Effects of Dislocation Filtering Layers on Optical Properties of Third Telecom Window Emitting InAs/InGaAlAs Quantum Dots Grown on Silicon Substrates.

Integrating light emitters based on III-V materials with silicon-based electronics is crucial for further increase in data transfer rates in communication systems since the indirect bandgap of silicon prevents its direct use as a light source. We investigate here InAs/InGaAlAs quantum dot (QD) structures grown directly on 5° off-cut Si substrate and emitting light at 1.5 μm, compatible with established telecom platform.

High yield and wide lateral size growth of α-MoC: exploring the boundaries of CVD growth of bare MXene analogues.

Synthesis of MoC bare MXenes, without surface terminations groups, via chemical vapor deposition (CVD) on metal foils is scientifically a very intriguing crystal growth process, and there are still challenges and limited fundamental understanding to overcome to obtain high yield and wide crystal size lateral growth. Achieving large area coverage via direct growth is scientifically vital to utilize the full potential of their unique properties in different applications. In this study, we sought to expand the boundaries of the current CVD growth approach for MoC MXenes and gain insights into the possibilities and limitations of large area growth, with a particular focus on controlling Mo concentration.

Sol-Gel Derived Silica-Titania Waveguide Films for Applications in Evanescent Wave Sensors-Comprehensive Study.

Composite silica-titania waveguide films of refractive index ca. 1.8 are fabricated on glass substrates using a sol-gel method and dip-coating technique.

Role of Temperature in Arsenic-Induced Antisurfactant Growth of GaN Microrods.

Due to the antisurfactant properties of arsenic atoms, the self-induced dodecagonal GaN microrods can be grown by molecular beam epitaxy (MBE) in Ga-rich conditions. Since temperature is a key parameter in MBE growth, the role of temperature in the growth of GaN microrods is investigated. The optimal growth temperature window for the formation of GaN microrods is observed to be between 760 and 800 °C.

2D Intrinsic Ferromagnetic MnP Single Crystals.

2D intrinsic ferromagnetic materials are highly anticipated in spintronic devices due to their coveted 2D limited magnetism. However, 2D non-layered intrinsic ferromagnets have received sporadic attention, which is largely attributed to the fact that their synthesis is still a great challenge. Significantly, manganese phosphide (MnP) is a promising non-layered intrinsic ferromagnet with excellent properties.

Improving carrier transport in CuO thin films by rapid thermal annealing.

Cuprous oxide (CuO) is a promising material for large scale photovoltaic applications. The efficiencies of thin film structures are, however, currently lower than those for structures based on CuO sheets, possibly due to their poorer transport properties. This study shows that post-deposition rapid thermal annealing (RTA) of CuO films is an effective approach for improving carrier transport in films prepared by reactive magnetron sputtering.

Stranski-Krastanov and Volmer-Weber CVD Growth Regimes To Control the Stacking Order in Bilayer Graphene.

Aside from unusual properties of monolayer graphene, bilayer has been shown to have even more interesting physics, in particular allowing bandgap opening with dual gating for proper interlayer symmetry. Such properties, promising for device applications, ignited significant interest in understanding and controlling the growth of bilayer graphene. Here we systematically investigate a broad set of flow rates and relative gas ratio of CH to H in atmospheric pressure chemical vapor deposition of multilayered graphene.

Two-dimensional membrane as elastic shell with proof on the folds revealed by three-dimensional atomic mapping.

The great application potential for two-dimensional (2D) membranes (MoS2, WSe2, graphene and so on) aroused much effort to understand their fundamental mechanical properties. The out-of-plane bending rigidity is the key factor that controls the membrane morphology under external fields. Herein we provide an easy method to reconstruct the 3D structures of the folded edges of these 2D membranes on the atomic scale, using high-resolution (S)TEM images.

Low voltage transmission electron microscopy of graphene.

The initial isolation of graphene in 2004 spawned massive interest in this two-dimensional pure sp(2) carbon structure due to its incredible electrical, optical, mechanical, and thermal effects. This in turn led to the rapid development of various characterization tools for graphene. Examples include Raman spectroscopy and scanning tunneling microscopy.

