Role of cleaning methods on bond quality of Ti coated glass/imidex system

Thin film materials are widely used in the fabrication of semiconductor microelectronic devices. In thin film deposition, cleanliness of substrate surface have become critically important as over 50% of yield losses in integrated circuit fabrication are caused by microcontamination [1]. There are many wafer cleaning techniques. The most successful approach for silicon wafer cleaning technique is RCA clean [2]. But for glass substrate it is still not known which procedure of cleaning is the best. This paper provides an understanding of the right way of glass wafer cleaning method, with a focus towards identifying good bond strength. Two wafer cleaning techniques have been used for cleaning glass substrates in the context of laser micro-joining of dissimilar substrates. First cleaning procedure involves two steps, first cleaning in acetone solution and then in DI water solution. After each step dried with N₂. Second cleaning procedure involves four steps, first cleaning with 1% Alconox solution, second in DI water, third in acetone solution and finally in a methanol solution and dried with N₂ after each step. Deposition of Ti thin film on top of these two types of substrate using DC magnetron sputtering method also showed better adhesion of Ti film on glass for the second type of cleaning method. Scanning electron microscopy (SEM) analyses of the lap shear tested failed surfaces for these two kinds of samples revealed strong bond for samples prepared by second cleaning method compared to first cleaning method. Characterization of these two sets of samples using X-ray photoelectron spectroscopy (XPS) has shown excellent contamination removal for the second cleaning method. This modification is believed to be due to reduction of carbon contamination.     

Fabrication and Investigation of Photovoltaic Converters Based on Polycrystalline Silicon Grown on Borosilicate Glass

The microcrystalline Si layers with grain sizes of up to several tens of micrometers were grown. The physical vapor deposition (PVD), amorphous–liquid–crystalline (ALC) transition technique and a steady-state liquid phase epitaxy (SSLPE) are used for the fabrication of three different samples. The first sample under consideration was prepared first by deposition of a-Si onto glass substrates by PVD at room temperature, followed by heating from the front side to ~300°C and deposition of an indium metallic solvent. At the preparation of the second sample, an additional silicon layer with the thickness of 400 nm was deposited. A sample, when after that a c-Si was grown on the seed layer by SSLPE from indium solution is referred as a third sample. The resulting samples have a strong absorption edge in the mid-infrared region around 1960 cm^?1. Six well-resolved oscillations with an average period of δB = 0.1214 T are revealed on the third sample’s magnetoresistance curve at gradually increasing of the magnetic field from zero up to 1.6 T. It is assumed that either Aharonov–Bohm effect or kinetic phenomena taking place in the grains boundaries at lateral current flow are responsible for those oscillations. Quantitative evaluations show that due to the strong absorption in mid-infrared region, enlargement of the photoresponse spectrum will occur and the efficiency of solar and other thermal energy conversion should be around ~10–15% higher than that of traditional PV cells based on silicon on glass structures.     

Self-assembling of metal nanoparticles on patterned semiconductor surfaces (Au/GaAs)

The fabrication of selectively deposited arrays of metal nanoparticles on textured semiconductor surfaces is reported. Gold nanoparticles were grown on previously textured surfaces using photostimulated chemical deposition from an aqueous solution of AuCl₃ salt. Surfaces with random and periodic microreliefs were used as templates of sites for nanoparticle deposition. Dendrite-like and quasi-grating-like microreliefs were produced by anisotropic etching of GaAs (100) substrates. Periodic reliefs (diffraction gratings and bi-gratings) were fabricated by the holographic photochemical etching of the same substrates. Our results from AFM, SEM and EDX show that gold predominantly locates on the tops of the microreliefs. Since the surface relief strongly affects the topology of metal deposition, the use of microprofiling of semiconductor surfaces allows designing nanostructure deposition.     

