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Reactive sintering is currently considered as a promising production route for titanium aluminides in many research works. However, the published descriptions of the reaction mechanism are contradictory or lacking, especially at the temperatures below the melting point of aluminium. This work aims to fill this gap, providing the description of the reactive sintering process at the temperatures between 400 and 900 °C. The phases’ formation sequence and reaction kinetics were studied and explained using experimental model (Ti/Al diffusion couple) and real reactively sintered samples of equiatomic Ti-Al compressed powder blend. Moreover, phase formation was thermodynamically assessed. It was revealed that Ti2Al5 phase formed preferentially. This phase has not been reported previously as a starting phase in reactive sintering. According to results obtained by experimental model, its formation is controlled by diffusion at 700 °C. This phase reacted with aluminium forming pure TiAl3 phase or with titanium, resulting in TiAl phase. Subsequently, TiAl phase reacted with titanium, leading to the Ti3Al phase, or with already present Ti2Al5 phase yielding TiAl2 intermetallic compound. Titanium-rich Ti3Al phase could form only at the temperature of 600 °C or above.

3D hybrid perovskites (APbX3) have made a significant impact on the field of optoelectronic materials due to their excellent performance combined with facile solution deposition and up-scalable device fabrication. Nonetheless, these materials suffer from environmental instability. To increase material stability, the organic cation (A) is substituted by the non-volatile cesium cation. However, the desired photoactive cesium lead(II) iodide black phase is metastable in ambient conditions and spontaneously converts into the photo-inactive yellow δ-phase. In this work, the black phase is stabilized by the formation of a quasi-2D perovskite containing a benzothieno[3,2-b]benzothiophene (BTBT) large organic ammonium cation. Thermal analysis shows that degradation of the butylammonium (BA)-based quasi-2D perovskite (BA)2CsPb2I7 sets in at ≈130 °C, while (BTBT)2CsPb2I7 is phase-stable until ≈230 °C. Additionally, the (BTBT)2CsPb2I7 film does not show any sign of degradation after exposure to 77% Relative Humidity in the dark for 152 days, while (BA)2CsPb2I7 degrades in a single day. Photoconductor-type detectors based on (BTBT)2CsPb2I7 demonstrate an increased external quantum efficiency and a similar specific detectivity compared to the BA-based reference detectors. The results demonstrate the utility of employing a BTBT cation within the organic layer of quasi-2D perovskites to significantly enhance the stability while maintaining the optoelectronic performance.

In this paper, a novel synthesis for a chemical precursor for nanocrystalline VO2 coatings is elaborated. The compatibility of the precursor towards the substrate is optimized for spin coating. This is done by subjecting multiple solvents to contact angle measurements. A suitable thermal treatment is developed to densify the coating and to induce crystallization. Afterwards the microstructure of the coating is investigated using X-Ray diffraction, electron microscopy and ellipsometry techniques. To assess the thermochromic properties of the fabricated device, optical transmission experiments were conducted both at room temperature and at elevated temperature. A correlation between these thermochromic properties and coating thickness was investigated in order to obtain an optimized thermochromic device, where both high visual transparency and prominent thermochromic switching abilities are aimed for. In this work, an optimal coating thickness is proposed for a thermochromic coating with high switching ability and solar modulation.

In this work, Ni–14Al, Ni–30Al and Ni–58Al alloys representing Ni3Al, NiAl and NiAl3 phases were studied. First of all, they were prepared by reactive sintering to show which phases are present in the obtained microstructure. Subsequently, reactions between nickel and aluminum were observed below and above the melting point of aluminum allowing to propose reaction mechanism and to determine kinetics. Experiments below melting point were carried out as annealing of the powder mixture and phase composition was studied while experiments at higher temperatures used special experimental model consisting bulk nickel and molten aluminum. Results showed that Ni2Al3 phase formed preferentially in all alloy composition, which was supported by in-situ diffraction analysis, and the whole process was controlled by diffusion. Its preferential formation was confirmed by annealing of powder mixture and by the experimental model as well. This model allowed observing the phases' formation at the interface of bulk nickel and molten aluminum at high temperature. The appropriate ongoing reactions were compiled for each alloy with calculated Gibbs energy and enthalpy of reaction.

