Diamond as an active sensor material

Diamond has attractive properties as an advanced electronic material. Its combination of high carrier mobility, electric breakdown, and thermal conductivity results in the largest calculated figures of merit for speed and power of any material. Previously (J.L. Davidson, W.P. Kang, Examples of diamond sensing applications, Proceedings 3rd International Symposium on Diamond Film (ISDF-3), Polytechnical Institute of Russian Academy of Science, St. Petersburg, Russia, 16–19 June 1996) we reported the discovery and development of useful ‘secondary’ effects in diamond and applying them to interesting sensor applications. For example, boron-doped diamond piezoresistors for strain micro-gauges on rugged MEMS (microelectromechanical structures) pressure and acceleration sensors. This paper will present some recent developments with chemically vapor-deposited diamond for microelectromechanical sensing applications such as a new design all diamond pressure microsensor that measures pressure at high temperatures and an accelerometer with over 45 kHz resonant frequency. Also, presented are recent results on layered diamond films that behave as chemical sensors measuring hydrogen, oxygen and many other chemicals’ concentration. For example, a diamond-based chemical gas sensor using Pt/SnO_x/i-diamond/p⁺-diamond metal–insulator–semiconductor diode structure for oxygen sensing is described. In addition, the latest emission properties of fabricated diamond microtips for field emitters are reviewed.