Surface-enhanced Raman scattering active substrates by liquid flame spray deposited and inkjet printed silver nanoparticles

Surface-enhanced Raman scattering (SERS) active substrates were made via liquid flame spray deposition and inkjet printing of silver nanoparticles. Both processes are suitable for cost-effective fabrication of large-area SERS substrates. Crystal violet (CV) solutions were used as target molecules and in both samples the detection limit was approximately 10 nM. In addition, sintering temperature of the inkjet printed silver nanoparticles was found to have a large effect on the SERS activity with the higher curing temperature of 200 °C resulting in contamination layer on silver and cancelation of the SERS signal. This layer was characterized using an X-ray photoelectron spectroscopy (XPS).     

High temperature growth of InN on various substrates by plasma-assisted pulsed laser deposition

InN has attracted much attention due to its optical and electrical properties that make it suitable for the fabrication of infrared optical devices and high-speed electronic devices. In this work we report on the structural properties and morphology of InN thin films grown on different substrates by radiofrequency plasma beam assisted pulsed laser deposition. Sapphire and silicon substrates were considered for the growth of these films. The influence of substrate type and growth parameters on the morphology and structural properties of the resulting InN thin films is discussed. The structural analysis of the samples was performed by means of X-ray diffraction. The morphology of the thin films was investigated through atomic force microscopy. Although growth of InN from a metallic In target using nitrogen radiofrequency plasma assisted pulsed laser deposition was achieved for all the samples, growth conditions were found to play an important role on the crystal quality of the resulting thin films.     

钙钛矿太阳电池综述

基于有机-无机杂化钙钛矿材料(CH₃NH₃PbX₃)制备的太阳电池效率自2009年从3.8%增长到19.6%, 因其较高的光吸收系数, 较低的成本及易于制备等优势获得了广泛关注. 钙钛矿材料不仅可以作为光吸收层, 还可用作电子和空穴传输层, 以此制备出不同结构的钙钛矿太阳电池: 介孔结构、介观超结构、平面结构、无HTM层结构和有机结构. 除此之外, 钙钛矿材料制备方法的多样性使其更具吸引力, 目前已有一步溶液法、两步连续沉积法、双源共蒸发法和溶液-气相沉积法. 本文主要介绍了钙钛矿太阳电池的发展历程、工作原理及钙钛矿薄膜的制备方法等. 详细阐述了电池每一层的具体作用和针对现有的钙钛矿结构各层材料的优化, 最后介绍了钙钛矿太阳电池所面临的问题和发展前景, 以期对钙钛矿太阳电池有进一步的了解, 为制备新型高效的钙钛矿太阳电池打下坚实的基础.     

在乙醇水溶液中组装三维胶体光子晶体薄膜

近几年来，用垂直沉积法制备胶体晶体得到了人们的广泛关注。用乙醇水溶液为溶剂，用垂直沉积法制备了二氧化硅胶体晶体薄膜。用这种方法一次制备的样品厚度可达20微米以上，并且将较大微球组装成了有序性较好的胶体晶体薄膜。用扫描电镜（SEM）和光学方法检测了样品的质量和厚度。     

Fabrication of high-quality colloidal photonic crystals with sharp band edges for ultrafast all-optical switching

Application of the pressure controlled isothermal heating vertical deposition method to the fabrication of colloidal photonic crystals is systematically investigated in this paper. The fabricated samples are characterized by scanning electron microscope and transmission spectrum. High-quality samples with large transmissions in the pass bands and the sharp band edges are obtained and the optimum growth condition is determined. For the best sample, the transmission in the pass bands approaches 0.9 while that in the band gap reaches 0.1. More importantly, the maximum differential transmission as high as 0.1/nm is achieved. In addition, it is found that the number of stacking layers does not increase linearly with concentration of PS spheres in a solution, and a gradual saturation occurs when the concentration of PS spheres exceeds 1.5 wt.%. The uniformity of the fabricated samples is examined by transmission measurements on areas with different sizes. Finally, the tolerance of the fabricated samples to baking was studied.     

