Highly efficient silver particle layers on glass substrate synthesized by the sonochemical method for surface enhanced Raman spectroscopy purposes

A fast method for preparing of silver particle layers on glass substrates with high application potential for using in surface enhanced Raman spectroscopy (SERS) is introduced. Silver particle layers deposited on glass cover slips were generated in one-step process by reduction of silver nitrate using several reducing agents (ethylene glycol, glycerol, maltose, lactose and glucose) under ultrasonic irradiation. This technique allows the formation of homogeneous layers of silver particles with sizes from 80 nm up to several hundred nanometers depending on the nature of the used reducing agent. Additionally, the presented method is not susceptible to impurities on the substrate surface and it does not need any additives to capture or stabilize the silver particles on the glass surface. The characteristics of prepared silver layers on glass substrate by the above mentioned sonochemical approach was compared with chemically prepared ones. The prepared layers were tested as substrates for SERS using adenine as a model analyte. The factor of Raman signal enhancement reached up to 5·10⁵. On the contrary, the chemically prepared silver layers does not exhibit almost any pronounced Raman signal enhancement. Presented sonochemical approach for preparation of silver particle layers is fast, simple, robust, and is better suited for reproducible fabrication functional SERS substrates than chemical one.     

Detection of Deposited Particles from the Backside of a Glass Plate

Microcontamination of product surfaces by deposited particles is an important problem in clean technologies. A most sensitive product to contamination by particles is a wafer during chip production. Therefore, methods for monitoring particle deposition on wafer surfaces have been developed in the last decade. A wafer with an unstructured and reflecting surface is inserted into the process equipment. After some time, depending on the process, this wafer is removed from the process equipment and is analysed with respect to the number of deposited particles using a wafer scanner. However, in situ particle detection in a process chamber is not possible with this technique. This would be possible if, instead of a monitor wafer, a transparent glass plate is mounted, e.g. in the housing of the process equipment. Then the illuminating and scattered light detection equipment can be mounted outside the process equipment. Since both the illuminating laser beam and the scattered light have to be transmitted through the glass plate, losses will occur, which will reduce the lower limit of detection with respect to particle size. In this article we estimate the detection possibilities theoretically and experimentally. A simple model based on Mie and vector scattering theory has been developed to describe the light-scattering behavior of a single spherical particle on a glass plate with random surface irregularities. The scattered light of individual particles of four particle sizes (1.03, 1.6, 2.92 and 4.23 μm) on the same glass surface and from the uncontaminated area of the glass plate was measured for unpolarized and normally incident light. The values of the scattered light from this model were compared with the experimental results. The comparison shows a reasonable agreement of the angular distribution of the scattered light. The developed model is used to predict the lower limit of detection for particles on a transparent surface. The theoretical estimations show that it should be possible to detect particles of a diameter down to 0.2 μm with the described measurement technique.     

Synthesis of periodic plasmonic microstructures with copper nanoparticles in silica glass by low-energy ion implantation

Ion implantation was used to locally modify the surface of silica glass to create periodic plasmonic microstructures with Cu nanoparticles. Nanoparticles were synthesized by Cu-ion irradiation of the silica glass at the ion energy of 40 keV, dose of 5×10¹⁶ ions/cm² and current density of 5 μA/cm². This procedure involves low-energy ion implantation into the glass through a mask placed at the surface. Formation of nanoparticles was observed by optical spectroscopy and atomic force microscopy. The presented results clearly demonstrate how the low-energy ions can be used for the fabrication of photonic microstructures on dielectric surfaces in a single-step process.     

