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Analysis of TiO <sub/>2</sub> Atomic Layer Deposition Surface Chemistry and Evidence of Propene Oligomerization using Surface-Enhanced Raman Spectroscopy
摘要： Atomic layer deposition (ALD) of TiO2 was performed in tandem with in-situ surface-enhanced Raman spectroscopy (SERS) to monitor changes in the transient surface species across multiple ALD cycles. A self-assembled monolayer of 3-mercaptopropionic acid was used as a capture agent, to ensure that nucleation of the titanium precursor (titanium tetraisopropoxide [TTIP]) occurs. Comparisons between the Raman spectra of the neat precursor and the SER spectra of the 1st ALD cycle of TiO2 reveal typical ligand exchange chemistry taking place, with self-limiting behavior and intact isopropoxide ligands. However subsequent cycles show drastically different chemistry, with no isopropoxide ligands remaining at any point during the 2nd and 3rd cycles. Continuous exposure of either TTIP or isopropanol after the 1st cycle shows unlimited, chemical vapor deposition (CVD)-type growth. Comparisons with alternative precursors (aluminum isopropoxide, titanium tert-butoxide, and titanium propoxide) and DFT calculations reveal that for the TTIP precursor, isolated TiO2 sites play a role in the dehydration of off-gassing isopropanol. The resulting propene then undergoes oligomerization into six-carbon olefins, before polymerizing into indistinguishable carbon products that accumulate on the surface. The emergence of the dehydration chemistry is expected to be exclusively the result of these isolated TiO2 sites, and as such is expected to occur on other surfaces where TiO2 ALD is feasible. This work showcases how seemingly innocuous ALD can evolve into a CVD process when the products can participate in various side reactions with newly made surface sites.
关键词： Oligomerization,TiO2,Surface-enhanced Raman spectroscopy,TTIP,Atomic layer deposition,Dehydration chemistry
更新于2025-09-23 15:19:57
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Atomic layer deposition for membrane interface engineering
摘要： In many applications, interfaces govern the performance of membranes. Structure, chemistry, electrostatics, and other properties of interfaces can dominate the selectivity, flux, fouling resistance, and other critical aspects of membrane functionality. Control over membrane interfacial properties, therefore, is a powerful means of tailoring performance. In this Minireview, we discuss the application of atomic layer deposition (ALD) and related techniques in the design of novel membrane interfaces. We discuss recent literature in which ALD is used to (1) modify the surface chemistry and interfacial properties of membranes, (2) tailor the pore sizes and separation characteristics of membranes, and (3) enable novel advanced functional membranes.
关键词： membrane interface engineering,pore size tuning,surface modification,functional membranes,atomic layer deposition
更新于2025-09-19 17:15:36
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Growth of Atomic Layer Deposited Ruthenium and Its Optical Properties at Short Wavelengths Using Ru(EtCp)2 and Oxygen
摘要： High-density ruthenium (Ru) thin films were deposited using Ru(EtCp)2 (bis(ethylcyclopentadienyl)ruthenium) and oxygen by thermal atomic layer deposition (ALD) and compared to magnetron sputtered (MS) Ru coatings. The ALD Ru film growth and surface roughness show a significant temperature dependence. At temperatures below 200 °C, no deposition was observed on silicon and fused silica substrates. With increasing deposition temperature, the nucleation of Ru starts and leads eventually to fully closed, polycrystalline coatings. The formation of blisters starts at temperatures above 275 °C because of poor adhesion properties, which results in a high surface roughness. The optimum deposition temperature is 250 °C in our tool and leads to rather smooth film surfaces, with roughness values of approximately 3 nm. The ALD Ru thin films have similar morphology compared with MS coatings, e.g., hexagonal polycrystalline structure and high density. Discrepancies of the optical properties can be explained by the higher roughness of ALD films compared to MS coatings. To use ALD Ru for optical applications at short wavelengths (λ = 2–50 nm), further improvement of their film quality is required.
关键词： optical properties,sputtering,structural properties,XUV,ruthenium,soft X-ray,thin film,atomic layer deposition
更新于2025-09-19 17:15:36
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New Patterning Technology by Integrating Atomic Layer Deposition Process to the Etching Flow
摘要： We introduce a state-of-the-art patterning process developed by new patterning technology using Atomic Layer Deposition (ALD) towards 5/7 nm generation. In the patterning process, critical dimension (CD) shrink technique without CD loading is one of the key requirements. However, in the conventional CD shrink technique, CD loading can?t be solved in principle. To overcome this issue, by integrating ALD process into the etching flow, we developed a new CD shrink technique without causing CD loading. Furthermore, CD shrink amount can be precisely controlled by the number of ALD cycles while keeping the excellent CD shrink uniformity across a wafer. This is obtained by utilizing a conformal layer with characteristics of ALD?s self-limiting reaction, which is independent of the pattern variety.
