Search Results - (Author, Cooperation:Y. W. Zheng)

2013-07-05

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; Cell Differentiation ; Cell Lineage ; Drug-Induced Liver Injury/therapy ; Endothelial Cells/cytology/metabolism/transplantation ; Gene Expression Profiling ; Humans ; Induced Pluripotent Stem Cells/*cytology/metabolism/transplantation ; Liver/*blood supply/embryology/metabolism/*physiology ; Liver Failure/therapy ; Liver Transplantation ; Mesoderm/cytology/metabolism/transplantation ; Mice ; Regenerative Medicine/*methods ; Tissue Culture Techniques

1089-7550

AIP Digital Archive

Physics

In this study, laser cleaning efficiencies to remove 2.5 μm particles have been investigated with different incident angles ranging from 0° to 60°. It is found that when the laser light irradiated normally to the substrate surface, the particle could be removed most efficiently. In this direction, the cleaning efficiency was also most sensitive to the light intensity. A sharp drop of cleaning efficiency occurred with a small change of the incident angle. Theoretical calculations based on the Lorentz–Mie theory and an accurate solution of the boundary problem, indicate that the light intensity near the contacting point is sensitive to the incident angle even though the incident light is uniform. © 2001 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The experimental analysis of dry laser cleaning efficiency is done for certified spherical particle (SiO2, 5.0, 2.5, 1.0, and 0.5 μm) from different substrates (Si, Ge, and NiP). The influence of different options (laser wavelength, incident angle, substrate properties, i.e., type of material, surface roughness, etc.) on the cleaning efficiency is presented in addition to commonly analyzed options (cleaning efficiency versus laser fluence and particle size). Found laser cleaning efficiency demonstrates a great sensitivity to some of these options (e.g., laser wavelength, angle of incidence, etc.). Partially these effects can be explained within the frame of the microelectronics engineering (MIE) theory of scattering. Other effects (e.g., influence of roughness) can be explained along the more complex line, related to examination of the problem "particle on the surface" beyond the MIE theory. The theory of dry laser cleaning, based on one-dimensional thermal expansion of the substrate, demonstrates a great sensitivity of the cleaning efficiency on laser pulse shape. For the reasonable pulse shape this theory yields the threshold fluence by the order of magnitude larger than the experimental one. At the same time the theory, which takes into account the near-field optical enhancement and three-dimensional thermal expansion effects, yields the correct values for threshold. © 2001 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Laser cleaning is a prospective cleaning method that can be widely used in microelectronics fabrication, archive restoration, and optical apparatus cleaning. Removal of particles from a solid substrate is an important aspect of laser cleaning. Although many studies have been carried out on this subject, few of them are objected to the characterization of the ejected particles in laser cleaning. In this article, a method was developed to "capture" the particles ejected from the substrate after laser irradiation. Detection of both angular distribution and ejection energies was achieved with this method. It was found that the angular distribution of the ejected particles fitted to a Gaussian curve when the laser irradiated normally to the substrate. The distribution curve for the particles ejected from a rough surface has a wider full width at half maximum than that from a smooth substrate. It was also found that the particle ejection energy increased obviously with laser fluence, therefore the laser cleaning efficiency was promoted sharply as laser fluence increased. © 2000 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Laser-induced removal of spherical silica particles from silicon wafers was investigated. The cleaning efficiency and laser cleaning thresholds for particles with diameters of 0.5, 1.0, 2.5, and 5.0 μm were carefully measured. It is found that the cleaning efficiency is more sensitive to laser fluence than laser pulse number and repetition frequency. The particle ejecting energies were found to increase with laser fluence. The threshold laser fluences for removing particles with sizes of 0.5 and 1.0 μm are 225 and 100 mJ/cm2, respectively, when KrF excimer laser is used. The threshold laser fluences are only a value below 5.0 mJ/cm2 for particles with a size of 2.5 and 5 μm. A model including both linear expansion and elastic deformation model was proposed to explain the experimental results. With this model, the particle movement and deformation in laser cleaning process were calculated. The expressions for threshold laser fluences were derived. The theoretical predictions are found to be greater than the experimental results. The difference can be explained by the enhancement of light intensity near the contacting area, due to the focusing and scattering by spherical particles. This model is useful to the study of laser cleaning as well as particle adhesion and deformation on solid surfaces. © 2000 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Nanostructure fabrication using lasers in combination with a scanning tunneling microscope has been reported in the past several years. Different mechanisms have been discussed for the formation of these nanostructures. However, they are controversial. In this study, we investigated the mechanism of nanostructure fabrication on both gold films and hydrogen-passivated Ge surfaces. Current-distance curves for a gold film and for an H-passivated Ge surface under an electrochemically etched tungsten tip were measured to determine the tip-sample distance. An analytical model was proposed to explain different mechanisms for nanostructure fabrication on gold films and on H-passivated Ge surfaces. Thermal expansion of the tip under laser irradiation was calculated. With comparison between the tip-sample distance and the thermal expansion of the tip, we can determine whether the mechanism is based on optical enhancement or on thermal mechanical indentation. © 2000 American Institute of Physics.

Electronic Resource

1090-6487

42.82.Cr ; 85.40.Hp

Springer Online Journal Archives 1860-2000

Physics

Abstract Spherical 0.5-μm silica particles were placed on a silicon (100) substrate. After laser illumination with a 248-nm KrF excimer laser, hillocks with size of about 100 nm were obtained at the original position of the particles. The mechanism of the formation of the subwavelength structure pattern was investigated and found to be the near-field optical resonance effect induced by particles on the surface. Theoretically calculated near-field light intensity distribution was presented, which was in agreement with the experimental result. The method of particle-enhanced laser irradiation has potential applications in nanolithography.

Electronic Resource