Determination of the element distribution in films deposited using the plasma focus facility by Rutherford backscattering

The C, Cu and W element profiles in films deposited using a plasma focus facility are studied by the Rutherford backscattering of 2-MeV He⁺ ions. The films are deposited onto glass substrates in Ar plasmaforming gas. The element profiles are found to depend significantly on the kinetic energy of particles. The penetration depth of particles with the velocity ~10⁵ m/s is about 1.5 μm. The corresponding element profiles showing the distribution of elements over the thickness of the glass are non-linear. For each element, the maximum layer depth is observed under the glass surface. The formation of Cu, W and C layers under the glass surface and their overlapping is a feature of films deposited using the plasma focus facility. Such an arrangement of layers evidences the significant difference between this method of film deposition and conventional techniques at low rates of atom deposition, as well as diffusion-based methods. The obtained films are found to have dielectric properties.     

Nanostructuring of thin Au films by means of short UV laser pulses

The particle size distribution, morphology and optical properties of the Au nanoparticle (NP) structures for surface enhanced Raman signal (SERS) application are investigated in dependence on their preparation conditions. The structures are produced from relatively thin Au films (10–20 nm) sputtered on fused silica glass substrate and irradiated with several pulses (6 ns) of laser radiation at 266 nm and at fluencies in the range of 160–412 mJ/cm². The SEM inspection reveals nearly homogeneously distributed, spherical gold particles. Their initial size distribution of the range of 20–60 nm broadens towards larger particle diameters with prolonged irradiation. This is accompanied by an increase in the uncovered surface of the glass substrate and no particle removal is observed. In the absorption profiles of the nanostructures, the broad peak centred at 546 nm is ascribed to resonant absorption of surface plasmons (SPR). The peak position, halfwidth and intensity depend on the shape, size and size distribution of the nanostructured particles in agreement with literature. From peak intensities of the Raman spectra recorded for Rhodamine 6G in the range of 300–1800 cm⁻¹, the relative signal enhancement by factor between 20 and 603 for individual peaks is estimated. The results confirm that the obtained structures can be applied for SERS measurements and sensing.     

CuO薄膜的制备及其光伏特性

通过反应磁控溅射在n型硅和玻璃衬底上制备了p型CuO薄膜.使用X射线衍射仪和紫外-可见光-近红外光度计研究了p型CuO薄膜的结构和光学特性,得出其平均晶粒尺寸和光学带隙分别为8 nm和1.36 eV.通过研究其电压-电流关系确定了在p型CuO薄膜和n型硅衬底之间形成了p-n结.在AM 1.5光照条件下p-CuO/n-Si电池的开路电压为0.33 V,短路电流密度为6.27 mA/cm², 填充因数和能量转化效率分别为0.2和0.41%.     

Ag掺杂p型ZnO薄膜及其光电性能研究

采用超声喷雾热分解法在石英衬底上以醋酸锌水溶液为前驱体,以硝酸银水溶液为Ag掺杂源生长了Ag掺杂ZnO(ZnO：Ag)薄膜.研究了衬底温度对所得ZnO：Ag薄膜的晶体结构、电学和光学性质的影响规律.所得ZnO：Ag薄膜结构良好,在室温光致发光谱中检测到很强的近带边紫外发光峰,透射光谱中观测到非常陡峭的紫外吸收截止边和较高的可见光区透过率,表明薄膜具有较高的晶体质量与较好的光学特性.霍尔效应测试表明,在500℃下获得了p型导电的ZnO：Ag薄膜,载流子浓度为5.30×10¹⁵cm关键词： ZnO：Ag薄膜 p型掺杂 超声喷雾热分解 霍尔效应     

Preparation and characterization of transparent conducting Zn−Sn−O films deposited on organic substrates at low temperature

Transparent conducting Zn−Sn−O films were deposited on Polypropylene adipate thin-film substrates at low temperature by r. f. magnetron sputtering. The structural, electrical and optical properties of the deposited films were investigated. All the obtained films are of amorphous structure and have a very good adhesion to the substrates. The resistivity, carrier concentration and Hall mobility of the film are 1.3×10⁻² Ω·cm, 4.1×10¹⁹ cm⁻³ and 12.4 cm²· V⁻¹· s⁻¹, respectively. The transmittance of the film reaches 82%.     

