Explore the vast range of titles available.

We present an ultrafast thin-disk laser oscillator providing a record power of 550 W with 100-µJ, 852-fs pulses at a repetition rate of 5.5 MHz. This is enabled by a six-pass replicating-cavity multipass scheme and ion-implanted sapphire-bonded SESAMs.

High-precision digital (RS485 / Modbus) absolute pressure transducer based on “silicon on sapphire” structures for vacuum technology is presented.

Two-dimensional transition-metal dichalcogenides (TMDs) are of interest for beyond-silicon electronics 1 , 2 . It has been suggested that bilayer TMDs, which combine good electrostatic control, smaller bandgap and higher mobility than monolayers, could potentially provide improvements in the energy-delay product of transistors 3 – 5 . However, despite advances in the growth of monolayer TMDs 6 – 14 , the controlled epitaxial growth of multilayers remains a challenge 15 . Here we report the uniform nucleation (>99%) of bilayer molybdenum disulfide (MoS 2 ) on c -plane sapphire. In particular, we engineer the atomic terrace height on c -plane sapphire to enable an edge-nucleation mechanism and the coalescence of MoS 2 domains into continuous, centimetre-scale films. Fabricated field-effect transistor (FET) devices based on bilayer MoS 2 channels show substantial improvements in mobility (up to 122.6 cm 2  V −1  s −1 ) and variation compared with FETs based on monolayer films. Furthermore, short-channel FETs exhibit an on-state current of 1.27 mA μm −1 , which exceeds the 2028 roadmap target for high-performance FETs 16 . The epitaxial growth of bilayer molybdenum disulfide on sapphire enables the fabrication of field-effect transistor devices with improved performance in carrier mobility and on-state current over traditional monolayer films.

Two-dimensional (2D) semiconductors, in particular transition metal dichalcogenides (TMDCs), have attracted great interest in extending Moore’s law beyond silicon1–3. However, despite extensive efforts4–25, the growth of wafer-scale TMDC single crystals on scalable and industry-compatible substrates has not been well demonstrated. Here we demonstrate the epitaxial growth of 2 inch (~50 mm) monolayer molybdenum disulfide (MoS2) single crystals on a C-plane sapphire. We designed the miscut orientation towards the A axis (C/A) of sapphire, which is perpendicular to the standard substrates. Although the change of miscut orientation does not affect the epitaxial relationship, the resulting step edges break the degeneracy of nucleation energy for the antiparallel MoS2 domains and lead to more than a 99% unidirectional alignment. A set of microscopies, spectroscopies and electrical measurements consistently showed that the MoS2 is single crystalline and has an excellent wafer-scale uniformity. We fabricated field-effect transistors and obtained a mobility of 102.6 cm2 V−1 s−1 and a saturation current of 450 μA μm–1, which are among the highest for monolayer MoS2. A statistical analysis of 160 field-effect transistors over a centimetre scale showed a >94% device yield and a 15% variation in mobility. We further demonstrated the single-crystalline MoSe2 on C/A sapphire. Our method offers a general and scalable route to produce TMDC single crystals towards future electronics.Unidirectional alignment of MoS2 domains during epitaxial growth on C/A sapphire enables the realization of large-area MoS2 single crystals.

Single-crystal sapphire specimen (α-Al2O3) have been widely applied in the semiconductor industry, microelectronics, and so on. In order to shorten the production time and improve the processing efficiency of sapphire processing, an integrated fixed-abrasive tool (FAT) based on solid-phase reactions is proposed in this article. The optimal FAT composition is determined using a preliminary experiment and orthogonal experiments. The mass fraction of the abrasives is chosen as 55 wt%, and the mass ratio of SiO2/Cr2O3 is 2. Surface roughness Ra decreased from 580.4 ± 52.7 nm to 8.1 ± 0.7 nm after 150 min, and the average material removal rate was 14.3 ± 1.2 nm/min using the prepared FAT. Furthermore, FAT processing combined with chemical mechanical polishing (CMP) was shortened by 1.5 h compared to the traditional sapphire production process in obtaining undamaged sapphire surfaces with a roughness of Ra < 0.4 nm, which may have the potential to take the place of the fine lapping and rough polishing process.

