Abstract

We present the results of theoretical modeling and experimental testing of a diamond thin film sensor for flow studies. It is shown that the high thermal conductivity of a diamond film can enhance the frequency response of the flow sensor. One-dimensional heat diffusion equation was solved using the finite difference method for determining the frequency response. Two different sensor structures were analyzed: a Ni film on a quartz substrate (Ni/Q) and an intermediate layer of diamond film between the Ni film and quartz substrate (Ni/D/Q). The theoretical model predicts a frequency response for the Ni/D/Q sensor higher than that of the Ni/Q sensor. Diamond films for the Ni/D/Q sensor were deposited onto the quartz substrate by microwave plasma-enhanced chemical vapor deposition (MPECVD). The conditions for a high nucleation density were established for obtaining a continuous diamond thin film. A subsequent nickel film patterned and deposited serves as the sensing arm in the bridge circuit of an anemometer. The measured frequency response of the Ni/D/Q sensor combination is greater than 220 kHz, as compared to the Ni/Quartz sensor response of 120 kHz.

© 1995 Optical Society of America