In this work we provided a review of the study of MACE (metal-assisted chemical etching) of Si with Ag, Pt, Ni and Au films and clusters. Type and shape of the metal mask play an important role in determination of morphology of the nanostructured layer. It is possible to form both wide range of porous layer and nanowires array. The basic features of the MACE with various types and shape of the metal were revealed.
Applicability of porous anodic alumina formed in selenic acid based electrolyte as the matrix for formation and Raman characterization of nanomaterials is investigated. For that, Raman spectra of nanostructured CdS layers deposited on top of porous alumina matrices are obtained. These spectra were compared with the ones, registered for the composites prepared using the commonly used matrix formed in oxalic acid solution. It is shown that application of porous alumina matrix formed in selenic acid electrolyte afford to detect the peaks corresponding to the CdS layers even at small amounts of CdS. It happens due to the absence of luminescence background in such matrix, which exists in matrices produced in organic acid electrolytes, for example, in oxalic acid.
Study of new materials and composites based on porous silicon is of great interest for electronics and microelectronics industry. Functional characteristics of structured layers are closely associated with their morphology properties and treatment conditions correspondently. In this work a porous silicon layers formed by metal-assisted chemical etching (MACE) with the use of gas adsorption-desorption method, scanning electron microscopy (SEM) and fractal geometry have been examined. Specific surface area given by multi-point BET method was about of 7 m2/g and 13 m2/g for n-Si and p-Si specimens correspondently. Surface fractal dimension Ds was estimated for p-type mesoporous silicon from BET results using Neimark’s thermodynamic approach, the value is Ds=2.86. “Slit islands” Mandelbrot’s algorithm was applied for analysis of SEM images and calculations of surface fractal dimension Ds, computation gives Ds = 2.52 for n-Si sample and Ds = 2.84 for p-Si sample. The study testified the fractal nature of porous layers formed by MACE and exhibits correlation between different methods of fractal dimension estimation. The results can be applied for improvement of methods of structured solids characterization.
This work is devoted to the CVD-synthesis of arrays of carbon nanotubes (CNTs) on Co-Zr-N-(O), Ni-Nb-N-(O), Co- Ta-N-(O) catalytic alloy films from gas mixture of C2H2+NH3+Ar at a substrate temperature of about 550°C.Heating of the amorphous alloy causes its crystallization and squeezing of the catalytic metal onto the surface. As a result, small catalyst particles are formed on the surface. The CNT growth takes place after wards on these particles. It should be noted that the growth of CNT arrays on these alloys is insensitive to the thickness of alloy film, which makes this approach technically attractive. In particular, the possibility of local CNT growth at the ends of the Co-Ta-N-(O) film and three-level CNT growth at the end of more complex structure SiO2/Ni-Nb-N-O/SiO2/Ni-Nb-N-O/SiO2/Ni-Nb-N-O/SiO2 is demonstrated.
In this paper, the influence of the conditions of chemical and electrochemical nickel plating of nanostructured silicon and subsequent heat treatment on the phase composition of Si/Ni structures with advanced interface is studied. Nanostructured silicon formed by chemical and electrochemical etching was used for the formation of a developed interphase surface. The resulting Si/Ni samples were analyzed using scanning electron microscopy, energy dispersive X-ray analysis, and X-ray phase analysis. The experiments have revealed the differences in phase composition of the Si/Ni structures obtained by different methods, both before and after heat treatment.
Atmosphere water influence in the nanostructured silicon (NSS) was investigated by IR-spectroscopy and electron work function measurement. Long-term non-reversible dynamics of IR-spectra was found as a result of 100% humidity influence on the nanostructured silicon. It was indicated that air humidity affects on the work function. Dynamics of the electron work function consists of reversible and non-reversible components. Reversible component appears as strong anti-correlation between work function and humidity. Work function change of NSS is about 0.4 eV while the humidity changes between 0% and 100%. Reversible component can be explained by physical sorption of water molecules on the surface. Non-reversible component manifests as long-term decreasing trend of work function in humid atmosphere. Transition curve during abruptly humidity changes alters its shape. Non-reversible component can be explained by chemisorption of water.
The features of the formation of multi-component metal sulfide films (Cu2ZnSnS4 and Cu2SnS3) formed by various methods SILAR technology were studied. Using different investigate methods the comparative analysis of the properties and composition of the films were carry out. The formation of a multi-component film in the mixed cationic solution is accompanied by additional processes in the solution and by the appearance of complex compounds. This factors has a strong influence on the composition and purity of the formed films. The characteristics of the solar cell test structures with ultrathin absorbing layer based on Cu2ZnSnS4 and Cu2SnS3 were obtained. It’s necessity to introduce an interlayer and make more carefully study of the composition and interface of the absorber layer.
