Piezoresistive Property of p-type CVD Diamond Films

Abstract

Electrical and piezoresistive properties of chemical-vapor-deposited boron-doped p-type polycrystalline diamond films were investigated. The p-type polycrystalline diamond films of about 2μm thickness were grown on a flat insulating polycrystalline diamond layer using a conventional microwave plasma CVD system. The p-type CVD diamond film exhibited similar quality as homoepitaxial single crystalline diamond film with activation energy of 0.31-0.33eV. Piezoresistor (500μm long and 50μm wide) constituted from the optimized p-type polycrystalline diamond films were fabricated on diaphragm structure using photolithography and reactive-ion etching in an oxygen plasma. Relative change of the electrical resistance (-ΔR/R₀) of the diamond piezoresistor was almost proportional to the apphed strain ε, Gauge factor K for the p-type diamond piezoresistor was derived to be about 1000 at room temperature and above 700 even at 473K.