@article{LindeYadavalliSanter2013,
  author    = {Linde, Felix and Yadavalli, Nataraja Sekhar and Santer, Svetlana},
  title     = {Conductivity behavior of very thin gold films ruptured by mass transport in photosensitive polymer film},
  series = {APPLIED PHYSICS LETTERS},
  volume    = {103},
  journal   = {APPLIED PHYSICS LETTERS},
  number    = {25},
  publisher = {AMER INST PHYSICS},
  address   = {MELVILLE},
  issn      = {0003-6951},
  doi       = {10.1063/1.4850595},
  pages     = {4},
  year      = {2013},
  abstract  = {We report on conductivity behavior of very thin gold layer deposited on a photosensitive polymer film. Under irradiation with light interference pattern, the azobenzene containing photosensitive polymer film undergoes deformation at which topography follows a distribution of intensity, resulting in the formation of a surface relief grating. This process is accompanied by a change in the shape of the polymer surface from flat to sinusoidal together with a corresponding increase in surface area. The gold layer placed above deforms along with the polymer and ruptures at a strain of 4\%. The rupturing is spatially well defined, occurring at the topographic maxima and minima resulting in periodic cracks across the whole irradiated area. We have shown that this periodic micro-rupturing of a thin metal film has no significant impact on the electrical conductivity of the films. We suggest a model to explain this phenomenon and support this by additional experiments where the conductivity is measured in a process when a single nanoscopic scratch is formed with an AFM tip. Our results indicate that in flexible electronic materials consisting of a polymer support and an integrated metal circuit, nano-and micro cracks do not alter significantly the behavior of the conductivity unless the metal is disrupted completely. (C) 2013 AIP Publishing LLC.},
  language  = {en}
}
@article{YadavalliLindeKopyshevetal.2013,
  author    = {Yadavalli, Nataraja Sekhar and Linde, Felix and Kopyshev, Alexey and Santer, Svetlana},
  title     = {Soft matter beats hard matter - rupturing of thin metallic films induced by mass transport in photosensitive polymer films},
  series = {ACS applied materials \& interfaces},
  volume    = {5},
  journal   = {ACS applied materials \& interfaces},
  number    = {16},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1944-8244},
  doi       = {10.1021/am4006132w},
  pages     = {7743 -- 7747},
  year      = {2013},
  abstract  = {The interface between thin films of metal and polymer materials play a significant role in modern flexible microelectronics viz., metal contacts on polymer substrates, printed electronics and prosthetic devices. The major emphasis in metal polymer interface is on studying how the externally applied stress in the polymer substrate leads to the deformation and cracks in metal film and vice versa. Usually, the deformation process involves strains varying over large lateral dimensions because of excessive stress at local imperfections. Here we show that the seemingly random phenomena at macroscopic scales can be rendered rather controllable at submicrometer length scales. Recently, we have created a metal polymer interface system with strains varying over periods of several hundred nanometers. This was achieved by exploiting the formation of surface relief grating (SRG) within the azobenzene containing photosensitive polymer film upon irradiation with light interference pattern. Up to a thickness of 60 nm, the adsorbed metal film adapts neatly to the forming relief, until it ultimately ruptures into an array of stripes by formation of highly regular and uniform cracks along the maxima and minima of the polymer topography. This surprising phenomenon has far-reaching implications. This is the first time a direct probe is available to estimate the forces emerging in SRG formation in glassy polymers. Furthermore, crack formation in thin metal films can be studied literally in slow motion, which could lead to substantial improvements in the design process of flexible electronics. Finally, cracks are produced uniformly and at high density, contrary to common sense. This could offer new strategies for precise nanofabrication procedures mechanical in character.},
  language  = {en}
}