A copper sulfide and bismuth sulfide thin films were deposited on Si/Ti substrate by successive ionic layer adsorption and reaction method at room temperature, using cupric chloride, bismuth chloride, complexing Na2EDTA and sodium sulfide aqueous solutions as precursors. The surface morphology, structural and electrical properties of the as-deposited films were investigated by scanning electron and atomic force microscopy, energy dispersive X-ray analysis (EDS), and 2-point probe methods. The films were found to be amorphous, rough with thickness 30 nm and 20 nm for CuSx and BiSx, respectively. Average atomic percentage of Cu:S and Bi:S in the as-deposited films was calculated as 1:1.5 and 2.3:3. It was noted that films possess resistive switching behavior. Ionic conductivity of the CuSx film was found to be 25,8·10-3 Ohm-1·cm-1 . Ionic conductivity of the BiSx film was found to be 16·10-3 Ohm-1·cm-1. Set voltages UON defined by I-V curves were found to be in the range 0,75-0,8 V/cm for both films. Reset voltages UOFF were found to be in the range 0,6-0,7 V/cm for both films. Thus, formed films can be used as active layers for memory devices application.
We propose approach for modeling thin aluminum film anodization in three dimensions using variation of coupled lattice map on volumetric grid, which is capable of capturing porous and nonporous aluminum oxide growth and electrochemical polishing modes. Model derivation is based on Parkhutik and Shershulsky understandings. Numerical simulation results for various initial conditions are shown and compared to experimental data.
It is shown that copper thin film conductors (10-100 nm thickness) have not the defined temperature of melting. The melting of 20 nm copper thin film starts at 610 °C after 5 mm and, at the same time, at 470 °C after 3 h 40 mm. The melting of 100 nm copper thin film starts at 740 °C after 7 mm and at 640 °C after 2 h 25 mm. The kinetics of this phenomenon has been studied. The stages of process have been shown. The activation energies of thin film melting have been estimated. It is demonstrated that the activation energy of process is decreased with the copper film thickness reduction. The character of activation energy changes has been explained with point of view of the hydrodynamics.
The technology of fabrication of the self-organizing ranked mask on base porous aluminum for etching nanosize pores in silicon has been considered. The experiments on obtaining the nanosize matrix structures in silicon have been conducted.
We considered the basic principles of AIIBVI (CdS) semiconductor deposition from aqueous solution by ECD and SILAR methods. Obtained results confirm that quality of CdS film synthesized by electrodeposition is practically identical to single crystal quality. The SILAR deposition allowed us to investigate quantum confinement in CdS nanocrystals.
The influence of the thermal regimes on the formation of ordered porous anodic alumina was investigated. The process of the formation of the high ordered films of porous anodic alumina was developed.
Nanowires of various metals were embedded into porous anodic alumina (PAA) by ac electrochemical deposition while the PAA layers remained on the Al substrate. Semiconductor nanowires of MeSx and MeSey were formed by sulfurization and selenization of the metal precursors. Deposited metal and semiconductor wires were characterized by scanning electron microscopy, scanning probe microscopy, Auger-spectrometry, and x-ray diffraction. Optical properties of silver nanowires, embedded into PAA matrix were investigated by spectrophotometry. Photovoltage spectroscopy was applied to demonstrate semiconductor properties of CdS nanowires prepared by the proposed technique.
The combined method of trench filling by copper for damascene technology has been developed. The method is based on copper deposition by ordinary electroplating and following low temperature melting of copper layer. The thickness of wetting layer has been optimized. The importance of seed layer surface treatment is demonstrated. It is shown that the thermal annealing at 650oC allows to dispose of voids appearing at copper electrochemical deposition into trenches.
We experimentally demonstrate very efficient non-phase-matched second- and third-harmonic generation from a macroporous GaP. The generated second-harmonic signal is independent of crystallographic orientation, and its enhancement is believed to be due to the light localization for which conditions exist in the studied samples of porous GaP. The nonlinear optical results are correlated with linear optical scattering studies and atomic-force microscopic images of the studied surfaces.
Demonstration of porous anodic alumina application for photonics and optoelectronics is presented. Investigation of photonic structures and nanocomposites based on porous anodic alumina is performed. Techniques of highly ordered porous structure formation are demonstrated. Features of nanocrystal template deposition into nanopores are discussed.
Two different ways of oriented carbon nanotube (CNT) selective growth are investigated. At first, template assisted vertical oriented CNT formation is used. We developed a process of individual (isolated) CNT growth in porous anodic alumina at position determined by nanoimprinting. Additionally a new fabrication method of planar nanoelements based on carbon nanotubes is described. The prototypes of nanoelements using an autoemission are designed and experimentally realized. Obtained electric field thresholds are less than 3V/μm.
Recent advances in hard x-ray production from porous silicon targets have been reported. Experimental data on efficient hot electron generation in plasma, created by 200 fs laser pulses at intensity in excess of 1016 W/cm2 are discussed. The assessment of the hot electron temperature in single laser shot was made using simple modification of the well known x-ray filter method. X-ray quanta with energy of approximately 80 keV were observed at the 'moderate' intensity of 2 X 1016 W/cm2, revealing the existence of the second non-thermal electron component with the 'temperature' of 30-50 keV. Finally, we discuss the feasibility to design 2.5 MeV neutron source with peak flux of more than 1020 neutrons using deuterium enriched nanowire metallic arrays.
We present results on plasma formation in porous silicon (cluster like solid with mean cluster size of 3 nm, mean density 0.1 - 0.2 of crystalline silicon) by femtosecond laser pulses at intensity above 10 TW/cm2. We deduced hot electron temperature as high as 8 keV and fast ions of at least 2 MeV energy.
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