Nanopatterning of diarylethene films via selective dissolution of one photoisomer

Abstract

The ability to pattern nanometric features on various substrates with high throughput, accuracy, and uniformity is the key driving force enabling novel applications in nanophotonics, nanoelectronics, nano-electro-mechanical systems, and nanofluidics. Patterning via Optical Saturable Transitions (POST) is an optical nanopatterning technique that circumvents the far-field diffraction limit by exploiting the linear switching properties of thermally stable photochromic molecules. Previously, POST was enabled by an electrochemical oxidation “locking step.” In this letter, we report an electrode-free “locking step” that exploits the difference in solubility between the two isomeric states of a photochromic molecule in a polar solvent. The reported method obviates the need for a conducting underlayer and also reduces the number of required steps. Using this method, we demonstrated isolated lines of width ∼λ/4 and spacing between features as small as ∼λ/2.5 for an exposure wavelength of λ.

Spirothiopyran-Based Reversibly Saturable Photoresist

“…However, having a photochromic layer separate from the photoresist limits patterning to 2D. The use of electrochemically induced oxidation states or exploitation of slight differences in solubility between the two isomer forms , allows for the diarylethenes to be used as the resist itself. While the high extinction coefficient of the diarylethene molecule has effectively restricted even these strategies to 2D, such work strongly suggests that photochromic molecules are, in principle, prime candidates for developing a parallelized subdiffraction 3D writing system due to their fast reversible switching and low saturation thresholds.…”

Selection of the confining beam for laser direct writing with scanning absorbance modulation

“…During recent decades, a novel idea called absorbance modulation optical lithography (AMOL) [9][10][11][12][13][14][15][16], which is inspired by the stimulated emission depletion (STED) fluorescence microscopy [17], is proposed to obtain sub-wavelength patterns beyond the diffraction limit with far-field optics. A kind of photochromic material and two light beams, called writing beam and confining beam, respectively, are used in this technology.…”

“…The confining beam used in AMOL is typically a standing wave field, i.e. interference fringes [10][11][12][13][14]. Thus, it is suitable only for static exposure to generate patterns of gratings and is lack of an ability to produce freely designed patterns.…”

Patterning via optical-saturable transformations: A review and simple simulation model

“…Hence, it allowed us to realize preliminary experimental results from this approach. 5 We have recently developed a simple model to describe POST, which allows us to explain the observed experimental results well. The salient features of this model and related simulation analysis are summarized here.…”