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OBJECTIVE: To investigate the effect of biflavonoid 4′-O-methylochnaflavone (MF) on palmitic acid-induced endothelial dysfunction in rat cavernous endothelial cells (RCECs). METHODS: The isolated RCECs were commercially available and randomly divided into four groups: normal+BSA group (NC group), palmitic acid (PA) group, MF group, and icariside Ⅱ (ICA Ⅱ) group. The protein expression levels of protein kinase B (PKB/AKT) and endothelial nitric oxide synthase (eNOS) in each group were evaluated via Western blotting. The differences in the intracellular nitric oxide of RCECs treated by MF or ICA Ⅱ were detected by DAF-FM DA that served as a nitric oxide fluorescent probe. Effects of MF and ICA Ⅱ on cell proliferation of PA-stimulated RCECs were determined via CCK-8 assay. RESULTS: The content of nitric oxide in RCECs was significantly increased after the treatment of MF and ICA Ⅱ in comparison with the NC group (P < 0.05). Moreover, compared with ICA Ⅱ group, MF demonstrated a more obvious effect in promoting nitric oxide production (P < 0.05). Compared with the NC group, the expression levels of eNOS and AKT in the PA group were significantly decreased, indicating that a model for simulating the high-fat environment in vitro was successfully constructed (P < 0.05). Meanwhile, the intervention of MF and ICA Ⅱ could effectively increase the expression of eNOS and AKT, suggesting that MF and ICA Ⅱ could promote the recovery of endothelial dysfunction caused by high levels of free fatty acids (P < 0.05). The results of CCK-8 assays showed that PA could significantly reduce the proli-feration ability of RCECs (P < 0.05). Furthermore, the decreased cell viability induced by PA was significantly elevated by treatment with ICA Ⅱ and MF (P < 0.05). CONCLUSION: In RCECs, MF and ICA Ⅱ could effectively increase the content of nitric oxide. The down-regulation of the expression of proteins associated with the AKT/eNOS pathway after PA treatment revealed that this pathway was involved in the development of endothelial dysfunction, which could be effectively reversed by MF and ICA Ⅱ. In addition, the cell proliferation ability was significantly decreased following PA treatment, but MF and ICA Ⅱ could restore the above changes. Overall, biflavonoid MF has an obvious repairing effect on PA-stimulated endothelial dysfunction.

OBJECTIVE: Androgen deficiency is common in aging males and may have unfavourable health consequences. Large-scale studies suggested low testosterone level might increse mortality and morbidity in ageing males. However, young men with low testosterone level might be neglected. Recent studies reported young men with infertility may have reduced testosterone level. To investigate the incidence of androgen deficiency in males with infertility and possible factors affecting the low testosterone level. METHODS: Between January 2011 and December 2012, 407 men with infertility caused by varicocele (VC), obstructive azoospermia (OA) and nonobstructive azoospermia (NOA) in our center were included. The number of men in each group of OA, NOA and VC was 141, 97 and 169, respectively. All the eligible patients underwent a serum testosterone assessment by a single morning blood draw (between 8:00 to noon) to test for concentration of the total testosterone. All serum samples were determined by radioimmunoassay in our andrology laboratory. Androgen deficiency was defined as having a total testosterone level less than 300 ng/dL. RESULTS: The mean age was (30.4±5.8) years. The mean testosterone level was (4.18±1.64) ng/dL (range 0.30 to 11.32 ng/dL). The overall incidence of androgen deficiency was 26.5% (108/407). The incidences of androgen deficiency in NOA, OA and VC groups were 40.2% (39/97), 19.1% (27/141) and 24.9% (42/169), respectively, which were significantly higher in the NOA than in the VC and OA groups (P < 0.001). The incidences had no difference between the VC and OA groups (P=0.229). Univariate analysis revealed the cause of infertility, FSH and the mean testis volume as possible affecting factors for androgen deficiency. However, on multivariate analysis the only cause of infertility was an independent predictor. The incidence of androgen deficiency was the highest in the NOA group [OR 0.492 (95% confidence interval 0.288-0.840)]. CONCLUSION: NOA and varicocele might be risk factors of androgen deficiency. Young men with NOA may have a higher possibility of low testosterone level. Testosterone level should be followed up after NOA and varicocele treatment. Androgen deficiency should be assessed in males with infertility in clinical practice.