The solid solubility of the isomorphous monosilicides during the silicide reaction of Ni-Pt, Ni-Pd and Pt-Pd alloys on Si(100) is comparatively studied in the full composition range. Our study reveals that PtSi and PdSi, exhibiting a minor lattice mismatch, directly form a solid solution. In contrast, for larger differences in lattice parameters such as is the case for NiSi-PtSi and NiSi-PdSi, the mutually soluble phases coexist, prior to the formation of a solid solution at increased temperatures. Hence, it appears that the direct formation of a ternary monosilicide solid solution is inherently related to the lattice mismatch of the binary monosilicides. This finding provides an explanation for important differences observed in the elemental redistribution between the three systems, considered to be very similar up to now. Moreover, the different formation of a solid solution results in a fundamentally different nucleation of PdSi: while Ni lowers the nucleation barrier by reducing the contribution of the interface energy, Pt strongly increases the entropy of mixing which triggers the formation of the Pd-monosilicide at surprisingly low temperatures. Our results show that the lattice mismatch is a crucial parameter and determines the phase formation sequence and elemental redistribution during the silicide reaction.

This work aims to describe the effect of magnesium on the microstructure, phase composition, amount of undesirable Ti2Ni phase, martensitic transformation, mechanical properties, and corrosion resistance of NiTi alloy. To minimize the quantity of Ti2Ni phase, we use the magnesium as an element with high affinity to oxygen, because this phase is stabilized by oxygen. Various quantities of magnesium (1, 3, and 5 wt pct) were tested. Self-propagating high-temperature synthesis (SHS) was used as a production method of the alloys. The samples prepared by SHS were pulverized by a vibrating mill, and the obtained powders were used for consolidation by means of spark plasma sintering. Results showed a significant reduction of the content of undesirable Ti2Ni phase by the addition of magnesium. Further, magnesium increased corrosion resistance and yield strength.

Wide-bandgap nitride semiconductors are currently in development for high-power electronic applications. Compositional layered heterostructures of such nitrides result in a high polarization field at the interface, enabling a higher electron mobility, a higher power density, and a higher conversion efficiency. Further optimization of such GaN-based high-electron-mobility transistors can be achieved by evolving from a top Al x Ga 1 − x N barrier toward AlN or even In y Al 1 − y N. An ongoing challenge in using such hexagonal nitride semiconductors is the formation of a low-resistive, Au-free, ohmic contact far below 1 Ω mm. In this paper, we investigate the formation of ohmic contacts by Ti–Al–TiN-based metalization as a function of different annealing temperatures (up to 950 ° C), Ti–Al ratios (from 15 up to 35 at. %) and nitride barrier composition ( Al x Ga 1 − x N, GaN, AlN, and In y Al 1 − y N). Contacts processed on AlxGa1–x/GaN, and AlN/GaN heterostructures result in low contact resistance of, respectively, 0.30 and 0.55 Ω mm, whereas the same contact stack on In y Al 1 − y N results in resistance values of 1.7 Ω mm. The observed solid-phase reaction of such Ti–Al–TiN stacks were found to be identical for all investigated barrier compositions (e.g., Al x Ga 1 − x N , GaN, AlN, and In y Al 1 − y N), including the preferential grain alignment to the epitaxial nitride layer. The best performing ohmic contacts are formed when the bottom Ti-layer is totally consumed and when an epitaxially-aligned metal layer is present, either epitaxial Al (for a contact which is relatively Al-rich and annealed to a temperature below 660 ° C) or ternary Ti 2 AlN (for a relatively Ti-rich contact annealed up to 850 ° C). The observation that the solid-phase reaction is identical on all investigated nitrides suggests that a further decrease of the contact resistance will be largely dependent on an optimization of the nitride barriers themselves.

The thickness characterization of transparent protective coatings on functional, transparent materials is often problematic. In this paper, a toolbox to determine the thicknesses of a transparent coating on functional window films is presented. The toolbox consists of a combination of secondary ion mass spectrometry and profilometry and can be transferred to other transparent polymeric materials. A coating was deposited on designed model samples, which were characterized with cross-sectional views in transmission and in scanning/transmission electron microscopy and ellipsometry. The toolbox was then used to assess the thicknesses of the protective coatings on the pilot-scale window films. This coating was synthesized using straightforward sol-gel alkoxide chemistry. The kinetics of the condensation are studied in order to obtain a precursor that allows fast drying and complete condensation after simple heat treatment. The shelf life of this precursor solution was investigated in order to verify its accordance to industrial requirements. Deposition was performed successfully at low temperatures below 100 &deg, C, which makes deposition on polymeric foils possible. By using roll-to-roll coating, the findings of this paper are easily transferrable to industrial scale. The coating was tested for scratch resistance and adhesion. Values for the emissivity (&epsilon, ) of the films were recorded to justify the use of the films obtained as infrared reflective window films. In this work, it is shown that the toolbox measures similar thicknesses to those measured by electron microscopy and can be used to set a required thickness for protective coatings.

