Zinc Films Research Articles

In-situ fabrication of CuO/ZnO heterojunctions at room temperature for a self-powered UV sensor

This work presents a novel, low-cost, wet chemical fabrication technique to develop a self-powered photonic sensor. Thin films of zinc and copper were DC-sputtered on an ITO-coated glass slide, followed by an in-situ one-step oxidation of copper and zinc to form CuO (copper oxide) and ZnO (zinc oxide) heterojunctions at room temperature. The surface morphologies and chemical compositions characterized by a scanning electron microscope (SEM), X-ray diffraction (XRD), and an X-ray photoelectron spectroscopy (XPS) analysis confirmed the formation of heterojunctions between p-type CuO nanowires and n-type ZnO nanoparticles. The material's light absorbance was measured using ultraviolet-visible (UV–vis) spectroscopy. The fabricated device works in a photovoltaic mode; as photons strike the substrate, the built-in potential separates excitons, resulting in an electrical current without an external bias. The current-voltage characteristics of the device studied using a 365 nm centered laser radiation revealed an ideal p-n junction behavior. The sensor demonstrated stable and reproducible responsivity and photosensitivity of 0.108 A/W and 114, respectively, under a periodic UV radiation condition.

Dealloying-Derived Self-Supporting Nanoporous Zinc Film with Optimized Macro/Microstructure for High-Performance Solar Steam Generation.

Solar steam generation (SSG) is a promising technology for the production of freshwater that can help alleviate global water scarcity. Nanostructured metals, known for their localized surface plasmon resonance effect, have generated significant interest, but low-cost metal films with excellent water evaporation properties are challenging. In this work, we present a one-step dealloying route for fabricating self-supporting black nanoporous zinc (NP-Zn) films with a bicontinuous ligament/channel structure, using Al-Zn solid solution alloys as the precursors. The influence of alloy composition on the formation and macro/microstructure of NP-Zn was investigated, and an optimal Al98Zn2 was selected. Additionally, in situ and ex situ characterizations were conducted to unveil the dealloying mechanism of Al98Zn2 and phase/microstructure evolution of NP-Zn during dealloying, including the phase transition of Al(Zn) → Zn, significant volume shrinkage (89.8%), and the development of high porosity (81.3%). The nanoscale ligament/channel structure and high porosity endow the NP-Zn films with good broadband absorption and superior hydrophilicity and, more importantly, give them excellent SSG performance. The NP-Zn2 film displays high evaporation efficiency, superior stability, and good seawater desalination performance. The efficient SSG performance, material abundance, and low cost suggest that NP-Zn films have promising applications in metal-based photothermal materials for SSG.

Fabrication and evaluation of CMC-Ag and CMC-Zn-based composite films as biobased wound dressings

This work aims to enhance the efficiency and properties of carboxymethyl cellulose (CMC) by introducing silver and zinc ions. CMC incorporated with a silver (CMC-Ag) and CMC incorporated with zinc (CMC-Zn) composites and films were prepared, characterized and evaluated for biological activities respectively. The CMC-Ag and CMC-Zn composites and composite films showed notable antibacterial and antioxidant activities based on increasing Ag and Zn concentrations. The CMC-Ag composite films displayed the highest wound contraction 89.79% followed by CMC-Zn composite films 89.24% on the 10th day with low levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α). Histological images of wounds treated with these composite films exhibited healed epidermis and a clear view of collagen deposition. These findings demonstrate that our prepared composite films have auspicious features with eloquent antibacterial, antioxidant and wound-healing properties which could be used as biobased wound dressings.

The microstructure and protective properties of electroplating zinc films on NdFeB from a chloride-free nonaqueous bath.

