Tetrakis Dimethylamido Titanium Research Articles

Room temperature atomic layer deposition of zinc titanium oxide using sequential adsorption of dimethyl zinc and tetrakis(dimethylamino)titanium

Complex oxide films of TiO2 and ZnO are deposited by RT atomic layer deposition (ALD) with a sequential adsorption process. In this ALD, a Zn precursor of dimethyl zinc (DMZ) and a Ti precursor of tetrakis(dimethylamino)titanium (TDMAT) are used. In the sequential adsorption step, the DMZ saturation on the surface is followed by partial adsorption of TDMAT. It is assumed that the TDMAT molecule is adsorbed on the DMZ uncovered area. The mixed layer of DMZ and TDMAT is formed in the adsorption step, followed by being oxidized with the plasma-excited humidified Ar. All the ALD processes are performed at RT without any sample heating in the ALD chamber. The growth per cycle of the balanced Zn and Ti oxide deposition is recorded at 0.086 nm/cycle. The mixing ratio of Zn and Ti is controlled by the TDMAT exposure in the adsorption step. In this study, the reaction model and the related rate equations to calculate the mixing concentration ratio are proposed based on the in situ observation of the surface reaction by IR absorption spectroscopy.

Comparison of three titanium-precursors for atomic-layer-deposited TiO2 for passivating contacts on silicon

Atomic layer-deposited (ALD) TiO2 thin films on silicon were deposited using titanium tetrachloride (TiCl4), titanium tetraisopropoxide (TTIP), and tetrakis(dimethylamino)titanium (TDMAT) together with water vapor as the oxidant at temperatures ranging between 75 and 250 °C. The Si surface passivation quality of as-deposited and isothermally annealed samples was compared using photoconductance lifetime measurements in order to calculate their effective surface recombination velocities Seff. A low Seff of 3.9 cm/s (J0s=24fA/cm2) is achieved for as-deposited TiCl4-TiO2 at 75 °C when a chemically grown (i.e., from RCA cleaning) SiOx interface layer is present. Depositing TTIP-TiO2 at 200 °C on a chemically grown SiOx interface layer yields equivalent Seff values; however, in this case, TTIP-TiO2 requires a 5–15 min postdeposition forming gas anneal at 250 °C. In contrast, TDMAT-TiO2 was not found to provide a similar level of passivation with/without a chemically grown SiOx interface layer and postdeposition anneal. Modeling of the effective lifetime curves was used to determine the magnitude of the effective charge densities Qf in the TiO2 films. In all cases, Qf was found to be of the order of ∼1011 q cm−2, meaning field-effect passivation arising from ALD TiO2 is relatively weak. By comparing the material properties of the various TiO2 films using ellipsometry, photothermal deflection spectroscopy, Raman spectroscopy, elastic recoil detection analysis, x-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, we find experimental support for the role of Cl (in conjunction with hydrogen) playing a beneficial role in passivating dangling bond defects at the Si surface. It is concluded that low deposition temperature TiCl4 processes are advantageous, by providing the lowest Seff without any postanneal and a comparatively high growth per cycle (GPC).

Effect of Adhesion Layer at the Pt/TiO2 Interface on the Degradation Pathways of TiO2-Protected III-V Water-Splitting Photocathodes

