Single Crystal Silicon Substrates Research Articles

Effect of temperature on microstructure and electrical properties of TaSi 2 thin films grown on Si substrates

Tantalum silicide (TaSi 2) thin films were deposited on n-type silicon single crystal substrates using a dual electron-gun system and with Ta and Si targets. The thicknesses of TaSi 2 thin films considered in this study are in the range 200–500 nm, respectively. The TaSi 2/Si samples were annealed at temperature 1173 K for 2 h in a vacuum of 10 −8 mbar. The structure of the tantalum silicide thin films was investigated by X-ray diffraction (XRD). X-ray diffraction results show changes in the structure of TaSi 2 thin films from amorphous to crystalline after annealing. According to XRD analysis, a complete conversion to single-phase disilicide TaSi 2 was achieved from a sample composition of Ta:Si = 1:2. DC conductivity was measured for the TaSi 2 thin films in the temperature range 300–900 K before and after annealing. It has been observed that the DC conductivity and activation energy was affected by changing the TaSi 2 film thickness and by annealing. The experimental results indicate that, the conduction phenomena of the investigated sample proceeded via two distinct mechanisms. The first one in the low-temperature range T < 500 K can be described by thermally-assisted tunneling of the carriers in the localized states near the band edge. The value of the pre-exponential factor before and after annealing is less than 10 4 Ω −1 cm −1. The other process appears in the high temperature region T > 500 K, where thermally activated conduction occurs through the extended states. Here the value of the pre-exponential factor before and after annealing is larger than 10 4 Ω −1 cm −1. The conductivity is greater in the crystalline phase than in the amorphous phase. The activation energy Δ E for our films before and after annealing is increased with increasing film thickness.

Structure and photoelectric properties of Si1 − x Sn x epilayers

Epitaxial layers of n-type Si1 − x Snx (0 ≤ x ≤ 0.04) solid solution were grown by liquid phase epitaxy from tin-based solution melt confined between two horizontal Si(111) single crystal silicon substrates. The structure of epilayers was determined and the photosensitivity spectra of pSi-nSi1 − x Snx (0 ≤ x ≤ 0.04) structures were studied at various temperatures. It is established that Si0.96Sn0.04 films have a perfect single crystal structure with (111) orientation and a subgrain size of 60 nm. The photosensitivity edge of the pSi-nSi0.96Sn0.04 structure is shifted to longer wavelengths as compared to that of the pSi-nSi structure. The photosensitivity of the pSi-nSi0.96Sn0.04 structure in the impurity absorption range depends on the temperature.

ChemInform Abstract: Low Temperature CVD of SiO2 Films Using Novel Precursors.

Novel precursors, hydridospherosiloxanes, for SiO 2 deposition were synthesized for the first time in high yields from HSiCl 3 . This procedure resulted in a mixture of two hydridospherosiloxanes, namely, HT8 (O h -H 8 Si 8 O 12 ) and HT10 (D 5h -H 10 Si 10 O 15 ). Excellent quality SiO 2 thin films were successfully deposited on single crystal silicon substrates using the above mentioned precursor mixture by chemical vapor deposition

Stress‐induced nanostructures through laser‐assisted scanning probe nanolithography

We demonstrate a methodology using a laser-assisted scanning probe nanolithography (LASPN) technique to generate organized nanostructures. Experimental approach combined with finite element analysis was utilized to study the interfacial interactions between a gold-coated probe of an atomic force microscope and a single crystal silicon substrate. Research results proved that the tip temperature had been raised via LASPN to 900 K at a laser power of 12 mW. Nanolines were formed during sliding while the silicon substrate was heated at a laser power of 5 mW. We propose an energy model to explain the phenomenon.

Surface characterization on graphitization of nanodiamond powder annealed in nitrogen ambient

AbstractA nanodiamond thin film is deposited on a single crystal silicon substrate by dip‐coating technique. Surface characterization of the unannealed nanodiamond sample, and the samples annealed at various temperatures in nitrogen ambient, is conducted by XPS and Raman spectroscopy. The fitting data of the C1s core level XPS peak reveal that the sp2/sp3 ratio in the unannealed sample and the sample annealed at 900 °C and 1500 °C are 0.44, 0.55 and 6.08 respectively. All spectra including the C1s core level XPS spectrum, the plasmon energy‐loss spectrum associated with C1s peak, C KVV Auger spectrum of the sample annealed at 900 °C are similar to those of the unannealed sample. However, the spectra of the sample annealed at 1500 °C are very different. Annealing at 900 °C fails to produce appreciable graphitization, and an onion‐like carbon structure with a small diamond core is formed when the nanodiamond is heated to 1500 °C. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Synthesis, thermal and optical properties of metal(II) complexes with a novel ligand derived from pyrazolone-5

