Fracture Toughness Measurement of Transparent Conductive Films Deposited on Polymer Substrates
In the field of aerospace transparencies,the fracture toughness of thin transparent conductive films on thick polymer substrates is the key mechanical property to quantify the crack resistance.Therefore,the fracture toughness is evaluated based on nanoindentation and channel cracking tests.Indium tin oxide(ITO)films are deposited on polycarbonate(PC)substrates by magnetron sputtering.Brittle fracture is induced on the ITO films by nanoindentation,and fracture toughness is calculated by integrating the load-depth curves;crack strain of channel crack is obtained through the in situ scanning electron microscopy(SEM)test under uniaxial tension,and fracture toughness is calculated based on the mechanical model.The results show that relatively consistent fracture toughness is obtained by the above two methods without considering residual stresses,with the fracture toughness of 500 nm thick ITO films ranging from 1.62 to 1.81 MPa·m1/2.Of these,the channel cracking test is preferable for determining fracture toughness for thin films below 200 nm thick or films with large residual stresses.
transparent conductive films on polymer substratesfracture toughnessnanoindentationchannel crackingin situ test
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