Photoelectrochemical (PEC) water splitting has been identified as a promising route towards the production of green hydrogen as a solar fuel to meet the global energy demands [1]. Highly efficient photoelectrodes made of III-V compounds are promising candidates to reach the goal of >15% solar-to-hydrogen efficiency [2]. However, the main bottle neck of these materials is their poor stability in direct contact with acidic electrolytes, which is needed to ensure efficient mass transport and an efficient hydrogen evolution reaction (HER). Atomic layer deposited (ALD) titanium dioxide (TiO2) is commonly utilized as a protective layer to shield the absorber from the electrolyte [3]. To reduce HER overpotentials, the TiO2 film needs to be modified with a catalyst layer. In a demonstration of a TiO2 protected III-V PEC device, Cheng et al. proposed that the detachment of the catalyst layer induced the degradation of the protective TiO2 film in a pH 0 electrolyte which eventually led to the corrosion of the photoabsorber [4].In this work, GaInP/GaAs/Ge photocathodes for water reduction were protected with ALD TiO2 layers deposited from tetrakis(dimethylamido)titanium (TDMAT) and water precursors with varying thicknesses. A 2 nm catalytic Pt layer was deposited via electron beam evaporation (EBE) to reduce the overpotential of the HER. The conformal coverage of the absorber with TiO2 was confirmed with atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). None of the TiO2 films were able to stabilize the illuminated III-V electrodes for 60 min at 0 V versus the counter electrode (CE) in a pH 0 electrolyte (1 M H2SO4). Characterization of the electrochemical potential at the electrode’s front side revealed an unstable regime for the TiO2 protection layer. ICP-MS of the electrolytes, SEM/EDX and electrochemical analyses revealed the detachment of the catalytic Pt layer that led to the dissolution of the TiO2 and the III-V degradation (Figure 1A). The adhesion of Pt on TiO2 was improved by depositing a 2 nm Ti layer via EBE at the Pt/TiO2 interface (Figure 1B). The adhesion layer acts as a wetting layer for Pt, reducing the nucleation energy barrier and increasing the number of nucleation sites compared to Pt/TiO2. The enhanced wetting is due to the formation of Ti−Pt chemical bonds [5] and the overpotential @ 10 mA/cm2 to perform HER was 60 mV, similar to that of a pristine EBE Pt layer. The Ti layer greatly improves the stability of TiO2/III-V photoelectrodes, confirming the results of Cheng et al. and illustrating the importance of a stable catalyst layer.Figure 1. A) SEM micrograph of degradation of Ge/GaAs/GaInP/TiO2/Pt photocathode after 60 min. of photocurrent measurements at 0 V vs. CE in 1 M H2SO4. B) Accelerated stability test in dark for 2 nm Pt/15 nm TiO2 on FTO with (red curve) and without (black curve) a 2 nm Ti adhesion layer in between the Pt and TiO2 layers.

Growth Mechanism and Film Properties of Atomic-Layer-Deposited Titanium Oxysulfide

Titaniumoxysulfide (TiOxSy) is a technologically-relevant material for batteries, catalysis and, the area of our focus: photovoltaics. One of the key merits of TiOxSy is the wide range of electrical conductivity and optical absorption that can be achieved by tuning its composition. In this contribution, we present a supercycle-based ALD approach for TiOxSy which combines ALD of amorphous TiO2 and semimetallic two-dimensional (2D) TiS2, and uses tetrakis(dimethylamido)titanium (TDMATi), H2O and H2S as precursors. While ALD with supercycles is generally acknowledged to give a high level of control over film composition, in this case of TiOxSy we show through a variety of in-situ techniques that many effects occur during the ALD supercycles that strongly affect the film growth and resulting film properties. Yet, by understanding and taking these effects into account, the supercycle process allows for accurate tailoring between pure TiOx and TiSx. The effects of study focus mainly on exchange reactions and the film crystal morphology and its effect on the growth rate. Exchange reactions: QMS measurements show that during supercycle ALD, strong exchange reactions occur during the H2O dosing step, where exchange occurs between underlying TiSx and H2O, resulting in the formation of TiOx and release of H2S. The exchange reactions and their effect on the film growth were studied in-depth using in-situ SE. From these studies, it was found that during ALD TiO2 cycles on TiSx, the exchange reactions behave similarly at 100 and 150 °C, while being more pronounced at 200 °C. Specifically, at 100 and 150 °C, the reactions persist for about seven cycles and stop once approximately 3−4 Å of TiO2 has grown, while at 200 °C, the reactions are more prominent and persist for about nine cycles and stop once approximately 5 Å of TiO2 has grown. This TiO2 forms both through back-oxidation of underlying TiSx and by ALD of TiO2 on top. These exchange effects are thus less prominent at lower growth temperatures, facilitating more accurate control over composition. Film crystallinity: Interestingly, the pure ALD TiO2 and TiS2 processes yield films of very different morphology. Whereas ALD TiO2 at these temperatures results in smooth, amorphous films that grow with a constant growth-per-cycle (GPC), in the case of pure ALD 2D-TiSx the growth process is more intricate: Electron microscopy shows that these 2D films initially have crystal growth that occurs laterally, up to the point of coalescence where the 2D layers start to grow out of plane. As ALD growth on the sideplanes of the 2D material is much faster, the GPC of these films keeps increasing as the film thickness progresses. When combining ALD TiO2 and TiS2 in a supercycle, the TiO2 cycles interrupt the growth of the 2D TiS2 crystals. This not only leads to a lower crystallinity of the film, but due to suppression of the reactive 2D-TiS2 edges, also the GPC is strongly reduced. As such, this effect has a strong influence on the resulting film thickness and composition, which is markedly different than would be expected than on the basis of the constituent ALD cycles in the supercycle.Based on the insights, we present a model that can explain the relation between supercycle ratio, deposition temperature and the resulting film properties. This enables the control over film conductivity over six orders of magnitude, where Hall measurements show that S-rich films exhibit both higher carrier densities and carrier mobility. Similary, controlling the composition allows tuning the optical properties between opaque, semimetallic 2D-TiS2 and transparent, dielectric TiO2 with a bandgap a little over 3 eV.Since exchange reactions and film crystallinity are common factors in ALD films, we expect these results to be of broader interest to the ALD community, for those preparing multicomponent materials using supercycles Figure 1

