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2D transition metal dichalcogenides (TMDs) for advanced logic transistor technologies are deposited by various modifications of the chemical vapor deposition (CVD) method using a wide variety of precursors. Being a major electrical performance limiter, the TMD crystal grain size strongly differs between the various CVD precursor chemistries from nano‐ to millimeter‐sized crystals. However, it remains unclear how the CVD precursor chemistry affects the nucleation density and resulting TMD crystal grain size. This work postulates guiding principles to design a CVD process for highly crystalline TMD deposition using a quantitative analytical model benchmarked against the literature. The TMD nucleation density reduces favorably under low supersaturation conditions where the metal precursor sorption on the starting surface is reversible and the corresponding metal precursor desorption rate exceeds the overall deposition rate. Such reversible precursor adsorption guarantees efficient long‐range gas‐phase lateral diffusion of precursor species in addition to short‐range surface diffusion, which vitally increases crystal grain size. The proposed model explains the large spread in experimentally observed TMD nucleation densities and crystal grain sizes for state‐of‐the‐art CVD chemistries. Ultimately, it empowers the reader to interpret and modulate precursor adsorption and diffusion reactions through designing CVD precursor chemistries. [ABSTRACT FROM AUTHOR]

The growth of interfacial carbon (IFC) layers at the epitaxial sapphire/metal interface could unlock the transfer process for large-scale epitaxial thin films, such as graphene. To assess the feasibility of the application of IFC, understanding of the growth mechanisms of IFC layers at the epitaxial metal/sapphire interface is required. In this study, atmospheric pressure chemical vapor deposition is used to directly synthesize wafer-scale multilayer carbon at the interface between the Al2O3(0001) substrate and epitaxial Cu(111) layer. Characterization by Raman spectroscopy, AFM, and XRD, indicates the IFC layers exhibit low defect density and sp2 bonding character. Furthermore, IFC as thick as 100 nm could be synthesized. The effect of the partial pressure of reaction gases is systematically investigated, and a growth mechanism is proposed based supported by experimental observations and simulation results. Finally, a mechanical lift-off of a Cu(111) film with the aid of the IFC layer is demonstrated as a proof-of-concept application. [ABSTRACT FROM AUTHOR]

Graphene and carbon nanotubes (CNTs) are both carbon-based materials with remarkable optical and electronic properties which, among others, may find applications as transparent electrodes or as interconnects in microchips, respectively. This work reports on the formation of a hybrid structure composed of a graphitic carbon layer on top of vertical CNT in a single deposition process. The mechanism of deposition is explained according to the thickness of catalyst used and the atypical growth conditions. Key factors dictating the hybrid growth are the film thickness and the time dynamic through which the catalyst film dewets and transforms into nanoparticles. The results support the similarities between chemical vapor deposition processes for graphene, graphite, and CNT. [ABSTRACT FROM AUTHOR]

Electrodeposition is an excellent method for a site-selective and direct fabrication of catalyst nanoparticles for subsequent carbon nanotube (CNT) growth. Nickel nanoparticles with densities as high as 1011 cm-2 and diameters down to 15 ± 4 nm are deposited on blanket and pattemed TiN wafers. Ni nanoparticles are selectively placed at the bottom of submicrometer vias by through-mask electrodeposition. The spherical nanoparticles all produce aligned multiwalled CNTs. The CNT diameter is directly determined by the diameter of the as-deposited nanoparticles, which is tailored by the electrodeposition conditions. Such control of CNT size, density, and location represents an important step toward the implementation of CNTs in device fabrication. [ABSTRACT FROM AUTHOR]

The authors demonstrate high-performing n-channel transistors with a HfO2/TaN gate stack and a low thermal-budget process using solid-phase epitaxial regrowth of the source and drain junctions. The thinnest devices have an equivalent oxide thickness (EOT) of 8 Å, a leakage current of 1.5 A/cm² at VG = 1 V, a peak mobility of 190 cm²/V · s, and a drive-current of 815 μA/μm at an OFF-state current of 0.1 μA/μm for VDD = 1.2 V. Identical gate stacks processed with a 1000-°C spike anneal have a higher peak mobility at 275 cm²/V · s, but a 5-Å higher EOT and a reduced drive current at 610 μA/μm. The observed performance improvement for the low thermal-budget devices is shown to be mostly related to the lower EOT. The time-to-breakdown measurements indicate a maximum operating voltage of 1.6 V (1.2 V at 125 °C) for a ten-year lifetime, whereas positive-bias temperature-instability :measurements indicate a sufficient lifetime for operating voltages below 0.75 V. [ABSTRACT FROM AUTHOR]

Graphene is considered as potential candidate for future nano-interconnects. In this respect we study the Brønsted acid doping effect of single layer graphene (SLG) and few layer graphene (FLG) synthesized by chemical vapor deposition (CVD). A sheet resistance reduction of 50% is achieved by HNO 3 doping of SLG, and the resulting resistivity of 9.1 μΩ·cm is comparable to alternative metals to copper (e.g. Ru). On the other hand, synthetic FLG shows higher sheet resistance due to higher defect density. Mobility degradation at increased carrier concentration is a main limiting factor for sheet resistance reduction of CVD graphene. [ABSTRACT FROM AUTHOR]

Abstract: We propose an empirical law correlating the average number of walls and the average diameter in a population of multi-wall carbon nanotubes grown by catalytic chemical vapor deposition. The relationship and its dispersion are derived from the statistical analysis of a database of TEM images of nanotubes collected from more than 60 publications in literature and from our group in the last years. Considering the nanotubes were grown from independent sources in a variety of conditions and tools, it has general validity. The relationship may find applicability in a wide range of fields as it provides a simple model to quickly estimate the number of walls most likely present in a population of nanotubes from only the measure of their average diameter. [Copyright &y& Elsevier]

Abstract: We propose to use carbon nanotube (CNT)–CNT contacts instead of CNT–metal contacts as a route towards low resistance CNT horizontal interconnects. We characterize by electrical transport measurements and Kelvin probe force microscopy the contacts present in CNT horizontal interconnects grown by chemical vapor deposition between titanium nitride electrodes. When two CNTs with diameter around 30nm grow from opposing electrodes and touch each other with their outermost shells, typical contact resistances around 16kΩ are obtained. The corresponding contact resistivity of about 14Ωμm2 is one order of magnitude smaller than the contact resistivity of a CNT touching the TiN surface with its outermost shell. On the other hand, the contact resistance of a CNT grown from a nickel catalyst particle deposited on a TiN electrode is negligibly small when compared to the above mentioned contact resistances. Our results demonstrate that we are able to grow from opposing electrodes CNTs that touch each other with a corresponding high density (up to 1011 cm−2) of CNT–CNT contacts. This may offer an effective solution towards the growth of low resistance CNT horizontal interconnects. [Copyright &y& Elsevier]