Papers by Keyword: AFM

Abstract: The impact on doping profile, surface roughness and defect production of each process step for a suggested Multiple epitaxy and implantation (MEI) process for Super-junction has been investigated through Secondary Ion Mass Spectrometer (SIMS), Atomic Force Microscope (AFM), Deep Level Transient Spectroscope (DLTS) and Molten KOH etching. Results show that the suggested process can possibly reduce the cost of the original fabrication and speed up the process.

Abstract: Local electrical properties of a 4H-Silicon Carbide SiC(0001) 4°off macrostepped surface, obtained after liquid Si melting in a SiC/Si/SiC sandwich configuration, are investigated by Atomic Force Microscopy (AFM) in both DC and RF modes. On the same sample, macrosteps that are wide enough for allowing spatial resolution of the signal from terraces and step risers, but also some unreacted areas with standard flat surface (without macrosteps) are characterized. Scanning Spreading Resistance (SSRM, DC mode) reveals homogeneous conductivity on the wide terraces of the 4H-SiC(0001) macrosteps. On unreacted areas, which contain many step risers, the resistance is found higher than on the wide terrasses but it is also noisier. In addition, the AFM-RF scanning Microwave Impedance Microscopy (sMIM) mapping confirms the previous results by revealing lower conductivity on the unreacted areas than on the terraces of the macrosteps. Based on these results, some points defects located at the step risers which contribute negatively to the electrical properties of 4H-SiC(0001) surface are identified and electrically characterized.

Abstract: Cu₃SnS₄ films were grown on glass substrates via method of spin coating, followed by annealing at 550 °C in a furnace under H₂S:Ar (1:9) sulfur rates of 30 and 40 sccm for 15, 30, and 60 minutes. The effect of the sulfur rate and annealing time on the structural, morphological, and optical behaviors of the samples was systematically investigated using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), photoluminescence (PL), Hall effect, and UV-Vis spectroscopy. The XRD patterns revealed that all the Cu₃SnS₄ samples had a polycrystalline structure. The crystallite size, dislocation density, interplaner distance, micro-strain, and crystallite number of the Cu₃SnS₄ samples were calculated from the XRD spectra. Among all the samples, the CTS sample annealed for 15 minutes under a 30 sccm H₂S:Ar (1:9) gas flow showed the best crystalline structure. The surface morphology of the samples showed spherical micro-crystal formations. Analysis of the Cu₃SnS₄ samples indicated that the surfaces were composed of valley and peak regions. The valley regions appeared relatively smooth, while the peak regions displayed a crystal structure with specific orientations. When examining the energy band gap values, it is observed that the energy band gap of the films increases significantly with the increase in sulfur flow rate. PL analysis revealed emission peaks at approximately 1.41 eV and 1.80 eV, along with broad emission bands at 549 nm, 567 nm, 689.42 nm, and 882.6 nm. An increase in sulfur content led to a reduction in peak intensity, which is attributed to conduction band fluctuations and the formation of structural defects. The carrier concentration of the samples is found to be on the order of 10¹⁷ cm⁻³ and 10¹⁸ cm⁻³, which is more appropriate for thin-film solar cells (TFCSs).

Abstract: Ni₈₀Fe₂₀ thin films have been manufactured onto monocrystalline silicon substrates, utilizing a physical vapor evaporation technique under vacuum. The thickness of these Permalloy films fluctuates between 16 and 45 nm. The structure and morphology of the Permalloy film are studied as a function of the thickness of the deposited magnetic layer. Rutherford’s backscattering spectroscopy technique was used to quantify the samples. X-ray diffraction method has been used to examine the structure, and the atomic force microscope scrutinizes the surface topography and performs the film roughness. These techniques allowed to infer that all the films crystallize in the face-centered cubic structure and exhibit <111> preferred orientation. The size of the crystallites is directly proportional to the thickness of the magnetic layer. The films are under stress and the lattice parameter increases with thickness. The 45 nm thickest film exhibits the roughest topographic surface with root mean square roughness near 2.4 nm, while the 16 nm thinnest film exhibits the smoothest topographic surface, not exceeding 3 Å. These results, and others, will certainly contribute to a better understanding of the physical properties of Permalloy material, and improve their technological applications

Abstract: In this work, an investigation of the mechanically exfoliated MoS₂ under the influence of heat treatment was carried out. Optical and atomic force microscopy techniques were applied to determine the number of layers. Resonant Raman investigation was performed, which clearly showed systematic layer-dependent spectral features. The surface morphology of MoS₂ was investigated with the STM. Atomic-resolution images of MoS₂ is were obtained. Three types of atomic defects were identified as substitutions of donor and acceptor atoms in the Mo atomic layer below the topmost sulfur layer.