Automatic recognition and evaluation of micro-contaminant particles on ultra-smooth optical substrates using image analysis method

Micro-contaminant particles on surface of optical substrate have unfavorable influence on light characteristics and instability of optical devices. Proper recognition and evaluation of micro-contaminant particles on post-cleaning substrate are important in fabricating high-performance optical substrates. Based on image analysis and difference of gray scale threshold in image zones, this paper presents a technique for automatically recognizing micro-contamination, and the relevant software developed for on-line evaluation of the level of cleanliness on ultra-smooth optical substrate. Using the self-developed software incorporating high-resolution microscope, optical yttrium iron garnet (YIG) and K8 substrate surfaces of post-chemical mechanical polishing (CMP) were investigated. Results from analyzing the YIG and K8 optical substrates before-and-after laser cleaning illustrated the success of the developed automatic recognition and on-line evaluation system in identifying the micro-contaminant particles on the ultra-smooth substrate surface.     

Preparation and characterization of iron oxide thin films by spray pyrolysis using methanolic and ethanolic solutions

Iron oxide thin films have been obtained by spray pyrolysis using 100% methanolic and ethanolic solutions of iron tri-chloride. The films were deposited onto ITO-coated glass substrates. The preparative conditions have been optimized to obtain compact, pin-hole-free and smooth thin films which are adherent to the substrate. The structural, morphological and compositional characterizations have been carried out by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The films deposited using ethanolic solution results into pure hematite; α-Fe₂O₃ thin films, however, films deposited using methanolic solution consists of hematite and maghemite-c phases of iron oxide. The films are nanocrystalline with particle size of 30-40 nm. The optical absorbance of the film was of the order of 10⁵ cm⁻¹. The optical band gap of films was found to be 2.26 and 2.20 eV for the films deposited using methanolic and ethanolic solutions, respectively.     

Simultaneous Measurement of Particle Size and Particle Velocity by the Spatial Filtering Technique

The objective of this study was to compare the measuring results of a fiber‐optical probe based on a modified spatial filtering technique with given size distributions of different test powders and also with particle velocity values of laser Doppler measurements. Fiber‐optical spatial filtering velocimetry was modified by fiber‐optical spot scanning in order to determine simultaneously the size and the velocity of particles. The fiber‐optical probe system can be used as an in‐line measuring device for sizing of particles in different technical applications. Spherical test particles were narrow‐sized glass beads in the range 30–100 μm and irregularly shaped test particles were limestone particles in the range 10–600 μm. Particles were dispersed by a brush disperser and the measurements were carried out at a fixed position in a free particle‐laden air stream. Owing to the measurement of chord lengths and to the influence of diffraction and divergent angle, the probe results show differences from the given test particle sizes. Owing to the particle‐probe collisions, the mean velocity determined by the probe is smaller than the laser Doppler mean velocity.     

Pulsed Nd:YAG laser depositions of ITO and DLC films for OLED applications

Indium-tin oxide (ITO) films deposited on heated and non-heated glass substrates by a pulsed Nd:YAG laser at 355 nm and ∼2.5 J/cm² were used in the fabrication of simple organic light-emitting diodes (OLEDs), ITO/(PVK + Alq₃ + TPD)/Al. The ITO was deposited on heated glass substrates which possessed resistivity as low as ∼3 × 10⁻⁴ Ω cm, optical transmission as high as ∼92% and carrier concentration of about ∼5 × 10²⁰ cm⁻³, were comparable to the commercial ITO. Substrate heating transformed the ITO microstructure from amorphous to polycrystalline, as revealed by the XRD spectrum. While the polycrystalline ITO produced higher OLED brightness, it was still lower than that on the commercial ITO due to surface roughness. A DLC layer of ∼1.5 nm deposited on this ITO at laser fluence of >12.5 J/cm² improved its device brightness by suppressing the surface roughness effect.     

