Parallelized two-photon lithography enables submicrometer additive microfabrication
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Focus Parallelized two-photon lithography enables submicrometer additive microfabrication
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dditive microfabrication—threedimensional (3D) printing on the micron and submicron level—is relatively new and is expected to have a broad niche market especially in biomedical and wearable electronics industries. The available microprinting techniques, however, suffer from either low throughput that constrains their scaling up to mass production, or poor resolution on the micron scale. A team of researchers has increased the printing speed by more than 1000-fold without sacrificing resolution of the printed pattern. The research team at Lawrence Livermore National Laboratory (LLNL) and The Chinese University of Hong Kong, led by Sourabh K. Saha and Shih-Chi Chen, succeeded in parallelizing two-photon lithography (TPL), a higher resolution lithography method.
domain wall in the film required an electric field 3–6 times larger than in conventional BFO systems. This suggested that the defects exerted local strain that effectively pinned the domain walls in place. To study the extent of the pinning, the researchers formed domains of various sizes using a tip voltage of –9 V and a pulse duration ranging from 5 ms to 200 ms. They imaged the film with high-resolution piezoresponse force microscopy, which simultaneously captured topography and ferroelectric domains, during a span of 8904 hours. Even after more than one year, the diameters of the domains remained essentially the same. The normalized polarization retention of this system was at least one to two orders of magnitude better than other ferroelectric systems, the researchers reported. Furthermore, the stability persisted across domains of all sizes. This was surprising because small domains normally decay faster than large domains, and indicates the system’s potential for high-density memory applications that utilize small domains. With an optimally sharp tip, the researchers estimate they
may be able to achieve a storage density up to 1300 Gbit/in2. “[This] work shows a promising path forward to producing superior high-density nonvolatile memories based on ferroelectric materials,” according to Matthew Dawber, an expert on ferroelectric materials at Stony Brook University, The State University of NewYork, who was not associated with this project. “[The researchers] show that introduced defects can help stabilize tiny domains for very long times. This is a win-win, normally it’s hard work to get rid of defects, and conversely, it’s not too hard to introduce them,” Dawber says. The team focused on one kind of defect in this research, but Seidel says that there are many options for pinning domain walls and further improvement may be possible. “Another interesting aspect is the intrinsic properties of domain walls themselves, which can be exploited for nanoelectronics,” he says. “[Domain walls have] been known for a long time, but insight into their intrinsic properties and functionality has been investigated in more detail only recently.” Kendra Redmond
TPL is typical
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