TY  - JOUR
A1  - Yadavalli, Nataraja Sekhar
A1  - Linde, Felix
A1  - Kopyshev, Alexey
A1  - Santer, Svetlana
T1  - Soft matter beats hard matter - rupturing of thin metallic films induced by mass transport in photosensitive polymer films
JF  - ACS applied materials & interfaces
N2  - 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.
KW  - metal/polymer interface
KW  - rupturing of metal film
KW  - forces generated during surface relief grating formation
KW  - in situ atomic force microscopy
KW  - azobenzene
KW  - two beam interferometry
Y1  - 2013
U6  - https://doi.org/10.1021/am4006132w
SN  - 1944-8244
VL  - 5
IS  - 16
SP  - 7743
EP  - 7747
PB  - American Chemical Society
CY  - Washington
ER  -