Papers by Keyword: Scanning Probe Microscopy

Abstract: To generate both two-dimensional electron gas (2DEG) and two-dimensional hole gas (2DHG) at will in SiC polytype heterojunctions, simultaneous lateral epitaxy (SLE) method has been extended to form epilayers of alternating stacks of 4H-and 3C-SiC, which includes the first formation of single-domain 4H-SiC on 3C-SiC. The process starts with a spontaneous generation of mononuclear 3C-SiC on the atomically flat wide terrace on 4H-SiC, which expands parallel to the basal plane to form a single-domain 3C-SiC layer having the coherent interface with the underlying 4H-SiC layer. Step-controlled epitaxy is then applied using the adjacent 4H-SiC steps to grow an alternative 4H-SiC layer on top of the 3C-SiC surface, forming another coherent interface. The crystal structure, the interface structure, and the carrier distribution of this stacked epilayers was analyzed. Finally, it is demonstrated that 2DEG occurs at the coherent interface between the 3C-SiC Si-and 4H-SiC C-faces and 2DHG at the 3C-SiC C-and 4H-SiC Si-faces.

Abstract: The suitability of scanning probe methods based on atomic force microscopy (AFM) measurements is explored to investigate with high spatial resolution the elementary cell of 4H-SiC power MOSFETs. The two-dimensional (2D) cross-sectional maps demonstrated a high spatial resolution of about 5 nm using the scanning spreading resistance microscopy (SSRM) capabilities. Furthermore, the scanning capacitance microscopy (SCM) capabilities enabled visualizing the fluctuations of charge carrier concentration across the different parts of the MOSFETs elementary cell.

Abstract: We investigate the characteristics of polycrystalline Silicon (poly-Si) thin films for solar cells produced by very high frequency (VHF) plasma enhanced chemical vapor deposition using a conductive scanning probe microscope (SPM). We measure the surface morphology and local current images are simultaneously of the poly-Si layers with a thickness, d=2 mm, formed on textured Ag/SnO₂/glass in the range of RMS based-textured substrate (a) s=85nm, (b) s=42nm and (c) s=2nm respectively. Influences of the substrate texture on the crystal growth as well as the local current flow are discussed. Where we found that the average of local current proportional with crystallinity, where the poly-Si layer that has rich crystallinity indicated low conductivity that yield high local current.

Abstract: Titania nanotube arrays were formed by electrochemical anodic etching of titanium from glycerol solutions with addition of 0.5% HF and analyzed by scanning probe microscopy and ellipsometric analyzes. Potentiostatic curves allow identifying several different stages of growth of nanotubes of titanium dioxide, however, this method does not establish specific parameters of the surface. We demonstrated that analysis of the spectrum ellipsometric parameters Psi and Delta can used as a criterion of quality, frequency, depth and other characteristics of the obtained arrays of titania nanotube. The use of these methods of analysis allowed to fully characterize the different stages of growth of titania nanotube from glycerol solutions and can be used for quality control the resulting structures for various applications.

Abstract: The paper provides an overview of the results obtained when using the method of scanning probe microscopy for exploring surfaces of aluminum matrix composite (АC12+2.38%Cu+0.06%SiC) and modified aluminum alloy (АL2) samples with nanohardness measuring device “NanoScan-3D”. The authors describe a calibration process of the device, which was implemented via precise positioning the optical axis of nanohardness measuring device “NanoScan-3D” with the indenter axis. The paper highlights that the structure images of materials under study obtained in the process of optical metallographic tests are similar to results of scanning probe microscopy. The second major finding is that the modules of elasticity of phase components in materials АC12+2.38%Cu+0.06%SiC and АL2 can be appropriately measured using the method of scanning probe microscopy with nanohardness measuring device “NanoScan-3D”. The paper identifies that modules of elasticity of alpha solid solution grains, eutectic and released silicon are comparable in aluminum matrix composite АC12+2.38%Cu+0.06%SiC and modified aluminum alloy АL2. The authors also point out the convergence of modules of elasticity in the zones with embedded particles of silicon carbide with the data given in literature. The paper reports practical approval of the procedure for detecting the strengthening particles of silicon carbide in aluminum matrix composite АC12+2.38%Cu+0.06%SiC using the method of scanning probe microscopy with device “NanoScan-3D”.

Abstract: The switching current of the PZT domain patterns was detected by the conductive atomic force microscopy. The impact of the scan rate on the current contrast was studied. Successive current images of domain evolution during the polarization switching process were obtained. The impact of the local force exerted by the tip and the polarization cycles of the patterns were studied. The results suggested that the compressive strain exerted by the tip can decrease the piezoelectric coercive field and the polarization fatigue can increase the piezoelectric coercive field in the polarization inversion process from bottom to top.

Abstract: This work provides a comparative study of the mechanical properties of composite materials based on aluminum reinforced with carbon nanostructures. The study involved the tensile strength testing, as well as sclerometry and indentation in the submicron range. We determined the correlation of the values obtained for yield strength and hardness, and the tensile strength and morphology of the residual scratches.

Abstract: Surface properties of nanoscale iron garnet films of different compositions prepared by reactive ion beam sputtering were examined by means of scanning probe microscopy. Atomic force microscope images of the film surfaces are represented for the films of different compositions and deposition times. The article presents the dependences of the roughness parameters on the film composition and thickness and on the energy of Ar⁺ ions by which the substrates were pre-treated. It was shown that the roughness parameters of the films' surface increase with the increase of Ar⁺ ions energy and the films' thickness.

Abstract: Electronically active dopant profiles of epitaxially grown n-type 4H-SiC calibration layer structures with concentrations ranging from 3.10¹⁵ cm^-3 to 1·10¹⁹ cm^-3 have been investigated by non-contact Scanning Probe Microscopy (SPM) methods. We have shown that Kelvin Probe Force Microscopy (KPFM) and Electrostatic Force Microscopy (EFM) are capable of resolving two-dimensional carrier maps in the low doping concentration regime with nanoscale spatial resolution. Furthermore, different information depths of this wide band gap semiconductor material could be assessed due to the inherent properties of each profiling method. We additionally observed a resolution enhancement under laser illumination which we explain by reduced band-bending conditions. To gauge our SPM signals, we utilized epitaxially grown layers which were calibrated, in terms of dopant concentration, by C-V measurements.

Abstract: A comparative study of the mechanical properties of the extruded and flattened nanostructured composites Al-C₆₀ has been made using two different methods of destructive and non-destructive testing: tensile and compression macro-tests and sub-micron range sclerometry (scratch test). Direct correlation was found between the dominant types of deformation during scratching and the type of “stress-strain” dependencies. The results are useful for understanding the extrusion process and quality control at different load scale.