X-ray diffraction (XRD) and electron paramagnetic resonance spectroscopy (EPR) were combined to study the structural transformations induced by temperature, pressure and air humidity of the "breathing" metal-organic framework (MOF) MIL-53(Al), doped with paramagnetic V

Surface engineering of micro- and nanoparticles is of great importance in fields such as catalysis, energy and sensing. For many of these applications particles are required with different bulk and surface properties. A popular technique to achieve this is to coat the particle surface with a nanometer thick layer. Only a few techniques have been explored for depositing such thin conformal coatings. Chemical vapor deposition (CVD) has been used extensively for this purpose, but suffers from a lot of disadvantages, such as imperfect control over layer thickness and uniformity of the coating over all individual particles, particle agglomeration and formation of additional undesired particles due to gas phase reactions between the CVD reactants. In contrast, atomic layer deposition (ALD) is known as a reliable technique for covering complex 3D objects with ultrathin conformal coatings. However, to perform ALD on large quantities of powders, the individual particles need to be fluidized or agitated. Fluidized bed reactors are most often used for ALD on particles, but this reactor concept does not seem to be compatible with plasma enhanced ALD, which is advantages for e.g. coating on temperature sensitive polymer particles or deposition of metals and metal nitrides. In this work, a rotary reactor was used to agitate particles, enabling the deposition of conformal coatings by thermal and plasma-enhanced ALD. Particles ranging from nanometer size to millimeter size were successfully coated with layers of Al2O3, TiO2, AlN and TiN.[1]In-situ mass spectroscopy confirmed that ALD was performed by detecting the expected reaction products. By monitoring the formation of these reaction products over time, it was possible to optimize precursor and reactant usage, which is linearly dependent on the effective surface area of the particles. In the case of plasma enhanced ALD, in-situ optical emission spectroscopy confirmed the mass spectroscopy data. X-ray fluorescence revealed the expected linear relationship between the amount of ALD cycles and the deposited amount of material, while X-ray photo-electron spectroscopy was used to confirm the composition and purity of the coatings. Transmission electron spectroscopy finally showed that the individual particles were coated uniformly and conformally. Our results prove that the proposed rotary reactor enables conformal deposition on nano- and micropowders by thermal and plasma enhanced ALD. In this way, surface engineering of such particles can be achieved. [1] D. Longrie et al., Surface & Coating Technology 213 (2013) 183-191

This work aims to describe the mechanism of intermediary phases formation in TiAl20 (wt. %) alloy composition during reactive sintering. The reaction between titanium and aluminum powders was studied by in situ diffraction and the results were confirmed by annealing at various temperatures. It was found that the Ti2Al5 phase formed preferentially and its formation was detected at 400 &deg, C. So far, this phase has never been found in this alloy composition during reactive sintering processes. Subsequently, the Ti2Al5 phase reacted with the titanium, and the formation of the major phase, Ti3Al, was accompanied by the minor phase, TiAl. Equations of the proposed reactions are presented in this paper and their thermodynamic and kinetic feasibility are supported by Gibbs energies of reaction and reaction enthalpies.

Crystalline vanadium dioxide (VO 2 ) thin films were prepared by annealing amorphous VO 2 films which were deposited by atomic layer deposition on a SiO 2 substrate. A large influence of the oxygen partial pressure in the annealing ambient was observed by means of in-situ X-ray diffraction. In the range between 1 and 10 Pa of oxygen the interesting VO 2 (R) phase crystallized near 450 °C. Between 2 and 10 Pa of oxygen, metastable VO 2 (B) was observed as an intermediate crystalline phase before it transformed to VO 2 (R). Anneals in inert gas did not show any crystallization, while oxygen partial pressures above 10 Pa resulted in oxidation into the higher oxide phase V 6 O 13 . Film thickness did not have much effect on the crystallization behavior, but thinner films suffered more from agglomeration during the high-temperature crystallization on the SiO 2 substrate. Nevertheless, continuous polycrystalline VO 2 (R) films were obtained with thicknesses down to 11 nm. In the case where VO 2 (R) was formed, the semiconductor–metal transition was observed by three complementary techniques. This transition near 68 °C was characterized by X-ray diffraction, showing the transformation of the crystal structure, by spectroscopic ellipsometry, mapping optical changes, and by sheet resistance measurements, showing resistance changes larger than 2 orders of magnitude between the low-temperature semiconducting state and the high-temperature metallic state.