Thermal conductivity of mechanically joined semiconducting/metal nanomembrane superlattices.

The decrease of thermal conductivity is crucial for the development of efficient thermal energy converters. Systems composed of a periodic set of very thin layers show among the smallest thermal conductivities reported to-date. Here, we fabricate in an unconventional but straightforward way hybrid superlattices consisting of a large number of nanomembranes mechanically stacked on top of each other.

Free-standing single-atom-thick iron membranes suspended in graphene pores.

The excess of surface dangling bonds makes the formation of free-standing two-dimensional (2D) metals unstable and hence difficult to achieve. To date, only a few reports have demonstrated 2D metal formation over substrates. Here, we show a free-standing crystalline single-atom-thick layer of iron (Fe) using in situ low-voltage aberration-corrected transmission electron microscopy and supporting image simulations.

A universal transfer route for graphene.

Often synthetic graphene requires transfer onto an arbitrary substrate prior to use because the substrate it was originally synthesized on is inappropriate for either electrical measurement or characterization. While a variety of routes have been developed they are substrate dependant and often involve the use of harsh treatments. Here we present a facile and cheap route that can be applied to graphene over any substrate.

Rolled-up nanomembranes as compact 3D architectures for field effect transistors and fluidic sensing applications.

We fabricate inorganic thin film transistors with bending radii of less than 5 μm maintaining their high electronic performance with on-off ratios of more than 10(5) and subthreshold swings of 160 mV/dec. The fabrication technology relies on the roll-up of highly strained semiconducting nanomembranes, which compacts planar transistors into three-dimensional tubular architectures opening intriguing potential for microfluidic applications. Our technique probes the ultimate limit for the bending radius of high performance thin film transistors.

van der Waals epitaxial growth of graphene on sapphire by chemical vapor deposition without a metal catalyst.

van der Waals epitaxial growth of graphene on c-plane (0001) sapphire by CVD without a metal catalyst is presented. The effects of CH(4) partial pressure, growth temperature, and H(2)/CH(4) ratio were investigated and growth conditions optimized. The formation of monolayer graphene was shown by Raman spectroscopy, optical transmission, grazing incidence X-ray diffraction (GIXRD), and low voltage transmission electron microscopy (LVTEM).

Programmable sub-nanometer sculpting of graphene with electron beams.

Electron beams in transmission electron microscopes are very attractive to engineer and pattern graphene toward all-carbon device fabrication. The use of condensed beams typically used for sequential raster imaging is particularly exciting since they potentially provide high degrees of precision. However, technical difficulties, such as the formation of electron beam induced deposits on sample surfaces, have hindered the development of this technique.

Understanding the growth of amorphous SiO2 nanofibers and crystalline binary nanoparticles produced by laser ablation.

The pulsed-laser evaporation synthesis of silica nanofibers and crystalline binary nanoparticles is investigated in detail. By careful adjustment of the synthesis parameters one can tailor the product to form high yield nanofibers or binary nanoparticles. Some control on their diameters is also possible through the synthesis parameters.

Sexithiophene encapsulated in a single-walled carbon nanotube: an in situ Raman spectroelectrochemical study of a peapod structure.

The interaction of single-walled carbon nanotubes (SWCNTs) and α-sexithiophene (6T) was studied by Raman spectroscopy and by in situ Raman spectroelectrochemistry. The encapsulation of 6T in SWCNT and its interaction causes a bleaching of its photoluminescence, and also small shifts of its Raman bands. The Raman features of the SWCNT with embedded 6T (6T-peapods) change in both intensity and frequency compared to those of pristine SWCNT, which is a consequence of a change of the resonant condition.

In situ observations of fullerene fusion and ejection in carbon nanotubes.

We present in situ experimental observations of fullerenes seamlessly fusing to single-walled carbon nanotubes. The morphing-entry of a fullerene to the interior of a nanotube is also captured. The confined (1D) motion of the newly-encapsulated fullerene within its host attests to the actual change from the exterior to interior.