Reactive Ion Etching (RIE) induces defects in semiconductor materials. These defects can serve as local non-radiative recombination centres for electron-hole pairs, affecting the radiative lifetimes and luminescence efficiencies of the semiconductors. Argon (Ar) and sulphur hexafluoride (SF6) gases were used as etching gases to investigate the influence of ion energy on the RIE induced optical damage of Gallium Nitride (GaN). The significant result of etching by Ar and SF6 gases was that these etching induce defects, but as the total PL does not greatly change, it appears that this process is not increasing the density of nonradiative centres.

Many speakers of current Australian English often use a high-rising intonation in statements. This usage, which has been termed Australian Questioning Intonation (AQI), has a nonpropositional, interactive meaning (checking for listener comprehension) and interacts with the turn-taking mechanism of conversation. A quantitative study of the use of AQI in Sydney reveals that it has the social distribution characteristic of a language change in progress: higher rates of usage among working-class speakers, teenagers, and women. Real time data confirm this, showing that the form was almost nonexistent in this speech community two decades earlier. The social motivations of this innovation are examined in terms of local identity and the entry of new ethnic groups into the community, and possible linguistic sources are discussed. The utility of quantitative methods in studying meaningful linguistic variables is demonstrated. (Australian English, language change in progress, intonation, sociolinguistic variation, social class, social motivation)