To determine whether chloroquine (CQ), an often used inhibitor of late autophagy and autophagosome/lyosome fusion, can inhibit proliferation of renal carcinoma cells and investigate its effect on sunitinib (ST)-induced apoptosis.Renal carcinoma cell line 786 O and ACHN had been used as cellular model and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay was carried out to detect the cell viability in response to CQ or ST treatment. Both transmission electron microscope and immunoblotting had been employed to observe apoptotic and autophagic process. To examine the involvement of autophagy in ST-dependent apoptosis, autophagy had been inhibited either chemically or genetically via utilizing autophagy inhibitor or specific small interference RNA (siRNA) targeted to either Ulk1 (unc-51-like kinase 1) or LC3 (microtubule associated protein 1 light chain 3 fusion protein), two essential autophagic proteins.Both ST and CQ induced cell viability loss, indicating that either of them could inhibit renal cancer cell proliferation. Clone formation experiments confirmed the aforementioned results. Furthermore, the combined ST with CQ synergistically promoted the loss of cell viability. By transmission electron microscopy and immunoblotting, we found that the ST induced both autophagy and caspase-dependent apoptosis. While 3-MA, an early autophagy inhibitor, reduced the ST-induced cleavage of poly (ADP-ribose) polymerase-1 (PARP-1), a substrate of caspase 3/7 and often used marker of caspase-dependent apoptosis, CQ promoted the ST-dependent PARP-1 cleavage, indicating that the early and late autophagy functioned differentially on the ST-activated apoptotic process. Moreover, the knock down of either Ulk1 or LC3 decreased the ST-caused apoptosis.Interestingly, we observed that rapamycin, a specific inhibitor of mTOR (mammalian target of rapamycin) and an inducer of autophagy, also showed to inhibit cell viability and increased the cleavage of PARP-1 in the ST-treated cells, suggesting that autophagy was likely to play a dual role in the regulation of the ST-induced apoptosis.ST activates both apoptotic and autophagic process in renal carcinoma cells. Although autophagy precedes the ST-induced apoptosis, however, early and late autophagy functions differentially on the apoptotic process induced by this compound. Additionally, ST can coordinate with the inducer of autophagy to inhibit the cell proliferation. Further research in this direction will let us illuminate to utilize CQ as a potential drug in the treatment of renal carcinoma.

Phase change materials have great potential for data storage applications owing to the large optical and electrical contrasts during rapid switching between their amorphous and crystalline phases. Hence, significant efforts have been made to identify and understand their unique characteristics. Here, we report a distinct optical characteristic of phase change materials and explain its presence via electronic structure considerations. The optical response of phase change materials and non-phase change materials are investigated via experiments. Annealing them from room temperature to 400 °C, we observed that Sb2Te3 exhibits phase change properties but not Bi2Te3, despite their similar crystal structures. A red shift in the absorption spectra is observed for crystalline Sb2Te3 with respect to its amorphous phase. From first-principles calculations, we explain that the delocalized electrons in crystalline Sb2Te3 films are responsible for this red shift. In contrast, the electrons in Bi2Te3 films are localized and no absorption red shift is observed. The absorption red shift is also observed in other phase change materials from the GeTe–Sb2Te3 pseudo-binary system; hence the detection of such a red shift may be used for identifying potential phase change materials.

Magnetoresistance having a field and current dependence like that of GMR (but a rather small magnitude) has been observed in Co70Fe30/GeTe and Co70Fe30/Ge2Sb2Te5 granular films. Film stacks were fabricated using tandem (multilayer) deposition and annealing was required for the films to develop the GMR-type response. This GMR-type behavior is distinct from AMR, which is observed before annealing. With films having the structure [CoFe 4 nm/GeTe 6 nm]10, a magnetoresistance (MR) of 0.19 %, which has the GMR-type character can be observed after an optimal annealing temperature of 450 °C. TEM and X-ray reflectometry suggest that columnar granules with layered Fe form during deposition and with annealing. Magnetoresistive transport is believed to be between the discontinuous layers in each columnar grain. These discontinuous layers are observed to be superparamagnetic in SQUID ZFC-FC measurements measured from 5–300 K. Magnetoresistance can be fitted by the quadratic relation appropriate for GMR in granular films, especially at higher GeTe compositions. When Ge2Sb2Te5 is used instead of GeTe, higher anneal temperatures are required before the MR with GMR character appears. This GMR type response does not appear when pure Fe is used instead of the CoFe alloy, with the samples showing only AMR in this case. This is due to the absence of Co which seems to cause a more granular growth.

Bi(Fe 0.5 Sc 0.5 )O 3 –PbTiO 3 (BSFPT) films have been fabricated on Pt/TiO 2 /SiO 2 /Si substrates by pulsed laser deposition. The microstructure, chemical state, ferroelectric and magnetic properties were investigated. The leakage mechanism of the BSFPT thin film showed bulk limited, space charge limited current characteristics from 200 to 220 K, whereas bulk limited Poole–Frenkel emission and interface limited Fowler–Nordheim tunneling coexisted at temperatures between 250 and 300 K. The substitution of Sc 3+ for Fe 3+ ions was considered to improve the valence stability and, therefore, decrease the overall leakage current.

