Ultrasonic-assisted anodic oxidation of 4H-SiC (0001) surface

Yang, Xiaozhe; Yang, Xu; Kawai, Kentaro; Arima, Kenta; Yamamura, Kazuya

doi:10.1016/j.elecom.2019.01.012

Cited by 28 publications

(9 citation statements)

References 26 publications

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“…The nonbound disulfide ratio (black line in Figure 3a−c) is slightly higher for the Si monolayer, compared to that formed on ITO and GC. This is possibly due to nanoscale oxidation of the Si surface that blocks some of the active surface sites, 37 consistent with some silicon oxide observed in XPS (Figure S1d,e). The peak at 168.3 eV at the Si surface S 2p region is attributed to the Si plasmon loss resulting from the strong interaction between the Si and the emitted photoelectrons.…”

Section: ■ Results and Discussionsupporting

confidence: 78%

Ultrasonic Generation of Thiyl Radicals: A General Method of Rapidly Connecting Molecules to a Range of Electrodes for Electrochemical and Molecular Electronics Applications

Dief

Darwish

2020

ACS Sens.

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Herein, we report ultrasonic generation of thiyl radicals as a general method for functionalizing a range of surfaces with organic molecules. The method is simple, rapid, can be utilized at ambient conditions and involves sonicating a solution of disulfide molecules, homolytically cleaving S–S bonds and generating thiyl radicals that react with the surfaces by forming covalently bound monolayers. Full molecular coverages on conducting oxides (ITO), semiconductors (Si–H), and carbon (GC) electrode surfaces can be achieved within a time scale of 15–90 min. The suitability of this method to connect the same molecule to different electrodes enabled comparing the conductivity of single molecules and the electrochemical electron transfer kinetics of redox active monolayers as a function of the molecule–electrode contact. We demonstrate, using STM break-junction technique, single-molecule heterojunction comprising Au–molecule–ITO and Au–molecule–carbon circuits. We found that despite using the same molecule, the single-molecule conductivity of Au–molecule–carbon circuits is about an order of magnitude higher than that of Au–molecule–ITO circuits. The same trend was observed for electron transfer kinetics, measured using electrochemical impedance spectroscopy for ferrocene-terminated monolayers on carbon and ITO. This suggests that the interfacial bond between different electrodes and the same molecule can be used to tune the conductivity of single-molecule devices and to control the rate of charge transport in redox active monolayers, opening prospects for relating various types of interfacial charge-transfer rate processes.

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Section: ■ Results and Discussionsupporting

confidence: 78%

Ultrasonic Generation of Thiyl Radicals: A General Method of Rapidly Connecting Molecules to a Range of Electrodes for Electrochemical and Molecular Electronics Applications

Dief

Darwish

2020

ACS Sens.

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“…Yang [69] proposed an ultrasonic-assisted electrochemical mechanical polishing (UAECMP) technology, which combined ultrasonic vibration with ECMP. The effect of ultrasonic vibration on the anodic oxidation rate of a 4H-SiC (0001) surface was studied.…”

