No abstract

Transition metal dichalcogenides (TMDCs) such as tungsten disulfide (WS2) are studied for advanced electronic and optical devices because of their unique and versatile electrical, optical and mechanical properties. For the use of TMDC films in next-generation flexible electronics, large-area bottom-up synthesis on flexible substrates needs to be mastered, understood and controlled. In this study, we performed a detailed study on the nucleation and growth of WS2 layers deposited by metalorganic chemical vapor deposition (MOCVD) on crystalline van-der-Waals material muscovite mica as a model substrate and on the alkali-metal free flexible glass AF 32® eco. The deposition of the WS2 layers was performed using an all nitrogen-coordinated bis-imido-bis-amido tungsten based precursor in combination with elemental sulfur as the co-reactant. On both substrates, crystalline growth of WS2 at a moderate growth temperature of 600 ○C was verified by Raman spectroscopy and X-ray diffraction (XRD). However, the growth mode and nucleation density differ significantly. On mica, an initially planar growth of WS2 triangular islands is observed, whereas untreated glass reveals an out-off plane growth. Detailed XRD and Raman analysis show tensile strain in the WS2 films on both substrates, indicating a strong interaction from CVD grown TMDC films with the underlying carrier material. In order to avoid such substrate-semiconductor interaction, a substrate pre-treatment is required. A plasma pre-treatment prior to the deposition leads to a planar growth even on amorphous glass substrates.

devices has driven academic and industrial research on alternatives such as cobalt (Co) and ruthenium (Ru) to a new dimension. [1,2] These endeavors are based on the inherent limitations of Cu thin films as interconnect in the back end of line (BEOL) and middle of line (MOL) facing scale-down toward 2 nm. At these dimensions, Cu layers are exhibiting lower resistance toward electromigration as well as the tendency toward diffusion under thermal or current-induced stress. [3,4] Both, Co and Ru provide more suited physical, mechanical, and electrical properties. Especially shorter electron mean free paths and higher chemical stability are to be named in this regard. [1,[5][6][7] Recent studies have shown that the chosen metallization approach may decide which of the two is favored: Murdoch and co-workers demonstrated superior performance of Ru thin films in semidamascene structures outperforming those of Cu and Co layers. [8] Beyond great promise for IC applications, Ru catalysts are garnering significant interest, foremost in the context of electrocatalysis for hydrogen production through water splitting. Specifically, their outstanding performance in the oxygen Two novel ruthenium complexes belonging to the Ru(II)(DAD)(Cym) (DAD = diazadienyl) (Cym = cymene) compound family are introduced as promising precursors. Their chemical nature, potential for chemical vapor deposition (CVD), and possibly atomic layer deposition (ALD) are demonstrated. The development of nonoxidative CVD processes yielding high-quality Ru thin films is realized. Chemical analyses are exercised that vitiate the deceptive assumption of Ru(DAD)(Aryl) complexes being zero-valent through clear evidence for the redox noninnocence of the DAD ligand. Two different CVD routes for the growth of Ru films are developed using Ru( tBu2 DAD)(Cym). Ru thin films from both processes are subjected to thorough and comparative analyses that allowed to deduce similarities and differences in film growth. Ru thin films with a thickness of 30-35 nm grown on SiO 2 yielded close-to-bulk resistivity values ranging from 12 to 16 µΩ cm. Catalysis evaluation of the films in the acidic oxygen evolution reaction (OER) results in promising performances based on overpotentials as low as 240 mV with Tafel slopes of 45-50 mV dec −1 . Based on the degradation observed during electrochemical measurements, the impact of OER conditions on the layers is critically assessed by complementary methods.

The formation of laser-induced periodic surface structures (LIPSSs) on the atomic layer-deposited (ALD) molybdenum disulfide (MoS2) upon femtosecond laser processing is studied experimentally. Laser-processing parameters such as average laser power and the scan speed at which the formation of the periodic nanostructures takes place are identified. Optical and scanning electron microscopy are applied to identify the parameter regions for the different LIPSS formations and transitions between them. High- and low-spatial frequency LIPSS (HSFL and LSFL) with two distinct periods λLSFL ≈ 1.1 μm and λHSFL ≈ 83 nm can be observed. The HSFL are dominating at higher and the LSFL at lower laser average powers. Formation of LIPSS is found to inhibit laser ablation at lower scan speeds.