Two-dimensional (2D) transition metal dichalcogenides (TMDCs), such as molybdenum disulfide ( MoS 2 ), have significant potential as materials for the next generation of flexible electronics. They offer advantages over conventional semiconductors, particularly due to their tunable crystal phases. However, precise control of phase transformation in 2D layers deposited using low-temperature processes in a bottom-up approach for future electronics has not yet been mastered, which limits their integration into scalable device technology. This study demonstrates the control of the phase composition of plasma enhanced atomic layer deposited (PEALD) MoS 2 films by direct writing with focused Li + and Ga + ion beams, and retransformation into the 2H phase by ultrashort pulse laser processing. The ion beam-treated films exhibit excellent long-term stability and are therefore suitable for industrial processes.

Precise control of ion energy distribution functions (IEDFs) is crucial for selectivity as well as control over sputter rate and substrate damage in nanoscale plasma processes. In this work, a low frequency (100 kHz) tailored pulse-wave-shaped bias voltage waveform is applied to the substrate electrode of an inductively coupled plasma (ICP) and its effects on the IEDF, electron density, electron dynamics and the etch rates of silicon dioxide as well as amorphous silicon are investigated in a commercial 200 mm reactive ion etching reactor. While the tailored waveform substrate bias hardly affects the electron density above the substrate and the spatio-temporally resolved electron power absorption dynamics, it is found to affect the ion flux to the substrate at high ICP source powers. Monoenergetic IEDFs with a full width at half maximum below 10 eV are realized with mean ion energies ranging from 20 eV to 100 eV in both argon and SF6. Using a modified voltage allows generating two independently controllable peaks in the IEDF. The monoenergetic IEDFs are used to determine the Ar ion sputter threshold energies of amorphous silicon and silicon dioxide to be 23 eV and 37 eV, respectively. This enables selective etching of these two materials by Ar ion sputtering based on tailoring the IEDF to ensure that all incident ions are within this narrow ion energy selectivity window.

Processes at the plasma boundaries, including the electrodes, can significantly influence plasma properties, among them the plasma density, the flux-energy distribution of various particle species, etc. The emission of secondary electrons, in particular, can lead to ionization avalanches, which strongly increase the plasma density and change the discharge operation mode as a function of the operating conditions. Using reliable values to characterize the efficiency of such processes is indispensable for accurate numerical modeling. There is, however, a lack of such data for surface coefficients for arbitrary combinations of the plasma species and electrode materials and surface conditions. In this work, we investigate the alpha- to gamma-mode mode transition induced by changes of the operating conditions (voltage, pressure) in capacitively coupled argon plasmas for different electrode surface materials (copper, nickel, gold, aluminum, and stainless steel) and target the determination of the effective in-situ secondary electron emission coefficient, gamma & lowast;. The first is accomplished by phase-resolved optical emission spectroscopy applied to measure the spatio-temporal distribution of the electron-impact excitation rate from the ground state into a high-threshold-energy level of a tracer gas (neon). The studies are conducted for pressures between 50 Pa and 200 Pa and voltage amplitudes ranging from 150 V to 350 V at a driving frequency of 13.56 MHz. A transition from the alpha- to the gamma-mode is shown to take place at different pressures for different materials. The combination of these measurements with particle-in-cell / Monte Carlo collisions simulations employing a range of gamma & lowast; values allows the determination of the effective 'in-situ' electron yield for the given set of operating conditions. The simulations also shed light on the contributions of the various species, argon ions, metastable atoms, and vacuum-ultraviolet photons to electron emission from the electrodes. The findings suggest that for precise modeling individual secondary electron yields specific to different electrode surface materials should be used and multiple species should be included in the models that describe secondary electron emission at the electrodes.

AbstractIn this paper, the formation of laser‐induced periodic surface structures (LIPSS) on atomic‐layer deposited MoS2 layers are studied experimentally. The process parameters (laser fluence and the pulse overlap) corresponding to formation of low‐ and high‐spatial frequency LIPSS as well as ablation and modification of the layers are identified for different pulse durations in the range from 0.2 to 10 ps. The role of the temperature accumulation is evaluated by changing the repetition rate from 0.2 to 2 MHz. The negative accumulation effect, i.e., the ablation of the layers becomes more difficult at higher laser pulse overlaps, is also observed. A simple model explaining the transition between different types of the LIPSS and the decrease of the ablation efficiency with the pulse overlap is suggested.