Underground mine caving may induce collapse of the ground during ore caving, particularly when there is a loose material on top of the mine. In the present paper, a laboratory test is performed to model this mining problem which is followed by a particle flow simulation to simulate the interaction and movement between the two materials. For this nonhomogeneous problem, an interesting columniform channel for the loose material is formed during the drawing in both the experiment tests and the numerical modeling. The formation of this channel greatly affects the efficiency of ore drawing and the stability of the mine caving. The numerical modeling can be used for the optimization of ore drawing, ore drawing management and the prediction of ore loss and dilution indexes. The importance of the moisture content on ore drawing process and the efficiency of ore drawing are also investigated by both experimental and numerical tests, and useful results are found from the present study.

We present structural and magnetic properties of ZnO films doped with rare-earth Gd ions at various concentrations, achieved by ion implantation technique and pulsed laser deposition (PLD) on ZnO (0001) single crystals and sapphire. X-ray diffraction shows Gd doping in ZnO and crystal quality degrades with increasing Gd concentration. Magnetization as a function of temperature revealed a positive magnetization at 305 K and a concave trend was observed for all samples for both implanted and PLD grown samples. The highest saturation magnetization was achieved for Gd concentration of x = 7.9 % (0.7 µ B / Gd ) and at dosage of 9.0 × 1015 cm -2 (2.6 µ B / Gd ) for the PLD grown and implanted samples, respectively. We believe that the Gd ion solubility limit in the implanted and PLD grown samples, of around 3% and 7.9%, respectively, are reached.

During the plastic packaging process, mold flash is usually formed on a heat sink. In order to keep efficient heat transfer from the integrated circuit device to the exterior environment, the mold flash must be removed from the heat sink surface. In this paper, we demonstrate that a Nd:YAG laser deflashing is only available to remove thin flash of a few micrometers from heat sinks and cannot remove thick flash without damage to the heat sink, both from experimental and numerical analysis. Based on optical and thermal properties of heat sink and mold flash materials, we develop a two-laser deflashing technique for thick flash removal. A CO2 laser is used to remove the top layer of thick flash followed by Nd:YAG laser at low laser fluence and pulse number, which is used to remove the remaining thin flash without damaging the heat sink.

Laser processing has found an important application in the hard disk drive (HDD) industry to fabricate bumps for screen testing of the manufactured magnetic disk media prior to HDD assembly. The flying height of the head slider needs to be calibrated by a specifically designed bump array. With areal density of HDD already exceeds 100Gbits/in2, the head slider flies at 6 nm flying height and will become even lower. Sub-10nm bump height, as low as 3.5nm, is required to match future slider flying height. In this study, bump arrays with sub- 10nm bump height, good height uniformity and precise distribution was fabricated on glass disk substrate using an integrative control system consisting of a pulsed CO2 laser and a high precision stage. The bump disk requirements were demonstrated successfully and compared with industrial specifications.

Diluted magnetic semiconductor Co-doped ZnO film has been synthesized by a dual beam pulsed laser deposition method. The magnetic, electrical, and optical properties of the Zn0.985Co0.015O0.67 film are studied in this paper. The film shows ferromagnetic behavior with a coercivity of about 300 Oe at room temperature, and semiconductor behavior with carrier concentration of 2.2×1018 cm-3, and a resistivity of 102 mΩ cm. Structural investigations indicated that the film has similar lattice constants to that of ZnO. It is shown that the film exhibits excellent optical properties with a band gap energy of 3.31 eV, which is close to that of ZnO. The origins of the magnetism are also discussed.

Previous analysis of dry laser cleaning within the frame of a one-dimensional (1D) model with homogeneous surface heating shows that this model disagrees with experiments by one–two orders of magnitude. The particle on the surface produces an inhomogeneous intensity distribution in its vicinity due to scattering and diffraction. This produces a nonstationary 3D distribution of the temperature and nonstationary 3D thermal deformations of the surface. If one uses the Mie theory for calculation of inhomogeneous intensity then in some region of the parameters, the 3D model predicts results close to the experimental ones. The next step was done when the scattering effects for radiation reflected from the surface was taken into account (so-called “particle on surface” problem). This approach yields results close to the experimental one within the wide range of parameters.

When a high-power laser beam is focused into liquid, it results in a shock wave emission and cavitation bubble generation. Upon inserting a rigid substrate into the liquid, the bubbles migrate towards the substrate due to the Bjerknes attractive force. Due to bubble–substrate and/or bubble–free-surface interaction, a high-speed liquid jet is formed during bubble collapse, and a collapse shock wave is generated at the moment of bubble collapse near the substrate. These shock waves and liquid jet induce large forces acting on the substrate to remove particles from it. For a substrate several millimeters away from the laser focus point, the collapse shock wave and liquid jet play key roles in removal of particles. The cleaning efficiency increases with an increase of laser fluence and decreases with an increase of distance between substrate surface and laser beam focus point or depth below liquid surface. In a case of bubbles close to substrate and liquid-surface boundaries, implosion of the bubbles will give rise to shock waves and liquid jets oblique to the substrate surface with the parallel and perpendicular components of the forces onto the particles. These oblique liquid jets and shock waves result in high cleaning efficiency. A liquid, such as alcohol and commercial washing solution, as the surrounding medium, rather than air or vacuum, can reduce adhesion force and enhance cleaning efficiency.