Atomic Layer Deposition of Titanium Oxide-Based Films for Semiconductor Applications-Effects of Precursor and Operating Conditions.

Two widely used atomic layer deposition precursors, Tetrakis (dimethylamido) titanium (TDMA-Ti) and titanium tetrachloride (TiCl4), were investigated for use in the deposition of TiOx-based thin films as a passivating contact material for solar cells. This study revealed that both precursors are suited to similar deposition temperatures (150 °C). Post-deposition annealing plays a major role in optimising the titanium oxide (TiOx) film passivation properties, improving minority carrier lifetime (τeff) by more than 200 µs. Aluminium oxide deposited together with titanium oxide (AlOy/TiOx) reduced the sheet resistance by 40% compared with pure TiOx. It was also revealed that the passivation quality of the (AlOy/TiOx) stack depends on the precursor and ratio of AlOy to TiOx deposition cycles.

Electron-Enhanced Atomic Layer Deposition of Titanium Nitride Films Using an Ammonia Reactive Background Gas

Electron-enhanced atomic layer deposition (EE-ALD) of titanium nitride (TiN) films was achieved using sequential exposures of tetrakis(dimethylamido)titanium (TDMAT) and low energy electrons in the presence of a continuous NH3 reactive background gas (RBG). Performing EE-ALD concurrently with a RBG is a new ALD film growth technique. The TiN EE-ALD was performed utilizing a hollow cathode plasma electron source (HC-PES). The HC-PES can deliver a high electron flux into background gases at pressures up to several mTorr. The TiN EE-ALD was conducted at temperatures of 30–70 °C using an electron acceleration voltage of 100 V and a NH3 pressure of ∼1 mTorr. The incident electron flux promotes electron stimulated desorption (ESD) and facilitates rapid nucleation and low temperature film growth. The TiN EE-ALD film growth was achieved on a variety of substrates including a native oxide on silicon, a SiO2 thermal oxide, and in situ silicon nitride films grown using electron-enhanced chemical vapor deposition (EE-CVD). Growth rates of 0.75 to 1.8 Å per cycle were measured using in situ four-wavelength ellipsometry for different TDMAT precursor exposures. Ex situ X-ray photoelectron spectroscopy (XPS) studies indicated that the TiN films were high purity and slightly nitrogen-rich. The in situ ellipsometry also measured low resistivities of ∼120 μΩ cm for the TiN films with thicknesses of ≥60 Å. These low resistivities were confirmed by ex situ four-point probe measurements and ex situ spectroscopic ellipsometry. X-ray diffraction investigations determined that the TiN EE-ALD films were crystalline. X-ray reflectivity studies also indicated that the thin TiN films had densities similar to bulk films. The high quality of the TiN EE-ALD films is attributed to the NH3 RBG. Interaction between the low energy electrons and the NH3 RBG is believed to form •NH2 and •H radical species that react with the surface during EE-ALD and improve film purity. The reactive •NH2 and •H species likely lead to nitridation and carbon removal from the films. RBGs greatly expand the possibilities for tuning film composition and properties during EE-ALD. In addition, TiN EE-ALD was accomplished on insulating substrates such as an SiO2 thermal oxide. The TiN EE-ALD is believed to be possible on insulating substrates because the secondary electron yield for electron energies of ∼100 eV is greater than unity.

