Jorit Obenlüneschloß

The application of a liquid and volatile Ru precursor ([η5-C5H5Ru(CO)2(CH2)3N(CH3)2] or dicarbonyl(η5-cyclopentadienyl)(3-(dimethylamino)propyl)ruthenium, trade name HeRu31) in an atomic layer deposition (ALD) process yielded high-purity and conductive Ru metal thin films. The films were deposited at temperatures from 200–300 °C on Si substrates, exhibiting self-limiting, linear growth behavior with a growth per cycle (GPC) of 1.1 Å at a deposition temperature (Tdep) of 280 °C. Comprehensive characterization of Ru thin films validates the growth of closed, nanocrystalline Ru films with resistivities in the range of 24–29 μΩ cm. These unprecedented findings offer further insights into the impact of the Ru precursor, paving the way to explore Ru films for microelectronic applications.

Atomic layer deposition (ALD) of zinc oxide (ZnO) has been widely researched using diethyl zinc (DEZ)-based methods. The significant importance of thin films of ZnO as transparent conductive oxides (TCO) in optoelectronic devices and photovoltaics warrants examining alternative Zn precursors for ZnO ALD as potential replacements for the pyrophoric DEZ. In this study, we investigated three alternative Zn precursors: Zn(EEKI)₂, Zn(DMP)₂, ZnEt(HMDS), in the process development for high-quality ZnO thin films and compared them to DEZ. The ALD processes were studied using in situ spectroscopic ellipsometry. The properties of the ALD ZnO films were characterized using ex situ X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry and nuclear reaction analysis (RBS/NRA), X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), and ultraviolet-visible (UV/Vis) spectrophotometry. These measurements confirmed the formation of pure, stoichiometric, and polycrystalline ZnO films using all four Zn precursors. Although the selected precursors are chemically diverse Zn compounds, they all yielded saturating ALD processes and high-quality ZnO thin films at 200 °C. This study highlights the potential benefits of alternative zinc precursors in designing ALD processes for ZnO thin films.

Atomic/molecular layer deposition (ALD/MLD) offers a comprehensive process and application portfolio for metal–organic thin films; however, ALD/MLD process development for transition‐metal‐based materials remains very limited, despite the versatile functional properties of their compounds. In this work, to enrich the chemistry of transition metal precursors in ALD/MLD, an all‐nitrogen‐coordinated cobalt complex, Co(tmsaedma) ₂ (tmsaedma = Bis(N,N‐dimethyl(N’‐trimethylsilyl)ethane‐1‐amino‐2‐amido), was employed as the metal precursor for the first time. The Co‐N coordination provides an optimal reactive site for a variety of organic linker groups, as demonstrated here by three organic precursors that share the same rigid benzene backbone but differ in reactive groups: 1,4‐benzenediol (hydroquinone; HQ), 1,4‐benzenedithiol (BDT), and 1,4‐benzenedicarboxylic acid (terephthalic acid; BDC). A comprehensive set of characterization techniques, combined with first principles density functional theory (DFT) calculations, is used to systematically investigate the three new ALD/MLD processes and the stability of the resulting Co(II)‐organic thin films: Co‐HQ, Co‐BDT, and Co‐BDC. The reactivity and stability trends of the organics are found as BDC>HQ>BDT and BDC>>BDT>>HQ, respectively. Decomposition mechanisms are provided for Co‐HQ and Co‐BDT. Furthermore, the preparation of low‐density, porous CoO thin films with tunable structural and optical properties, difficult to achieve otherwise, is demonstrated via calcination in N ₂ of the Co‐BDC thin films.

Ru( ii ) carbonyl amidates are introduced as a new precursor class for ALD. Substitution pattern engineering yielded volatile and liquid complexes, which are predicted to interact favorably with O ₂ , O radicals, and NH ₃ .

