Analysis of piezoresistive properties of CVD-diamond films on silicon

The piezoresistive properties of CVD-diamond are still very much in discuss ion since not only the materials energy band structure properties have to b e considered but also the grain boundaries and internal stress distribution . Here, the experimental Piezoresistive properties of CVD-diamond-on-silico n layers for free standing structures have been investigated comprehensivel y. The longitudinal gauge factor k(1) has been extracted using freestanding diamond cantilevers on silicon. The piezoresistors have been grown selecti vely onto the surface of diamond cantilevers near the mechanical suspension and doped with boron (acceptor). The electrical contacts are based on the tunneling mechanism with a silicon-based multilayer metalization leading to a linear IV-characteristic. Gauge factor values, k(1) have been extracted on various structures with different doping concentrations and diamond film quality (highly oriented and textured, textured, randomly oriented), depen ding on temperature (room temperature, -350 degreesC) and intrinsic stress. Highly oriented and textured films with grain sizes between 3 and 10 mum h ave been used to realize,single grain' resistor structures enabling the inv estigation of grain boundaries in the electrical current path of the piezor esistor. Raman measurements have been performed to measure the intrinsic st ress in the diamond grains. Gauge factors, k(1) of between 4 and 28 have be en extracted. Largest k(1) values were observed on piezoresistors on highly oriented and textured diamond (HOD) films. Results of this work have been used in piezoresistive sensor applications. (C) 2001 Elsevier Science B.V. All rights reserved.