  
Simple Strategy ◽  
Custom Made ◽  
Graphene Derivatives ◽  
The Impact

In the present work the impact of in situ photoreduction, by means of ultraviolet (UV) irradiation, on the nonlinear optical response (NLO) of some graphene oxide (GO), fluorographene (GF), hydrogenated fluorographene (GFH) and graphene (G) dispersions is studied. In situ UV photoreduction allowed for the extended modification of the degree of functionalization (i.e., oxidization, fluorination and hydrogenation), leading to the effective tuning of the corresponding sp2/sp3 hybridization ratios. The nonlinear optical properties of the studied samples prior to and after UV irradiation were determined by means of the Z-scan technique using visible (532 nm), 4 ns laser excitation, and were found to change significantly. More specifically, while GO’s nonlinear optical response increases with irradiation time, GF and GFH present a monotonic decrease. The graphene dispersions’ nonlinear optical response remains unaffected after prolonged UV irradiation for more than an hour. The present findings demonstrate that UV photoreduction can be an effective and simple strategy for tuning the nonlinear optical response of these graphene derivatives in a controllable way, resulting in derivatives with custom-made responses, thus more suitable for different photonic and optoelectronic applications.

Nanotribological Investigation of Magnetic Rigid Disks Lubricated with Perfluoropolyether Lubricant Under Varying Conditions

2008 ◽  
Vol 8 (5) ◽  
pp. 2719-2723 ◽  
Author(s):  
E. Liu ◽  
K. S. Tan ◽  
H. I. Tan
Keyword(s):  
Mechanical Properties ◽  
Uv Irradiation ◽  
Uv Light ◽  
Irradiation Time ◽  
Experimental Results ◽  
Light Irradiation ◽  
Loading Conditions ◽  
Uv Treatment ◽  
Uv Light Irradiation ◽  
Rigid Disks

This paper studies the nanotribological behavior of magnetic rigid disks dip-coated with ultra thin perfluoropolyether (PFPE) Z-Dol 4000 lubricant layers up to 4 nm thick prior to or after exposure to ultraviolet (UV) light irradiation. Lube bonding ratios (LBRs) of 43–91% were achieved by varying the UV irradiation time. The nanotribological and mechanical properties of the disks were measured with a nanotribometer under varying loading conditions. The effect of the LBR on the nanotribological behavior of the disks was also elucidated. We found that the lubricated disks after UV treatment performed better compared to the lubricated disks without UV treatment. The experimental results indicated that the LBR of about 50% could achieve the best contact-start–stop and flyability performances.

scholarly journals Creation of Interface States at the Silicon/Silicon Dioxide Interface by UV Light Without Hole Trapping

1989 ◽  
Vol 148 ◽  
Author(s):  
W. K. Schubert ◽  
C. H. Seager ◽  
K. L. Brower
Keyword(s):  
Silicon Dioxide ◽  
Silicon Substrate ◽  
Uv Light ◽  
Interface States ◽  
Metal Oxide Semiconductor ◽  
Oxide Semiconductor ◽  
Mos Capacitors ◽  
Hole Trapping ◽  
Creation Rate ◽  
Silicon Silicon

ABSTRACTPhotoinjection of electrons into silicon dioxide in metal-oxide-semiconductor (MOS) capacitors with 3.5 eV light is shown to create interface states with no apparent hole trapping precursor. The creation rate of these interface states depends strongly upon whether injection is from the gate metal or the silicon substrate, and on the forming gas annealing sequence used to passivate growth-induced interface states. A mechanism involving electron-induced release of hydrogen in the oxide is consistent with some aspects of the data.

Systematic Investigation of Interface Properties in 4H-SiC MOS Structures Prepared by Over-Oxidation of Ion-Implanted Substrates

2010 ◽  
Vol 645-648 ◽  
pp. 495-498 ◽  
Author(s):  
Dai Okamoto ◽  
Hiroshi Yano ◽  
Tomoaki Hatayama ◽  
Takashi Fuyuki
Keyword(s):  
Interface State ◽  
Systematic Investigation ◽  
Implantation Dose ◽  
State Density ◽  
Interface State Density ◽  
Oxide Semiconductor ◽  
Conduction Band Edge ◽  
Strong Reduction ◽  
Mos Capacitors ◽  
Mos Structures

A change in the interface state density in 4H-SiC metal–oxide–semiconductor (MOS) structures by incorporation of various elements was systematically investigated. B, N, F, Al, P, and Cl ions were implanted prior to the oxidation and introduced at the SiO2/SiC interface by subsequent thermal oxidation. Interface state density near the conduction band edge for Al-, B-, F-, and Cl-implanted MOS capacitors increased with implantation dose. On the other hand, a strong reduction of the interface state density was observed for N- and P-implanted samples when the implantation dose was larger than 5.0 × 1012 cm−2. It was found that the interface state density can be reduced by P as well as N.

Aging Behavior of the Polyether Polyurethane Films Irradiated by UV

2013 ◽  
Vol 748 ◽  
pp. 16-21 ◽  
Author(s):  
Hai Yan Wang ◽  
Yu Wen Liu ◽  
Bin Sun ◽  
Shi Jie Huang ◽  
Ji Feng Tian
Keyword(s):  
Aromatic Ring ◽  
Uv Irradiation ◽  
Uv Light ◽  
Irradiation Time ◽  
Color Difference ◽  
Molecular Structures ◽  
Hydroxyl Group ◽  
Failure Behavior ◽  
Polyurethane Film

The failure behavior of polyether polyurethane films irradiated by UV depends on its molecular structures evolvement. The molecular structure evolvement of the polyether polyurethane films under UV irradiation were studied by in-situ FTIR spectra in this paper. It has been found that some oxygen contained groups such as hydroxyl group and carbonyl group increase; on the contrary, ether bond and CH2 decrease with the UV irradiation time. The aromatic ring maintains changeless. However, -NH group has not be determined due to the interference of the-OH and O-C=O. Results from FTIR and SEM have shown that UV photodegradative processes participated by oxidization occur mostly in ether segments and is accompanied by crosslinkage. Using the absorbance band of aromatic ring as the base the service life of polyether polyurethane can be determined by the change rate of C-O-C and-CH2 during UV irradiation. After UV irradiation, the polyether polyurethane film has higher color difference value and lower UV light transparence.

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