We have investigated the different mechanisms of photoluminescence (PL) of silicon nanocrystals due to the quantum confinement effect (QCE) and interface states. Si nanocrystals were formed by pulsed-laser deposition in inert argon and reactive oxygen gas. The collisions between the ejected species greatly influence the morphology of the Si nanocrystals and cause a transition from a film structure to a porous cauliflowerlike structure, as the ambient gas pressure increases from 1 mTorr to 1 Torr. The oxygen content of the Si nanocrystals increases with increasing O2 ambient pressure, and nearly SiO2 stoichiometry is obtained when the O2 pressure is higher than 100 mTorr. Broad PL spectra are observed from Si nanocrystals. The peak position and intensity of the PL band at 1.8–2.1 eV vary with ambient gas pressure, while intensity changes and blueshifts are observed after oxidation and annealing. The PL band at 2.55 eV shows vibronic structures with periodic spacing of 97±9 meV, while no peak shift is found...

The periodic microfringe structures were induced on the front silicon surface by pulsed CO2 laser irradiation with the existence of a painting or coating layer on the bottom surface of silicon substrate. The microfringes were formed under single pulse irradiation due to the laser induced periodic surface structure (LIPSS) effect. The nanodot were self-organized in chains under cumulative laser pulse irradiation, and located along the microfringe ridges. The silicon surface was patterned with a nanocone array of two different average sizes at even higher laser intensity. The larger cones distributed in rows, and the smaller cones scattered between the two adjacent rows of the larger cones. The far-infrared absorption of silicon is promoted by the increase of free carrier concentration and thermal energy resulting from the laser interaction with the coating/painting materials at the substrate bottom surface.

Laser cleaning of printed circuit boards (PCB) has been studied in this paper. It is demonstrated that laser cleaning is a powerful tool to remove resin contaminants from printed circuit boards. A Nd:YAG laser is used as a light source for laser cleaning. The beam profile of the YAG laser is reshaped and homogenized into a square beam with uniform energy distribution in the focal plane of the focusing lens by using an optical system. The printed circuit board surfaces before and after laser cleaning were inspected by an optical microscope, analysed by X-ray photoelectron spectroscopy and monitored by an acoustic wave detection method. The cleaning threshold is about 75 mJ/cm 2 and no damage is observed below 400 mJ/cm 2 .

Laser-induced removal of flash from heat sinks in integrated circuit (IC) packages has been studied. It is found that flash can be effectively removed from heat sinks in plastic IC packages by laser deflashing. An optical microscope, an α-step surface profiler and X-ray photoelectron spectroscopy are used to analyze the deflashing efficiency. Laser deflashing of IC packages is based on laser ablation of flash materials. With an increase of laser fluence, the ablation rate increases. The laser fluence is selected between the ablation threshold of flash materials and that of heat-sink materials. An acoustic wave is generated by laser ablation of flash materials. Acoustic wave detection is used to monitor the surface cleanness during laser deflashing and to determine the ablation threshold of flash materials.

The effects of optical resonance and near field in the interaction of transparent particles on a substrate with laser light have been examined experimentally and theoretically. It is found that pits can be created at the contacting point between the particle and the metallic surface by laser irradiation (KrF,λ=248 nm) with a single pulse. The influence of the particle size and the laser fluence on the structuring of the surface has been investigated. The size of the particle ranges from 1.0 μm to 140 nm in diameter. The morphologies of the holes created have been characterized by an atomic force microscope and a scanning electron microscope. For constant laser fluence, the created hole is sensitive to the particle size. For higher-laser fluence, the corresponding hole becomes larger and deeper. With a low fluence of 300 mJ/cm2 and for 140 nm particles, the lateral dimensions of created pits can be down to 30 nm. With a high fluence of 750 mJ/cm2 and 1.0 μm particles, the diameter and the depth of created holes are about 350 and 100 nm, respectively. Theoretical calculations and an accurate solution of a boundary problem indicate that incident light could excite some resonance modes inside the particle and produce enhanced light intensities on the contacting area (substrate surface). The light intensity on the contacting area is nonuniform and sensitive to the particle size parameter. Experimental results are explained and are very consistent with those of theoretical calculations. The experimental results also provide direct evidence of the optical resonance and near-field effects in the interaction of transparent particles on the substrate with laser light.

