The standard AT-cut, 1 in. (25.4 mm) diameter crystal, pioneered by INFICON, is used primarily in research applications with the INFICON RQCM (Research Quartz Crystal Microbalance). These research crystals are designed for use with INFICON rugged, easy to use crystal holders and are used for in-situ monitoring of deposited films or liquids. Geometry AT-cut quartz has superior mechanical and piezoelectric properties. The 1 in. (25.4 mm) diameter allows optimal distance between the active area of the crystal and the mounting o-ring. This improves the overall stability of the crystal by reducing the frequency changes due to mounting stress. Finish INFICON 1 in. (25.4 mm) research crystals are available with either an unpolished or polished finish. Polished crystals allow for a good correlation between theory and measurement during liquid immersion experiments. Electrode Material INFICON 1 in. (25.4 mm) research crystals are available in a variety of electrode materials including Gold, Platinum, and Titanium. Crystals with custom electrode materials are available on request. INFICON also offers Gold electrode crystals with an additional SiO2 outer layer to create a hydrophilic surface needed for some biological applications. Temperature Even though AT-cut crystals are designed to minimize the change in frequency due to temperature, the effect of temperature can be significant when attempting to resolve small mass (frequency) changes over long periods of time. INFICON offers AT-cut crystals optimized for two operating temperatures, 90ºC and 25ºC. These crystals have very good frequency stability when operating close to their specified temperature.