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Nowadays, the interaction of additive technologies and methods for designing or optimizing porous structures has yielded good results. Construction with complex microarchitectures can be created using this approach. Varying the microarchitecture leads to changes in weight and mechanical properties. However, there are problems with geometry reconstruction when dealing with complex microarchitecture. One approach is to use Voronoi cells for geometry reconstruction. In this article, an extension of the Voronoi diagram algorithm to orthotropic space for material structural design is presented. The inputs for the method include porosity, ellipticity, and ellipticity direction fields. As an example, a beam with fixed end faces and center kinematic loading was used. To estimate robust results for different numbers of clusters, 50, 75, and 100 clusters are presented. The porosity for smoothed structures ranged from 21.5% up to 22.8%. The stress–strain state was determined for the resulting structures. The stiffness for the initial and smoothed structures was the same. However, in the case of 75 and 100 clusters, local stress factors appeared in the smoothed structure. The maximum von Mises stress decreased by 20% for all smoothed structures in the area of kinematic loading and increased by 20% for all smoothed structures in the area of end faces. [ABSTRACT FROM AUTHOR]

The volumetric distribution of bone tissue can be analysed in terms of orthotropic medium. In this case, it is important to define the orthotropic directions. Nowadays, computed tomography methods allow getting such information. The method for automation such analysis is presented. Firstly, the threshold of binarization should be calculated. Then the sample should be meshed and each element should be binarized. After that fabric tensor, eigenvalues, eigenvectors and fractional anisotropy can be calculated for each element. Statistical methods were used to analyse the field of the obtained data. Described methods were used on a bone sample. It was shown that for a sample the fabric tensor is constant and the fractional anisotropy is close to zero. That’s means that the medium in the sample was isotropic.

High quality sub-10 nm high-k dielectrics are deposited on top of MoS2 and evaluated using a dual-gate field effect transistor configuration. Comparison between top-gate HfO2 and an Al2O3/HfO2 bilayer shows significant improvement in device performance due to the insertion of the thin Al2O3 layer. The results show that the Al2O3 buffer layer improves the interface quality by effectively reducing the net fixed positive oxide charge at the top-gate MoS2/high-k dielectric interface. Dual-gate sweeping, where both the top-gate and the back-gate are swept simultaneously, provides significant insight into the role of these oxide charges and improves overall device performance. Dual-gate transistors encapsulated in an Al2O3 dielectric demonstrate a near-ideal subthreshold swing of ∼60 mV/dec and a high field effect mobility of 100 cm2/V·s. [ABSTRACT FROM AUTHOR]

A high quality Al2O3 layer is developed to achieve high performance in top-gate MoS2 transistors. Compared with top-gate MoS2 field effect transistors on a SiO2 layer, the intrinsic mobility and subthreshold slope were greatly improved in high-k backside layer devices. A forming gas anneal is found to enhance device performance due to a reduction in the charge trap density of the backside dielectric. The major improvements in device performance are ascribed to the forming gas anneal and the high-k dielectric screening effect of the backside Al2O3 layer. Top-gate devices built upon these stacks exhibit a near-ideal subthreshold slope of ~69 mV/dec and a high Y-Function extracted intrinsic carrier mobility (μo) of 145 cm2/V.s, indicating a positive influence on top-gate device performance even without any backside bias. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides (TMDs) have attracted intensive attention due to their atomic layer-by-layer structure and moderate energy bandgap. However, top-gated transistors were only reported in a limited number of research works, especially transistors with a high-k gate dielectric that are thinner than 10 nm because high-k dielectrics are difficult to deposit on the inert surface of the sulfide-based TMDs. In this work, the authors fabricated and characterized top-gated, few-layer MoS2 transistors with an 8 nm HfO2 gate dielectric. The authors show that the cleaning effect of ultrahigh vacuum annealing before high-k deposition results in significantly reduced gate leakage current of HfO2, and they show that N2 or a forming gas anneal after device fabrication affects the threshold voltage, drive current, dielectric leakage, and C-V frequency dependence. This work demonstrates how the fabrication process can affect the yield and the electrical characterization of top-gated TMD transistors, which in effect can help researchers further enhance the performance of their devices. [ABSTRACT FROM AUTHOR]

The electronic properties of the HfO 2 /MoS 2 interface were investigated using multifrequency capacitance-voltage (C-V) and current-voltage characterization of top-gated MoS 2 metal-oxide-semiconductor field effect transistors (MOSFETs). The analysis was performed on few layer (5-10) MoS 2 MOSFETs fabricated using photolithographic patterning with 13 and 8 nm HfO 2 gate oxide layers formed by atomic layer deposition after in-situ UV-O 3 surface functionalization. The impedance response of the HfO 2 /MoS 2 gate stack indicates the existence of specific defects at the interface, which exhibited either a frequency-dependent distortion similar to conventional Si MOSFETs with unpassivated silicon dangling bonds or a frequency dispersion over the entire voltage range corresponding to depletion of the HfO 2 /MoS 2 surface, consistent with interface traps distributed over a range of energy levels. The interface defects density (D it ) was extracted from the C-V responses by the high-low frequency and the multiple-frequency extraction methods, where a D it peak value of 1.2 × 10 13 cm -2 eV -1 was extracted for a device (7-layer MoS 2 and 13 nm HfO 2 ) exhibiting a behavior approximating to a single trap response. The MoS 2 MOSFET with 4-layer MoS 2 and 8 nm HfO 2 gave D it values ranging from 2 × 10 11 to 2 × 10 13 cm -2 eV -1 across the energy range corresponding to depletion near the HfO 2 /MoS 2 interface. The gate current was below 10 -7 A/cm 2 across the full bias sweep for both samples indicating continuous HfO 2 films resulting from the combined UV ozone and HfO 2 deposition process. The results demonstrated that impedance spectroscopy applied to relatively simple top-gated transistor test structures provides an approach to investigate electrically active defects at the HfO 2 /MoS 2 interface and should be applicable to alternative TMD materials, surface treatments, and gate oxides as an interface defect metrology tool in the development of TMD-based MOSFETs.