In this study, the nanostructure fabrication on metallic surfaces using a pulsed laser in combination with an AFM is reported. Nanopatterns such as pit and multilines were created. Dependence of pit apparent depth on the laser fluence and laser pulse numbers has been investigated. Chemical components of the modified features were analyzed by Auger electron spectroscopy ~AES!. The morphologies of created features were characterized by AFM and scanning electron microscope ~SEM!. Thermal expansion of the tip, the field enhancement underneath the tip and the sample heating were estimated. Experimental results and mechanisms of nanostructure formation are discussed. We hope that our experiments will contribute further to the study of mechanisms of the photoassisted nanoprocessing.

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...

Completely (0 0 1)-oriented Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) thin films deposited on (1 0 0)-silicon wafers with SrTiO 3 (STO)/MgO as a buffer layer system and YBCO as a electrode, were prepared by using KrF excimer pulsed-laser deposition. The epitaxial relationships, i.e. PZT(0 0 1) ∥ YBCO(0 0 1) ∥ SrTiO 3 (1 0 0) ∥ MgO(1 0 0) ∥ Si(1 0 0) and PZT(1 1 0) ∥ YBCO(1 1 0) ∥ SrTiO 3 (0 1 1) ∥ MgO(0 1 1) were detected using X-ray θ –2 θ scans and pole figures or ϕ -scans. Grain size and surface morphologies of the as-prepared films were examined using atomic force microscopy and scanning electron microscopy.

Laser cleaning has emerged as an effective cleaning technique for removing contaminants from solid surfaces. Dry laser cleaning and steam laser cleaning have been developed recently, relying on pulsed laser heating of the surface without and with the presence of a thin liquid coating. A cleaning model was established for removal of particles from solid surfaces by taking Van der Waals force, capillary force and cleaning force into account. The model can not only explain the influence of laser fluence on cleaning efficiency, but also predict the cleaning thresholds. Laser-induced removal of film-type contaminants from solid surfaces has been studied. Laser cleaning mechanisms and its applications in disk drive industry will be discussed in this article.

Scanning tunnelling microscopy (STM) study and modification of hydrogen (H)-passivated Ge(100) surfaces have been investigated. Thermal oxidation procedures were used to minimise surface roughness. Ge samples were passivated in HF solution after thermal oxidation. STM and atomic force microscope (AFM) imaging showed that, using HF etching after thermal oxidation, we can obtain a natural H-passivatedtopographically and chemically flat Ge(100) surface. The root-mean-square (rms) roughness ofa H-passivatedGe(100) surface measured both by STM and AFM is less than 2 A. Electric properties of H-passivatedGe(100) surfaces were studied by scanning tunnelling spectroscopy (STS) in nitrogen ambient. STS showed that the H-passivated Ge surfaces were not pinned. Modification on H-passivated Ge(100) surfaces was carried out using STM by applying an electric voltage between the sample and tip in air. Modified features were characterised by STM and AFM imaging. On the H-passivated Ge(100) surfaces, stable, low-voltage, nanometer-scale modified features can be produced.

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.

A novel method for nanofabrication, i.e., laser-induced nano-modification on hydrogen (H)-passivated Si surfaces under a tip of a scanning tunneling microscope (STM) is proposed. The theory and mechanism are discussed. Enhanced laser irradiation under a STM tip induces a local temperature rise on the nanometer scale, which causes thermal desorption of hydrogen atoms on an H-passivated Si surface. Oxidation occurs after desorption of hydrogen atoms. A vertical polarized Nd:YAG pulsed laser with a duration of 7 ns was used in our investigation. STM tips were electrochemically (EC) etched from a tungsten wire. A 3×2 dot array and a single line were created. The sizes of the dots are from 20 to 30 nm, and the width of the line is less than 30 nm. The dependence of the apparent depth on the laser intensity shows that there is a threshold of the intensity and a saturation value of the apparent depth is reached at high intensity.

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.

An energy model to explain particle removal mechanism has been developed. This model is based on a detailed investigation of contact deformation of a particle on a solid surface, as well as particle motion during the process of substrate surface expansion under uniform laser irradiation. Calculation results show that small particles mainly gain kinetic energy during pulsed laser irradiation, whereas large particles mainly gain elastic deforming potential energy. The particle removal condition is derived from the viewpoint of energy. The relationship of particle removal efficiency with laser fluence and particle size is discussed. Theoretical results are compared with experimental results.

Laser cleaning can efficiently remove tiny particles from a silicon surface on which a liquid film has been previously deposited when the laser fluence is large enough. The cleaning force is due to the high pressure of stress wave generated through the rapid growth of vapor bubbles inside the superheated liquid. The behaviors of this type of laser cleaning are theoretically described with deposition of two kinds of liquid film: acetone and ethanol. The cleaning threshold of laser fluence is different for these two kinds of liquids for some differences in their thermodynamic properties. For removal of alumina particles with a size of 1 μm, the lower cleaning threshold of laser fluence is obtained with deposition of acetone because of its lower boiling point and volume heat capacity. The theoretical result also indicates that the cleaning force with deposition of ethanol increases more quickly along with laser fluence than with acetone. This phenomenon is much useful for removal of smaller particles and can lead to high cleaning efficiency.