Section: Ultrasonic Vibration-assisted Polishingmentioning

confidence: 99%

A Review on Precision Polishing Technology of Single-Crystal SiC

Liu

et al. 2022

Crystals

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Single-crystal SiC is a typical third-generation semiconductor power-device material because of its excellent electronic and thermal properties. An ultrasmooth surface with atomic surface roughness that is scratch free and subsurface damage (SSD) free is indispensable before its application. As the last process to reduce the surface roughness and remove surface defects, precision polishing of single-crystal SiC is essential. In this paper, precision polishing technologies for 4H-SiC and 6H-SiC, which are the most commonly used polytypes of single-crystal SiC, such as chemical mechanical polishing (CMP), photocatalytic chemical mechanical polishing (PCMP), plasma-assisted polishing (PAP), electrochemical mechanical polishing (ECMP), and catalyst-referred etching (CARE), were reviewed and compared with emphasis on the experimental setup, polishing mechanism, material removal rate (MRR), and surface roughness. An atomically smooth surface without SSD can be obtained by CMP, PCMP, PAP, and CARE for single-crystal SiC. However, their MRRs are meager, and the waste treatment after CMP is difficult and expensive. Moreover, PAP’s operation is poor due to the complex polishing system, plasma generation, and irradiation devices. A high MRR can be achieved by ECMP. In addition, it is an environmentally friendly precision polishing process for single-crystal SiC since the neutral salt solution is generally used as the electrolyte in ECMP. However, the formation of the egglike protrusions at the oxide/SiC interface during anodic oxidation would lead to a bigger surface roughness after ECMP than that after PAP is processed. The HF solution used in CARE was toxic, and Pt was particularly expensive. Ultrasonic vibration-assisted single-crystal SiC polishing and electrolyte plasma polishing (EPP) were discussed; furthermore, the research direction of further improving the surface quality and MRR of single-crystal SiC was prospected.

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“…While some hydroxyl radical reacts into water and oxygen, some react with single-crystal 4H-SiC to form silicon dioxide. The electrochemical reactions occurring on the cathode and anode (single-crystal 4H-SiC) can be summarized as follows [8,[33][34][35][36].…”

Section: The Mechanism Of Plasma Electrolytic Processing and Mechanical Polishingmentioning

confidence: 99%

“…During the process of plasma electrolytic processing, with the increase of the oxide layer’s thickness, the upper oxide layer gradually becomes porous and microporosity appears in the oxide layer, as shown in Figure 1 . Since the porous oxide layer has a high ion permeability, the active ions can easily reach the SiC surface through the oxide layer [ 36 ].…”

Section: The Mechanism Of Plasma Electrolytic Processing and Mechanical Polishingmentioning

confidence: 99%

Combination of Plasma Electrolytic Processing and Mechanical Polishing for Single-Crystal 4H-SiC

et al. 2021

Micromachines

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Single-crystal 4H-SiC is a typical third-generation semiconductor power-device material because of its excellent electronic and thermal properties. A novel polishing technique that combines plasma electrolytic processing and mechanical polishing (PEP-MP) was proposed in order to polish single-crystal 4H-SiC surfaces effectively. In the PEP-MP process, the single-crystal 4H-SiC surface is modified into a soft oxide layer, which is mainly made of SiO2 and a small amount of silicon oxycarbide by plasma electrolytic processing. Then, the modified oxide layer is easily removed by soft abrasives such as CeO2, whose hardness is much lower than that of single-crystal 4H-SiC. Finally a scratch-free and damage-free surface can be obtained. The hardness of the single-crystal 4H-SiC surface is greatly decreased from 2891.03 to 72.61 HV after plasma electrolytic processing. By scanning electron microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) observation, the plasma electrolytic processing behaviors of single-crystal 4H-SiC are investigated. The scanning white light interferometer (SWLI) images of 4H-SiC surface processed by PEP-MP for 30 s shows that an ultra-smooth surface is obtained and the surface roughness decreased from Sz 607 nm, Ra 64.5 nm to Sz 60.1 nm, Ra 8.1 nm and the material removal rate (MRR) of PEP-MP is about 21.8 μm/h.

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Ultrasonic-assisted anodic oxidation of 4H-SiC (0001) surface

Cited by 28 publications

References 26 publications

Ultrasonic Generation of Thiyl Radicals: A General Method of Rapidly Connecting Molecules to a Range of Electrodes for Electrochemical and Molecular Electronics Applications

Ultrasonic Generation of Thiyl Radicals: A General Method of Rapidly Connecting Molecules to a Range of Electrodes for Electrochemical and Molecular Electronics Applications

A Review on Precision Polishing Technology of Single-Crystal SiC

Combination of Plasma Electrolytic Processing and Mechanical Polishing for Single-Crystal 4H-SiC

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