ABSTRACT
Table 8.1 summarizes the development and the state of the art of polymerization-based SPINs to produce fine patterns and increase resolution.The challenge of SPIN technology is to find critical materials selectively responding to the IDB and the IHB, which can preclude from the simultaneous excitation of the induction process for polymerization and the inhibition process for polymerization inhibition by either of these two beams. Additionally, intrinsic characteristic for each inhibition process has set up limitation in terms of inhibition strength weakened by undesired processes. For example, the inhibition process employing the photoluminescence process or the photodeactivation process, as listed in the Table 8.1, requires a high light intensity (as large as 1~100 MW/cm2) to realize the photoinhibition, which may cause the pronounced nonlinear absorption with the IHB for polymerization. Moreover, some inhibition processes have an inherent disability for the spatial inhibition, such as that the photochromism cannot implement three-dimensional SPIN. As a consequence, for certain photopolymerization, the selection of a suitable photoinhibition process is the precondition to realize the SPIN. In the next two sections, we will focus on the inhibition process based on the photoradical generation from inhibitors and present its role in reducing the feature size of polymerized patterns and increasing resolution, which potentially leads to high-density optical recording. In this case, the IHB with a doughnut shape produces inhibitor radicals as the inhibition species to react with activated primary radicals or carbon-centered free radicals for terminating the polymerization in the outer ring of the focal spot, leaving a polymerization volume in the center.