二次离子质谱深度剖面分析氢化微晶硅薄膜中的氧污染

运用二次离子质谱研究了甚高频等离子体增强化学气相沉积制备的不同硅烷浓度和功率条件下薄膜中的氧污染情况.结果发现：薄膜中的氧含量随硅烷浓度和功率的变化而改变.制备的微晶硅薄膜，晶化程度越高薄膜中的氧含量相对越多.另外，不同本底真空中的氧污染实验结果表明：微晶硅材料中的氧含量与本底真空有很大的关系，因此要制备高质量的微晶硅材料，高的本底真空是必要条件. 关键词： 甚高频等离子体增强化学气相沉积 二次离子质谱 氧污染     

Fabrication of microelectrodes using flow layer-by-layer self assembly of gold nanoparticles

Microelectrodes to be used in microfluidic devices were prepared from the layer-by-layer flow deposition of gold nanoparticles. Pre-designed microfluidic channels were used as templates for the flow driven deposition of the nanoparticles in sequence with poly (diallyldimethyl amonium chloride) (PDADMAC). The electrical resistivity of the gold nanoparticle assembly was found to be strongly dependant on the concentration of sodium citrate used in the gold nanoparticle synthesis. As the electrical properties of the film changed from insulating to conducting when decreasing the citrate concentration, a 4 point probe setup was used to measure the resistivity of the film. Near bulk conductivity (5.42 × 10⁻⁶ Ω cm) was achieved with only 10 layers of film. The thickness and morphology of the flow-printed multilayer microelectrode was characterized using atomic force microscopy (AFM) and a field emission scanning electron microscope (FE-SEM). To demonstrate its usefulness, the microelectrode assembly was then tested toward the detection of KCl in solution, having a concentration ranging from 1 to 20 mM using AC current detection in a simple setup. Good linearity and stability of the electrode confirmed that this method could be very convenient for the fabrication of microelectrodes for lab-on-chip applications.     

Micropatterned vertically aligned carbon-nanotube growth on a Si surface or inside trenches

The good field-emission properties of carbon nanotubes coupled with their high mechanical strength, chemical stability, and high aspect ratio, make them ideal candidates for the construction of efficient and inexpensive field-emission electronic devices. The fabrication process reported here has considerable potential for use in the development of integrated radio-frequency amplifiers or field-emission-controllable cold-electron guns for field-emission displays. This fabrication process is compatible with currently used semiconductor-processing technologies. Micropatterned vertically aligned carbon nanotubes were grown on a planar Si surface or inside trenches, using chemical vapor deposition, photolithography, pulsed-laser deposition, reactive ion etching, and the lift-off method. This carbon-nanotube fabrication process can be widely applied for the development of electronic devices using carbon-nanotube field emitters as cold cathodes and could revolutionize the area of field-emitting electronic devices. Received: 30 August 2001 / Accepted: 3 September 2001 / Published online: 20 December 2001     

Anisotropy characteristics in a Permalloy film induced by a nonuniform magnetic field

Inhomogeneities were observed for the first time in the magnetic structure of a thin Permalloy film, induced by a strongly nonuniform magnetic field applied in the plane of the substrate during fabrication of the samples. The films were obtained by vacuum deposition using a molecular-beam epitaxy system. A nonuniform field was created on the substrate using four samarium-cobalt magnets. The anisotropy of local sections of the samples was measured using a scanning-ferromagnetic-resonance spectrometer. A strong correlation was observed between the distribution of the magnitude and direction of the local magnetic anisotropy of the film and the magnetic-field distribution in the plane of the substrate. Fiz. Tverd. Tela (St. Petersburg) 40, 1291–1293 (July 1998)     

Towards laser-manipulated deposition for atom-scale technologies

We have developed an apparatus for nanostructure fabrication based on direct deposition of laser-manipulated cesium vapors onto pyrolitic graphite. Key features of our apparatus are production and manipulation of a longitudinally cooled atom beam, which allows for straightforward operation in the moderate to low flux density conditions. Both unstructured and structured low surface coverage depositions have been carried out and samples carefully analyzed at the atom scale by in situ tunneling microscopy. Results represent a step forward to the realization of a novel technology for space-controlled deposition of few, eventually single, atoms.     

