The crystal orientation relation and macroscopic surface roughness in hetero-epitaxial graphene grown on Cu/mica.

Clean, flat and orientation-identified graphene on a substrate is in high demand for graphene electronics. In this study, the hetero-epitaxial graphene growth on Cu(111)/mica(001) by chemical vapor deposition is investigated to check the applicability for top-gate insulator research on graphene, as well as graphene channel research, by transferring graphene on to SiO2/Si substrates. After adjusting the graphene growth conditions, the surface roughness of the graphene/Cu/mica substrate and the average smoothed areas are ∼0.34 nm and ∼100 µm(2), respectively. The orientation of graphene in the graphene/Cu/mica substrate can be identified by the hexagonal void morphology of Cu. Moreover, we demonstrate a relatively high mobility of ∼4500 cm(2) V(-1) s(-1) in graphene transferred on the SiO2/Si substrate. These results suggest that the present graphene/Cu/mica substrate can be used for top-gate insulator research on graphene.

Reflection confocal microscope readout system for three-dimensional photochromic optical data storage.

We propose to use a reflection confocal microscope (RCM) as a readout system for digital data stored in a three-dimensional (3D) photochromic optical memory. We describe the merits and the difficulties for 3D optical memory that are associated with the use of such a RCM.It is shown by means of 3D Fourier space analysis that successful reading of 3D data can be obtained by selection of the appropriate parameter for the RCM.The system parameters include the numerical aperture of the objective lens and the wavelength of the light used for analysis (reading). Experimental results of multilayer recording and reflection confocal reading in photochromic-molecule-doped poly(methyl methacrylate) are presented. Good-contrast images are obtained.

Nondestructive readout of a three-dimensional photochromic optical memory with a near-infrared differential phase-contrast microscope.

A three-dimensional (3D) rewritable optical memory using photochromic material is described for high-density memory. The bits are recorded in a 3D volume of photochromic material. A transformation of the photochromic molecule between two isomers with different absorption spectra can be stimulated by irradiation with appropriate wavelengths. We show that a nondestructive readout of photochromic memory is possible by use of a small difference in the refractive index of the photochromic isomers in the near-IR range. For this purpose a near-IR laser-scan differential phase-contrast microscope is used. Experimental results of 3D recording and nondestructive reading are presented.