Three novel metal(II) complexes, CoL2, NiL2 and CuL2 (L = (Z)-4-(2-(1,3-dimethyl-5-oxo-1H-pyrazol-4(5H)-ylidene)hydrazinyl)-1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one were synthesized. Their structures were postulated based on elemental analyses, 1H NMR, ESI-MS, FT-IR spectra and UV-vis spectra. The effect of different central metal(II) ions on absorption bands of the metal(II) complexes in CHCl3 solutions was researched. The result indicates that the bathochromic shift is CuL2 > NiL2 > CoL2. The absorption properties of thin films and thermal stability of these complexes are also discussed. In addition, the optical constants (complex refractive index N=n+ik) and thickness of the complex thin films on polished single-crystal silicon substrates were measured by spectroscopic ellipsometry. Results indicate that the metal(II) complexes would be a promising recording medium candidate for blu-ray recordable optical storage system due to good absorption at 405 nm, high thermal stability and sharp thermal decomposition, and a high n values of 1.35–1.45 and a low k values of 0.33–0.39.

Preparation of Iron and Gold Silicide Nanodomains on Silicon (111) by the Reaction of Gold, Iron−Gold Core−Shell, and Alloy Nanoparticles with Triethylsilane

This study describes a strategy to use composite colloidal nanoparticles and triethylsilane as precursors to synthesize nanometer size structures on single-crystal silicon substrate. The concept is demonstrated by depositing gold, iron-gold alloy, and iron-gold core-shell nanoparticles on silicon (111). Upon heating, the nanoparticles form new crystalline phases on the Si (111) surface. Atomic force microscope (AFM) data show the collapse of the iron gold core-shell and alloy nanoparticles at temperatures 100-200 degrees C higher than gold nanoparticles, indicating the efficient tethering of iron containing nanoparticles on silicon (111). Both structural analysis and X-ray spectroscopy show that the iron-gold alloy and iron-gold core-shell nanoparticles successfully form the semiconducting beta-FeSi(2) phase at relatively low temperature. The stabilities of the silicide are assessed at elevated temperatures. Silicon successfully nucleates on the created nanostructures, which suggests strong catalytic activity towards producing further nanostructures on the surface.

Evaluation of nucleic acid duplex formation on gold over layers in biosensor fabricated using Czochralski-grown single-crystal silicon substrate

With a view to developing an economical and elegant biosensor chip, we compared the efficiencies of biosensors that use gold-coated single-crystal silicon and amorphous glass substrates. The reflectivity of light over a wide range of wavelengths was higher from gold layer coated single-crystal silicon substrates than from glass substrates. Furthermore, the efficiency of reflection from gold layers of two different thicknesses was examined. The thicker gold layer (100 nm) on the single-crystal silicon showed a higher reflectivity than the thinner gold film (10 nm). The formation of a nucleic acid duplex and aptamer-ligand interactions were evaluated on these gold layers, and a crystalline silicon substrate coated with the 100-nm-thick gold layer is proposed as an alternative substrate for studies of interactions of biomolecules.

OPTIMAL SYNTHESIS OF C-AXIS ORIENTED ALN THIN FILMS

ABSTRACT C-axis oriented AlN thin films have been deposited by reactive sputtering at room temperature. The crystallographic properties of layered film structures consisting of a piezoelectric layer, aluminum nitride (AlN), synthesized on fused silica as well as on single crystal silicon substrates, have been examined. Aluminum nitride thin films were deposited by reactive pulsed-DC magnetron sputtering using an aluminum target in an Ar/N2 gas mixture. The influence of the most critical deposition parameters on the AlN thin film crystallography has been investigated by means of X-ray diffraction (XRD) analysis of the Full Width at Half Maximum (FWHM) of the rocking curve of the AlN (0002) peak. The relationship between the deposition conditions and the crystallographic orientation of the films is discussed and a guide is given on how to optimize these conditions to obtain highly c-axis oriented AlN thin films without substrate heating.

Erosion Mechanism of Ultrasonic Vibration Abrasive Waterjet in Micro Machining

In this paper, a study on erosion mechanism of Ultrasonic Vibration Abrasive Waterjet is presented. Theoretical analysis of the total effective erosion kinetic energy of UVAWJ is performed. By using a UVAWJ machining system with an Ultrasonic Vibration Power Workbench, the comparative experiment is conducted. The erosion surfaces of the single crystal silicon substrate were measured by Optical Profiler and observed with Scanning Electron Microscope. The material removal mechanisms are discussed. It is concluded that the erosion by UVAWJ, with the aid of high-frequency ultrasonic vibration, can obtains a high material removal, less cracks and good finish surface.

