Jaihyung Won

PHOTOTHERMAL FIXATION OF LASER-TRAPPED POLYMER MICROPARTICLES ON POLYMER SUBSTRATES

Photothermal fixation of polymer microparticles onto a polymer substrate is demonstrated by using a laser manipulation technique. Individual microparticles were sequentially trapped by a 1064 nm Nd3+:yttrium–aluminum–garnet (YAG) laser light and pressed on a polymer substrate. Dye molecules that are doped into a substrate or dissolved into a solvent absorb the second harmonic pulse of a Nd3+:YAG laser and convert the absorbed light to thermal energy. It is considered that the local temperature elevation led to the local melting of the microparticle and substrate, resulting in mutual adhesion. The processes and microfixation conditions are presented, and the mechanism is discussed.

Effect of boron doping on the crystal quality of chemical vapor deposited diamond films

Boron doping of chemical vapor deposited (CVD) diamond films plays an important role for modification of their electrical properties, as well as it improves crystallinity of the resulting films. A comparative study of crystalline quality has been made for boron doped and undoped CVD diamond. It is also found that the edge emission near 240 nm in cathodoluminescence (CL) is significantly intensified by boron incorporation. It is observed that the hydrogen plasma etching rate of B‐doped CVD diamond is much smaller than the etching rate of undoped diamond. This proves the fact, that boron incorporation during CVD growth of diamond films can lead to better crystal quality.

The investigation of defect formation in chemical vapor deposited diamond using photoluminescence by ultraviolet synchrotron radiation

Photoluminescence (PL) of microwave assisted chemical vapor deposited (CVD) diamond was obtained using ultraviolet synchrotron radiation. The PL spectrum of the 5RL band (intrinsic defect), which cannot be detected in cathodoluminesence, was observed for both undoped (as grown) and boron doped (200 ppm) CVD diamond. The defect formation was characterized in the thin near‐surface layer. The peak of boron related origin (2.3 eV) was detected in the boron doped CVD while band A (2.9 eV) was not observed. After remote hydrogen plasma treatment (RHPT), the near‐surface defect related peak in the PL spectra disappeared. During RHPT the diamond was rehybridized by hydrogen radicals without etching.

Investigation of distribution of defects and impurities in boron-doped CVD diamond film by cathodoluminescence spectroscopy

Abstract Distribution of defects and impurities was investigated by cathodoluminescence spectroscopy on as-grown boron-doped diamond film synthesized by microwave plasma chemical vapor deposition method. Luminescence profiles in a boron-doped diamond film were observed by cross-section CL images. Intense emission of 535 nm (~2.32 eV) band was found in a thin layer of the growth surface and in a rather thick layer of interface to the silicon substrate. Complementary to the 535-nm emission, the edge emission appeared in the bulk region excluding the surface layer. The origination of the 535-nm band can be explained by a boron-vacancy center.

Structural study of chemical-vapor-deposited diamond surface by high-resolution electron microscopy

A structural study of the chemical-vapor-deposited (CVD) diamond surface using high-resolution electron microscopy (HREM) is presented. The CVD diamond used for HREM study was directly deposited onto molybdenum grids by a microwave plasma-assisted chemical vapor deposition method. The HREM images reveal a thin amorphous layer of which average thickness is about 0.8–1.2 nm on the as-grown diamond surface, whereas the average thickness of the surface amorphous layer is decreased to less than 0.4–0.5 nm for the samples annealed in air following deposition. When the samples annealed in air were exposed to hydrogen plasma for 10 min, a distinct damaged layer on the diamond surface was observed. HREM study demonstrates that such a damaged layer consists of amorphous solid and small diamond bumps, and its thickness is about 1.5–2 nm. It is also found that hydrogen plasma has a much higher etching speed in the rough regions, edges and protuberances than that in the smooth regions on the diamond surface.

Effects of remote hydrogen plasma treatment (RHPT) on ion-implanted CVD diamond☆

Abstract Ion implanted poly- and single-crystal CVD diamond, following remote hydrogen plasma treatment (RHPT), was investigated using cathodoluminescence (CL) by a 5–20-keV CL electron energy (0.3–4.0 μm) penetration measuring technique at 30 K. RHPT at nearly room temperature created a shower of hydrogen radicals. After the RHPT, the intensity of the 5RL center (intrinsic defect of C) was diminished without formation of the 2.16-eV center (N-V center) which is caused by thermal annealing. It seems that the diamond was rehybridized by RHPT in a way other than thermal annealing. It was observed that the change in the CL spectra proceeded from the surface layer to the deep layer with irradiation time, which would be due to diffusion of the hydrogen radical into diamond. Photoluminescence (PL) was also carried out for characterization of the near surface layer of as-grown CVD diamond. The near surface layer of 40 A contained a substantially higher density of intrinsic defects. Defect formation coupled with a vacancy or nitrogen were not found in the near surface layer after ion implantation.

Remote hydrogen plasma treatment (RHPT) of ion implanted CVD diamond

Abstract Defects formation of chemical vapor deposition (CVD) diamond on 4 He 2+ irradiation and after remote hydrogen plasma treatment (RHPT) were investigated by cathodoluminescence (CL). For the RHPT, the substrate was kept away from direct plasma ball while it was treated for 0.5 to 2 h. As calculated in the TRIM simulation, the light elements of 4 He 2+ can be penetrated into the diamond bulk structure at 3–4 μm depth. The effects of the implantation region were observed when 5–20 keV electron energy (understanding of 0.3–4.0 μm) of CL measurement was irradiated to diamond at a temperature of 80 K. After the RHPT, rehybridization of irradiation damaged diamond was studied. The intensity of 5RL center (intrinsic defect of C) was diminished. The 2.16 eV center (N-V center) occurring usually by annealing could not be seen after RHPT. It seemed that the diamond was not influenced to reconvert its structure by high temperature annealing. The diamond was rehybridized by hydrogen radicals without etching by the RHPT.

Electron microscopic analysis of chemical-vapour-deposited diamond surface by a novel method

Abstract A novel method has been employed to study chemical-vapour-deposited (CVD) diamond surfaces using high-resolution electron microscopy (HREM) without thinning the specimens. The CVD diamond used for the HREM study was directly deposited onto molybdenum grids by microwave plasma-assisted CVD. The HREM images reveal a thin amorphous layer with an average thickness of about 0.8–1.2 nm on the as-grown diamond surface, whereas the average thickness of the surface amorphous layer is decreased to less than 0.4–0.5 nm for samples annealed in air following deposition. When the samples annealed in air are exposed to a hydrogen plasma for 10 min, a distinct damaged layer on the diamond surface is observed. The HREM study demonstrates that this damaged layer consists of an amorphous phase and small diamond bumps, with a thickness of about 1.5–2 nm. The experimental results also illustrate that transmission electron microscopy (TEM) is convenient and effective for the characterization of the surface or near-surface structural features of polycrystalline thin films as long as the grains can be grown on TEM grids.