Modelling laser cleaning of low-absorbing substrates: the effect of near-field focussing

A three-dimensional model for laser cleaning of spherical, transparent particles on low-absorbing substrates has been developed. It takes into account near-field focussing of the laser radiation by the particles. The intensity distribution under a particle was found using Mie theory together with the geometrical optics approximation. This permits the estimation of the beam width at the substrate surface and the focal distance of the radiation coming from the spherical particle. These parameters are used to find the distribution of intensity within the low-absorbing substrate from the formula for a focussed Gaussian beam. This is in contrast with most other models of laser cleaning, which assume that all absorption occurs at the surface of the substrate. The energy criterion was used to calculate the threshold fluence. The model predicts threshold fluences of the order of 10³ J/cm² for silica spheres having a diameter of the order of a micron on silica substrates, assuming adhesion by van der Waals force. As this is well above the damage threshold for silica, it effectively predicts that laser cleaning of silica spheres from silica will be impossible. For glass slides the threshold fluence is predicted to be a factor of 10^-4 times smaller than that for silica slides (about 0.1 J/cm²). This is due to the much higher absorption of glass compared to that of silica at 248 nm. PACS 42.62.Cf; 81.65.Cf     

Preparation of pulse plated GaAs films

Thin GaAs films were prepared by pulse plating from an aqueous solution containing 0.20 M GaCl₃ and 0.15 M As₂O₃ at a pH of 2 and at room temperature. The current density was kept as 50 mA cm⁻² the duty cycle was varied in the range 10-50%. The films were deposited on titanium, nickel and tin oxide coated glass substrates. Films exhibited polycrystalline nature with peaks corresponding to single phase GaAs. Optical absorption measurements indicated a direct band gap of 1.40 eV. Photoelectrochemical cells were made using the films as photoelectrodes and graphite as counter electrode in 1 M polysulphide electrolyte. At 60 mW cm⁻² illumination, an open circuit voltage of 0.5 V and a short circuit current density of 5.0 mA cm⁻² were observed for the films deposited at a duty cycle of 50%.     

Modification of photocathode of dye-sensitized nanocrystalline solar cell with platinum by vacuum coating,thermal decomposition and electroplating

Conducting glass substrates are modified with platinum by vacuum coating, thermal decomposition and electrochemical sedimentation methods. A dye-sensitized nanocrystalline solar cell (DSC) is assembled by using a substrate modified with platinum as photocathode. The surface status of the photoanode is observed, the surface resistance of the substrate is measured, and the influence of the photoanode on the photoelectrical efficiency of the DSC is investigated. It is found that the platinum film prepared by the electrochemical sedimentation method with a plane, shining and uniform appearance shows lower surface resistance and better photoelectric efficiency than that prepared by the other two methods. The surface resistance is 12.4 Ω · cm^?1, using it as photoanode, and the DSC's open circuit voltage, short current and fill factor is 6.2 mA/cm², 0.662 V and 52.3%, respectively.     

CEMS and SEM studies of the ion-beam mixed Ni−Sn and Al−Sn systems

Metallic¹¹⁹Sn was vapour deposited on Al and Ni substrates to form layers about 40nm thick and subsequently irradiated with 100keV Xe⁺ at fluences 1, 5 and 10·10¹⁵ Xe⁺/cm². Irradiation with 100keV N⁺ at 5·10¹⁶N⁺/cm² fluence was also accomplished on an Al sample on which a layer of 100nm¹¹⁹Sn was previously electrodeposited. Surface evolution of the deposited layers due to irradiation has been observed by SEM and loss of Tin due to sputtering has been evidenced by EDX microanalysis. Changes of chemical structure at the irradiated surfaces have been followed by CEMS: β-Sn, SnO, SnAl₂O₄, SnO₂ and SnAl₂O₅ or β-Sn, dissolved Tin in Nickel, SnO₂, Ni₃Sn and Ni₃Sn₂ phases were recognized on the surface of Aluminium and Nickel substrates respectively.     

