TY  - JOUR
A1  - König, Tobias
A1  - Papke, Thomas
A1  - Kopyshev, Alexey
A1  - Santer, Svetlana
T1  - Atomic force microscopy nanolithography fabrication of metallic nano-slits using silicon nitride tips
JF  - Journal of materials science
N2  - In this paper, we report on the properties of nano-slits created in metal thin films using atomic force microscope (AFM) nanolithography (AFM-NL). We demonstrate that instead of expensive diamond AFM tips, it is also possible to use low cost silicon nitride tips. It is shown that depending on the direction of scratching, nano-slits of different widths and depths can be fabricated at constant load force. We elucidate the reasons for this behavior and identify an optimal direction and load force for scratching a gold layer.
Y1  - 2013
U6  - https://doi.org/10.1007/s10853-013-7188-x
SN  - 0022-2461
VL  - 48
IS  - 10
SP  - 3863
EP  - 3869
PB  - Springer
CY  - New York
ER  - 
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  - 
TY  - JOUR
A1  - Kopyshev, Alexey
A1  - Galvin, Casey J.
A1  - Genzer, Jan
A1  - Lomadze, Nino
A1  - Santer, Svetlana
T1  - Opto-mechanical scission of polymer chains in photosensitive diblock-copolymer brushes
JF  - Langmuir
N2  - In this paper we report on an opto-mechanical scission of polymer chains within photosensitive diblock-copolymer brushes grafted to flat solid substrates. We employ surface-initiated polymerization of methylmethacrylate (MMA) and t-butyl methacrylate (tBMA) to grow diblock-copolymer brushes of poly(methylmethacrylate-b-t-butyl methacrylate) following the atom transfer polymerization (ATRP) scheme. After the synthesis, deprotection of the PtBMA block yields poly(methacrylic acid) (PMAA). To render PMMA-b-PMAA copolymers photosensitive, cationic azobenzene containing surfactants are attached to the negatively charged outer PMAA block. During irradiation with an ultraviolet (UV) interference pattern, the extent of photoisomerization of the azobenzene groups varies spatially and results in a topography change of the brush, i.e., formation of surface relief gratings (SRG). The SRG formation is accompanied by local rupturing of the polymer chains in areas from which the polymer material recedes. This opto-mechanically induced scission of the polymer chains takes place at the interfaces of the two blocks and depends strongly on the UV irradiation intensity. Our results indicate that this process may be explained by employing classical continuum fracture mechanics, which might be important for tailoring the phenomenon for applying it to poststructuring of polymer brushes.
Y1  - 2013
U6  - https://doi.org/10.1021/la403241t
SN  - 0743-7463
VL  - 29
IS  - 45
SP  - 13967
EP  - 13974
PB  - American Chemical Society
CY  - Washington
ER  -