Solid freeform fabrication of alumina using laser-assisted ESAVD

Electrostatic spray assisted vapour deposition (ESAVD) has been used successfully to produce films and coatings. A combination of laser-assisted (LA) deposition and ESAVD has been developed for the direct fabrication of alumina ceramics. This novel laser-assisted ESAVD technique involves spraying a liquid precursor onto a substrate whilst a laser beam is simultaneously used to heat the precursor and cause the decomposition and chemical reactions of the precursor in order to produce a solid deposit. A desired three-dimensional (3-D) object can be formed through layer-by-layer deposition using a computer-controlled platform. Dense or porous alumina ceramics can be deposited on the substrate by optimizing the processing parameters. This paper reports the fabrication of alumina parts by the laser-assisted ESAVD method. The effect of processing parameters including laser scanning speed, laser beam size and laser power on the microstructure will be presented. Scanning electron microscope (SEM) and X-ray diffraction (XRD) have been used to characterise the phase and structure of the deposited alumina parts.     

Polycarbonate activation for electroless plating by dimethylaminoborane absorption and subsequent nanoparticle deposition

Electroless plating of metal films on polymer substrates usually requires the presence of metal particles acting as catalytically active nuclei for the deposition reaction. Herein, we present a novel and versatile approach towards the activation of polycarbonate substrates with metal nanoparticles. It is based on the diffusion of dimethylaminoborane into the polymer matrix, followed by reaction of the sensitized substrates with metal salt solutions. The reducing agent uptake was controlled by changing the duration of the sensitization and the dimethylaminoborane concentration in the sensitization solution. Different seed types (Ag, Au, Pd, Pt and Rh) were deposited by variation of the activation solution. The proposed mechanism was confirmed with FTIR and TEM measurements. In addition, AFM revealed that apart from a slight roughening in the nanometer range, the surface morphology of the polymer remained unchanged, rendering the method viable for template-based nanomaterial fabrication. Due to its pronounced variability, the new technique allows to tailor the activity of polymer substrates for consecutive electroless plating. The feasibility and nanoscale homogeneity of the process were proven by the electroless fabrication of well-defined Au and Pt nanotubes in ion-track etched polycarbonate templates. The combination of features (use of simple and easily scalable wet-chemical processes, facile seed variation, high activation quality on complex surfaces) renders the outlined technique promising for the fabrication of intricate nanomaterials as well as for the metallization of macroscopic work pieces.     

Creating room temperature Ohmic contacts to 4H-SiC: studied by specific contact resistance measurements and X-ray photoelectron spectroscopy

The use of a silicon interface pre-treatment to produce low resistance Ohmic nickel contacts to 4H-SiC, circumventing the need for contact post annealing, is reported. The effects of two different SiC pre-metal deposition surface preparation techniques: RCA cleaning (control sample) and a silicon interlayer pre-treatment (SIP), are discussed. Electrical characterization of contacts on treated surfaces, using circular transfer length measurements (CTLM), revealed that contacts to RCA cleaned samples were Schottky in nature, unless annealed at temperatures greater than 700 °C. In contrast, contacts formed on SIP SiC surfaces exhibited Ohmic behaviour directly after fabrication, without the need for post metallisation annealing. Average contact resistances as low as 1.3E−05 Ω cm² have been recorded for SIP samples. This fabrication process has distinct technological advantages compared to standard techniques for forming Ohmic contacts to SiC. To consolidate our findings the chemical and electrical nature of the SIP nickel-SiC interface, as it was sequentially formed and annealed, was examined using X-ray photoelectron spectroscopy (XPS). Based on these results, a model is proposed to explain the as-deposited Ohmic contact nature of the SIP sample.     

