Piranha etch

Using P(F)S49-f>-PLA192, various different FTO surface modifications were tested, including piranha etch, RCA clean, ultraviolet and plasma etch in combination... 

Wafer cleaning uses strong acids and oxidizer mixtures, including piranha etch, to clean away any organic materials adhering to the wafer. Hydrofluoric acid is used to remove any oxide on the wafer. These processes are conducted in a wet-process hood to control vapor off-gassing and with substantial personal protective equipment to avoid contact with these corrosive and reactive materials. Acid exposure by vapor causes severe irritation of the upper respiratory tract. Eyes and mucous membranes exposed to acid vapors can be damaged and exposures to nitric acid can discolor the cornea and skin. 

Kg. 11 (A) Schematic drawing of the ITO-epoxy-ITO dual-plate junction assembly. (B) Scanning electron micrograph of the ITO-epoxy-ITO dual-band electrode. (C) Scanning electron micrograph of the ITO-epoxy-ITO dual-plate electrode after Piranha etch. (D) and (E) Schematic diagrams of the diffusion fields at band electrodes and plate electrodes respectively (taken from ref. 59). 

Fig. 17 Schematic drawing of (A) the assembly of two gold electrodes, (B) trench formation with Piranha etching, and (C) Ming with redox active oil. (D) SEM image of the gold-gold micro-trench electrode (with chromium sputter coating, taken from ref. 60).

After the mechanical pre-treatment, the electrode can be subjected to a chemical and/or electrochemical pre-treatement. Chemical treatment consists mainly of etching of a few layers of the metal, including possible contaminants. A well-known etching solution for gold is the so-called piranha solution. Other reported solutions are kali, which is a concentrated KOH solution to remove fats and oils and etch off a layer of platinum. 

Gate Piranha clean Gate evaporation Photo Etch Strip 30 minutes in fresh, hot solution 5nm Cr/lOOnm An (e-beam or thermal) Gate mask KI, rinse, chromium etchant, rinse Soak in stripper 10 min, rinse in water soak in fresh stripper 10 min, rinse in water, dry... 

Fig. 5. Deionized water-contact angle vs position (mm) for gradient-etched SiH/Si substrates as a function of both immersion rate and Piranha solution H2SO4 composition. Immersion rate and mass fraction H2SO4 are as follows circles, 2.0 mm/s and 30% triangles, 0.1 mm/s and 30% diamonds, 2.0 mm/s and 40%. Standard uncertainty in contact angle is 2°.

Glass Bonding The etched glass substrate and another cover glass with drilled via-holes were cleaned using boiling Piranha solution for 10 min and then rinsed by DI... 

Fabrication of simple dual-band and dual-plate junction electrodes (similar to microgap electrode systems" ) was recently demonstrated with the development of ITO-epoxy-ITO electrodes. These electrodes consist of two ITO-coated glass slides stuck together with epoxy resin (cured under pressure from a weight to minimise gap size). The end of the electrode was sliced off with a diamond blade to reveal two ITO nano-bands separated by a layer of epoxy. This type of dual-band electrode was further improved by etching out the epoxy with Piranha solution to create a dual-plate... 

Ultra-thin Hquid films of PDMS or poly(methyl-hydrodimethyl)siloxane on siHcon substrates were also prepared [50], The silicon wafers were cleaned by immersion in a freshly prepared piranha solution (a mixture of 70% sulfuric acid and 30% hydrogen peroxide), rinsing with deionized water, followed by etching in HF solution. Then the wafers were rinsed with deionized water and blown dry under a stream of nitrogen. The uniform thin films were spread by dipping the clean substrates in dilute solutions of silicone polymers in hexane and withdrawing the wafers at a constant speed. It was shown that solution concentration and withdrawal speed affected the final film thickness. Typical thickness was in the range of 3-8 nm. 

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