Titanium Carboxylate Molecular Layer Deposited Hybrid Films As Protective Coatings for Lithium-Ion Batteries

Thirty years after the release of the first commercial lithium-ion battery, capacity fading due to complex ageing mechanisms remains one of the major concerns in lithium-ion battery research. Lithium-ion battery cathodes age due to phenomena as transition metal dissolution, electrolyte oxidation and volume expansions.[1] To suppress these effects, a protective coating can be applied to the cathode’s surface to avoid direct contact with the liquid electrolyte. Many studies exist in literature, showing the protective effect of conformal and pinhole-free Atomical Layer Deposited (ALD) coatings. However, the inorganic coatings deposited by ALD are rigid and will crack upon volume expansion of the cathode.[2]Molecular Layer Deposition (MLD) offers the same benefits as ALD but can be used to deposit hybrid inorganic/organic flexible films that can accommodate potential volume expansions of the cathode. To our knowledge, apart from ‘metalcones’ i.e. MLD films grown using a metal containing precursor and an alcohol, MLD films remain to be explored as protective and flexible coatings for lithium-ion batteries.[3] In this work, hybrid MLD titanium carboxylate thin films are deposited using tetrakis(dimethylamido)titanium (TDMAT) and various dicarboxylic acid precursors: oxalic acid, malonic acid, succinic acid, glutaric acid and 3,6-dioxaoctanedioic acid. The latter containing two ethylene oxide units per molecule, potentially increasing the lithium-ion conductivity.[4]The growth of the titanium carboxylate MLD processes is studied using in situ ellipsometry at a substrate temperature of 100 °C and 160 °C. Only the TDMAT/oxalic acid process is found to display good saturation behavior, while a parasitic CVD component is present during the TDMAT pulse for the other processes. The structure of the as-deposited films is physically characterized using Fourier Transform IR spectroscopy (FTIR) and X-Ray Photoelectron Spectroscopy (XPS), confirming the successful deposition of titanium carboxylate films. The films are found to be stable in air up to 50 days as shown by FTIR. This is in contrast to many metalcone MLD films which are considered to be air sensitive as the organic backbone degrades upon air exposure. In addition, FTIR, X-Ray Reflectivity (XRR) and X-Ray Fluorescence (XRF) measurements show that the titanium carboxylate films remain intact upon immersion into a solution of 1 M LiClO4 in propylene carbonate, the liquid electrolyte used for electrochemical characterization.The electrochemical properties of a 5 nm TDMAT/oxalic acid, TDMAT/3,6-dioxaoctanedioic acid and TDMAT/glycerol film (conventional titanicone film [5]) are tested on top of three ideal electrode systems: anatase TiO2, TiN and LiMnO2 (LMO). The titanium carboxylate films are observed to have little to no effect on the lithium-ion kinetics of the TiO2 electrode system compared to the uncoated electrode. This is in contrast to the titanicone film displaying a detrimental effect on the kinetics. All films are observed to effectively suppress electrolyte oxidation when exposing the TiN electrode system to elevated potentials. On the LMO electrode an activation step is necessary for all films, after which a good lithium-ion mobility through the titanium carboxylate films is observed without the severe irreversible reactions detected in the potential profile for the titanicone films. Overall, the explorative tests on thin film electrodes in this work indicate that the electrochemical properties of the titanium carboxylate films seem promising candidates as protective and flexible coating of lithium-ion battery cathodes.[1] Vetter, J., Novák, P., Wagner, M. R., Veit, C., Möller, K. C., Besenhard, J. O., ... & Hammouche, A. (2005). Ageing mechanisms in lithium-ion batteries. Journal of power sources, 147(1-2), 269-281.[2] Ban, C., & George, S. M. (2016). Molecular layer deposition for surface modification of lithium‐ion battery electrodes. Advanced Materials Interfaces, 3(21), 1600762.[3] Zhao, Y., Zhang, L., Liu, J., Adair, K., Zhao, F., Sun, Y., ... & Sun, X. (2021). Atomic/molecular layer deposition for energy storage and conversion. Chemical Society Reviews, 50(6), 3889-3956.[4] Xue, Z., He, D., & Xie, X. (2015). Poly (ethylene oxide)-based electrolytes for lithium-ion batteries. Journal of Materials Chemistry A, 3(38), 19218-19253.[5] Van de Kerckhove, K., Mattelaer, F., Deduytsche, D., Vereecken, P. M., Dendooven, J., & Detavernier, C. (2016). Molecular layer deposition of “titanicone”, a titanium-based hybrid material, as an electrode for lithium-ion batteries. Dalton Transactions, 45(3), 1176-1184.

