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edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 23 NO. 1 48 researchers primarily focused on trying tomake their IC’s gate insulator and substrate more resistant to radiation. “When designing our radiation-immune IC, we drew inspiration fromthe liquidmetal robot T-1000 in the classic science fictionmovie ‘Terminator 2,’” Zhang said. “Weused a quasi-liquid gate insulator, ion gel, and a ‘transparent’ substrate. Ion gel gates promote the formationof electrical double layers at the surface of theCNT channel, whichpro- vides amuch higher gate efficiency and allows the gate to be recoveredafter suffering radiationdamage. Meanwhile, by replacing the Si/SiO 2 substrate of a conventional FET with a thin polyimide substrate, we eliminated effects resulting from high energy particles being scattered and reflected in a heavy and thick substrate.” “The transistors and ICs demonstrated in this work are just prototypes,” Zhang added. “We will now try to improve the performance and integration density of the IC by scaling the CNT FETs and optimizing the structure and process. In fact, this kind of radiation-hardened IC only has practical value if its performance and density reach certain thresholds.” For more information, visit english.pku.edu.cn . MOVING MICROSCOPY BEYOND THE RESOLUTION LIMIT A Polish-Israeli team from the physics faculty of the University of Warsaw and the Weizmann Institute of Science has produced a significant achievement in fluo- rescent microscopy. In the pages of the journal Optica the team presented a new method of microscopy which, in theory, has no resolution limit. The team has demon- strated a fourfold improvement over the diffraction limit in practice. The continued development of biological sciences, microelectronics, and medicine requires the ability to examine ever smaller objects. Scientists need to see into the structure of, and the mutual relationships between, proteins in cells, for example. At the same time, the samplesbeingobservedshouldnot differ fromthenatural- ly occurring structures, which rules out the use of aggres- sive procedures and reagents. Although it revolutionized the natural sciences, the classical optical microscope is clearly insufficient today. Due to the wave nature of light, an optical microscope does not allow imaging structures smaller than about 250 nm. As a result, objects closer to each other than half the wavelength of light (which is about 250 nm for green light) cannot be discerned. This phenomenon, known as the diffraction limit, is one of the main obstacles in observing the tiniest structures that sci- entists have long attempted to overcome. Electronmicro- scopes provide orders of magnitude better resolution but only allow the examination of inanimate objects since the object must be placed in a vacuum and bombarded by an electron beam. For this reason, electron microscopy cannot be used for studying living organisms. This iswhere fluorescence microscopy steps in, hence the rapid devel- opment of super-resolution fluorescence microscopy as a field of physical sciences and two Nobel Prizes awarded for related research in 2008 and 2014. Currently several fluorescencemicroscopy techniques are available, and someof themhavebecomewidespread. Some methods, such as photoactivated localization microscopy, stochastic optical reconstruction micros- copy, or stimulated emission depletion microscopy, are characterized by ultrahigh resolution and provide resolu- tion down to a dozen nanometers or so. However, these techniques require long exposure times and a complex specimen preparation procedure. Other techniques, such A carbon nanotube FET could enhance the radiation resistance of ICs. Microtubules in a fixed cell sample. Upper left: image scanning microscopy, lower right: super-resolution optical fluctuation image scanning microscopy after Fourier reweighting.