Kurzfassung: Lithium ist das zentrale Element moderner Batterietechnologien, und die Herstellung von lithiumhaltigen Materialien mittels Atomlagenabscheidung (engl. Atomic Layer Deposition, ALD) bietet erhebliche Vorteile bei der Kontrolle der Schichtdicke und ‐zusammensetzung. In dieser Studie wird ein neuer mononuklearer, durch ein N‐heterocyclisches Carben (NHC) stabilisierter Lithiumkomplex, [Li( ^tBu NHC)(hmds)], als vielversprechender Präkursor für die ALD von lithiumhaltigen Dünnschichten vorgestellt. Die strukturelle Charakterisierung erfolgt durch den Vergleich von Dichtefunktionaltheorie (DFT) und Einkristall‐Röntgenbeugung (engl. Single‐Crystal X‐ray Diffraction, SC‐XRD), wobei die seltene mononukleare Struktur bestätigt wird. Thermogravimetrische Analysen (TGA) zeigen vorteilhafte thermische Eigenschaften für ALD‐Anwendungen. Die Verbindung weist einen niedrigen Schmelzpunkt, saubere Verdampfung und ermutigende Volatilitätsparameter im Vergleich zu anderen Lithium‐Präkursoren auf. ALD‐Experimente mit [Li( ^tBu NHC)(hmds)] und Ozon zeigen dessen Effektivität bei der Abscheidung von LiSi _x O _y ‐Filmen. Der ALD‐Prozess zeigt ein gesättigtes Wachstum pro Zyklus (engl. Growth per Cycle, GPC) von 0,95 Å. Die Zusammensetzung, analysiert mittels Rutherford‐Rückstreu‐Spektrometrie/Kernreaktionsanalyse (engl. Rutherford Backscattering Spectrometry/Nuclear Reaction Analysis, RBS/NRA), Röntgenphotoelektronenspektroskopie (engl. X‐ray Photoelectron Spectroscopy, XPS) und Glimmentladungsspektroskopie (engl. Glow Discharge Optical Emission Spectrometry, GD‐OES), bestätigt das Vorhandensein von Lithium und Silizium in den erwarteten Verhältnissen. Diese Arbeit stellt nicht nur einen neuen ALD‐Präkursor vor, sondern trägt auch zum Verständnis der Lithiumchemie bei und bietet Einblicke in die faszinierende Koordinationschemie und das thermische Verhalten von durch NHC‐Liganden stabilisierten Lithiumkomplexen.

Lithium is the core material of modern battery technologies and fabricating the lithium‐containing materials with atomic layer deposition (ALD) confers significant benefits in control of film composition and thickness. In this work, a new mononuclear N‐heterocyclic carbene (NHC) stabilized lithium complex, [Li( ^tBu NHC)(hmds)], is introduced as a promising precursor for ALD of lithium‐containing thin films. Structural characterization is performed, comparing density functional theory (DFT) and single‐crystal X‐ray diffraction (SC‐XRD), confirming a rare mononuclear structure. Favorable thermal properties for ALD applications are evidenced by thermogravimetric analysis (TGA). The compound exhibits a low melting point, clean evaporation, and its volatility parameters are encouraging compared to other lithium precursors. ALD trials using [Li( ^tBu NHC)(hmds)] with ozone demonstrate its effectiveness in depositing LiSi _x O _y films. The ALD process exhibits a saturated growth per cycle (GPC) of 0.95 Å. Compositional analysis using Rutherford backscattering spectrometry/nuclear reaction analysis (RBS/NRA), X‐ray photoelectron spectrometry (XPS), and glow discharge optical emission spectrometry (GD‐OES), confirms the presence of lithium and silicon in the expected ratios. This work not only presents a new ALD precursor but also contributes to the understanding of lithium chemistry, offering insights into the intriguing coordination chemistry and thermal behavior of lithium complexes stabilized by NHC ligands.

Growth rates, environmental impact, and functionality of Zn(DMP)₂ are explored for the spatial ALD of ZnO and compared to DEZ.

The atomic/molecular layer deposition (ALD/MLD) technique combining both inorganic and organic precursors is strongly emerging as a unique tool to design exciting new functional metal‐organic thin‐film materials. Here, this method is demonstrated to work even at low deposition temperatures and can produce highly stable and conformal thin films, fulfilling the indispensable prerequisites of today's 3D microelectronics and other potential industrial applications. This new ALD/MLD process is developed for Zn‐organic thin films grown from non‐pyrophoric bis‐3‐( N,N ‐dimethylamino)propyl zinc [Zn(DMP) ₂ ] and 1,4‐benzene dithiol (BDT) precursors. This process yields air‐stable Zn‐BDT films with appreciably high growth per cycle (GPC) of 4.5 Å at 60 °C. The Zn/S ratio is determined at 0.5 with Rutherford backscattering spectrometry (RBS), in line with the anticipated (Zn─S─C ₆ H ₆ ─S─) _n bonding scheme. The high degree of conformality is shown using lateral high‐aspect‐ratio (LHAR) test substrates; scanning electron microscopy (SEM) analysis shows that the film penetration depth (PD) into the LHAR structure with cavity height of 500 nm is over 200 µm (i.e., aspect‐ratio of 400). It is anticipated that the electrically insulating metal‐organic Zn‐BDT thin films grown via the solvent‐free ALD/MLD technique, can be excellent barrier layers for temperature‐sensitive and flexible electronic devices.