Post-deposition Annealing Research Articles

Reticulated mesoporous TiO2 scaffold for self-cleaning surfaces

Interest in self-cleaning coatings is rising due to their potential to enhance comfort and quality of life in polluted urban environments, driving the search for materials with optimal physical properties. Convergent with this goal, this study investigates the wetting properties and photo-catalytic efficiency of reticulated TiO2 layers. It shows that these properties are significantly influenced by the topographical characteristics of the TiO2 surface, which can be precisely controlled through variations in pulverization pressure and low-temperature post-annealing treatments. Post-deposition annealing of the TiO2 layers achieves 100 % self-cleaning efficiency for both thick and thin films, with optical transmission ranging from approximately 60 %–80 % in the visible spectrum. Additionally, the TiO2 layers exhibited promising capabilities for eliminating pathogenic microorganisms and disinfecting surfaces. The underlying causal factors of these remarkable and technologically promising surface features are explored and discussed.

Effects of post-deposition annealing on the structural and electrical properties of magnesium-doped SB<sub>2</sub>S3 thin films deposited by chemical bath deposition technique

Effects of post-deposition annealing on the structural and electrical properties of magnesium-doped SB<sub>2</sub>S3 thin films deposited by chemical bath deposition technique

Experimental investigation of dipole formation and modulation at Hf0.5Zr0.5O2/SiO2 interface

HfO2-doped ferroelectric field-effect transistors have been extensively studied since the discovery of ferroelectricity in HfO2. A metal/ferroelectric/insulator/semiconductor structure is widely used in FeFETs. The dipole at the doped-HfO2/SiO2 interface is not well understood, though it plays an important role in the flat voltage shift and band alignment which strongly affects charge trapping. This study investigates the band alignment and dipole distribution at the Hf0.5Zr0.5O2 /SiO2 interface using x-ray photoelectron spectroscopy. The band bending of the Hf0.5Zr0.5O2 /SiO2/Si structure is found to vary with Hf0.5Zr0.5O2 layer thickness. The valence band offset (VBO) at the Hf0.5Zr0.5O2 /SiO2 interface decreases with increasing Hf0.5Zr0.5O2 thickness. It is confirmed that the dipole contributes to the dependence of band bending and VBO on Hf0.5Zr0.5O2 thickness. Dipole formation is caused by the charge neutral level mismatch between Hf0.5Zr0.5O2 and the SiO2/Si stack, which induces electron transfer and band bending. O2 post deposition annealing (PDA) can modulate the dipole distribution and generate a larger dipole at the Hf0.5Zr0.5O2 /SiO2 interface than that of the sample not subjected PDA.

Effect of optical and electronic structure on the photocatalytic activity of Al doped ZnO ALD thin films on glass fibers

Photocatalytic water treatment can be promising for eliminating toxic pollutants via a more sustainable approach using renewable sources. However, the technique still requires materials design to optimize/maximize the performance of the photocatalytic materials. Immobilizing the thin film photocatalytic materials onto high surface area textile substrates via atomic layer deposition (ALD) can offer a practical design approach. Al-doped ZnO (AZO) ALD films are deposited onto glass fabric substrates, and their photocatalytic performances were investigated in relation to the FESEM, XRD, XPS, UV–Vis, and PL characterizations. The amount of Al and the post-deposition annealing changed the materials structure, thus the photocatalytic activity of the films. Maximum performance was achieved with the 20 % Al-doped ZnO films after a post-deposition thermal annealing step at 450 °C. The sample also showed the highest UV–Vis absorption and PL emission among the samples. However, this sample didn’t show any crystal peaks in the XRD analysis. Furthermore, the charge carrier concentrations and the mobility of the films were investigated via Hall-Effect, which showed that the 20 % AZO sample has very different features with a p-type nature compared to the other AZO films.

The Influence of Annealing on the Compositional and Crystallographic Properties of Sputtered Li–Al–O Thin Films

Li–Al–O materials are interesting for several applications. Herein, a Li–Al–O thin‐film materials library, deposited by inert magnetron sputtering and postdeposition annealing in O2 atmosphere, is used to study the effects of different annealing temperatures (300–850 °C) and durations (1 min to 7 h) on crystallinity and composition of the films. X‐ray photoelectron spectroscopy depth profiling reveals inhomogeneous compositional depth profiles of conventionally annealed films (300–650 °C, 3–7 h) with increased Li contents toward the film surface and increased Al contents toward the film–substrate interface, as confirmed by a combination of Rutherford backscattering spectrometry and deuteron‐induced nuclear reaction analysis. The minimum temperature for the formation of crystalline LiAlO2 in the otherwise amorphous films is 550 °C. The undesired inhomogeneous depth profiles are transformed into homogeneous ones by rapid thermal annealing (750–850 °C, 1–10 min), while simultaneously causing the formation of crystalline LiAlO2. Therefore, rapid thermal annealing is shown to be more suitable than conventional annealing for the thermal processing of Li–Al–O thin films. Moreover, this conclusion is expected to have broader relevance beyond Li–Al–O materials, as it is likely to apply to other Li metal oxides, of which there are many technologically relevant ones.