The traditional aqueous electroplating of zinc film causes significant corrosion of NdFeB during the electroplating process, which is accompanied by hydrogen evolution reactions. In this study, electroplating zinc film is carried out from a chloride-free nonaqueous bath using zinc acetate (Zn(OAc)2) as the main salt, sodium acetate (NaOAc) as the conducting salt, and ethylene glycol (EG) as the solvent. The electrochemical properties of the EG bath with Zn(OAc)2 and NaOAc are characterized by means of cyclic voltammetry (CV) and linear sweep voltammetry (LSV) together with a Hull cell test on brass. The results of the experiment show that the Zn(OAc)2 concentration, current density, and temperature significantly impact the deposition behavior of zinc. Moreover, the open circuit potential (OCP) test and scanning electron microscopy (SEM) results demonstrated that the corrosion of NdFeB in the EG bath containing 0.7 M Zn(OAc)2 and NaOAc is effectively inhibited compared to when using the traditional aqueous zinc plating bath. A dense zinc film with a metallic appearance is successfully deposited on the NdFeB surface from the EG bath containing 0.7 M Zn(OAc)2 and NaOAc at 6 mA cm-2 and 60 °C. Comparative experiments demonstrate that the as-deposited Zn film exhibits superior protective performance and exerts less damage to NdFeB compared to the aqueous electroplating film.

Surface energy and stress driven growth of extremely long and high-density ZnO nanowires using a thermal step-oxidation process.

Formation of highly crystalline zinc oxide (ZnO) nanowires with an extremely high aspect ratio (length = 60 μm, diameter = 50 nm) is routinely achieved by introducing an intermediate step-oxidation method during the thermal oxidation process of thin zinc (Zn) films. High-purity Zn was deposited onto clean glass substrates at room temperature using a vacuum-assisted thermal evaporation technique. Afterwards, the as-deposited Zn layers were thermally oxidized under a closed air ambient condition at different temperatures and durations. Structural, morphological, chemical, optical and electrical properties of these oxide layers were investigated using various surface characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoemission spectroscopy (XPS). It was noticed that the initial thermal oxidation of Zn films usually starts above 400 °C. Homogeneous and lateral growth of the ZnO layer is usually preferred for oxidation at a lower temperature below 500 °C. One-dimensional (1D) asymmetric growth of ZnO started to dominate thermal oxidation above 600 °C. Highly dense 1D ZnO nanowires were specifically observed after prolonged oxidation at 600 °C for 5 hours, followed by short-step oxidation at 700 °C for 30 minutes. However, direct oxidation of Zn films at 700 °C resulted in ZnO nanorod formation. The formation of ZnO nanowires using step-oxidation is explained in terms of surface free energy and compressive stress-driven Zn adatom kinetics through the grain boundaries of laterally grown ZnO seed layers. This simple thermal oxidation process using intermittent step-oxidation was found to be quite unique and very much useful to routinely grow an array of high-density ZnO nanowires. Moreover, these ZnO nanowires showed very high sensitivity and selectivity towards formaldehyde vapour sensing against few other VOCs.

Attempts to Electrochemically Synthesize Palladium Superhydrides By High Pressure Method – Combination of Electrolytic Hydrogen Charging and Electroplating of Protective Coatings –

IntroductionIncited by the possibility of room-temperature superconductors in superhydrides, numerous them have been synthesized using a diamond anvil cell under high pressures up to several hundred GPa. Although palladium has widely researched for a long time as a prototype hydrogen-absorbing metal, the palladium superhydrides has not yet been obtained under such high pressures. A recent theorical calculation has predicted that the palladium superhydrides (e.g., PdH10) may be synthesized by combing electrolysis and high pressure1), but it is not certain whether it can be achieved. In this study, we attempted to synthesize the palladium superhydrides by using electrolytic hydrogen charging under high pressures, and subsequently applied protective coatings to suppress the hydrogen desorption from the palladium hydrides at ambient pressure.ExperimentalFigure shows a schematic illustration of the high-pressure apparatus. The high-pressure apparatus can apply the pressure of up to 400 MPa to the electrolyte in the electrolytic cell by pumping water into a sealed high-pressure vessel using a plunger pump and pressure multipliers. A cold-rolled palladium foil of 30 ~ 40 μm in thickness was used as a cathode, and a zinc plate was utilized as a soluble anode. Hydrogen was electrochemically loaded into the palladium foil at 0 V vs. Zn in an electrolyte consisting of 0.1 mol dm-3 sulfuric acid and 4.6 mmol dm-3 zinc sulfate under various pressures for 6 hours. Subsequently, the palladium foil was coated with the zinc film at constant current density 25 mA cm-2 for 120 seconds under the high pressure. The specimen was removed from the electrolytic cell in the high-pressure vessel at ambient pressure, and the hydrogen concentration of the palladium hydride PdH x was determined by thermal desorption spectroscopy. Structural analysis was conducted using X-ray diffraction and scanning electron microscopy.Results and discussionA number of bubbles were observed on the palladium foil surface during the electrolytic charging at ambient pressure. On the other hand, no bubbles were observed at 300 MPa. The zinc film with approximately 1.4 μm thick was coated on the PdH x surface after the electrolytic hydrogen charging. The hydrogen concentration of the PdH x was approximately x = 0.7 immediately after synthesis, which decreased to x = 0.2 without the zinc coating. On the other hand, the hydrogen concentration of the PdH x was maintained at least 1 week with the zinc coating. This result indicates that the zinc film acts as a barrier to hydrogen desorption from PdH x , and suggests that if the palladium superhydrides could be synthesized by electrolytic hydrogen charging under high pressure, it could be taken out to ambient pressure while maintaining its concentration.Reference1) W. Guan, R. J. Hemley, and V. Viswanathan, PNAS, 118, e2110470118 (2021) Figure 1

