This review article summarizes the key areas of self-cleaning coatings, primarily focusing on various materials that are widely used in recent research and also in commercial applications. The scope of this article orbits around hydrophobic and hydrophilic coatings, their working mechanism, fabrication techniques that enable the development of such coatings, various functions like Anti-icing, Electro-wetting, Surface switchability and the areas where selfcleaning technology can be implemented. Moreover, different characterization techniques and material testing feasibilities are also analyzed and discussed. Though several companies have commercialized a few products based on self-cleaning coating technology, much potential still remains in this field.

A review on self-cleaning coatings

SiO2 is one of the most abundant materials on Earth. It is cost-effective and also environmentally benign when used as an energy material. Although SiO2 was inactive to Li, it was engineered to react directly by a simple process. It exhibited a strong potential as a promising anode for Li-ion batteries.

Quartz (SiO2): a new energy storage anode material for Li-ion batteries

We study the paired-pulse-induced response of a NiOx-based memristor. The behavior of the memristor is surprisingly similar to the paired-pulse facilitation of a biological synapse. When the memristor is stimulated with a pair of electrical pulses, the current of the memristor induced by the second pulse is larger than that by the first pulse. In addition, the magnitude of the facilitation decreases with the pulse interval, while it increases with the pulse magnitude or pulse width.

/pdf/emulating-the-paired-pulse-facilitation-of-a-biological-1zmf4vfz65.pdf

Emulating the paired-pulse facilitation of a biological synapse with a NiOx-based memristor

The well-known Ebbinghaus forgetting curve, which describes how information is forgotten over time, can be emulated using a NiO-based memristor with conductance that decreases with time after the application of electrical pulses. Here, the conductance is analogous to the memory state, while each electrical pulse represents a memory stimulation or learning event. The decrease in the conductance with time depends on the stimulation parameters, including pulse height and width and the number of pulses, which emulates memory loss behavior well in that the time taken for the memory to be lost depends on how the information is learned.

/pdf/emulating-the-ebbinghaus-forgetting-curve-of-the-human-brain-1li2c8hqyy.pdf

Emulating the Ebbinghaus forgetting curve of the human brain with a NiO-based memristor

A striking correlation between infrared photoinduced absorption spectra and the photoluminescence from silicon nanocrystals indicates that quantized electronic sublevels of the nanocrystals are resonantly coupled to surface vibrational modes via a polarization field produced by coherent longitudinal polar vibrations. Our experimental results and model support the assumption that the mechanism responsible for the efficient photoluminescence from silicon nanocrystals should be assigned to inhibition of nonradiative channels rather than enhancement of radiative channels.

Resonant coupling between surface vibrations and electronic states in silicon nanocrystals at the strong confinement regime.

X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy are used to study Si nanocrystal formation in Si-implanted SiO2 films as a function of thermal annealing. Analysis of the XPS Si 2p peaks shows the existence of five chemical structures corresponding to the Si oxidation states Sin+ (n = 0, 1, 2, 3, and 4) in the SiO2 films, and the concentration of each oxidation state is determined quantitatively. The XPS results show a clear picture of the evolution of the chemical structures and the formation of Si nanocrystals as functions of annealing temperature and annealing time. The evolution of the concentrations of the five oxidation states with annealing is explained in terms of the thermal decompositions of the suboxides corresponding to the three oxidation states Sin+ (n = 1, 2, and 3) and the thermal oxidation of the implanted Si.

https://iopscience.iop.org/article/10.1088/0022-3727/36/19/L02/pdf

A study on Si nanocrystal formation in Si-implanted SiO2 films by x-ray photoelectron spectroscopy

In this work, we report a mapping of charge transport in silicon nanocrystals (nc-Si) embedded in SiO2 dielectric films with electrostatic force microscopy. The charge diffusion from chargednc-Si to neighboring uncharged nc-Si in the SiO2 matrix is found to be the dominant mechanism for the decay of the trapped charge in the nc-Si. The trapped charge and the charge decay have been determined quantitatively from the electrical force measurement. An increase in the area of the charge cloud due to the charge diffusion has been observed clearly. In addition, the blockage and acceleration of charge diffusion by the neighboring charges with the same and opposite charge signs (i.e., positive or negative), respectively, have been observed.

/pdf/visualizing-charge-transport-in-silicon-nanocrystals-3w0xjyny3r.pdf

Visualizing charge transport in silicon nanocrystals embedded in SiO2 films with electrostatic force microscopy

The static dielectric constant of isolated silicon nanocrystals (nc-Si) embedded in a SiO2 thin film synthesized by Si+ implantation has been determined from capacitance measurement based on the Maxwell–Garnett effective medium approximation and the stopping and range of ions in matter simulation. For the nc-Si with a mean size of ∼4.5nm, the dielectric constant so determined is 9.8, being consistent with a theoretical prediction. This value is significantly lower than the static dielectric constant (11.9) of bulk crystalline Si, indicating the significance of nc-Si size effect. The information of nc-Si dielectric constant is not only important to the fundamental physics but also useful to the design and modeling of nc-Si-based memory devices.

/pdf/static-dielectric-constant-of-isolated-silicon-nanocrystals-418snxhk58.pdf

Static dielectric constant of isolated silicon nanocrystals embedded in a SiO2 thin film

We report a study of influence of charging and discharging in Si nanocrystals (nc-Si), which are embedded throughout the gate oxide in metal-oxide-semiconductor (MOS) structures, on the current-voltage and capacitance-voltage characteristics of the MOS structures. Very large current and capacitance are observed for the as-fabricated structures. However, charge trapping in the nanocrystals can reduce both the current and the capacitance dramatically. The trapped charges can also tunnel out from the nc-Si, leading to the recovery of both the current and the capacitance. The current reduction is attributed to the breaking of the nc-Si tunneling paths due to charge trapping in the nc-Si, while capacitance reduction is explained by an equivalent circuit in terms of the change of the nc-Si capacitance as a result of the charge trapping. © 2004 The Electrochemical Society. All rights reserved.

/pdf/charging-effect-on-electrical-characteristics-of-mos-41yd0sryv8.pdf

Charging Effect on Electrical Characteristics of MOS Structures with Si Nanocrystal Distribution in Gate Oxide

The thermal annealing effect on band gap and dielectric functions of silicon nanocrystals (nc-Si) embedded in a SiO2 matrix synthesized by Si ion implantation is investigated by spectroscopic ellipsometry. A large band-gap expansion of nc-Si relative to bulk crystalline silicon has been observed. The band gap of the nc-Si for the nonannealing condition (i.e., as implanted) is 1.78eV while it is 1.72eV for the annealing at 1000°C for 100min. The slight decrease in the band gap is attributed to the slight increase in the nc-Si size with annealing. The dielectric functions of nc-Si show a significant suppression, as compared to bulk crystalline silicon, due to the quantum size effect. Annealing results in a small change in the static dielectric constant, which can be explained in terms of the size effect also.

/pdf/thermal-annealing-effect-on-the-band-gap-and-dielectric-2lgo0573ab.pdf

Y. Liu

Papers

A study on Si nanocrystal formation in Si-implanted SiO2 films by x-ray photoelectron spectroscopy

Visualizing charge transport in silicon nanocrystals embedded in SiO2 films with electrostatic force microscopy

Static dielectric constant of isolated silicon nanocrystals embedded in a SiO2 thin film

Charging Effect on Electrical Characteristics of MOS Structures with Si Nanocrystal Distribution in Gate Oxide

Thermal annealing effect on the band gap and dielectric functions of silicon nanocrystals embedded in SiO2 matrix