PIEZORESISTIVE PROPERTY OF CVD DIAMOND FILMS

Electrical and piezoresistive properties of chemical vapor-deposited b oron-doped p-type polycrystalline diamond films were investigated. The p-type polycrystalline diamond films of about 2 mu m thickness were g rown on a flat insulating polycrystalline diamond substrate using a co nventional microwave plasma CVD system. The optimized p-type polycryst alline CVD film exhibited similar quality to homoepitaxial single crys talline diamond film with activation energy of 0.31-0.33 eV and small effects of grain boundaries. Piezoresistors (500 mu m long and 50 mu m wide) constituted from the optimized p-type polycrystalline diamond f ilms were fabricated on diaphragm structure using photolithography and reactive-ion etching in an oxygen plasma. Relative change of the elec trical resistance (Delta R/R-0) of the p-type diamond piezoresistor wa s almost proportional to the applied strain. Gauge factor K for the p- type diamond piezoresistor was derived to be similar to 1000 at room t emperature and > 700 even at 200 degrees C. (C) 1997 Elsevier Science S.A.