Growth Mechanism and Film Properties of Atomic-Layer-Deposited Titanium Oxysulfide

In this work, atomic layer deposition (ALD) has been employed to prepare titanium oxysulfide (TiOxSy) thin films. Compositional control was achieved through a supercycle approach, where the ALD processes of TiOx and TiSx were interleaved. ALD was performed at 100, 150, and 200 °C, and tetrakis(dimethylamino)titanium (TDMAT), H2S, and H2O were used as precursors. It is shown that the conductivity and transparency of the film are highly tunable by controlling the composition of TiOxSy between pure TiSx and TiOx. Specifically, the incorporation of S enables the film resistivity to be reduced by up to 6 orders of magnitude, while the visible light absorption is increased significantly. It is furthermore shown that the resulting films are significantly more oxygen-rich than would be expected on the basis of the supercycle ratio, an effect which is more pronounced at higher deposition temperatures. Through mass spectrometry and in situ ellipsometry studies, this low S content is shown to originate from exchange reactions where S is replaced by O on the growth (sub)surface during H2O exposure. This is contrary to the common finding for ALD zinc, indium, and tin oxysulfide films, for which exchange reactions are known to favor S-rich films. These exchange reactions are shown to be more prominent at higher deposition temperatures and to persist until approximately 3–5 Å of TiOx has formed.

Kinetic study on initial surface reaction of titanium dioxide growth using tetrakis(dimethylamino)titanium and water in atomic layer deposition process: Density functional theory calculation

The initial steps in the growth process of atomic layer deposition (ALD) of titanium dioxide at room temperature (RT) were investigated using tetrakis(dimethylamino)titanium (TDMAT) and H2O as the titanium and oxygen sources, respectively, in the adsorption and reaction processes, respectively. Density functional theory at the B3LYP/6-31G(d,p) level was used to calculate the process characteristics. Energy pathways were used to investigate the reaction mechanism in the pre-adsorption, adsorption and reaction steps and the results were compared with other published experimental data. The calculated pathways implied that all the relative energies were located below the reactant levels, indicating the possibility of depositing the TiO2 thin film in ALD at RT. This work kinetically elucidated the agility of the ALD process and identified that the purity of the film could be improved with a temperature increase within a range of low temperatures. The effects were discussed of the levels of the computational method and cluster sizes on the realism of the reaction mechanism.

Kinetic Study of Tetrakis(Dimethylamido)Titanium and Titanium Tetrachloride Adsorption on a Silicon Surface in Atomic Layer Deposition: A DFT Calculation

The adsorption characteristics were studied at room temperature (RT) of tetrakis(dimethylamido)titanium (TDMAT) and titanium chloride (TiCl4) on the Si(100)-2 × 1 surface in atomic layer deposition (ALD) of titanium dioxide (TiO2). Density functional theory (DFT) with the B3LYP/6-31G(d,p) level through Gaussian 09 was used to calculate the adsorption characteristic and the mechanism of surface reaction. The potential energy profile was evaluated to investigate the reaction mechanisms. All the states in the adsorption step were found below the reactant level, indicating that the TDMAT molecule is adsorbed on the silicon surface spontaneously at RT. The reaction mechanisms were started by breaking of O–H bond, followed by breaking the Ti–N and Ti–O bonds, respectively. To clarify the reaction mechanism in the adsorption step, the transition state was divided into two sub-stages, namely the O–H break (TS1) and the Ti–N break (TS2). In addition, the initial adsorption of TiCl4 on the hydroxylated silicon surface was calculated. The reaction mechanism and the energy profile of TDMAT and TiCl4 were discussed.

Schottky-type GaN-based UV photodetector with atomic-layer-deposited TiN thin film as electrodes.

