The interplay between residual stress state, cohesive and adhesive properties of coatings on substrates is reviewed in this article. Attention is paid to thin inorganic coatings on polymers, characterized by a very high hygro-thermo-mechanical contrast between the brittle and stiff coating and the compliant and soft substrate. An approach to determine the intrinsic, thermal and hygroscopic contributions to the coating residual stress is detailed. The critical strain for coating failure, coating toughness and coating/substrate interface shear strength are derived from the analysis of progressive coating cracking under strain. Electrofragmentation and electro-fatigue tests in situ in a microscope are described. These methods enable reproducing the thermo-mechanical loads present during processing and service life, hence identifying and modeling the critical conditions for failure. Several case studies relevant to food and pharmaceutical packaging, flexible electronics and thin film photovoltaic devices are discussed to illustrate the benefits and limits of the present methods and models.

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Damage occurring under tensile loading and the resulting increase in electrical resistance of tin-doped indium oxide and amorphous graphite coatings on various polymer substrates are investigated, using an electrofragmentation method in situ in an optical microscope. The electrical resistance is modeled as a function of damage state assuming that the resistance of coating cracks is proportional to their opening, and that there exists a conducting path of constant thickness at the coating/substrate interface across the crack. The model reproduces the experimental data with good accuracy apart from the damage initiation and saturation stages where it underestimates the measured coating resistance. This is due to the presence of stable cracks of finite length in the initiation stage and delamination in the saturation stage. Impedance spectroscopy measurements confirm the purely resistive nature of the conducting path, whose resistivity is found to be three to four orders of magnitude higher than that of the uncracked coating.

A simple and most promising oxide-assisted catalyst-free method is used to prepare silicon nitride nanowires that give rise to high yield in a short time. After a brief analysis of the state of the art, we reveal the crucial role played by the oxygen partial pressure: when oxygen partial pressure is slightly below the threshold of passive oxidation, a high yield inhibiting the formation of any silica layer covering the nanowires occurs and thanks to the synthesis temperature one can control nanowire dimensions.