X-ray diffraction (XRD) and electron paramagnetic resonance spectroscopy (EPR) were combined to study the structural transformations induced by temperature, pressure and air humidity of the breathing metalorganic framework (MOF) MIL-53(Al), doped with paramagnetic VIV ions, after activation. The correlation between in situ XRD and thermogravimetric analysis measurements showed that upon heating this MOF in air, starting from ambient temperature and pressure, the narrow pore framework first dehydrates and after that makes the transition to a large pore state (lp). The EPR spectra of VIV[double bond, length as m-dash]O molecular ions, replacing AlOH in the structure, also allow to distinguish the as synthesized, hydrated (np-h) and dehydrated narrow pore (np-d), and lp states of MIL-53(Al). A careful analysis of EPR spectra recorded at microwave frequencies between 9.5 and 275 GHz demonstrates that all VIV[double bond, length as m-dash]O in the np-d and lp states are equivalent, whereas in the np-h state (at least two) slightly different VIV[double bond, length as m-dash]O sites exist. Moreover, the lp MIL-53(Al) framework is accessible to oxygen, leading to a notable broadening of the VIV[double bond, length as m-dash]O EPR spectrum at pressures of a few mbar, while such effect is absent for the np-h and np-d states for pressures up to 1 bar.

In this work the formation of intermetallics in the Ni-Ti system by reactive sintering at 800-900 degrees C was studied. The mechanism and kinetics of the reactions, which led to Ni-Ti phases, were determined by thermal analysis, in-situ XRD and the application of an experimental model consisting of nickel-plated titanium. It was found that the formation of Ni-Ti phases below the transformation temperature of titanium is controlled by diffusion. Above this temperature, the reactions switch to the rapid Self-propagating High-temperature Synthesis (SHS) mode.

Anisotropic deposition profiles of TiO2 in Zeotile-4 ordered mesoporous silica material are obtained using Atomic Layer Deposition (ALD) involving alternating pulses of tetrakis(dimethylamino) titanium (TDMAT) and water. TiO2 concentration profiles visualized by transmission electron microscopy (TEM) on particle cross sections reveal the systematic deeper penetration of the deposition front along the main channels and the more limited penetration in the perpendicular direction through the narrower slit-like mesopores. In ordered mesoporous material with one-dimensional pore system ALD leads to pore plugging. Diffusion limited ALD is shown to be useful for TiO2 deposition in anisotropic mesoporous support materials. This work was supported by the Flemish IWT in the frame of the strategic basic research (SBO) project and by the Flemish FWO. JAM. acknowledges the Flemish government for long term structural funding. C.D. acknowledges the European Research Council for an ERG Starting Grant (Grant 239865), and J.D. acknowledges the Flemish FWO for a Ph.D. research grant.

This communication reports an approach based on plasma-enhanced atomic layer deposition of aluminium oxide for the functionalization of polytetrafluoroethylene (PTFE or "Teflon") surfaces. Alternating exposure of PTFE to oxygen plasma and trimethylaluminium causes a permanent hydrophilic effect, and a more than 10-fold improvement of the "glueability" of PTFE to aluminium.

TaCN films were deposited using atomic layer deposition (ALD) using PDMAT and H"2/Ar plasma. Calculations based on density functional theory (DFT) indicate a high energy barrier and a low reaction energy for reducing the +5 Ta oxidation state in the PDMAT precursor by using pure H radicals. Through the assistance of Ar radicals, low resistivity of TaCN films of 230@m@Wcm could be deposited by using H"2/Ar plasma. By employing in situ X-ray diffraction during annealing, the activation energy for Cu diffusion through the TaCN barrier was evaluated at 1.6eV.

Synchrotron-based X-ray fluorescence (XRF) is introduced as a promising in situ technique to monitor atomic layer deposition cycle-per-cycle. It is shown that the technique is greatly suitable to study initial nucleation on planar substrates. The initial growth of TiO2 from tetrakis(dimethylamino)titanium (TDMAT) and H2O is found to be linear on thermally grown SiO2, substrate-inhibited on H-terminated Si and substrateenhanced on atomic layer deposited Al2O3. Furthermore, in situ XRF is employed to monitor the Ti uptake during deposition of TiO2 in nanoporous silica films. In mesoporous films, the Ti content varied quadratically with the number of cycles, a behavior that is attributed to a decreasing surface area with progressing deposition. In microporous films, the XRF data suggest that 1−3 ALD cycles shrunk the pore diameters below the kinetic diameter of the TDMAT molecule.