关键词： patterning technology,self-limiting reaction,atomic layer deposition,critical dimension loading
更新于2025-09-19 17:15:36
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Systematic Study of the SiOx Film with Different Stoichiometry by Plasma-Enhanced Atomic Layer Deposition and Its Application in SiOx/SiO2 Super-Lattice
摘要： Atomic scale control of the thickness of thin film makes atomic layer deposition highly advantageous in the preparation of high quality super-lattices. However, precisely controlling the film chemical stoichiometry is very challenging. In this study, we deposited SiOx film with different stoichiometry by plasma enhanced atomic layer deposition. After reviewing various deposition parameters like temperature, precursor pulse time, and gas flow, the silicon dioxides of stoichiometric (SiO2) and non-stoichiometric (SiO1.8 and SiO1.6) were successfully fabricated. X-ray photo-electron spectroscopy was first employed to analyze the element content and chemical bonding energy of these films. Then the morphology, structure, composition, and optical characteristics of SiOx film were systematically studied through atomic force microscope, transmission electron microscopy, X-ray reflection, and spectroscopic ellipsometry. The experimental results indicate that both the mass density and refractive index of SiO1.8 and SiO1.6 are less than SiO2 film. The energy band-gap is approved by spectroscopic ellipsometry data and X-ray photo-electron spectroscopy O 1s analysis. The results demonstrate that the energy band-gap decreases as the oxygen concentration decreases in SiOx film. After we obtained the Si-rich silicon oxide film deposition, the SiO1.6/SiO2 super-lattices was fabricated and its photoluminescence (PL) property was characterized by PL spectra. The weak PL intensity gives us greater awareness that more research is needed in order to decrease the x of SiOx film to a larger extent through further optimizing plasma-enhanced atomic layer deposition processes, and hence improve the photoluminescence properties of SiOx/SiO2 super-lattices.
关键词： plasma-enhanced atomic layer deposition (PEALD),stoichiometry,SiOx,SiO2,superlattice
更新于2025-09-19 17:15:36
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Advanced thin gas barriers film incorporating alternating structure of PEALD-based Al2O3/organic-inorganic nanohybrid layers
摘要： In this work, we reported excellent plasma-enhanced atomic layer deposition (PEALD)-based Al2O3/organic-inorganic (O-I) nanohybrid gas barrier film which exhibits ultralow water vapor transmission rate (WVTR), high activation energy for permeation, high optical transmission in visible light and sufficient flexibility. The values of WVTR and activation energy for permeation of our PEALD-based Al2O3/O-I nanohybrid 4 pair gas barrier film are obtained to be 7.83 × 10?5 g/m2/day (60 °C, 90% RH) and 103.10 kJ/mol via the electrical calcium test. Optical transmission in visible light is 96.14% and critical bending radius 7 mm–9 mm. Introduction of O-I nanohybrid layers between PEALD-based Al2O3 layers improved the properties of gas barrier films on anticorrosion, adhesion, and flexibility.
关键词： Anticorrosion,Encapsulation,Plasma enhanced atomic layer deposition (PEALD),Sol-gel,Nanoparticles,Organic-inorganic nanohybrid,Al2O3
更新于2025-09-19 17:15:36
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Texture and phase variation of ALD PbTiO <sub/>3</sub> films crystallized by rapid thermal anneal
摘要： PbTiO3 (lead titanate) thin films were deposited by atomic layer deposition (ALD) and crystallized via rapid thermal anneal. The films were grown using lead bis(3-N,N-dimethyl-2-methyl-2-propanoxide) and tetrakis dimethylamino titanium as cation precursors. A combination of H2O and ozone was used as oxidizers. Phase-pure, stoichiometric PbTiO3 was confirmed using x-ray diffraction, Rutherford backscattering spectroscopy, and scanning transmission electron microscopy. Ferroelectric hysteresis loops obtained by patterning circular capacitors with areas of 4.92 × 10?4 cm2 indicate a Pmax = 48 μC/cm2, 2Pr = 60 μC/cm2, Ec1 = ?73 kV/cm, Ec2 = 125 kV/cm, and a leakage current density of 15 μA/cm2 at 138 kV/cm. Capacitance versus voltage measurements were used to obtain a maximum dielectric constant of 290 at 85 kV/cm and loss tangent under 4% tested in the range of ±275 kV/cm. ALD PbTiO3 grown with near-ideal cation ratios crystallized into randomly oriented perovskite grains when grown on a sputtered Pt-coated Si substrate. A variation of rapid thermal anneal temperatures, ramp rates, and nucleation layers was investigated and did not have a significant effect on perovskite grain orientation.
