Hydrogen terminated silicon surfaces have been utilized to develop sensors for semiconductor and environmental applications. The interaction of these surfaces with different environments has also been studied in detail. The sensor assembly relevant to the semiconductor industry utilizes a silicon-based sensor to detect trace levels of metallic contaminants in hydrofluoric acid. The sensor performance with respect to two non-contaminating reference electrode systems was evaluated. In the first case, conductive diamond was used as a reference electrode. In the second case, a dual silicon electrode system was used with one of the silicon-based electrodes protected with an anion permeable membrane behaving as the quasi reference electrode. Though both systems could function well as a suitable reference system, the dual silicon electrode design showed greater compatibility for the on-line detection of metallic impurities in HF etching baths. The silicon-based sensor assembly was able to detect parts- per-trillion to parts-per-billion levels of metal ion impurities in HF. The sensor assembly developed for the environmental application makes use of a novel method for the detection of Ni2+using attenuated total reflection (ATR) technique. The nickel infrared sensor was prepared on a silicon ATR crystal uniformly coated by a 1.5 micron Nafion film embedded with dimethylglyoxime (DMG) probe molecules. The detection of Ni2+ was based on the appearance of a unique infrared absorption peak at 1572 cm-1 that corresponds to the C=N stretching mode in the nickel dimethylglyoximate, Ni(DMG)2, complex. The suitable operational pH range for the nickel infrared sensor is between 6-8. The detection limit of the nickel infrared sensor is 1 ppm in the sample solution of pH=8. ATR - FTIR spectroscopy was used to study the changes that the hydride mode underwent when subjected to different environments. The presence of trace amounts of Cu2+ in HF solutions was found to roughen the silicon surface as observed ATR-IR spectroscopy. The initial stages of oxidation in UPW and Cu2+ / UPW was studied. Trace amounts of Cu2+ were found to drastically increase the rate of oxidation, while the rate of oxidation was found to be retarded on removing dissolved oxygen that was present in UPW.