Papers by Keyword: Depth Profile

Abstract: For precise investigation of distribution for impurity or composition at SiO₂/SiC interface, dual-beam Time-of-flight Secondary ion mass spectrometry (TOF-SIMS) with low energy sputtering beam was available. In addition to the experimental profiles, simulation using MRI model, in which Mixing, Roughness and Information depth were employed as parameters, enabled to acquire a more authentic distribution at the SiO₂/SiC interface. Slight discrepancy on depth profiles between samples with different surface roughness was duplicated on the convoluted profiles in the simulation. Moreover, reconstructed profile of nitrogen indicated a real distribution with less impact of mixing and roughness, although that may contain uncertainty due to incompletion in the simulation model or variation of the distribution owing to detection species in the experiment. From the result of carbon profiles of both experimental and convoluted profiles, the relative discrepancy on the carbon distribution between samples was clarified, which suggested the possibility that a carbon thin layer at the SiO₂/SiC interface would be found in the future.

Abstract: The influence of different indentation parameters including loading type, loading/strain rate, frequency and amplitude on nanohardness depth profiles on DC-MS W-C based coatings thick from 300 to 850 nm were investigated with the aim to determine the best conditions for the measurement of hardness of thin films during sinusoidal loading cycle. Nanohardness tests were performed on G200 (Agilent Technologies) and NHT (CSM Instruments) nanoindenters using standard loading/unloading cycle, CMC (continuous multicycle) mode and continuous stiffness measurement method (CSM) or sinus mode, respectively. The increase of strain rate and sinus amplitude results in decrease of maxima hardness of profiles while the increase of frequency caused its increase.

Abstract: Ultra-shallow junctions (USJs) were formed by low-energy As ion implantation with the subsequent furnace annealing. It was found that the significant amount of oxygen is redistributed from the silicon bulk to the arsenic-implanted region. We present the effect of oxygen gettering at the creation of arsenic-doped USJs using the marker layer created by ion implantation of ¹⁸O isotope.

Abstract: Depth profile of subsurface chemical composition and free volume in segmented polyurethane-urea/clay nanocomposites was studied by angle resolved X-ray photoelectron spectroscopy (ARXPS) and Doppler broadening energy spectroscopy (DBES) using slow positron beam. The ARXPS studies revealed increasing N/C atomic ratio (hard segment to soft segment ratio) at any given depth for the clay loaded samples compared to the neat polymer. DBES study revealed significant microstructure modification with clay loading. Self segregation of hard and soft segments in neat polymer and their interspersing with clay loading was observed from DBES measurements.

Abstract: The doping of Cu in the BaSi₂ films grown by molecular beam epitaxy (MBE) with various Cu concentrations for the suitability of the solar cells was studied in this paper. The main objective of the present work is to investigate and compare the carrier concentration of Cu-doped BaSi₂ films grown with different Cu Knudsen cell temperatures and qualify as a potential candidate for more efficient solar cells. The reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD) measurements and secondary ion mass spectroscopy (SIMS), were used to determine the structure, depth profile and composition of the grown samples. The electrical properties like resistivity as well as carrier concentration were measured by using a four point probe method and Van der Pauw technique, respectively. During the MBE growth, different temperatures for Cu Knudsen cell ranging from 800 to 1200 °C were chosen and the optimum growth condition for both heavily doped n-type as well as p-type in the MBE was investigated. In our previous work, the Al, Sb doped BaSi₂ were used as a potential candidate for the formation of pn-junction for solar cells, but the result was not encouraging one due to diffusion and segregation problems in the surface and BaSi₂/Si interface regions. In the present work n-type BaSi₂ layers with their dopant atoms uniformly distributed in the grown layers for the formation of high-quality of BaSi₂ pn-junction with single crystal nature were successfully developed. The realizations to develop cost effective and more efficient solar cells are inevitable for both terrestrial as well as space applications.

Abstract: This study deals with the interfacial reactions and electrical properties of Ta/4H-SiC contacts. Tantalum thin films (~100 nm) were deposited onto SiC wafer at room temperature by argon ion beam sputtering. The samples were then heated in high vacuum at 650°C, 800°C or 950°C for 30 min. X-ray photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (XRD), Auger electron spectroscopy (AES) and current-voltage (I-V) technique were used for characterising the samples. Ohmic contact is formed in the studied samples after annealing at or above 800°C even though considerable amount of metallic Ta still exists. The reaction zone possesses a layered structure of Ta2C/Ta2C+Ta5Si3/SiC. High enough temperature is needed to provide for sufficient interface change to tailor the contact properties.

Abstract: Low-temperature diffusion in thin films of the stable isotopes, 56Fe/57Fe, was studied by applying secondary ion mass spectrometry (SIMS). Processing of the concentration profiles obtained was done by using the Hall – Morabitto “median gradient” method. The bulk and intergrain selfdiffusion coefficients were determined.

Abstract: Pearlitic steel and pure tungsten specimens were ground using a table-type grinding machine. The thin surface layers affected by the grinding process were characterized using focussed ion beam milling and microscopy. The strongly graded zone altered due to severe plastic deformation and recrystallisation was found to be less than 3m thick. The microstructure in that zone depends on the grinding parameters. Using synchrotron X-ray diffraction, the residual stresses were measured for penetration depths ranging from 0.25 m to 9 m. Based on the approach by Dölle and Hauk, the residual shear stresses were separated from the residual normal stresses. In pearlitic steel, residual shear stresses of opposite sign were observed in the two phases (ferrite and cementite) and found to be compensating each other, while shear stresses were proved to be absent in single-phase tungsten. These results underline that residual shear stresses caused by severe plastic shear deformation exist only as micro-stresses.

Abstract: A quantitative approach to determination of depth profiles of optical properties of Si-implanted SiO2 films based on spectroscopic ellipsometry (SE) is presented. From the SE measurements, the depth profiles of the complex refractive index of SiO2 films containing Si nanocrystals (Si-nc) are obtained with an effective medium approximation (EMA) in the wavelength range of 400-1200nm. The optical profiles obtained imply the existence of a wave-guide in the Si-doped SiO2 films.