2D molybdenum disulfide (MoS2) is a promising material for the application in the flexible electronic, where large, uniform, crystalline films on flexible substrates are desired. The utilization of low-temperature plasma-enhanced atomic layer deposition (PEALD) facilitates the production of large-area, uniform, polycrystalline MoS2 films on temperature-sensitive substrates. However, for next-generation electronics, the crystallite size does not fulfill requirements. In order to enhance the degree of crystallinity conventional high temperature post treatments of the whole sample, which are not compatible with flexible substrates, needs to be avoided. In this study, a method for increasing the crystallinity of polycrystalline MoS2 films on SiO2/Si and glass substrate deposited by plasma enhanced ALD processed with femtosecond laser pulses (lambda = 1030 nm, t(p) = 200 fs), in a "cold" annealing process is presented. The laser fluence range varies from fmin = 3.0 mJ cm(-2) to f(max) = 30.00 m J(-2) with scanning speeds from v(scan, min) = 1 mm s(-1) to v(scan, max) = 1000 mm s(-)1, at a repetition rate of f(rep) = 2000 kHz. The crystallization and the influence of the processing parameters on the film topography are analyzed in detail by Raman spectroscopy and scanning electron microscopy. Finally, the influence of the laser processing on the film resistivity is investigated.

2D materials like transition metal dichalcogenides (TMDCs) have been widely studied and are a gateway to modern technologies. While research today is mostly carried out on a laboratory scale, there is an intensive need for reliable processes on a wafer‐scale, starting with monolayer‐precise deposition of high‐quality films. In this work, a plasma‐enhanced atomic layer deposition (PEALD) process is developed on a 200 mm SiO2/Si substrate. The layers are investigated regarding crystallinity, composition, homogeneity, microstructure, topography, and electrical properties. The process is then applied on 200 mm alkali‐free glass wafers aiming toward flexible electronics and compatibility with Si processes. A complete coverage of the wafer with a satisfying uniformity is achieved on both substrates and direct polycrystalline growth of MoS2 films is verified on the entire wafer at a substrate temperature of T = 230 °C. On glass, the deposited MoS2 films exhibit a higher crystallinity and are more planar compared to the SiO2/Si substrate. Furthermore, application relevant few‐nanometer thick layers are investigated in detail. This low‐temperature process inspires optimism for future direct integration of 2D‐materials in an economical bottom‐up approach on a wide variety of substrates, thus paving the way for industrial mass production.

Abstract HfO2 thin films are appealing for microelectronic applications such as high‐κ dielectric layers, memristors, and ferroelectric memory devices. To fulfill the different requirements of each application, the properties of the deposited material need to be tuned accordingly. In this context, plasma‐enhanced atomic layer deposition (PEALD) is a powerful processing route to tailor the properties of HfO2 thin films, especially at low temperatures. Herein, a comprehensive bottom‐up approach is presented, ranging from the synthesis of molecularly engineered Hf precursors to the development of a HfO2 PEALD process and a detailed evaluation where plasma can be exploited to tune the dielectric properties. With the example of the newly synthesized bis‐(dialkylamido)‐bis‐(formamidinato) Hf(IV) precursor, [Hf{η2‐(iPrN)2CH}2(NMe2)2] which is reactive, thermally robust and volatile, successful implementation in a PEALD process for HfO2 at low temperatures is demonstrated. The typical atomic layer deposition (ALD) characteristics of precursor saturation, linearity, and ALD temperature window are demonstrated with constant growth of 0.7 Å per cycle from 125 to 200 °C, yielding high‐purity layers. The effect of plasma pulse duration on the chemical composition alongside structural, topographical, as well as dielectric properties of the films is investigated. For the latter, the films are incorporated in metal‐insulator semiconductor (MIS) structures.

2D materials like transition metal dichalcogenides (TMDCs) are promising materials for the next generation of flexible devices. With low-temperature Atomic Layer Deposition a direct large area deposition of these materials on temperature sensitive substrates becomes possible. Due to these substrates conventional post- and further processing methods, like thermal annealing, are not suitable. With the usage of ultrashort pulsed Laser a moification of these films with very small heat-affected zones can be done. This allows a selective increase of crystallinity in amorphous MoS2 films or phase engineering between the metallic and semiconducting phase in MoS2 independent of the growing substrate.

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.

To implement 2D molybdenum disulfide (MoS 2 ) in the flexible electronic industry, large, uniform, and crystalline films on flexible substrates are needed. Thermal atomic layer deposition (ALD) generates large‐area uniform MoS 2 films at low temperatures directly on temperature‐sensitive substrates. But if the grown films are amorphous, a high‐temperature posttreatment of the whole sample, which may cause thermal degradation of the substrate or other layers, needs to be avoided. In this article, the crystallization of amorphous MoS 2 layers deposited by thermal ALD processed with picosecond laser pulses ( λ = 532 nm), in a “cold” annealing process, is reported. The laser fluence range varies from = 8.73 mJ cm −2 to = 18.25 mJ cm −2 with scanning speeds from = 240 mm s −1 to = 2640 mm s −1 . The crystallization and the influence of the processing parameters on the film morphology are analyzed in detail by Raman spectroscopy and scanning electron microscopy. Furthermore, a transition of amorphous MoS 2 by laser annealing to self‐organized patterns is demonstrated and a possible process mechanism for the ultrashort‐pulsed (usp)‐laser annealing is discussed. Finally, the usp laser annealed films are compared to thermally and continuous‐wave‐laser‐annealed samples.

