The effect of fluorine substitution on the aromaticity of polycyclic hydrocarbons (PAH) is investigated. Magnetically induced current densities, current pathways, and current strengths, which can be used to assess molecular aromaticity, are calculated using the gauge-including magnetically induced current method (GIMIC). The degree of aromaticity of the individual rings is compared to those obtained using calculated nucleus-independent chemical shifts at the ring centers (NICS(0) and NICS(0)(zz)). Calculations of explicitly integrated current strengths for selected bonds show that the aromatic character of the investigated polycyclic hydrocarbons is weakened upon fluorination. In contrast, the NICS(0) values for the fluorinated benzenes increase noteworthy upon fluorination, predicting a strong strengthening of the aromatic character of the arene rings. The integrated current strengths also yield explicit current pathways for the studied molecules. The current pathways of the investigated linear polyacenes, pyrene, anthanthrene, coronene, ovalene, and phenanthro-ovalene are not significantly affected by fluorination. NISC(0) and NICS(0)(zz) calculations provide contradictory degrees of aromaticity of the fused individual ring. Obtained NICS values do not correlate with the current strengths circling around the individual rings.

Herein, we report an atomic layer deposition (ALD) process for Cu 2 O thin films using copper(II) acetate [Cu(OAc) 2 ] and water vapor as precursors. This precursor combination enables the deposition of phase-pure, polycrystalline, and impurity-free Cu 2 O thin films at temperatures of 180–220 °C. The deposition of Cu(I) oxide films from a Cu(II) precursor without the use of a reducing agent is explained by the thermally induced reduction of Cu(OAc) 2 to the volatile copper(I) acetate, CuOAc. In addition to the optimization of ALD process parameters and characterization of film properties, we studied the Cu 2 O films in the fabrication of photoconductor devices. Our proof-of-concept devices show that approximately 20 nm thick Cu 2 O films can be used for photodetection in the visible wavelength range and that the thin film photoconductors exhibit improved device characteristics in comparison to bulk Cu 2 O crystals.

Two heteroleptic titanium precursors were investigated for the atomic layer deposition (ALD) of titanium dioxide using ozone as the oxygen source. The precursors, titanium (N,N'-diisopropylacetamidinate)tris(isopropoxide) (Ti(O(i)Pr)3(N(i)Pr-Me-amd)) and titanium bis(dimethylamide)bis(isopropoxide) (Ti(NMe2)2(O(i)Pr)2), exhibit self-limiting growth behavior up to a maximum temperature of 325 °C. Ti(NMe2)2(O(i)Pr)2 displays an excellent growth rate of 0.9 Å/cycle at 325 °C while the growth rate of Ti(O(i)Pr)3(N(i)Pr-Me-amd) is 0.3 Å/cycle at the same temperature. In the temperature range of 275-325 °C, both precursors deposit titanium dioxide in the anatase phase. In the case of Ti(NMe2)2(O(i)Pr)2, high-temperature X-ray diffraction (HTXRD) studies reveal a thickness-dependent phase change from anatase to rutile at 875-975 °C. X-ray photoelectron spectroscopy (XPS) indicates that the films have high purity and are close to the stoichiometric composition. Reaction mechanisms taking place during the ALD process were studied in situ with quadrupole mass spectrometry (QMS) and quartz crystal microbalance (QCM).

Thin films of rare-earth (RE) oxides (Y2O3, PrO x , Gd2O3, and Dy2O3) were deposited by atomic layer deposition from liquid heteroleptic RE­( i PrCp)2( i Pr-amd) precursors with either water or ozone as the oxygen source. Film thickness, crystallinity, morphology, and composition were studied. Saturation was achieved with Gd2O3 when O3 was used as the oxygen source at 225 °C and with Y2O3 with both oxygen sources at as high temperature as 350 °C. The growth rates were 0.90–1.3 Å/cycle for these processes. PrO x was challenging to deposit with both oxygen sources but with long, 20 s purges after the water pulses uniform films could be deposited. However, saturation was not achieved. With Dy2O3, uniform films could be deposited and the Dy­( i PrCp)2( i Pr-amd)/O3 process was close to saturation at 300 °C. The different oxygen sources had an effect on the crystallinity and impurity contents of the films in all the studied processes. Whether ozone or water was better choice for oxygen source depended on the metal oxide material that was deposited.

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In this article, three novel cyclopentadienyl precursors are evaluated for the atomic layer deposition (ALD) of erbium oxide, with either ozone or water as the oxygen source. The erbium precursors evaluated are Er(iPrCp)3, Er(MeCp)2(iPr‐amd), and Er(nBuCp)3. The films are deposited on silicon within the temperature range 200–400°C. Self‐limiting growth is achieved with all three precursors, with both ozone and water. It is found that the water processes of all three precursors present significantly higher growth rates when compared to the ozone processes. An up to three‐fold increase in the growth rate is observed for the water processes of Er(iPrCp)3 and Er(MeCp)2(iPr‐amd) (amd: amidinate) when compared to their ozone processes. The films are smooth and uniform, as determined by atomic force microscopy (AFM) (rms roughness < 3% of film thickness). The composition of the films is investigated by means of X‐ray photoelectron spectroscopy (XPS). It is found that the films contain small amounts of carbon as an impurity, especially in the case of ozone‐processed films. Using Er(nBuCp)3 together with ozone as the oxygen source, a highly conformal Er2O3 thin film is deposited on a 1:60 high‐aspect‐ratio substrate. This is the first report of the conformal growth of Er2O3 thin films by ALD on a high‐aspect‐ratio structure.

In this work, a growth mechanism of an intermetallic Co3Sn2 thin film is studied in situ with a quartz crystal microbalance (QCM) and quadrupole mass spectrometer (QMS). The film is deposited by atomic layer deposition (ALD) from CoCl2(TMEDA) and Bu3SnH precursors (TMEDA = N,N,N′,N′-tetramethylethylenediamine). Balanced reaction equations are resolved by fitting the QMS and QCM data, and a step-by-step growth mechanism is determined for the process. During the CoCl2(TMEDA) pulse, only 1-chlorobutane is formed as a byproduct. However, during the Bu3SnH pulse, two byproducts, BuCl and Bu3SnCl, were clearly detected, indicating that two competing reaction pathways exist during that pulse. Preliminary studies on another intermetallic ALD process, Ni3Sn2, revealed that the reactions occur similarly as in the Co3Sn2 process.

In this work, we have studied the applicability of Co(BTSA)2(THF) (BTSA = bis(trimethylsilyl)amido) (THF = tetrahydrofuran) in atomic layer deposition (ALD) of cobalt oxide thin films. When adducted with THF, the resulting Co(BTSA)2(THF) showed good volatility and could be evaporated at 55 °C, which enabled film deposition in the temperature range of 75-250 °C. Water was used as the co-reactant, which led to the formation of Co(II) oxide films. The saturative growth mode characteristic to ALD was confirmed with respect to both precursors at deposition temperatures of 100 and 200 °C. According to grazing incidence X-ray diffraction measurements, the films contain both cubic rock salt and hexagonal wurtzite phases of CoO. X-ray photoelectron