The W-based diffusion barriers W, WC and WCN barriers were investigated for Cu metallization. The thermal stability of the W, WC and WCN barriers was compared by X-ray diffraction and four point probe. It shows comparable stability for the W and WC barriers while the ternary WCN barrier has superior performance. The agglomeration of the Cu films (100nm) on these barriers is quite different. The formation of voids was observed for the annealed copper film on the WC or WCN barriers and the activation energy values determined from Kissinger equation are low comparing with Cu on W barrier. Twins were also observed in the as-deposited and annealed Cu films on the WC and WCN barriers. The twin formation and its correlation with void formation for Cu films onto the C-containing diffusion barrier were discussed through the stress relaxation and stress-induced vacancy migration mechanism.

Ruthenium films were grown by plasma enhanced atomic layer deposition (ALD) on Si(100) and ALD TiN. X-ray diffraction (XRD) showed that the as-deposited films on Si(100) were polycrystalline, on TiN they were (002) oriented. After annealing at 800^oC for 60s, all Ru films were strongly (002) textured and very smooth. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) demonstrated that the lateral grain size of the annealed films was several 100nm, which was large compared to the 10nm thickness of the films. No ruthenium silicide was formed by annealing the ALD Ru films on Si(100). Comparison with sputter deposited films learned that this occurred because the ammonia plasma created a SiO"xN"y reaction barrier layer prior to film growth.

The solid state reaction between a thin (30nm) Ir film and different Si substrates (p-type Si(100), n- and p-type Si(111), silicon on insulator (SOI) and polycrystalline Si) was studied using a combination of in situ X-ray diffraction (XRD), in situ sheet resistance and laser light scattering measurements. No significant influence of either the dopants or the substrate orientation was detected as a phase formation sequence of IrSi, Ir"3Si"4,Ir"3Si"5 and IrSi"3 was found for all samples. The presence of a thin (

Ru thin films were sequentially deposited onto TaN (5 nm) by plasma enhanced atomic layer deposition using Ru(EtCp) 2 and NH 3 as precursors. The effect of growth temperature on the electrical resistivity and morphology of the Ru films were studied. It was found that the Ru films can achieve a low resistivity of 14 µΩ cm and a low root-mean-square roughness at a growth temperature of 270 °C. The thickness of the underlying TaN film was found to affect the Ru film growth. The oxidation of the very thin TaN film was correlated with the island growth of Ru. Ex and in-situ X-ray diffraction was employed to verify the copper diffusion barrier properties of a Ru (3 nm)/TaN (5 nm) bi-layer structure.

TiN was grown by atomic layer deposition (ALD) from tetrakis(dimethylamino)titanium (TDMAT). Both thermal and plasma enhanced processes were studied, with N"2 and NH"3 as reactive gases. Using an optimized thermal ammonia based process, a growth rate of 0.06nm/cycle and a resistivity of 53x10^[email protected]@Wcm were achieved. With an optimized plasma enhanced NH"3 process, a growth rate of 0.08nm/cycle and a resistivity of 180 @[email protected] cm could be obtained. X-ray photo electron spectroscopy (XPS) showed that the difference in resistivity correlates with the purity of the deposited films. The high resistivity of thermal ALD films is caused by oxygen (37%) and carbon (9%) contamination. For the film deposited with optimized plasma conditions, impurity levels below 6% could be achieved. The copper diffusion barrier properties of the TiN films were determined by in-situ X-ray diffraction (XRD) and were found to be as good as or better than those of films deposited with physical vapor deposition (PVD).

The formation and degradation of NiSi in the presence of Co and Fe alloying elements have been investigated. Alloyed Ni layers were characterized with in situ techniques to determine the stability of the NiSi phase on single crystalline and on polycrystalline Si substrates. It is shown that the phase stability is decreased with the addition of Co or Fe. The formation of the NiSi2 phase on Si(100) is initiated at a temperature that is more than 200 °C lower for the Ni alloys than for a reference Ni layer. Thereby a few percent of Co or Fe results in the formation of a polycrystalline NiSi2 phase on a single crystalline substrate. The low formation temperature of the NiSi2 phase in the presence of Co or Fe can be attributed to a mixing entropy effect. The morphological stability of the silicide films on Si(100) and on polycrystalline Si is improved due to the early formation of NiSi2 and is related to an increased film thickness and also to a higher deformation temperature for the poly-Si.