In this work, a GaN-based UV photodetector with an asymmetric electrode structure was fabricated by atomic layer deposition (ALD) of TiN layers. The thickness of the TiN can be monitored in situ by a quartz crystal microbalance (QCM) and precisely controlled through the modulation of deposition cycles. During the ALD process, periodic variation in the QCM frequency was observed and correlated to the physical adsorption, chemical bonding, and the excessive precursor exhaust, which included tetrakis(dimethylamino)titanium (TDMAT) and N sources. The asymmetric TiN/GaN/TiN photodetector showed excellent photosensing performance, with a UV-visible rejection ratio of 173, a responsivity of 4.25 A/W, a detectivity of 1.1×1013 Jones, and fast response speeds (a rise time of 69 μs and a decay time of 560 μs). Moreover, the device exhibits high stability, with an attenuation of only approximately 0.5% after 360 nm light irradiation for 157 min. This result indicates the potential of TiN as a transparent contact electrode for GaN-based optoelectronic devices.

Plasma-Synthesized Nitrogen-Doped Titanium Dioxide Nanoparticles With Tunable Visible Light Absorption and Photocatalytic Activity

Abstract Titanium dioxide in its pure wide bandgap “white” form is a non-toxic, efficient, and practical photocatalyst, but predominately absorbs light in the ultraviolet range of the spectrum. The absorption range, however, can be extended into the visible by doping with oxygen vacancies or impurities, such as nitrogen, giving the material a black or brown appearance. To date, nitrogen-doped titanium dioxide has primarily been produced with approaches that require long processing times or multi-step synthesis protocols. Here, we present a fast (timescale of tens of milliseconds) all-gas-phase process, which enables the seamless tuning of the optical properties of titanium dioxide nanoparticles from white to brown. Titanium dioxide particles were synthesized through injection of tetrakis (dimethylamido)titanium (TDMAT), argon, and oxygen into a nonthermal plasma. The positions of the electrode and oxygen inlet relative to the precursor inlet are found to strongly influence particle properties. Variation of these parameters allowed for control over the produced particle optical properties from large bandgap (white) to small bandgap (brown). In addition, the particle microstructure can be tuned from amorphous to crystalline anatase phase titanium dioxide. The photocatalytic performance was tested under solar irradiation and amorphous particles exhibit the highest degree of photocatalytic decomposition of the dyes methyl orange and methylene blue.

Interface Engineering of TiO2 Photoelectrode Coatings Grown by Atomic Layer Deposition on Silicon.

Titanium dioxide (TiO2) can protect photoelectrochemical (PEC) devices from corrosion, but the fabrication of high-quality TiO2 coatings providing long-term stability has remained challenging. Here, we compare the influence of Si wafer cleaning and postdeposition annealing temperature on the performance of TiO2/n+-Si photoanodes grown by atomic layer deposition (ALD) using tetrakis(dimethylamido)titanium (TDMAT) and H2O as precursors at a growth temperature of 100 °C. We show that removal of native Si oxide before ALD does not improve the TiO2 coating performance under alkaline PEC water splitting conditions if excessive postdeposition annealing is needed to induce crystallization. The as-deposited TiO2 coatings were amorphous and subject to photocorrosion. However, the TiO2 coatings were found to be stable over a time period of 10 h after heat treatment at 400 °C that induced crystallization of amorphous TiO2 into anatase TiO2. No interfacial Si oxide formed during the ALD growth, but during the heat treatment, the thickness of interfacial Si oxide increased to 1.8 nm for all of the samples. Increasing the ALD growth temperature to 150 °C enabled crystallization at 300 °C, which resulted in reduced growth of interfacial Si oxide followed by a 70 mV improvement in the photocurrent onset potential.

Electrochemical Stability of n-Si Photoanodes Protected by TiO2 Thin Layers Grown by Atomic Layer Deposition

This work investigates the n-Si photoanodes corrosion protection by Atomic Layer Deposition (ALD) of a TiO2 film. A specific electrochemical experimental sequence (including successive rest potential measurements and voltammetries under illumination or not) has been established to study the stability of the electrodes in KOH. Depending on the deposition conditions (precursor composition and temperature), the electrochemical properties of the layers are different. The photoanodes coated using titanium tetraisopropoxide (TTIP) at low temperature exhibit a low photocurrent (j ph) that is progressively enhanced during the electrochemical sequence and their stability decreases. When using tetrakis(dimethylamido)titanium (TDMAT), the j ph is almost constant and the film prevents from corrosion. The characterizations show that the ALD parameters drive the microstructure of the layer that is found critical for the electrochemical response. A hydrogen doping occurring during the open circuit potential measurements under illumination is evidenced by IR spectroscopy. It is mainly localized at the grain boundaries and pores of the layers as well as in the n-Si and it modifies the charge transfer at the electrode/solution junction and the hydrogen diffusion weakens the film causing the Si corrosion. The different charge transfer mechanisms are finally proposed depending on the ALD conditions and the film thickness.

