Yoshitada Shimizu

Preparation of BiSrCaCuO Multilayers by Use of Slower Q-switched 266 nm YAG Laser

Multilayers of Bi2Sr2Ca1Cu2Ox/Bi2Sr2Cu1Ox were prepared by pulsed laser deposition (PLD) using the fourth harmonic 266 nm YAG. Compared to an excimer laser, YAG PLD required the higher oxygen atmosphere. The higher oxygen pressure together with the lower energy generated by YAG laser collapsed the region of plume emission. In order to produce the same energy density as an excimer, only Q-switch was modulated by 2 Hz while the flash lamp kept the original repetition rate of 10 Hz. With the rate of 2 Hz, we obtained the higher energy density per pulse, and more stable laser output of the fourth harmonics, 266 nm. To characterize the multilayers, reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) were employed, and indicative of epitaxial layers with limited in-plane order. The resistivities of multilayers were measured by the Van der Pauw method, and showed the temperatures of superconducting transition, Tc0 (R=0), around 65 K on the multilayers.

Structural modulation on multilayered bismuth cuprate observed by x-ray reciprocal space mapping

Epitaxial Bi2Sr2Ca1Cu2Ox(Bi-2212)∕Bi2Sr2Cu1Ox(Bi-2201) multilayer was investigated by x-ray diffraction methods in order to investigate the effect of internal strain on structural modulation. In multilayered structure, the effect of internal strain is more prominent than in an aliovalent substitution, such as a substitution of La3+ for Sr2+. X-ray reciprocal space mapping (XRSM) was taken on the ω-2θ plane (cross-section XRSM) in order to estimate the lattice constants along the in-plane and out-of-plane directions, and θ-2θ scan was used to verify the multilayered structure. Another XRSM method, plan-view XRSM, was employed to verify the in-plane symmetry of structural modulation on the ω-ψ plane. The structural modulation was observed on both the cross-section and plan-view XRSM. The lattice constants together with the modulation vector in multilayer were varied by the multilayer periods without any substitution in the original structure.

Modulation derived satellite peaks in x-ray reciprocal mapping on bismuth cuprate superconductor film

X-ray reciprocal space mapping (XRSM) was employed to investigate epitaxial Bi2Sr2Ca1Cu2Ox(Bi-2212) film. Ordinal cross section XRSM (ω-2θ) and plan view XRSM (ω-ψ) clearly indicated asymmetric intensity distribution of four satellite peaks caused by supercell structure of Bi-2212 film. Modulation vector estimated by XRSM was q=0.2b*+0.9c*. The XRSM image simulated by sawtooth wave vector showed good agreement with asymmetric satellite peaks observed on epitaxial film.

Effect of Buffer Layer on Epitaxial Growth of YSZ Deposited on Si Substrate by Slower Q-switched 266 nm YAG Laser

Yttria-stabilized zirconia (YSZ) was grown on Si(100) substrate by pulsed laser deposition (PLD). The laser used in this study was a 266 nm YAG laser with a second function generator modulating only the Q-switch while the primary generator modulated the flash lamp (slower Q-switch). Epitaxial growth was verified on YSZ film deposited without oxygen gas followed by primary deposition in oxygen atmosphere on Si substrate with a ~0.4-nm-thin oxide layer. The crystallinity was strongly dependent on the thickness of the buffer layer deposited prior to the primary deposition of YSZ. The epitaxial growth was confirmed by scan, and ω scan (rocking curve) showed the full width at half maximum (FWHM) of 1.1 deg. The required oxygen pressure for epitaxial growth was quite high compared to that of excimer deposition.

Structural Modulation in Oxygen Deficient Epitaxial Bi2Sr2Ca1Cu2OX Observed by X-ray Reciprocal Space Mapping

X-ray reciprocal space mapping (XRSM) was employed to investigate the effect of oxygen deficiency on supercell (SC) modulation in an epitaxial Bi2Sr2Ca1Cu2Ox (Bi-2212) single layer. Cross section XRSM (ω–2θ plane) was used to estimate both the lattice constants and SC periodicity in epitaxial Bi-2212, and plan view XRSM (ω–ψ plane) to verify the symmetry of an in-plane SC structure. The SC periodicity expanded along both the b- and c-axes on the Bi-2212 film post annealed in nitrogen atmosphere.

Multigraphene growth on lead-pencil drawn sliver halide print paper irradiated by scanning femtosecond laser

Drawings were made on various types of paper using lead pencils of grades from 4H through 10B. Raman spectroscopy verified both G and D peaks on all the drawings on PC print paper, PC photopaper, kent paper, and paper for silver halide print. After irradiation with a scanning femtosecond laser, silver halide paper drawn on with a 10B lead pencil maintained its surface flatness compared with the other types of paper. Raman spectroscopy on silver print paper showed a high-intensity G peak and a low-intensity D peak. After irradiating the scanning femtosecond laser on silver halide paper drawn on with a 10B lead pencil, Raman spectroscopy showed a high-intensity G peak and less intense of D peak together with a 2D peak around 2,700 cm−1 corresponding to the existence of multigraphene.

Graphen growth: 10B lead pencil, print paper, and femtosecond laser

Wide range grade of pencils were used to draw on variety of sheet of papers. Raman spectroscopy and multimeter evaluate graphite structure and resistance of the area on the drawn paper before laser irradiation. The 10B grade of lead pencil draw on silver-halide print paper, and femtosecond laser was employed to irradiate the area of various papers drown by 10B lead pencil with varied scanning speed and laser power. At optimal conditions of laser irradiation, Raman spectroscopy verified the multi-graphene on the B10 pencil drawn silver-halide print paper irradiated by femtosecond laser.