Carbon nitride thin films were deposited on silicon wafers by pulsed KrF excimer laser (wavelength 248 nm, duration 23 ns) ablation of graphite in a nitrogen atmosphere. Different excimer laser fluences and pressures of the nitrogen atmosphere were used in order to achieve a nitrogen content as high as possible in the deposited thin films. Fourier transform infrared and x-ray photoelectron spectroscopies were used to identify the binding structure and the content of the nitrogen species in the deposited thin films. The N/C ratio 0.42 was obtained at an excimer laser fluence of 0.8 J cm−2 at a repetition rate of 10 Hz under a nitrogen pressure of PN=100 mTorr. A high content of C=N double bond instead of C≡N triple band was indicated in the deposited thin films. Ellipsometry was used to analyze the optical properties of the deposited thin films. The carbon nitride thin films have amorphous-semiconductorlike characteristics with an optical band gap Eopt of 0.42 eV.

Carbon nitride thin films were deposited by 532 nm Nd:YAG laser ablation of graphite assisted by a nitrogen ion beam bombardment on silicon substrates. Different nitrogen ion beam energies (200, 400, and 600 eV) were used while the laser parameters remained fixed. X-ray photoelectron spectroscopy (XPS) and ellipsometry measurements were carried out to analyze the electronic and optical properties. The XPS C 1s spectrum for the C–N binding is at 286.5 eV while the N 1s spectrum has a corresponding peak of C–N binding at 396.9 eV. The optical gap Eopt is on the order of magnitude of 10−1 eV and increases with the N/C ratio in the deposited film. Linear dependence of the refractive index n and the extinction coefficient k on photon energy E in the range of 1.5–3.5 eV are established.

In laser cleaning of micro-particles from a solid surface, the adhesion force between the particles and the substrate surface, and the thermal expansion of both particles and substrate play important roles in determining the threshold laser fluence. Taking into account Van der Waals force and cleaning force due to fast thermal expansion of particles and substrate surface induced by pulsed laser irradiation, a cleaning model was established for the removal of tiny particles from substrate surfaces. The cleaning condition and cleaning threshold can be obtained from this model. This model can qualitatively and quantitatively predict the laser cleaning process depending on laser incident direction, laser wavelength, particle size, particle material and substrate material.

Pulsed laser cleaning was demonstrated to be an efficient way for removing submicron particles from the nickel-phosphorus (NiP) surface both experimentally and theoretically. Experimentally, it is found that using KrF excimer laser with a pulse width of 23 ns the cleaning threshold is about 20 mJ / cm 2 for removing quartz particles from the NiP surface and laser cleaning efficiency increases rapidly with increasing laser fluence. The theoretical analysis shows that the peak cleaning force (per unit area) is larger than the adhesion force (per unit area) for submicron quartz particles on the NiP surface when it is irradiated by excimer laser with a fluence above 10 mJ / cm 2 . Therefore, it is possible to remove submicron quartz particles from NiP surfaces by laser irradiation. The difference between the cleaning force (per unit area) and the adhesion force (per unit area) increases with increasing laser fluence, leading to a higher cleaning efficency for quartz particles on the NiP surface.

A theoretical model for laser cleaning of microparticles from solid surfaces was established by taking the adhesion force (van der Waals force) and cleaning force (due to thermal expansion) into account. The cleaning conditions and threshold can be obtained from this model. Theoretical predictions have been verified by the experimental results for removing aluminium particles from a quartz substrate. It was found that laser irradiation from the back of the substrate is more effective in removing particles with different sizes than that from the front. With laser irradiation from the back, large particles can be removed more easily than small ones. However, with laser irradiation from the front, smaller particles can be removed more easily.

O3. Based on Auger Electron Spectroscopy analyses and optical microscopic observations, γ-Fe2O3 and Fe3O4 are formed on the stainless steel surface in laser cleaning in the air. Since laser can induce high temperature rise in stainless steel surfaces, the above phenomenon can be explained by a thermochemical reaction between oxygen in the air and the stainless steel. With increasing laser fluences, the temperature rise in the irradiated area of stainless steel surface increases, which enhances oxygen diffusion into the surface and oxidation reaction within the irradiated area. In order to avoid discoloration of stainless steel surfaces, a vacuum system was used to reduce the oxidation reaction between oxygen and stainless steel.