Plasma-Enhanced Atomic Layer Deposition of TiN Thin Films as an Effective Se Diffusion Barrier for CIGS Solar Cells.

Plasma-enhanced atomic layer deposition (PEALD) of TiN thin films were investigated as an effective Se diffusion barrier layer for Cu (In, Ga) Se2 (CIGS) solar cells. Before the deposition of TiN thin film on CIGS solar cells, a saturated growth rate of 0.67 Å/cycle was confirmed using tetrakis(dimethylamido)titanium (TDMAT) and N2 plasma at 200 °C. Then, a Mo (≈30 nm)/PEALD-TiN (≈5 nm)/Mo (≈600 nm) back contact stack was fabricated to investigate the effects of PEALD-TiN thin films on the Se diffusion. After the selenization process, it was revealed that ≈5 nm-thick TiN thin films can effectively block Se diffusion and that only the top Mo layer prepared on the TiN thin films reacted with Se to form a MoSe2 layer. Without the TiN diffusion barrier layer, however, Se continuously diffused along the grain boundaries of the entire Mo back contact electrode. Finally, the adoption of a TiN diffusion barrier layer improved the photovoltaic efficiency of the CIGS solar cell by approximately 10%.

RBS and NRA analysis for films with high growth rate prepared by atomic layer deposition

We present the design and operation of a specialized Atomic Layer Deposition (ALD) system, dedicated to stable isotopic tracing experiments of oxide film growth, using isotopically labelled water as the oxide reactant. A small chamber volume allows operation with only very small quantities of water vapor, minimising the consumption of the isotopically labelled water. The first results for growth of ZnO and TiO2 using Diethlyzinc (DEZ) and Tetrakis(dimethylamino)titanium (TDMAT) as the zinc and titanium precursors, and unlabelled water as reactant, are presented, to establish the growth conditions for stoichiometric ZnO and TiO2 on silicon. Absolute film compositions and thickness are determined by RBS and NRA as a function of vapor pulse duration, number of ALD cycles and substrate temperature. Physical thickness is determined by ellipsometry. The first results obtained for growth of ZnO using water highly enriched in 18O are also presented.

Growth of thin film ferroelectric PZT, PHT, and antiferroelectric PHO from atomic layer deposition precursors

AbstractWe present a conformal method of growing ferroelectric lead hafnate‐titanate (PbHfxTi1−xO3, PHT) and lead zirconate‐titanate (PbZrxTi1−xO3, PZT) using atomic layer deposition (ALD) precursors. The 4+ cation precursors consist of tetrakis dimethylamino titanium (TDMAT), tetrakis dimethylamino zirconium (TDMAZ) and tetrakis dimethyl amino hafnium (TDMAH) for Ti, Zr, and Hf, respectively. The Pb (2+) precursor was Lead bis(3‐N,N‐dimethyl‐2‐methyl‐2‐propanoxide) [Pb(DMAMP)2]. PZT was limited to lead titanate (PTO)‐rich compositions, where x <0.25 for PbZrxTi1−xO3, and exhibited a remnant polarization of 26‐27 µC/cm2 with a coercive field between 150 and 170 kV/cm. The 3D‐structure coating capability of PZT was demonstrated by deposition on micromachined trench sidewalls 45 µm deep. We fabricated Microelectromechanical systems (MEMS) cantilever arrays with PZT thin films grown using the present method and demonstrated piezoelectric actuation. Alternatively, PHT was deposited with Ti and Hf compositions within ±1 at.% of the morphotropic phase boundary (MPB). The PHT exhibited a remanent polarization of 7.0‐8.7 µC/cm2 with a coercive field between 84‐100 kV/cm. We applied the same Pb and Hf precursors from the PHT process to grow antiferroelectric lead‐hafnate (PHO), which showed the characteristic electric field‐induced ferroelectric phase transition at approximately ±280 kV/cm and a maximum polarization of approximately ±32.8 µC/cm2.

