Etching, ultraviolet laser

Alternative dry etching techniques have recently been developed for the nitrides for low-damage applications. Photoassisted dry etching is set up analogously to CAIBE except that the ion beam source is replaced with an ultraviolet laser. Leonard and Bedair [25] reported on the photoassisted dry etching characteristics of GaN using HC1 gas and a 193 ran ArF excimer laser (1400 mJ/cm2) with the substrate... 

Srinivasan R, Braren B, Casey KG, Yeh M. (1990) The significance of a fluence threshold for ultraviolet laser ablation and etching of polymers./ylpp/TAj/s 67 1604. 

The absorption of laser radiation in polymers is governed by Beer s law and the etch depth exhibits a logarithmic dependence on the incident laser fluence above a threshold value [137, 304, 611]. The penetration depth of ultraviolet laser radiation is usually greater than the etch depth, so that the surface left behind after ablation has been exposed to laser radiation [1229]. 

Capillary electrophoresis is an excellent microseparation technique that has been used for the separation of a wide diversity of different molecules." Its separation capabilities extend to ions, small molecules (such as amino acids), and large biomolecules (such as peptides, proteins, and nucleic acids). Indeed the human genome project owes its success, in part, to the use of CE for the separation of DNA bases. In the past, CE has been combined with detection devices such as ultraviolet (UV) and laser-induced fluorescence (LIE) spectrophotometers. The detection of the separated analytes is carried out on column by etching the capillary. Unfortunately, UV detection lacks sensitivity and not every compound of interest will absorb in the UV region of the spectmm. Detection using LIE is sensitive, however, the analytes of interest may require derivatization with a fluorescent tag or have an aromatic amino acid in their structure (e.g., proteins and peptides). An advantage of MS detection that neither UV nor LIE detection provides is the information necessary to directly determine the structure of the detected analyte(s). 

Surface treatment prior to adhesive bonding typically consists of surface roughening and may be followed by acid etching or plasma, corona, ultraviolet or laser treatments. These increase surface functionality and improve bond strength. There are a number of recommended adhesives which are often based on epoxy resin chemistry. However, it should be remembered that many adhesives do not offer the very high-temperature performance of PAEK. 

Srinivasan, R., Sutdiffe, E and Braren, B. (1987) Ablation and etching of polymethyhnelhacrylate by very short (160fe) ultraviolet (308nm) laser pulses. Appl. Phys. Lett., 51, 1285-1287. 

Rauh and LeLievre (24) examined the intensity and total delivered energy dependence of hole diameters etched in n-GaAs with a focused 633 nm (HeNe laser) source. Unlike the results with ultraviolet excitation, the hole diameters grew sharply with etching time and no light guided structures were produced. However, shallow pits could be etched with... 

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