Carbon free TaN"x films were deposited by plasma enhanced atomic layer deposition (PEALD) using a combination of pentakis(dimethylamino)Ta (PDMAT) and either N"2 or NH"3 plasma. Good linearity and saturation behavior were observed for the TaN"x films grown with NH"3 plasma while non-ideal saturation features were observed for the films grown with N"2 plasma. The thermal stability of the TaN"x films could be improved by reducing the pressure of the reactants and by increasing the plasma exposure time. The TaN"x films deposited using N"2 plasma exhibit better diffusion barrier properties than the films deposited using NH"3 plasma.

Molecular layer deposition (MLD) of hybrid organic–inorganic thin films called “titanicones” was achieved using tetrakisdimethylaminotitanium (TDMAT) and glycerol (GL) or ethylene glycol (EG) as precursors. For EG, in situ ellipsometry revealed that the film growth initiates, but terminates after only 5 to 10 cycles, probably because both hydroxyls react with the surface. GL has a third hydroxyl group, and in that case steady state growth could be achieved. The GL process displayed self-limiting reactions for both reactants in the temperature range from 80 °C to 160 °C, with growth rates of 0.9 to 0.2 A per cycle, respectively. Infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the hybrid nature of the films, with a carbon atomic concentration of about 20%. From X-ray reflectivity, the density was estimated at 2.2 g cm−3. A series of films was subjected to water etching and annealing under air or He atmosphere at 500 °C. The carbon content of the films was monitored with FTIR and XPS. Almost all carbon was removed from the air annealed and water treated films. The He annealed samples however retained their carbon content. Ellipsometric porosimetry (EP) showed 20% porosity in the water etched samples, but no porosity in the annealed samples. Electrochemical measurements revealed lithium ion activity during cyclic voltammetry in all treated films, while the as-deposited film was inactive. With increasing charge current, the He annealed samples outperformed amorphous and anatase TiO2 references in terms of capacity retention.

In this work, we investigate binary Ag-Te thin films and their functionality as a cation supply layer in conductive bridge random access memory devices. A combinatorial sputter deposition technique is used to deposit a graded Ag(x)Te(1-x) (0x1) layer with varying composition as a function of the position on the substrate. The crystallinity, surface morphology, and material stability under thermal treatment as a function of the composition of the material are investigated. From this screening, a narrow composition range between 33 and 38 at% Te is selected which shows a good morphology and a high melting temperature. Functionality of a single Ag(2-δ)Te composition as cation supply layer in CBRAM with dedicated Al2O3 switching layer is then investigated by implementing it in 580 μm diameter dot Pt/Ag(2-δ)Te/Al2O3/Si cells. Switching properties are investigated and compared to cells with a pure Ag cation supply layer. An improved cycling behavior is observed when Te is added compared to pure Ag, which we relate to the ionic conducting properties of Ag2Te and the preferred formation of Ag-Te phases.

We demonstrate that the addition of alloying elements can substantially affect the formation and morphological stability of nickel silicide. A comprehensive study of phase formation was performed on 24 Ni alloys with varying alloying element concentrations. Using time resolved x-ray diffraction (XRD), we follow the formation of the silicide phases in real time during rapid thermal annealing. Simultaneous in situ resistance and light scattering measurements complement the XRD technique and show the onset of thermal degradation for the monosilicide films.

In order to narrow the band gap of TiO2, nitrogen doping by combining thermal atomic layer deposition (TALD) of TiO2 and plasma enhanced atomic layer deposition (PEALD) of TiN has been implemented. By altering the ratio between TALD TiO2 and PEALD TiN, the as synthesized TiOxNy films showed different band gaps (from 1.91 eV to 3.14 eV). In situ x-ray diffraction characterization showed that the crystallization behavior of these films changed after nitrogen doping. After annealing in helium, nitrogen doped TiO2 films crystallized into rutile phase while for the samples annealed in air a preferential growth of the anatase TiO2 along (001) orientation was observed. Photocatalytic tests of the degradation of stearic acid were done to evaluate the effect of N doping on the photocatalytic activity. © 2014 American Vacuum Society. ispartof: Journal of Vacuum Science & Technology A, Vacuum, Surfaces and Films vol:32 issue:1 pages:01- status: published

Thin vanadium nitride (VN) layers were grown by atomic layer deposition using tetrakis(ethylmethylamino)vanadium and NH3 plasma at deposition temperatures between 70 °C and 150 °C on silicon substrates and polymer foil. X-ray photoelectron spectroscopy revealed a composition close to stoichiometric VN, while x-ray diffraction showed the δ-VN crystal structure. The resistivity was as low as 200 μΩ cm for the as deposited films and further reduced to 143 μΩ cm and 93 μΩ cm by annealing in N2 and H2/He/N2, respectively. A 5 nm VN layer proved to be effective as a diffusion barrier for copper up to a temperature of 720 °C.