In this comparative study a thermal and a plasma assited atomic layer deposition (ALD) process of aluminumoxide (Al2O3) are presented. Each process takes place in the same ALD reactor using a trimethylaluminium (TMA) precursor using ozone or a capacitively coupled remote oxygen plasma (R-CCP) as oxidant respectively. The resulting film thickness and uniformity was determined by spectroscopic ellipsometer measurements and the dielectric properties of the films were evaluated by CV and IV-measurements of metal insulator semiconductor (MIS) capacitors. They reveal for both processes excellent relative permittivities around 8 and a breakdown voltages above 7 MV/cm. Standard deviations of thickness around 3% qualify these processes even for industrial fabrication.

The unique electronic and mechanical properties of transition metal dichalcogenides (TMDs) make them interesting for industry and research as the demand for two-dimensional (2D) material applications has been increased in the last decade. Most applications make use of the characteristic optical properties of the crystalline material. In this study, a low-temperature atomic layer deposition (ALD) process for layer-by-layer generation on 200 mm wafers is introduced. The deposited layers are characterized by XPS, XRD, Raman spectroscopy and AFM measurements. Four-point probe sheet resistance measurements show the high homogeneity of deposited layers. Compositional analysis reveals amorphous MoOxSy films and thickness measurements via SEM cross section and ellipsometry show a growth rate of about 0.1 nm/cycle. Further improvement of the film quality can be achieved by thermal annealing. MoS2 layers have also been found to be gas-sensitive to various gas molecules. For this application high crystallinity is not necessarily required and hence, this low-temperature wafer-scale process for 2D gas sensors can be integrated into already existing workflows for high-volume production on silicon wafers. Furthermore, it can also be applied on different substrates, for example on flexible thin glasses. The possible implementation to these substrates is also shown.

Transition metal dichalcogenides (TMDCs) such as tungsten disulfide (WS 2 ) 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 WS 2 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 WS 2 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 WS 2 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 WS 2 triangular islands is observed, whereas untreated glass reveals an out-off plane growth. Detailed XRD and Raman analysis show tensile strain in the WS 2 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.

We demonstrate direct polycrystalline growth of molybdenum disulphide (MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) via atomic layer deposition (ALD) on 200 mm Si/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> substrates. The synthesis of MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in wafer-scale is a first critical step for future 2D technology implemented by industry. Substantial progress has already been taken for films grown via chemical vapour deposition (CVD). Typically, as-deposited MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films by ALD at low temperatures are amorphous and show different characteristics and a non-ideal stoichiometry in comparison to CVD or high temperature ALD deposited crystalline counterparts. However, low temperature ALD is still indispensable for direct synthesis on for example polymeric or glass substrates for flexible electronics. Using an industrial ALD-reactor, this work proves the capability to combine both low temperature (T < 300 °C) and wafer-scale deposition of direct crystalline and continuous MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films with good morphology.

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 synthesis and characterization of a series of closely related Y(III) compounds comprising the formamidinate ligands (RNCHNR) (R = alkyl) is reported, with the scope of using them as prospective precursors for atomic layer deposition (ALD) of yttrium oxide (Y2O3) thin films. The influence of the side chain variation on the thermal properties of the resulting complexes is studied and benchmarked by thermal analysis and vapor pressure measurements. Density functional theory (DFT) studies give theoretical insights into the reactivity of the compounds towards water, which was targeted as a co-reactant for the deposition of Y2O3via thermal ALD in the next step. Among the four complexes analyzed, tris(N,N'-di-tert-butyl-formamidinato)yttrium(III) [Y(tBu2-famd)3] 1 was found to possess enhanced thermal stability and was selected for Y2O3 ALD process development. A broad ALD window ranging from 200 °C to 325 °C was obtained, yielding films of high compositional quality. Furthermore, with a film density of (4.95 ± 0.05) g cm-1 close to the bulk value, polycrystalline fcc Y2O3 layers with a smooth topography resulted in promising dielectric properties when implemented in metal insulator semiconductor (MIS) capacitor structures.

In this work, the application of tris(N,N′-diisopropyl-formamidinato)yttrium(iii) [Y(DPfAMD)3] as a precursor in a water-assisted thermal atomic layer deposition (ALD) process for the fabrication of device quality Y2O3 thin films is demonstrated.

Transition metal dichalcogenides (TMDs) have gained an enormous interest in the research as the material for the next generation flexible technology of electronic devices. Especially molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are promising electronic materials, due to their variable band gap depending on the thickness of the material. In bulk form, it possesses an indirect band gap while monolayers show direct band gaps. In this paper, Raman spectroscopy is used as a powerful non destructive tool to provide information about the quality of the deposited films throughout the fabrication process of TMD based devices. Firstly, the successful chemical vapor deposition of crystalline MoS2 and WS2 with new Mo and W precursors is confirmed by Raman measurements. Furthermore, the Raman spectra permits conclusion about interface effects, e.g. strain and defects, of large area grown WS2. Finally, an outlook for the usage of Raman spectroscopy in further production steps is given.