Light, (CCD) camera, action! Time‐resolved synchrotron X‐ray scattering measurements revealed that linear polarized light (LPL) caused reorientation of phase‐separated mesoscopic amorphous cylinders within a light‐responsive liquid crystalline (LC) matrix domain of a diblock copolymer (see scheme). Cooperative and synchronized motions occur at two hierarchical structures of the LC layer (molecular level) and the polymer domains (mesoscopic level).

The pathways toward linearly polarized light (LPL)-induced alignment switching in a diblock copolymer film composed of liquid crystalline (LC) azobenzene (Az) and amorphous poly(butyl methacrylate) (PBMA) blocks were studied in detail using polarized UV−vis absorption spectroscopy, grazing incidence small-angle X-ray scattering measurements, and polarized optical microscopy and transmission electron microscopy observations. The hierarchical structures of microphaseseparated cylinders of PBMA in a smectic LC Az layer matrix were prealigned by LPL and then irradiated by orthogonal LPL, which resulted in alignment switching to the orthogonal direction. In this process, the large prealigned domains were divided into substantially smaller domains at the submicrometer level, and then the structures were realigned in the orthogonal direction in a strongly cooperative manner, most likely through the domain rotation mechanism. The alignment change consisted of three stages: (i) fluctuations in the smectic layer of LC Az side chains in the initial state and breaking up of smaller grains to the submicrometer level before the orientation change (induction period), (ii) actual rotation of the divided domains driven by the photoinduced reorientation of Az mesogens (action period), and (iii) slower fusion and growth of smaller domains in the orthogonally realigned direction (postgrowth period). New aspects of dynamic self-assembly behavior in which different hierarchical structures are involved are proposed.

The realignment process of azobenzene-containing liquid crystalline (LC) block copolymer films by irradiation with linearly polarized light (LPL) was investigated in detail by time-resolved grazing incidence X-ray scattering measurements using a synchrotron beam. By using a newly synthesized diblock copolymer possessing a poly­(hexyl methacrylate (PHMA) block with a lowered glass transition temperature (T g = −5 °C), intense X-ray scattering signals were obtained, which favorably provided precise and detailed time course profiles and information on the interplay between the hierarchical structures involved along the realignment process. The LC layers were softened and fluctuated at an early stage by LPL irradiation which induced shrinkage of the cylinder to cylinder distance of microphase separation patterns before the alignment change. Interestingly, the ordering process of the MPS cylinder array of larger hierarchical structure proceeded faster than that of the azobenzene LC layer of smaller feature size in the realigned state. Decisive evidence was obtained to support the subdomain rotation mechanism in the realignment process.

A series of block copolymers composed of an amorphous poly(butyl methacrylate) (PBMA) block connected with an azobenzene (Az)-containing liquid crystalline (PAz) block were synthesized by changing the chain length and polymer architecture. With these block copolymer films, the dynamic realignment process of microphase separated (MPS) cylinder arrays of PBMA in the PAz matrix induced by irradiation with linearly polarized light was studied by UV-visible absorption spectroscopy, and time-resolved grazing incidence small angle X-ray scattering (GI-SAXS) measurements using a synchrotron beam. Unexpectedly, the change in the chain length hardly affected the realignment rate. In contrast, the architecture of the AB-type diblock or the ABA-type triblock essentially altered the realignment feature. The strongly cooperative motion with an induction period before realignment was characteristic only for the diblock copolymer series, and the LPL-induced alignment change immediately started for triblock copolymers and the PAz homopolymer. Additionally, a marked acceleration in the photoinduced dynamic motions was unveiled in comparison with a thermal randomization process.

This research investigated the mechanism for the reduction of grown-in defects in Czochralski silicon wafers by high-temperature annealing for various annealing temperatures and ambients. Annealing at 1300ЊC in an argon ambient could eliminate not only surface grown-in defects crystal originated particles (COPs), but also bulk grown-in defects at 100 m depth from the surface. Annealing at 1200 and 1250ЊC in an argon ambient also eliminated COPs, but their effects on bulk grown-in defects were limited to shallower regions from the surface with lower annealing temperatures. On the other hand, annealing in an oxygen ambient could not reduce grown-in defects even at 1300ЊC. It is thought that removal of oxide films on the inner walls of grown-in defects is the first step in the reduction process of the grown-in defects. Oxygen annealing cannot remove the oxide film, but rather enlarges them, and the grown-in defects remain. Argon annealing can remove the oxide films, and subsequent absorption of silicon self-interstitials reduces the grown-in defects.