The microstructure of sputter-deposited Cu films is shown to be unstable at room temperature (RT). The average grain size increases significantly during RT storage for a couple of hours after deposition. This RT grain growth is shown to be very dependent on the deposition parameters (substrate temperature and sputter gas pressure) and hence on the microstructure of the as-deposited film. The microstructure of sputter-deposited films is usually summarized in a structure-growth-zone model. It is found that significant RT grain growth only occurs for Cu layers with a zone-T-type, as-deposited microstructure.

Alumina was deposited on a non-woven polyester fiber substrate using both thermal and plasma enhanced atomic layer deposition (ALD). The textile was confined inside a one dimensional test structure. The coverage of the ALD film on the nonwoven as a function of depth in the test structure was determined by energy dispersive X-ray spectroscopy (EDX). A model is introduced which links the precursor transport in the nonwoven (transmission, reflection and deposition) with the nonwoven properties (density, fiber surface area, density of surface sites). The experimental results are compared to simulations of the coverage profile. It is shown that longer precursor exposure times result in deposition deeper inside the nonwoven. However, the majority of precursor molecules entering the nonwoven leave the test structure without contributing to film growth. ALD from TMA and oxygen plasma had a very limited penetration into the nonwoven because of radical recombination. This effect is relevant for plasma treatment of fibrous materials in general.

To conformally coat large amounts of particles using atomic layer deposition (ALD), agitation of the particles and efficient reactant usage are necessary. A rotary reactor was developed to enable both thermal and plasma-enhanced ALD growth on agitated particles. The effectiveness of the rotary reactor design was demonstrated by depositing Al 2 O 3 , TiO 2 and AlN by thermal and plasma-enhanced ALD on ZnO nanopowder, stainless steel micron sized powder, titanium granules and glass beads. In-situ optical emission spectroscopy (OES) and mass spectroscopy (MS) measurements were performed to monitor saturation of the ALD half reactions, while ex-situ X-ray fluorescence (XRF), X-ray photo-electron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) were used to confirm the composition and conformality of the deposited films.

Vanadium dioxide (VO2) has the interesting feature that it undergoes a reversible semiconductor-metal transition (SMT) when the temperature is varied near its transition temperature at 68°C.1 The variation in optical constants makes VO2 useful as a coating material for e.g. thermochromic windows,2 while the associated change in resistivity could be interesting for applications in microelectronics, e.g. for resistive switches and memories.3 Due to aggressive scaling and increasing integration complexity, atomic layer deposition (ALD) is gaining importance for depositing oxides in microelectronics. However, attempts to deposit VO2 by ALD result in most cases in the undesirable V2O5. In the present work, we demonstrate the growth of VO2 by using Tetrakis[EthylMethylAmino]Vanadium and ozone in an ALD process at only 150°C. XPS reveals a 4+ oxidation state for the vanadium, related to VO2. Films deposited on SiO2 are amorphous, but during a thermal treatment in inert gas at 450°C VO2(R) is formed as the first and only crystalline phase. The semiconductor-metal transition has been observed both with in-situ X-ray diffraction and resistivity measurements. Near a temperature of 67°C, the crystal structure changes from VO2(M1) below the transition temperature to VO2(R) above with a hysteresis of 12°C. Correlated to this phase change, the resistivity varies over more than 2 orders of magnitude.

High quality Ru thin film with low electrical resistivity (10~14 ??cm) was successfully deposited on the Si, atomic layer deposition (ALD) grown TiN(2nm)/Si and ALD TaN(5 nm)/Si substrates by using plasma enhanced atomic layer deposition (PEALD). Different growth mode and crystallization behavior were observed for the Ru films grown on these different substrates. Results show that the lowest surface roughness, lowest electrical resistivity and best crystallinity of the Ru films can be achieved on all three substrates with a growth temperature of 270°C. Ex and in-situ X-ray diffraction were employed to verify the good diffusion barrier properties of Ru/TiN and Ru/TaN bi-layer structure.