Polarization Behaviors and Morphology during Zinc Deposition and Dissolution in Zinc Flow Battery

A zinc flow battery is one of the candidates of secondary batteries for stationary energy storage system, and a zinc-air flow battery is the most promising device because of its high theoretical energy density, low cost of anode material, air-breathing cathode, and high safety of non-flammable aqueous electrolyte. The flow of the electrolyte, which is mostly KOH solutions, is believed to be effective to suppress the generation of zinc dendrite and non-uniform distribution of zinc and zinc oxide, while there has been little information on the effects of the charge-discharge conditions and the dimensions, design, and flow parameters of the cell on the polarization behaviors of the zinc anode and on the morphology during zinc deposition and dissolution in zinc flow secondary batteries.1,2 This paper reports the results on the potential measurements of the zinc anode at the current density up to 500 mA/cm2 and the observation of the morphology of zinc growth and dissolution during charge and discharge.The zinc anode was electrodeposited zinc alloy film supplied by Mitsui Mining & Smelting, Co., Ltd, which produces less than 1/100 of hydrogen compared to conventional rolled zinc film, indicating a high hydrogen overpotential and a quite low self-discharge rate. Two-electrode or three-electrode cells were equipped with the zinc film anode and a zinc wire reference electrode, of which the electrolyte was 6 mol/L KOH solutions saturated with ZnO. The electrolyte was pumped into the cell and the flow rate was changed. The potential of the zinc anode during charge and discharge was monitored while constant current electrolysis was performed at 100 mA/cm2 to 500 mA/cm2. The morphological change for zinc deposition and dissolution was observed by video camera during charge and discharge and by SEM after the operation.The results on the polarization of the zinc anode obtained at different current densities are shown in Fig. 1, in which the increase in polarization at the current density from 100 mA/m2 to 500 mA/cm2 was less than 50 mV for both of charge and discharge at 25 mL/min, suggesting that the electrolyte flow enhances the mass transport of zincate ions and suppresses the concentration overpotential. This is also supported by the fact that charge failed with no electrolyte flow. The dependence of the anode’s potential on the flow rate also indicated that the potential hardly increased when the flow rate changed from 250 mL/min to 25 mL/min. The observation of zinc deposition and dissolution was further carried out and some interesting features on the relationship between the morphology of zinc deposits and the operating conditions was found, implying the conditions to suppress zinc dendrite formation.This work was partly supported by JSPS Grant-in-Aid for Scientific Research No. 22H02187.References1) A. L. Zhu, D. P. Wilkinson, X. Zhang, Y. Xing, A. G. Rozhin, S. A. Kulinich, J. Energy Storage, 8, 35-50 (2016).2) A. Abbasi, S. Hosseini, A. Somwangthanaroj, R. Cheacharoen, S. Olaru, S. Kheawhom, Sci. Data, 7, 196 (2020). Figure 1

Laser-Induced Backward Transfer of Light Reflecting Zinc Patterns on Glass for High Performance Photovoltaic Modules.