Aluminum nitride on silicon: Role of silicon carbide interlayer and chloride vapor-phase epitaxy technology

A new approach to the deposition of aluminum nitride (AlN) layers with thicknesses ranging within ∼0.1–10 μm on silicon single crystal substrates by hydride-chloride vapor-phase epitaxy (HVPE) has been developed and implemented, which involves the formation of thin (∼100-nm-thick) intermediate silicon carbide (3C-SiC) interlayers. It is established that wavy convex bands with a height of about 40 nm are present on the surface of as-grown AlN layers, which are situated at the boundaries of blocks in the layer structure. It is suggested that the formation of these wavy structures is related to morphological instability that develops due to accelerated growth of AlN at the block boundaries. Experiments show that, at low deposition rates, AlN layers grow according to a layer (quasi-two-dimensional) mechanism, which allows AlN layers characterized by half-widths (FWHM) of the X-ray rocking curves of (0002) reflections about ωθ = 2100 arc sec to be obtained.

Thickness determination of SmCo films on silicon substrates utilizing X-ray diffraction

This paper presents a nondestructive measurement technique for the determination of the film thicknesses of Co and SmCo based magnetic films deposited by sputtering on single-crystal silicon (100) substrates. X-ray diffraction of Cu Kα radiation has been used to measure the intensity of the (400) reflection from bare silicon substrates and as attenuated by sputter coated Co and SmCo based films on Si substrates. A four-axis research diffractometer allowed the substrate orientation to be fine adjusted to maximize the (400) diffraction intensity. The thickness of SmCo based films was in a range from 0.05 to 5 μm. Co film thicknesses on Si could be measured to a few tens of nanometers. The accuracy of the thickness measurements depends on the effective mass attenuation coefficient of the film material. For the materials considered, the thicknesses determined by the X-ray attenuation method agree within at least several percent to values determined by other methods.

Oxygen pressure and measurement temperature dependence of defects related bands in zinc oxide films

The ZnO films were fabricated by pulsed laser deposition at various oxygen pressure on single crystal silicon substrate. The structural and optical properties were investigated at various measurement temperature. The results showed that all the films have good c-axis preferred orientation. The different defects in films were fabricated which can be caused by various oxygen pressure. The films deposited at 1 Pa oxygen pressure have the most intense and narrow UV emission, and did not exhibit the deep band emission at the various measurement temperature. With the decrease of measurement temperature, the V O -, O i - and O Zn -related band energy decreases, which is opposed to the V Zn -related defects, meanwhile, the intensity of O i -related emission peak has a sharp increase.

Blue Luminescent Properties of Silicon Nanowires Grown by a Solid-Liquid-Solid Method

Silicon nanowires (SiNWs) were grown directly from n-(111) single-crystal silicon (c-Si) substrate based on a solid-liquid-solid mechanism, and Au film was used as a metallic catalyst. The room temperature photoluminescence properties of SiNWs were observed by an Xe lamp with an exciting wavelength of 350 nm. The results show that the SiNWs exhibit a strongly blue luminescent band in the wavelength range 400–480 nm at an emission peak position of 420 nm. The luminescent mechanism of SiNWs indicates that the blue luminescence is attributed to the oxygen-related defects, which are in SiOx amorphous oxide shells around the crystalline core of SiNWs.

Cathode electrodeposition and characterization of Ru nanoparticles doped a-CN x:H composite films

Well-dispersed and stable Ru nanocrystalline particles with diameter in the range of 2–4 nm embedded in the amorphous carbon nitride matrix were synthesized on single crystal silicon (100) substrate by cathode electrochemical deposition using acetonitrile and Ru 3(CO) 12 as carbon source and dopant, respectively. The results obtained from high-resolution transmission electron microscopy showed that the Ru nanoparticles were presented in the form of hexagonal Ru crystal structure with preferred orientation of (101). X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy confirmed that the as-obtained films are composed of C, N, Ru and H. Raman spectroscopy indicated that the films contained tetrahedral (sp3) and trigonal (sp2) bonding structures. After doping Ru into the amorphous carbon nitride matrix, the conductivity of the composite films is commendably enhanced and the cyclic voltammograms tests show evident oxidation and visible reduction peaks of Ru, also indicating the presence of Ru immobile phase in the amorphous carbon matrix.