Abstract: This work focuses on the preparation of pure nanocrystalline SnO2 and SnO2:Cu thin films on cleaned glass substrates utilizing a sol-gel spin coating and chemical bath deposition (CBD) procedures. The primary aim of this study is to investigate the possible use of these thin films in the context of gas sensor applications. The films underwent annealing in an air environment at a temperature of 500 ^◦C for duration of 60 minutes. The thickness of the film that was deposited may be estimated to be around 300 nm. The investigation included an examination of the structural, optical, electrical, and sensing characteristics, which were explored across various preparation circumstances, specifically focusing on varied concentrations of Cu-doping (2, 4, and 6 wt.%). The deposited films were analyzed by several techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical absorption spectroscopy. The films generated by the spin coating method had a tetragonal rutile structure, while the films created via the chemical bath deposition (CBD) technique displayed both tetragonal rutile and orthorhombic structures. The spin coating technique was used to make films of several weight percentages (0, 2, 4, and 6 wt.%). The resulting crystallite sizes were examined and found to be 23 nm, 18 nm, 14 nm, and 10.5 nm, respectively. Similarly, films made using the chemical bath deposition (CBD) method exhibited crystallite sizes of 22, 13.9, 9.3, and 8.15 nm, respectively. The obtained findings from atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses indicate a consistent trend whereby, as the concentration of Cu-doped material rises, there is a decrease in the average grain size. The transmittance and absorbance spectra were examined within the wavelength range of 300 to 1000 nm. The films generated by both approaches exhibit a significant level of light transmission throughout the visible spectrum. The bandgap energy of spin coating and CBD films decreases with increasing Cu-doped concentrations; the values were (3.88, 3.8, 3.68, and 3.63) eV and (3.8, 3.78, 3.66, and 3.55) eV, respectively. The electrical characteristics of the films include direct current (DC) electrical conductivity, which indicates the presence of two activation energies, Ea₁ and Ea₂. These activation energies exhibit an upward trend when the concentration of Cu doping is increased. The films were examined for their ability to detect carbon monoxide (CO) gas at a concentration of about 50 ppm at normal room temperature conditions. The sensitivity of the films to carbon monoxide (CO) gas was assessed at various time intervals and temperatures. The results indicated that the film generated using spin coating exhibited a notably high sensitivity at a temperature of 200 °C, while the film prepared using the chemical bath deposition (CBD) approach had heightened sensitivity at a temperature of 150 °C. Keywords: Spin coating, SnO₂ thin films, CBD, AFM, XRD, gas sensor.

Abstract: Due to the expansion of defects like single Shockley-type Stacking Faults inside the SiC epitaxial drift layer, during high current stress, classical SiC MOSFETs can be victims of the degradation of their electrical characteristics. The introduction of an epitaxial SiC buffer layer between the substrate and the n- drift epilayer, called recombination-enhancing buffer layer, was shown to avoid this degradation. In this paper, TCAD simulations of the electrical behavior of such a commercial SiC MOSFET device with varying buffer layer thickness are studied, indicating only small modifications of the electrical characteristics. These simulations are combined with the characterization of the local electrical properties using an AFM-sMIM technique, allowing to determine the real thickness of the different layers of the device. These measurements highlight an inhomogeneous conductivity in the SiC substrate, being probably compensated by the introduction of the SiC buffer layer.

Abstract: Investigation of the doped areas in 4H-SiC power devices has been done by non-destructive characterization methods. It consists of local surface potential measurements by Kelvin Probe Force Microscopy (KPFM) coupled with scanning electron microscopy (SEM) and µ-Raman spectroscopy. Near-field mappings of the devices’ surface have been realized, allowing us to discern the differently doped areas.

Abstract: Nanostructuring of the surface occurs after annealing at high temperature of 4H-SiC samples. The surface morphology becomes needle-shaped like black silicon. The roughness of the surface also increases due to annealing and a slight etching of nanostructured zones occurs with an accentuated phenomenon at the boundaries. Electroluminescence is obtained by applied forward bias on fabricated PIN diode structures with localized nanostructurated windows in surface. Light intensity seems to be more sensitive to the initial orientation of the substrate and less to the annealing temperature in the 1500°C-1700°C range.

Abstract: Background: zirconium (Zr) implants are known for having an aesthetically pleasing tooth-like colour Unlike the grey cervical collar that develops over time when titanium (Ti) implants are used in thin gingival biotypes. However, the surface qualities of Zr implants can be further improved. This present study examined using thermal vapour deposition (TVD) to coat Zr implants with germanium (Ge) to improve its physical and chemical characteristics and enhance soft and hard tissue responses. Materials and methods: Zr discs were divided into two groups; the uncoated (control) group was only grit-blasted with alumina particles while the coated (experimental) group was grit-blasted then coated with Ge via TVD. Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), water contact angle test, and cross-hatch adhesion tests were then used for surface characterization Results: An XRD analysis of the Ge-coated Zr samples revealed the substrate while the FESEM results revealed a continuous coating with no cracks. The mean surface roughness and hydrophilicity of the Ge-coated Zr substrate was significantly higher than that of the uncoated Zr substrate (P≤0.01). The cross-hatch adhesion of all the samples was 0%, thereby indicating good coating adhesion. Conclusion: Therefore Coating Zr implants with Ge via TVD enhances its physical and chemical properties.