Commercially available photovoltaic (PV) modules typically consist of individual silicon half-cut cells that are electrically interconnected. This interconnection method results in gaps between the cells, which do not contribute to the overall PV output power. One approach to enhance the cell-to-module power ratio is the placement of white, diffuse reflecting plastic material within these gaps. Conventionally, the process of generating reflective patterns involves several discrete steps, including film deposition, resist patterning, etching, and resist stripping. This study presents an innovative single-step procedure for the direct deposition of zinc reflective patterns onto glass substrates using laser-induced backward transfer (LIBT) and a nanosecond pulsed laser system. The process successfully produced lines and squares, demonstrating its versatility in achieving diverse geometric patterns under ambient atmospheric pressure and room temperature conditions. The evaluation of the transferred patterns included an examination of geometric dimensions and surface morphology using a 3D microscope and scanning electron microscopy (SEM) analysis at the air/Zn interface. Additionally, the thickness of the zinc film and its adhesion to the glass substrate were quantified. The angular reflectance at a wavelength of 660 nm for both the glass/Zn and air/Zn interfaces was measured.

Hybrid Organic-Inorganic Additive for Robust Al Anode in Alkaline Aluminum-Air Battery.

Aluminum-air batteries (AABs), known for their high energy density, environmental friendliness, and cost-effectiveness, show immense promise in the realm of energy conversion applications. Nonetheless, their commercialization has encountered inherent challenges of Al anode corrosion and material degradation. In this study, economical hybrid electrolyte additives to inhibit the Al corrosion are developed, safeguarding the integrity of the Al anode. Due to the synergistic interplay between the organic compound dithiothreitol, and inorganic compounds zinc chloride, a robust zinc film is formed on the Al surface This Zn film plays a pivotal role in quelling parasitic hydrogen evolution reactions that typically can plague the Al electrode. Consequently, the as-prepared hybrid additive culminates in a remarkable enhancement to AABs, delivering exceptional discharge capacity of 1793.37mAhg-1 , high energy density of 2047Whkg-1 , and excellent battery longevity (over 20h in on/off cycling tests). This study, therefore, introduces a novel approach in utilizing hybrid electrolyte additives to effectively counteract corrosion-related challenges and boost the stability and performance of AABs.

Multidimensional characterization of Ni-Zn ferrite films based on laser-induced breakdown spectroscopy technology

Existing experimental results have suggested that doping different elements will significantly affect the properties of the thin film produced using the target material. In this study, the properties of the film were studied under different powers and different pressures through the magnetron sputtering method of preparation of three elements containing nickel, zinc, and iron thin film. First, the film is subjected to laser-induced breakdown spectroscopy (LIBS) detection, and the obtained spectral data are processed to obtain the energy spectrum and two-dimensional (2D) distribution of the elements. Next, the film thickness was examined under a scanning electron microscope (SEM) to verify the feasibility of LIBS technology in film thickness measurement. Another set of experiments was performed to estimate the film thickness based on the obtained data to determine the accuracy of film thickness measurement using LIBS technology. Subsequently, the transmittal rate and energy-dispersive X-ray spectroscopy (EDS) of the thin film that was obtained by the sputtering of Nickel-zinc ferrite film were examined. The optical band gap of the thin film was determined following the transmittal rate of the thin film. Besides, the variation trend of the optical band gap was plotted and then compared with the LIBS spectral data. The statistical data of the element proportion were obtained through EDS, and the calibration curve was generated in combination with the LIBS spectral data. As revealed by the above-mentioned results, the LIBS is capable of analyzing the change of element content in the binary doped thin films.

Nanocomposite Films of Zinc Oxide (ZnO) Nanorods/Polyacrylamide(PAM)/Polyvinyl alcohol (PVA) for Electronic Devices Applications

Novel nanocomposite films of Zinc oxide/polyacrylamide/polyvinyl alcohol (ZnO/PAM/PVA) were fabricated via casting methodology. The addition of ZnO nanoparticles affects the structural and physical properties of the PAM/PVA blend. The degree of the crystallinity was changed in the PAM/PVA blend after adding ZnO nanorods, as seen by X-ray diffraction analysis (XRD). The FT-IR spectra provided evidence of the interaction between the PAM/PVA polymeric chains and ZnO nanorods. The UV-visible measurement confirmed that the ZnO nanorods embedded in PAM/PVA outcomes lead to substantial modifications in the absorption coefficient and band gap. The FESEM images provided confirmation that ZnO induces the formation of pores on polymeric matrices as roughness parameters increase. This characteristic renders it useful in electronic and optical devices. The presence of increased active surface sites on the nanocomposites contributes to their enhanced functionality in these applications. HRTEM images show that ZnO has a rod-like shape with an average particle size of 40 nm. By raising the ZnO loading, the AC conductivity of the blend increased. In the semiconductor industry, these nanocomposite films improved optical characteristics and AC conductivity stimulating their widespread use.