A quantitative investigation of laser‐induced removal of particles from magnetic head slider surfaces has been carried out. The damage thresholds of magnetic head sliders for laser fluence and pulse number were found to be about 150 mJ/cm2 and 5000 pulses at 100 mJ/cm2, respectively. For laser fluence or pulse number above the damage threshold, laser irradiation onto magnetic head slider surfaces can cause microcracks around the pole tips. It is found that laser cleaning efficiency increases with increasing laser fluence and pulse number, but does not depend on repetition rate up to 30 Hz. Laser cleaning efficiency of removing particles from magnetic head slider surfaces can reach about 90% for Al particles and 100% for Sn particles, respectively, under appropriate conditions without causing damage. The mechanisms of laser cleaning of particles from magnetic head slider are laser‐induced surface vibration, particle vibration, particle thermal expansion, and ablation with high laser fluence, which produce forces strong enough to detach particles from slider surfaces. Based on the above cleaning mechanisms, the dependence of laser cleaning efficiency on laser parameters can be explained.

Films of crystalline and amorphous Fe 12 (Ge 2 Sb 2 Te 5 ) 88 were prepared using laser synthesis from a stoichiometric target. The crystalline film, prepared at 300 °C was found to be in the hexagonal close packed (HCP) structure while the film prepared at room temperature was found to be amorphous. The crystalline film showed clear magnetic hysteresis, while the amorphous and the 220 °C prepared film exhibited weaker magnetic properties. The crystallization temperature of the amorphous Fe 12 (Ge 2 Sb 2 Te 5 ) 88 as extracted from resistance temperature measurements was found to be 168 °C, comparable to 178 °C for pure Ge 2 Sb 2 Te 5 . Lastly, the reflectivity spectrum showed the typical reflectivity contrast between crystalline or amorphous Fe 12 (Ge 2 Sb 2 Te 5 ) 88 films — as expected from phase change films.

The field of nanoelectronics has evolved into a major area of investigation. Nanolithographic techniques such as atom beams [1, 2], electron beams [3], scanning probe tunneling [4‐6], and scanning nearfield optical lithography [7‐9] are expected to be potential methods in the fabrication of present and future nanodevices. However, due to their incompatibility with the present fabrication processing and their low throughput, the application of these methods is presently confined to the experimental stage. Meanwhile, traditional optical lithography is limited to the diffraction effect and always relates to complex system and high cost. In this letter, we report a novel, low-cost, and simple optical lithography technique using particleenhanced laser irradiation. Standard spherical silica particles (Duke [10]) packaged as low-residue aqueous suspensions were used in our experiment. The diameter of the particles is 0.5 μ m, with a deviation limited in a range of ∠ 5%. Silicon

Ultrashallow p+/n junctions formed by B+-ion implantation and annealed by spike rapid thermal annealing (RTA) or laser annealing were studied. The effect of the preamorphizing depth on the redistribution of boron atoms after annealing has also been investigated. Our results show that for ultrashallow junctions formed by ultra-low-energy ion implantation and spike RTA, the depth of the preamorphizing implant has very little impact on the junction depth. By optimizing the laser fluence and preamorphization depth, a highly activated, ultrashallow, and abrupt junction can be obtained using a 248 nm excimer laser. The secondary-ion-mass spectrometry results clearly indicate that a step-like profile with a junction depth of 370 A (for a B+ implant at 1 keV) can be formed with a single-pulse laser irradiation at 0.5 J/cm2.

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.

A polynuclear silver(I) complex {[(t-Bu) 4 N] 2 [Ag 6 I 8 ]} n 1 with iodo-bridging ligands has been prepared, the centrosymmetric cluster anion can be described as two [Ag 4 I 4 ] distorted cubane units sharing one [Ag 2 I 2 ] plane. This cluster polymer shows strong third-order nonlinear optical (NLO) absorption and refraction with absorption coefficient α 2 = 8.9 × 10 -10 m·w -1 and refractive index n 2 = -6.6 x 10 -17 m 2 ·w -1 .

In this paper, phase change random access memory (PCRAM) devices with two different geometric configurations were studied. The geometry effect on device functionalities in terms of thermal and electrical properties has been analyzed by simulation and experiments. Based on 0.35mum technology, 128 bits PCRAM array integrating with CMOS as the selection device were fabricated. The two types of PCRAM cells were implemented and characterized. The simulation results showed that both the bottom electrode and phase change layer geometry and the size of the interface between the phase change material and the bottom electrode were the determinant factors to the temperature profile and heat distribution. Both simulation and experimental results show that PCRAM device with type II structure required lower current to start phase change from crystalline state to amorphous state. However, it required a larger current to be fully RESET. A model was proposed in this paper to discuss this phenomenon

In this work, phase change random access memory (PCRAM) was studied theoretically and experimentally. Phase change materials were deposited and their physical parameters were measured. A simulation and design software for PCRAM was developed based on multidisciplinary theories including electrodynamics, thermal conduction, crystallization kinetics and numerical computations. By introducing physical models of PCRAM elements, a general macromodel of the phase change random access memory (PCRAM) elements for HSPICE-based computer simulator is proposed. PCRAM array were designed, fabricated, and tested by using a self built tester. Also, near field optical scan microscope incorporated with fs laser was used to fabricate nano scale PCRAM cells