Evolution of structural and optical properties of rutile TiO2 thin films synthesized at room temperature by chemical bath deposition method

Nanocrystalline thin films of TiO₂ were prepared on glass substrates from an aqueous solution of TiCl₃ and NH₄OH at room temperature using the simple and cost-effective chemical bath deposition (CBD) method. The influence of deposition time on structural, morphological and optical properties was systematically investigated. TiO₂ transition from a mixed anatase–rutile phase to a pure rutile phase was revealed by low-angle XRD and Raman spectroscopy. Rutile phase formation was confirmed by FTIR spectroscopy. Scanning electron micrographs revealed that the multigrain structure of as-deposited TiO₂ thin films was completely converted into semi-spherical nanoparticles. Optical studies showed that rutile thin films had a high absorption coefficient and a direct bandgap. The optical bandgap decreased slightly (3.29–3.07 eV) with increasing deposition time. The ease of deposition of rutile thin films at low temperature is useful for the fabrication of extremely thin absorber (ETA) solar cells, dye-sensitized solar cells, and gas sensors.     

Conducting boron-doped single-crystal diamond films for high pressure research

Epitaxial boron-doped diamond films were grown by microwave plasma chemical vapor deposition for application as heating elements in high pressure diamond anvil cell devices. To a mixture of hydrogen, methane and oxygen, diborane concentrations of 240–1200 parts per million were added to prepare five diamond thin-film samples. Surface morphology has been observed to change depending on the amount of diborane added to the feed gas mixture. Single-crystal diamond film with a lowest room temperature resistivity of 18 mΩ cm was fabricated and temperature variation of resistivity was studied to a low temperature of 12 K. The observed minima in resistivity values with temperature for these samples have been attributed to a change in conduction mechanism from band conduction to hopping conduction. We also present a novel fabrication methodology for monocrystalline electrically conducting channels in diamond and present preliminary heating data with a boron-doped designer diamond anvil to 620 K at ambient pressure.     

热丝加热电流对CH薄膜沉积速率和表面形貌的影响

 热丝辅助裂解法是结合气相沉积制备聚对二甲苯薄膜和热丝化学气相沉积而形成的一种制-CH薄膜的新方法。热丝辅助裂解法的最大特点就是在保持低衬底温度情况下可以获得高沉积速率，而热丝加热电流对薄膜沉积速率和薄膜表面形貌具有重要影响。研究表明，热丝加热电流越大，薄膜沉积速率越高，在加热电流9A时，薄膜沉积速率可达0.002mm/min，同时薄膜表面粗糙度随之增加，薄膜表面也开始出现其它元素污染，因此，一般热丝加热电流选择为7A附近。     

Titanium Oxide Film Deposition on Acrylic Resin by Atmospheric TPCVD

A dye-sensitized solar cell (DSC) is a solar cell that uses an anatase film as a photovoltaic device. Since the anatase film and dye play the roles of electron carrier and electron generator, respectively, in the DSC, porous anatase films are desirable. In this paper, in order to develop a low-cost fabrication process for the photovoltaic device of the DSC, photocatalytic titanium oxide film deposition was carried out by atmospheric thermal plasma CVD. Ar gas, which served as the working gas for the plasma jet and substrate, and a 20 $times$ 40 $times$ 3 mm transparent acrylic resin plate were used. Titanium tetra iso butoxide was used as feedstock. Consequently, by cooling the substrate, an anatase-dominant film could be deposited at 773 K in deposition temperature without meltdown of the substrate on the condition of 100 mm in deposition distance, even in the case of acrylic resin substrate use. By wettability and methylene-blue decoloration tests, it was confirmed that the film showed hydrophilic and decolored methylene blue perfectly by 8-h UV irradiation. Furthermore, the DSC in which the titanium oxide film deposited by this technique was included as a photovoltaic device generated a photoelectromotive force of 25 mV. From these results, these thermal plasma processes were found to have high potential for DSC fabrication.