Microreactor Based on Trimetallic Nano-Oxides Obtained by In Situ Growth from German Silver

Nanostructured films of copper, zinc, and nickel oxides were obtained from a controlled oxidation of the ternary nickel silver (Cu-Zn-Ni) substrates through a one-pot, green, and low temperature vapor-based treatment. Brief contact of the alloy with ammonia and hydrogen peroxide vapors at room temperature originates a mixture of nanometric copper, zinc, and nickel oxides at its surface. The growths evolve with time and temperature, generating a layered film with highly dispersed copper nano-oxides/hydroxides on a base of zinc and nickel oxides. The composition, configuration, and way of obtaining these films make them green catalysts, which are highly active and stable for a carbon monoxide oxidation reaction.

Corrosion-resistant superhydrophobic films on galvanized steel by one-step electrodeposition

A simple one-step electrodeposition method is proposed to fabricate corrosion-resistant superhydrophobic films on hot-dip galvanized steel without using low surface-energy materials. The effects of electrodeposition time on surface morphology, surface composition, surface roughness, wettability, and corrosion resistance of the electrodeposited zinc films were investigated. The results revealed that the morphological structures and roughnesses of the deposited zinc films were varied by the electrodeposition times. The roughened zinc films naturally reduced their surface energy during storage for 10 days as the formation of functional groups, transforming them to superhydrophobic and/or nearly superhydrophobic. The electrodeposited superhydrophobic films significantly enhanced the corrosion resistance of the hot-dip galvanized steel. Among them, the 20 min electrodeposition time gave the appropriate morphology and roughness to achieve a superhydrophobic surface with the optimum corrosion inhibition property.

Zinc film anodes for air microbatteries: fabrication, approaches, and utilization optimization

Portable and autonomous microdevices often require on-board power sources such as thin film microbatteries. Air microbatteries are an attractive power source for such devices due to their high specific energy density. One particularly appropriate air chemistry is based on Zn, due to the multiple microfabrication approaches compatible with Zn anode formation. We demonstrate fabrication approaches to realize Zn film anodes in different thickness regimes using microelectromechanical systems based fabrication techniques—evaporation, electrodeposition, and laser micromachining; and evaluate their relative performance as power sources in a primary battery configuration. These fabrication techniques enable films in thickness regimes ranging from the micron scale to hundreds of microns. The fabricated films have been characterized using scanning electron microscopy and energy dispersive x-ray spectroscopy, and were found to be dense and reasonably free from impurities. The electrochemical and discharge properties of the fabricated films were studied in an air battery configuration comprising a Zn anode-alkaline hydrogel electrolyte-metal catalyst stack, in which the anode had a surface area of 0.78 cm2. Evaporated Zn anodes (1–10 µms) yielded Zn utilizations of 96.5% and 82% at 10 and 1 mA discharge rates, respectively. The specific capacity of the evaporated Zn anodes was 791 mAh g−1 when discharged at 10 mA, close to the Zn theoretical specific capacity of 820 mAh g−1. Electrodeposited Zn anodes (10–100 µms) yielded utilizations of 90.2% and 75.6% at 10 and 1 mA discharge rates, respectively. Laser micromachined Zn anodes (250 µms) yielded Zn utilization of 90% when discharged at 10 mA. These fabrication techniques offer the potential to realize high energy density Zn anodes of different thickness ranges for thin film microbatteries, which can be tailored to microdevice-based applications of interest.