Understanding of the phase change in nano-scale, or so-called nano-phase change, and its related issues are important for its applications on both optical recording and phase change random access memory (PCRAM). Nano-phase change can be classified into thickness-dependent and structure dependent types. For PCRAM device performance, the film thickness-dependent thermal profile and materials' properties are the two important factors. In this work, the thickness dependence of nano-phase change for chalcogenide materials was studied by both simulation and experiments. A thermal model was built up to simulate the film thickness-dependent thermal profiles and its corresponding effects of line type PCRAM. The simulation results showed that the temperature profile, heating rate and cooling rate are strongly dependent on the thickness of phase change materials. Experiments had been conducted to investigate the thickness dependence of crystallization temperature for both nucleation-dominated and growth-dominated phase change material. It was found that the crystallization temperatures are function of the thickness for the both materials. Higher crystallization temperatures were obtained for thinner phase change films. The influence of above factors on the performance of PCRAM devices is discussed.

A thermal analysis of chalcogenide random access memory (C-RAM) cell, a non-rotational nonvolatile phase change memory cell, was conducted. A three-dimensional finite-element method was used in the simulation of C-RAM cell. The thermal effect generated by applying an electric pulse was calculated and analyzed. The dependence of its thermal performances due to electrical and geometrical variations was also investigated. Temperature performances including temperature profiles and history, the heating and cooling rates, and heat flow characteristics were obtained and analyzed.

Si nanocrystals (NCs) consisting of small crystals from 1 to 20 nm were formed by pulsedlaser deposition (PLD) in inert Ar gas and reactive O2 gas. The oxygen content of the Si NCs increases with increasing O2 ambient pressure and nearly SiO2 stoichiometry is obtained when O2 pressure is higher than 100 mTorr. The optical absorption of the Si NCs shows an indirect band transition. Broad PL spectra are observed from Si NCs. The peak position and intensity of the PL band at 1.8–2.1 eV are dependent on excitation laser intensity, while intensity changes and blue shifts are observed after oxidation and annealing. The PL band at 2.55 eV displays vibronic structures with periodic spacing of 97 ± 9 meV, while no peak shift is found before and after oxidation and annealing. The as-deposited Si NCs show a polycrystal structure and crystallinity improves after annealing. Combined with the PL of Si NCs obtained by crumbling electrochemical-etched porous Si layer, the results give strong evidence that the PL band at 1.8–2.1 eV is due to the quantum confinement effect (QCE) in Si NC core while the PL band at 2.55 eV is related to the localized surface states at SiOx/Si interface.

In order to develop laser cleaning technology to meet the need of industry, it is very important to investigate the cleaning efficiency and mechanism of this cleaning technology. Theoretical and experimental investigation on laser dry cleaning of particles from substrate surfaces is discussed in the paper.

Optical and thermal processes of an STM junction under laser irradiation were summarized. A general model for the near field of a tip, under polarised laser irradiation is presented in the case of imaging and processing by a laser-assisted scanning probe microscope (SPM). The near field of a tip was calculated using the method of moments. Our calculations show that a 3:1 silver SPM tip can achieve an optical field enhancement of /spl times/525 on a gold substrate surface. With such a large SPM tip, plasma resonance can be neglected, and the optical enhancement in this case is much less than that predicted for small conductive particle models. Field enhancement and intensity profiles strongly depend on the tip-sample geometry, laser properties and the dielectric properties of the tips and samples. The model can be used for rigorous calculations of the near field of a tip in a laser-assisted SPM. The temperature rise was analyzed in the cases of contact and non-contact occurring between the tip apex and the sample surface. Thermal expansion of the tip can be calculated and compared with the tip-sample distance of an STM junction to determine whether contact between the tip and sample surface occurs or not.

Laser microprocessing has been extensively studies with applications in microelectronics, data storage and photonics. In addition to the fundamental aspects of laser materials interactions, we have investigated various applications of laser microprocessing in different areas. Laser cleaning has been studies systematically both theoretically and experimentally for dry surface cleaning and steam surface cleaning. This technology has been applied for cleaning magnetic head, magnetic sliders, suspension, laser mold cleaning and laser deflash for IC packages. Laser texturing and related processes such as laser bumping, laser tagging have been studied for magnetic recording applications. The other laser works include real-time monitoring of laser surface processing, laser-induced controllable periodic structures, laser nanopatterning by scanning probe microscope tip-enhanced laser irradiation. The further prospects of using laser microprocessing for applications in formation of ultrashallow (less than 50 nm) pn junction for next-generation MOS devices, laser generation of Si nanoparticles for quantum-dot flash memory and light emission devices are addressed.