关键词： texture,ferroelectric,lead titanate,rapid thermal anneal,atomic layer deposition
更新于2025-09-19 17:15:36
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Theoretical evaluation of thermal decomposition of dichlorosilane for plasma-enhanced atomic layer deposition of silicon nitride: the important role of surface hydrogen
摘要： Silicon nitride (SiN) thin films have been widely employed for various applications including microelectronics, but their deposition presents a challenge especially when highly conformal layers are necessary on nanoscale features with high aspect ratios. Plasma-enhanced atomic layer deposition (PEALD) has been demonstrated to be a promising technique for controlled growth of SiN thin films at relatively low temperatures (o400 1C), in which thermal decomposition of Si-containing precursors on a N-rich surface is a critical step. Based on periodic density functional theory calculations, we present potential underlying mechanisms leading to facile thermal decomposition of dichlorosilane (DCS, SiH2Cl2) on the N-rich b-Si3N4(0001) surface. Our study highlights the importance of high hydrogen content on the N-rich surface, rendering primary and secondary amine groups. When the N-rich b-Si3N4(0001) surface is fully hydrogenated, the molecular adsorption of DCS is predicted to be exothermic by 0.6 eV. In this case, DCS decomposition appears to be initiated by nucleophilic attack by an amine lone-pair on the electrophilic Si, leading to the formation of a DCS-amine adduct intermediate followed by release of a Cl(cid:2) anion and a proton. The predicted activation barrier for the DCS decomposition reaction is only 0.3 eV or less, depending on its adsorption configuration. We also discuss the formation and desorption of HCl, the subsequent formation and nature of Si–N bonds, and the interaction between adsorbed DCS molecules. While clearly demonstrating the advantageous features of DCS as a Si precursor, this work suggests that the thermal decomposition of Si precursors, and in turn the ALD kinetics and resulting film quality, can be strongly influenced by surface functional groups, in addition to product accumulation and precursor coverage.
关键词： silicon nitride,plasma-enhanced atomic layer deposition,dichlorosilane,surface hydrogen,thermal decomposition,density functional theory
更新于2025-09-19 17:15:36
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Elucidating the origin of external quantum efficiency losses in cuprous oxide solar cells through defect analysis
摘要： Heterojunction Cu2O solar cells are an important class of Earth-abundant photovoltaics that can be synthesized by a variety of techniques, including electrochemical deposition (ECD) and thermal oxidation (TO). The latter gives the most efficient solar cells of up to 8.1% reported in the literature, but is limited by low external quantum efficiencies (EQE) in the long wavelength range (490–600 nm). By contrast, ECD Cu2O gives higher short wavelength EQEs of up to 90%. We elucidate the cause of this difference by characterizing and comparing ECD and TO films using impedance spectroscopy and fitting with a lumped circuit model to determine the trap density, followed by simulations. The data indicates that TO Cu2O has a higher density of interface defects, located approximately 0.5 eV above the valence band maximum (NV), and lower bulk defect density thus explaining the lower short wavelength EQEs and higher long wavelength EQEs. This work shows that a route to further efficiency increases of TO Cu2O is to reduce the density of interface defect states.
关键词： Atmospheric pressure spatial atomic layer deposition,chemical vapour deposition,Interface and bulk defects,Impedance spectroscopy,Cuprous oxide solar cells,Quantum efficiency
更新于2025-09-19 17:13:59
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Impact of pixel surface topography onto thin-film encapsulated top-emitting organic light-emitting diodes performances
摘要： Two di?erent designs of top-emitting green OLEDs (Organic Light-Emitting Diodes) have been studied. The ?rst one presents a planar OLED architecture. The second one presents an OLED having a topographic surface, so as to simulate a pixel partitioning of a display using an electrically insulating, 200 nm-thick, resist. It has been observed that the topography has a large impact on OLED performances. Studying devices using an ALD (Atomic Layer Deposition)-deposited Al2O3 barrier ?lm shows that topographic OLEDs have a lower stability under storage in 65 °C/85% RH conditions compared to planar ones, with a di?erence in ageing models between the two devices. As the ALD deposition technology has a high conformity, which implies that ALD-deposited Al2O3 barrier ?lms should be as good on topographic devices as on planar ones, we inferred that the topographic OLED Achilles’ heel lies rather in the OLED structure rather than in the Al2O3 encapsulation itself. Thus, topographic and planar unencapsulated OLEDs (without Al2O3) were studied: interestingly, it has been observed that planar OLEDs can live several weeks, while topographic OLEDs show a very short shelf lifetime (in laboratory atmosphere, at 21 °C/50% RH), of only a couple of hours. It will be shown that the topographic OLED surface tends to reduce the thickness of the PVD (Physical vapour Deposition)-deposited layers in the OLED, as this is expected for a non-conformal deposition PVD technique, on tapered angle regions of the resist (pixel edges). While this thickness variation would not be critical for thick electrodes, as for instance for bottom-emitting devices made on glass substrates, this thickness reduction turns out to be a critical point for the ultrathin, 15 nm, silver cathode, used as semi-transparent electrode in this top-emitting architecture and will therefore be discussed in the framework of using OLED top-emitting architectures in (micro)display technology.
关键词： Dark spots,Physical vapour deposition,Atomic layer deposition,Organic light-emitting diodes,Topography,Degradation
更新于2025-09-19 17:13:59