A new method for measurement of the toughness of brittle thin films

A new method is proposed to measure the toughness of brittle thin films pre pared on substrates. By partly etching the substrate under one edge of film , an overhang part of the film projecting out over the edge of substrate wa s prepared as the specimen to measure the film toughness. Mechanical load w as applied on this specimen by pushing down both sides of the notch, which was grooved from the free edge of the film to be the starter of crack exten sion. The crack extension behavior was recorded as the load-crack extension diagram, which was compared to the results of numerical simulations for th e crack extension with the assumed value of the toughness. With the corresp ondence of the load-crack extension diagrams which were obtained by both ex periment and simulation, the optimum value of assumed toughness could be de termined as the result of measurement. As an example of practical applicati on, the toughness of diamond films deposited on silicon substrate was obtai ned. (C) 2001 Elsevier Science B.V. All rights reserved.