Current design theories and models predominantly focus on evaluating innovation through design solutions, using measures of novelty and usefulness as indicators of creativity. In contrast, the assessment of creative potential of design problems has attracted far less attention. To systematically explore the creative potential of design problems, a comprehensive literature review is conducted, revealing significant gaps where existing methods have yet to be applied. To address these gaps, first, an extensive database of design problems has been constructed using data collected from design patents, surveys, and questionnaires. Three distinct quantitative methods have been developed: the first for assessing novelty using SAPPhIRE model of causality, the second for assessing usefulness using usefulness indicators, and the third for assessing creative potential. The novelty method quantifies the minimum distance between a current problem and the old problems in the database, using textual similarity at different levels of SAPPhIRE abstraction. Expert evaluation of the novelty method indicates substantial agreement with experts’ intuitive notion, in addition to higher effectiveness compared to existing methods. The first two methods have then been integrated into the third method for assessing the overall creative potential of a design problem. Statistical analyses confirmed the correlation of both novelty and usefulness with creative potential, supporting findings in the literature. To demonstrate the methods, detailed case studies have been presented, illustrating the application of the methods. This systematic approach provides a robust framework for objective assessment of creativity in design problems, facilitating better prioritization and decision-making in engineering design contexts.

The growth of wafer-scale single-crystal two-dimensional transition metal dichalcogenides (TMDs) on insulating substrates is critically important for a variety of high-end applications1–4. Although the epitaxial growth of wafer-scale graphene and hexagonal boron nitride on metal surfaces has been reported5–8, these techniques are not applicable for growing TMDs on insulating substrates because of substantial differences in growth kinetics. Thus, despite great efforts9–20, the direct growth of wafer-scale single-crystal TMDs on insulating substrates is yet to be realized. Here we report the successful epitaxial growth of two-inch single-crystal WS2 monolayer films on vicinal a-plane sapphire surfaces. In-depth characterizations and theoretical calculations reveal that the epitaxy is driven by a dual-coupling-guided mechanism, where the sapphire plane–WS2 interaction leads to two preferred antiparallel orientations of the WS2 crystal, and sapphire step edge–WS2 interaction breaks the symmetry of the antiparallel orientations. These two interactions result in the unidirectional alignment of nearly all the WS2 islands. The unidirectional alignment and seamless stitching of WS2 islands are illustrated via multiscale characterization techniques; the high quality of WS2 monolayers is further evidenced by a photoluminescent circular helicity of ~55%, comparable to that of exfoliated WS2 flakes. Our findings offer the opportunity to boost the production of wafer-scale single crystals of a broad range of two-dimensional materials on insulators, paving the way to applications in integrated devices.A dual-coupling-guided growth mechanism enables the realization of wafer-scale single-crystal WS2 on vicinal a-plane sapphire.

The a-GaN films were successfully grown on the r-sapphire substrate by MOCVD method. The structure of V-defects was investigated by AFM and SEM. The dependence of V-defects density on growth temperature of a-GaN film at a constant hydrogen flow through a TEG source was studied. The influence of V/III ratio on V-defects structure was investigated. Methods of V-defects density minimisation were purposed.

Solid-state wafers are indispensable components in material science as substrates for epitaxial homo- or heterostructures or carriers for two-dimensional materials. However, reliable determination of magnetic properties of nanomaterials in volume magnetometry is frequently affected by unexpectedly rich magnetism of these substrates, including significant magnetic anisotropy. Here, we describe a simplified experimental routine of magnetic anisotropy assessment, which we exemplify and validate for epi-ready sapphire wafers from various sources. Both the strength and the sign of magnetic anisotropy are obtained from carefully designed temperature-dependent measurements, which mitigate all known pitfalls of volume SQUID magnetometry and are substantially faster than traditional approaches. Our measurements indicate that in all the samples, two types of net paramagnetic contributions coexist with diamagnetism. The first one can be as strong as 10% of the base diamagnetism of sapphire [−3.7(1) × 10−7 emu/gOe], and when exceeds 2%, it exhibits pronounced magnetic anisotropy, with the easy axis oriented perpendicularly to the face of c-plane wafers. The other is much weaker, but exhibits a ferromagnetic-like appearance. These findings form an important message that nonstandard magnetism of common substrates can significantly influence the results of precise magnetometry of nanoscale materials and that its existence must be taken for granted by both industry and academia.