ZnO nanoparticles produced by novel reactive physical deposition process

This paper reports the deposition of ZnO nanoparticles with controlled sizes and different particle densities and their structural, composition and optical properties. They were deposited by means of a DC magnetron based vacuum nanoparticle source onto different substrates (GaAs, Si and Ti/SiO₂/Si). We believe that this is the first time that such nanoparticles have been produced using this unique technique. Zinc was used as sputtering target to produce zinc nanoparticles which were oxidized in-line using molecular oxygen. The structural properties and chemistry of the ZnO were studied by transmission electron microscopy. An average particle size of 6(±2) nm was produced with uniform size distribution. The particle density was controlled using a quartz crystal monitor. Surface densities of 2.3 × 10¹¹/cm², 1.1 × 10¹³/cm² and 3.9 × 10¹³/cm² were measured for three different deposition runs. The ZnO particles were found to be single crystalline having hexagonal structure. Photoluminescence measurements of all samples were performed at room temperature using a cw He-Cd laser at 325 nm excitation. The UV emission around 375 nm at room temperature is due to excitonic recombination and the broad emission centered at 520 nm may be attributed to intrinsic point defects such as oxygen interstitials.     

Effects of phase explosion in pulsed laser deposition of nickel thin film and sub-micron droplets

Nickel (Ni) thin films were deposited on glass substrates in high vacuum and at room temperature with third-harmonic or 355-nm output from a nanosecond Nd:YAG laser. At low laser fluence of 1 J/cm², the deposition rate was about 0.0016 nm/shot which increased linearly until 4 J/cm². Above 4 J/cm², the onset of phase explosion in the ablation abruptly increased the optical emission intensity from laser-produced Ni plume as well as thin-film deposition rate by about 6×. The phase explosion also shifted the size distribution and number density of Ni droplets on its thin-film surface. On the other hand, the surface structures of the ablated Ni targets were compared between the scan-mode and the fixed-mode ablations, which may suggest that droplets observed on the thin-film surface were caused by direct laser-induced splashing of molten Ni rather than vapour-to-cluster condensation during the plume propagation.     

Optical In Situ Size and Concentration Measurement of Particles Dispersed in Gases at Temperatures up to 1000°C

Based on previous experience, an optical particle counter has been designed which allows the direct measurement of the size and concentration of dust particles in gas flows at high temperatures. The instrument features a new optical measuring volume definition together with a signal control to avoid border‐zone error effects. The instrument has a free working distance of 200 mm. Hence it is possible to make true in situ measurements in pipe flows with a cross‐section of ca. 60 cm² and additionally to protect the device against heat and dust precipitation on the optical windows. The instrument was initially used to examine the separation behaviour of cake‐forming rigid ceramic barrier filters at temperatures up to 1000 °C. In particular, the fractional efficiencies and the time‐related concentration changes on the clean gas side caused by a pulse jet cleaning event could be determined. The results obtained so far demonstrate that ceramic barrier filters show basically the same behaviour as conventional filters, but possess a substantially higher separation efficiency at a corresponding higher pressure drop (fractional penetration values between 10⁻⁵ and 10⁻⁹ depending on the type of filter material and the cake formation).     

General design basis for a final optics assembly to decrease filamentary damage

The high-power laser beam in the final optics assembly of high-power laser facilities is often modulated by contamination particles, which may cause local high light intensity, thereby increasing the filamentary damage probability for optical components. To study the general design basis for a final optics assembly to decrease the risk of filamentary damage,different-sized contamination particles deposited on a component surface are simulated to modulate a 351-nm laser beam based on the optical transmission theory, and the corresponding simulation results are analyzed statistically in terms of the propagation characteristic and the light field intensity distribution of the modulated laser beam. The statistical results show that component thickness and distance between components can to some extent be optimized to reduce the appearance of local high light intensity, and the general design basis of component thickness and arrangement are given for different control levels of particle sizes. Moreover, the statistical results can also predict the laser beam quality approximately under the existing optics design and environmental cleanliness. The optimized design for final optics assembly based on environmental cleanliness level is useful to prolong the lifetime of optics and enhance the output power of high-power laser facilities.