Depth profiling potential damage

Ion beam analysis techniques form a suite of mature and well-understood techniques with potential for polymer surface and interface problems. Due to the size of the polymer chains, in addition to pure surface analysis techniques, polymer surface and interface science needs techniques that can provide depth profile information in the near-surface region i.e. from 1-10 nm to 1 jxm depth). This information can be provided by He ion beam techniques with energies of about 1-3 MeV. In order to avoid surface damage under the ion beam, low-damage conditions need to be developed. 

Implantable microelectronic devices for neural prosthesis require stimulation electrodes to have minimal electrochemical damage to tissue or nerve from chronic stimulation. Since most electrochemical reactions at the stimulation electrode surface alter the hydrogen ion concentration, one can expect a stimulus-induced pH shift [17]. When translated into a biological environment, these pH shifts could potentially have detrimental effects on the surrounding neural tissue and implant function. Measuring depth and spatial profiles of pH changes is important for the development of neural prostheses and safe stimulation protocols. 

The purpose of the detailed survey is to ensure a cost-effective repair in line with the client s requirements. This is done by accurately defining and measuring the cause, extent and severity of deterioration. In Chapter 7, we will discuss how test measurements may be used to model the deterioration rate, time to corrosion and life cycle costing. We will need to know how much damage has been done and what has caused the damage. Quantities for repair tenders will probably be based on the results of this survey, so a full survey of all affected elements may be required. Alternatively a full visual survey may be required, with a hammer (delamination) survey of all accessible locations. A number of representative areas may be selected for a detailed survey of cover depths, carbonation depths, chloride content or profile, half cell potentials and other techniques described in the following sections of this chapter. 

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