Enhancing the surface properties and functionalization of polymethyl methacrylate with atomic layer-deposited titanium(IV) oxide

Polymethyl methacrylate (PMMA) is a widely used polymer in applications such as engineering structural plastics, energy storage materials, and biomaterials. However, its poor surface properties lead to fracture and deformation. Functionalization of the PMMA surface can make it more resistant to aggressive environments and prevent it from biodegradation, discoloration, and increased surface roughness. Here, atomic layer deposition (ALD) was used to deposit TiO2 thin films from tetrakis(dimethylamido)titanium (TDMAT) and ozone on PMMA substrates to improve its surface properties without the need for plasma assistance or another interlayer. Spectroscopic ellipsometry was used for the first time to measure the metal oxide film thickness on thick PMMA substrates. Two different growth regimes were observed, one for initial and the other for later ALD cycles. Initially, the growth rate on PMMA was 1.39 A/cycle, which is ~ 3.5 times higher than that on stand-alone silicon (0.4 A/cycle); this is attributed to cyclic chemical vapor deposition of TDMAT and moisture within PMMA concomitant with TiO2 ALD from TDMAT and ozone. However, after the formation of ~ 30-nm-thick film on PMMA, the TiO2 growth rate became similar to that on silicon. Moreover, our results revealed that the presence of PMMA in the deposition reactor affects the TiO2 growth rate on silicon substrates as well. These findings are discussed and corroborated with residual gas analyzer and X-ray absorption near-edge structure data. The thermal stability of the PMMA samples was examined by thermogravimetric analysis. Chemical composition and surface roughness of coated PMMA were studied by X-ray photoelectron spectroscopy and optical profilometry, respectively. The TiO2 coating increased wettability by ~ 70% and surface hardness by 60%.

Dataset for TiN Thin Films Prepared by Plasma-Enhanced Atomic Layer Deposition Using Tetrakis(dimethylamino)titanium (TDMAT) and Titanium Tetrachloride (TiCl4) Precursor.

A dataset in this report is regarding an article “Ultrathin Effective TiN Protective Films Prepared by Plasma-Enhanced Atomic Layer Deposition for High Performance Metallic Bipolar Plates of Polymer Electrolyte Membrane Fuel Cells” [1]. TiN (Titanium Nitride) thin films were deposited by Plasma-Enhanced Atomic Layer Deposition (PEALD) method using well known two types of precursor: using tetrakis(dimethylamino)titanium (TDMAT) and titanium tetrachloride (TiCl4), and plasma. Summarized reports, growth characteristics (growth rate as a function of each precursor pulse time, plasma power, precursor and plasma purge time, thickness depending on the number of PEALD cycles), each precursor structural information and the atomic force micrographs (AFM) data are herein demonstrated. For TDMAT-TiN, N2 plasma was used as a reactant whereas, H2+N2 plasma was used as TiCl4-TiN reactant. To apply the bipolar plate substrate, two types of TiN thin films were introduced into Stainless steel (SUS) 316L.

Ultrathin effective TiN protective films prepared by plasma-enhanced atomic layer deposition for high performance metallic bipolar plates of polymer electrolyte membrane fuel cells

The stainless steel (SS)-based bipolar plate with high conductivity and corrosion resistance is one of the key components in recent polymer electrolyte membrane fuel cells. Therefore, an excellent corrosion protection and good electrical conductivity in SS316L-based bipolar plates can be achieved through plasma-enhanced atomic layer deposition (PEALD) of ultrathin (25–67 nm) TiN thin films. To this end, two types of TiN protective coatings deposited by PEALD using tetrakis(dimethylamino)titanium (TDMAT) and titanium tetrachloride (TiCl4) precursors were evaluated; the evaluations were conducted under conditions simulating the operating conditions of PEMFCs. Regardless of the precursor type, PEALD-TiN onto SS316L resulted in great improvements in electrical conductivity and corrosion resistance. Notably, the TiN thin films prepared using TDMAT exhibited excellent corrosion resistance (<1 μA/cm2) compared to those produced using TiCl4 as the precursor. Systematically structural, compositional, and electrochemical analysis revealed that a ~5-nm-thick ultrathin amorphous interfacial layer, formed and played a key role in the corrosion protection using TDMAT. Furthermore, the TiN thin films by TDMAT greatly lowered the interfacial contact resistance of SS316L from 35.868 to 15.239 mΩ∙cm2 at a compaction force of 127 N/cm2. Our study presents an interesting opportunity for the development of PEALD protective coating materials for SS-bipolar plates.