Studying the Structural and Optical Properties of ZnO how Prepared by oxidation free quick hating

In this study we oxidation thin film of Zinc on glass substrate in 510oC and oxidation time (10,20,30)sec . we intrusion the Zinc by using thermal diffusion. we exchange oven by appliance heater. the result show possibility relatively zinc oxide without using oxygen gas or closed oven and relatively so fast .this path is applied in production industrially and for large quantity. spectral analysis and elements analysis EDX explicit conversion zinc to zinc oxid purity 99% in oxidation time 30 sec . X-Ray analysis show that zinc oxid have Crystal system in crystal planes (002) and (101) .and AFM analysis show average nano dimension is 61.37nm .the study of optical properties clarifies the conversion. the result of energy gap for allow direct transmission 3.22eV and the energy gap for forbidden transmission 3.18eV .

Growth of ZnO nanowires using thermal oxidation process

Controlled thermal oxidation of thin zinc (Zn) films grown on glass substrate has been performed in an air ambient condition to achieve extremely long and uniform high quality ZnO nanowires. High purity Zn layers were thermally evaporated on ex situ chemically cleaned glass slides at room temperature using a vacuum coater unit under a base pressure < 10-5 mbar. Structural characterization and morphology studies of these thermally oxidized ZnO films using XRD and FESEM techniques. The chemical and optical properties of the ZnO nanostructures have also been tested using a Raman spectroscopy. All findings are complementary to each other and suggest that the oxidation starts at about 400 °C with a severe surface roughening of the Zn film. For lower oxidation temperature (<500 °C) lateral growth of ZnO film is preferred whereas at higher oxidation temperature (above 600 °C) asymmetric growth starts to dominates which finally leads to the formation of ZnO nano-wires of a very high aspect ratio of 1000.

Reduction of Cr6+ formation in the stellite hardfacing operation by a novel thin film of zinc coating on a stellite filler rod

Reduction of Cr6+ formation in the stellite hardfacing operation by a novel thin film of zinc coating on a stellite filler rod

Impact of zinc on the physical and morphological properties of sputtered copper oxide thin films

In this study, thin films of pure and zinc (Zn) doped copper oxides were successfully deposited on a glass substrate via reactive magnetron sputtering at varying Zn concentrations. The effects of oxygen/argon ratio and dopant dosage on the structure, morphology, and topography of films were analyzed by the X-ray diffraction technique (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray fluorescence (XRF), Raman, and atomic force microscopy (AFM). The investigations through XRD and Raman revealed the formation of CuO, and Cu2O phases during the copper oxide deposition at 20% oxygen partial pressure, while an increase in the oxygen partial pressure up to 50% resulted in the formation of single-phase CuO. XRD spectra of the Zn-doped films indicated the monoclinic structure of CuO with a gradual increase in the cell volume from 91 A3˙ in the undoped sample to 123 A3˙ in the sample with a high dopant concentration. By increasing the applied RF power from 10 to 40 W, the cationic ratio (Zn/Zn + Cu) increased from 0.007 to 0.039. AFM analysis figured out the decrease of surface roughness from 11.04 nm in the undoped sample to 3.57 nm in the highly Zn-doped sample. In FESEM images, semi-spherical particles with uniform distribution were observed. By increasing the oxygen partial pressure from 20% to 40% in undoped samples, the average grain size was reduced from 110 to 68 nm, but doping by Zn did not affect the grain size significantly.

Distinguishing Zinc from Zinc Using Model Samples from 64Zn‐Depleted Zinc Oxide: Proof of Concept

As a proof of concept, distinction of different zinc layers on top of each other is presented here. It can be used for studying chemical reactions or corrosion processes. The use of the nonradioactive and relatively cheap 64Zn‐depleted zinc oxide (DZO) is suggested, which yields a distinctly different isotope pattern with factor 72‐reduced 64Zn content. From electrochemical depth profiling and a detection by mass spectrometry, that is, inductively coupled plasma mass spectrometry, thickness information can be derived. The reasonable price allows preparations on the lab scale and provides an elegant experimental approach for mechanistic studies. DZO is used as a source to deposit zinc films from alkaline or acidic solutions onto pure Fe or pure Zn. A flow‐type scanning droplet cell microscope is used for electrochemical depths profiling. It can be demonstrated that depth profiling is possible not only for dissimilar element combinations such as Zn on Fe but also Zn on Zn when detection of the deviating isotopic pattern is used tracing the rising 64Zn signal. This method can also be used to prepare zinc films which are hardly radioactivated by neutrons. Further applications are in the determination of reaction mechanisms involving Zn or in the determination of Zn exchange current densities in electrochemistry.

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.