The results are presented of a study on grain growth in magnetron sputter deposited Cu films. Similarly to the well-known case of electroplated Cu, we observed significant changes in the microstructure of sputter deposited films during storage at room temperature, as evidenced by a decrease in sheet resistance (up to 40% decrease in less than 6 hours). Direct evidence for grain growth was observed by FIB and SEM and by a strong decrease in the XRD peak width. Moreover, a decrease in the total defect content of the film was observed as a function of storage time from positron annihilation experiments, probably reflecting the decreasing number of grain boundaries in the film. It is well known that the microstructure of an as-deposited film is strongly dependent on the deposition parameters. This relationship is summarized in the Thornton structure-growth zone diagram [7]. We have studied the kinetics of room temperature grain growth as a function of Ar pressure and substrate temperature for Cu films with a thickness between 50 nm and 1 micrometer. It is found that spontaneous grain growth during storage at room temperature occurs mainly for a zone T microstructure (at low Ar pressure and a substrate temperature below 40°C), while it does not occur for zone I (high Ar pressure, low substrate temperature) or zone II (substrate temperature > 100°C) microstructures.

Polypropylene (PP) and a blend of poly(ethylene terephthalate)/cotton (PET/cotton) nonwoven fiber felts were modified using aluminum and zinc oxides via thermal and plasma enhanced atomic layer deposition (ALD and PEALD). Deposition of aluminum or zinc oxide on PP induced a wetting transition from the hydrophobic behavior characteristic of the untreated PP to a hydrophilic behavior for ALD coated PP. PEALD needed a fewer number of cycles to induce hydrophilic effect, compared to thermal ALD. This correlated with the observation of an initial nucleation delay for thermal ALD on PP, while PEALD resulted in deposition of oxide material from the initial cycles. The hydrophilic effect could be achieved for a wider range of deposition temperatures for PEALD as compared to thermal ALD. PEALD of aluminum and zinc oxides did not alter the surface properties of the PET/cotton felts, as they stayed hydrophilic even after 400 cycles of deposition, while thermal ALD of zinc oxide transformed hydrophilic PET/cotton felts to hydrophobic.

Due to its high intrinsic mobility, germanium (Ge) is a promising candidate as a channel material (offering a mobility gain of approximately??2 for electrons and??4 for holes when compared to conventional Si channels). However, many issues still need to be addressed before Ge can be implemented in high-performance field-effect-transistor (FET) devices. One of the key issues is to provide a high-quality interfacial layer, which does not lead to substantial drive current degradation in both low equivalent oxide thickness and short channel regime. In recent years, a wide range of materials and processes have been investigated to obtain proper interfacial properties, including different methods for Ge surface passivation, various high-k dielectrics and metal gate materials and deposition methods, and different post-deposition annealing treatments. It is observed that each process step can significantly affect the overall metal?oxide?semiconductor (MOS)-FET device performance. In this review, we describe and compare combinations of the most commonly used Ge surface passivation methods (e.g. epi-Si passivation, surface oxidation and/or nitridation, and S-passivation) with various high-k dielectrics. In particular, plasma-based processes for surface passivation in combination with plasma-enhanced atomic layer deposition for high-k depositions are shown to result in high-quality MOS structures. To further improve properties, the gate stack can be annealed after deposition. The effects of annealing temperature and ambient on the electrical properties of the MOS structure are also discussed.

In this paper the annealing effects in N2 on the electrical characteristics of a TiN/HfO2/GeON/p-Ge capacitor are investigated. Well behaved capacitance–voltage curves were obtained for the sample annealed at 400 °C for 3 min in N2. A negligible hysteresis was demonstrated comparing with a hysteresis of 0.5 V for the as-deposited sample. The suppression of hysteresis is attributed to the reduction of electron traps in the dielectric layer, which is verified by the MOS pulse method. Besides, the interface states' density is also greatly reduced by annealing in N2 and confirmed by the conductance method.

Metal-oxide-semiconductor capacitor was fabricated using in situ O2 plasma passivation and subsequent deposition of a HfO2 high-k gate stack on Ge. By extracting flat band voltages from capacitors with different equivalent oxide thicknesses (EOT), the effect of forming gas annealing (FGA) and O2 ambient annealing on the fixed charge was systematically investigated. The O2 ambient annealing is more effective than FGA as it reduced fixed charge density to 8.3 × 1011 cm−2 compared to 4.5 × 1012 cm−2 for at the same thermal budget and showed no degradation of EOT. Further, the distribution of fixed charges in gate stack was discussed in detail.