X-ray photoelectron spectroscopy analysis of aluminum and copper cleaning procedures for the Advanced Photon Source

Abstract

The Advanced Photon Source (APS), presently under construction, will produce x rays of unprecedented brightness. The storage ring where the x rays will be produced will be constructed from an extruded 6063 aluminum alloy, while transition pieces (flanges, etc.) will be made from a 2219 aluminum alloy. In addition, cooled photon absorbers will be placed in strategic locations throughout the ring to intercept the majority of the unused high power-density radiation. These will be made of either CDA-101 (OFHC) copper or glidcop (a dispersion strengthened copper alloy). Before any of these components can be assembled they must be cleaned to remove surface contaminants so that the ultrahigh vacuum (<0.1 nTorr) necessary for successful operation can be achieved. Many recipes for cleaning aluminum and copper exist; however, most of them involve the use of chemicals that present safety and/or environmental concerns. We have undertaken an x-ray photoelectron spectroscopy study of the effects of a variety of commercially available cleaners on the surface cleanliness of aluminum and copper. Several important results have been identified in this study. A simple alkaline detergent in an ultrasonic bath cleans aluminum alloys as effectively as the more aggressive cleaning solutions. The detergent can be used at 65 °C to clean the 6063 alloy and at 50 °C to clean the 2219 alloy. A citric acid based cleaner was found to be effective at cleaning copper, although the surface oxidizes rapidly. To date, we have been unable to find a universal cleaning procedure, i.e., one that is optimal for cleaning both Al and Cu.

Influence of vacuum chamber impurities on the lifetime of organic light-emitting diodes

“…Aluminum alloy can be a source of outgassing because a natural oxide layer with a thickness of 10 nm or more is formed on the surface of the alloy after machining. This porous oxide layer can readily adsorb impurities and gasses that can be released in vacuum42. These results shed new light on some of the factors affecting the reproducibility of OLED lifetime, which is one of the great mysteries of OLEDs.…”

Characterization of an effective cleaning procedure for aluminum alloys: surface enhanced Raman spectroscopy and zeta potential analysis

“…Cleaning of aluminum alloy 6xxx series has been previously found to be most effective with mild alkaline detergents such as Almeco 18; surfaces cleaned with such detergents were found to have a thinner oxide, well depleted of Mg, compared to surfaces cleaned with strong alkaline detergents or solvents only [3]. Moffitt and co-workers found that an acid pickle was highly effective in removing Mg [11].…”

“…There are many large vacuum facilities requiring highcleanliness conditions, such as particle accelerators. Literature concerning the cleaning procedures used for vacuum chamber construction materials describes the use of alkaline detergent washing followed by deionized water rinsing for aluminum alloys (see, for example, [2][3][4][5]). However, to our knowledge, the use of a phosphoric acid etch prior to alkaline detergent washing has not been previously described as a standard cleaning protocol for aluminum vacuum chamber parts, nor has the problem of "smut" (loosely attached oxide and surface adsorbed particles) been addressed in this context.…”