Effect of Si(100)-c(4 × 12)-Al and Si(111)-(5.55 × 5.55)-Cu reconstructions on the deposition of cobalt onto silicon surface

The use of surface reconstructions for modifying properties of single crystal silicon substrates with a view to the creation of new nanostructures is a promising direction in the development of nanotechnologies. Systems Si(100)-c(4 × 12)-Al and Si(111)-(5.55 × 5.55)-Cu occupy special positions among stable reconstructions of the silicon surface, which have been recently demonstrated to be promising templates. The adsorption of cobalt on these surfaces at various temperatures has been studied using scanning tunneling microscopy. The room-temperature deposition leads to the formation of a weakly ordered layer of metallic Co with retained initial reconstructions at the Co/Si interface. An increase in the temperature leads to the formation of faceted cobalt silicide islands on both reconstructed surfaces.

One-Dimensional Zn-Doped In2O3−SnO2 Superlattice Nanostructures

One-dimensional (1D) Zn-doped In2O3−SnO2 superlattice nanostructures have been fabricated on single-crystal silicon substrates by the layer-by-layer growth mode via the thermal chemical vapor transport and condensation with Au catalysts. The morphology, structure, and composition of the as-synthesized 1D superlattice were analyzed in detail. To exploit the potential applications of the fabricated nanostructures, the field emission properties of samples were characterized. The growth mechanism of the 1D Zn-doped In2O3−SnO2 superlattice nanostructures was discussed on the basis of the vapor−liquid−solid process.

Controlled growth of silicon nanowires by solid-liquid-solid method and their formation mechanism

High quality silicon nanowires （SiNWs） were grown directly from n-（111） silicon single crystal substrate by using Au film as a metallic catalyst. The diameter and length of the formed nanowires are 30—60 nm and from several micrometers to sereral tens of micrometers, respectively. The effects of Au film thickness, annealing temperature, growth time and N2 gas flow rate on the formation of the nanowires were experimentally investigated. The results confirmed that the silicon nanowires with controlled diameter, length, shape and orientation can be obtained via reasonably choosing and optimizing various technical conditions. The formation process of the silicon nanowires is analyzed qualitatively based on solid-liquid-solid growth mechanism.

Film's Forming Materials for THz Spectral Range Purposes

At the presented work, we report the results of research of optical properties PbTe, ZnSe, ZnS, BaF2 and PbF2 thin fllms in a wide infrared spectral range. These materials are used for manufacturing thin fllm multilayer interference systems working in the mid-infrared and probably be applied in far infrared to submillimeter. Optical properties in our understand- ing are spectral dependences of refractive index and extinction coe-cient of layers. Films with thicknesses 3{7 microns were received by thermal vacuum deposition on single-crystal silicon sub- strates. Refractive index and extinction coe-cient dispersion in 1.5{150 microns spectral range (2{200THz) were determined by method based on analysis of the transmission and re∞ection interference spectra. Films of PbTe under consideration do not possess appreciable absorption bands in the investigated spectral range. While, other investigated fllms have intensive absorp- tion bands in the 25{100 microns region. With using of the investigated materials the \solar blind fllter for 1.0{50 microns spectral range on the single-crystal silicon substrate was designed and made.

Si quantum dots embedded in an amorphous SiC matrix: nanophase control by non-equilibrium plasma hydrogenation

Nanophase nc-Si/a-SiC films that contain Si quantum dots (QDs) embedded in an amorphous SiC matrix were deposited on single-crystal silicon substrates using inductively coupled plasma-assisted chemical vapor deposition from the reactive silane and methane precursor gases diluted with hydrogen at a substrate temperature of 200 degrees C. The effect of the hydrogen dilution ratio X (X is defined as the flow rate ratio of hydrogen-to-silane plus methane gases), ranging from 0 to 10.0, on the morphological, structural, and compositional properties of the deposited films, is extensively and systematically studied by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier-transform infrared absorption spectroscopy, and X-ray photoelectron spectroscopy. Effective nanophase segregation at a low hydrogen dilution ratio of 4.0 leads to the formation of highly uniform Si QDs embedded in the amorphous SiC matrix. It is also shown that with the increase of X, the crystallinity degree and the crystallite size increase while the carbon content and the growth rate decrease. The obtained experimental results are explained in terms of the effect of hydrogen dilution on the nucleation and growth processes of the Si QDs in the high-density plasmas. These results are highly relevant to the development of next-generation photovoltaic solar cells, light-emitting diodes, thin-film transistors, and other applications.