Tunable charge transport properties in non-stoichiometric SrIrO3 thin films

Delving into the intricate interplay between spin-orbit coupling and Coulomb correlations in strongly correlated oxides, particularly perovskite compounds, has unveiled a rich landscape of exotic phenomena ranging from unconventional superconductivity to the emergence of topological phases. In this study, we have employed pulsed laser deposition technique to grow SrIrO3 (SIO) thin films on SrTiO3 substrates, systematically varying the oxygen content during the post-deposition annealing. X-ray photoelectron spectroscopy (XPS) provided insights into the stoichiometry and spin-orbit splitting energy of Iridium within the SIO film, while high-resolution x-ray studies meticulously examined the structural integrity of the thin films. Remarkably, our findings indicate a decrease in the metallicity of SIO thin films with reduced annealing O2 partial pressure. Furthermore, we carried out magneto-transport studies on the SIO thin films, the results revealed intriguing insights into spin transport as a function of oxygen content. The tunability of the electronic band structure of SIO films with varying oxygen vacancy is correlated with the density functional theory calculations. Our findings elucidate the intricate mechanisms dictating spin transport properties in SIO thin films, offering invaluable guidance for the design and optimization of spintronic devices based on complex oxide materials. Notably, the ability to tune bandwidth by varying post-annealing oxygen partial pressure in iridate-based spintronic materials holds significant promise for advancing technological applications in the spintronics domain.

Internal strain identification of seed-layered ZrO2, aluminum-, and yttrium-doped ZrO2 thin films via grazing incidence x-ray diffraction

Grazing incidence x-ray diffraction reveals that conventional post-deposition-annealed ZrO2 and in situ crystallized (by local epitaxy) ZrO2 thin films (<15 nm) have different internal strain states. A comparison between single- and two-step grown films enables the diverse strain components to be discretely identified. In particular, thickness-dependent intrinsic growth strain is unevenly distributed within the film according to the Volmer–Weber growth. Furthermore, extrinsic thermal strain, locally present in the annealed seed layer, does not spread over the in situ crystallized upper main layer of the two-step film. Post-deposition annealing of the two-step film renders the strain state identical to the single-step films by imposing thermal strain on the in situ crystallized main layer. Local strains created by diffused aluminum and yttrium dopants are also examined. Since each stress factor plays a vital role in the phase formation and electrical behaviors of ZrO2 and other fluorite-structure films, this method will pave the way for understanding the film's internal strain distribution and accompanying performance engineering.

Effects of post-deposition annealing on structure and mechanical properties of multilayer Ti/DLC films

The multilayer (Ti/DLC) × 3 films were deposited using a DC arc evaporator with a titanium cathode and a pulsed cathode-spark evaporator with a graphite cathode. Following the deposition of the films, a heat treatment process was performed in air and Ar atmosphere at temperatures of 200 °C and 400 °C. The investigation of the films involved the examination of their structure, surface morphology, and chemical composition using AFM, SEM, XPS and Raman. Additionally, the mechanical properties of the films were assessed by nanoindentation, sclerometry and wear test. Changes in the structure, RMS roughness, С-sp2/С-sp3 ratio of carbon atoms in the film and the formation of Ti-C carbide were determined in relation to the heat treatment conditions. Studies have demonstrated that subjecting materials to heat treatment at temperatures of 400 °C results in a decrease in friction coefficient and an increase in hardness. The deposition of films on the working surfaces of microdrills with subsequent heat treatment leads to a reduction in wear, an extension of their service life, and an improvement in drilling accuracy as compared to microdrills without films. Furthermore, microdrills with (Ti/DLC) × 3 films annealed in air at 400 °C exhibit negligible size reduction and better drilling accuracy.

Cu1−xAlx films as alternatives to copper for advanced interconnect metallization

CuxAl1−x thin films with 0.2 ≤ x ≤ 0.7 have been studied as potential alternatives for metallization of advanced interconnects. First-principles simulations were used to obtain the CuxAl1−x electronic structure and cohesive energy to benchmark different intermetallics and their prospects for interconnect metallization. Next, thin CuxAl1−x films were deposited by PVD with thicknesses in the range between 3 and 28 nm. The lowest resistivities of 9.5 μΩ cm were obtained for 28 nm thick stoichiometric CuAl and CuAl2 after 400 °C postdeposition annealing. Based on the experimental results, we discuss the main challenges for the studied aluminides from an interconnect point of view, namely, control of the film stoichiometry, the phase separation observed for off-stoichiometric CuAl and CuAl2, as well as the presence of a nonstoichiometric surface oxide.

Impact of post deposition treatment on optoelectrical and microstructural properties of tin sulfide thin film for photovoltaic applications

Tin sulfide (SnS) has attracted significant interest due to its advantageous optoelectrical characteristics and abundant presence in nature. Post-deposition treatments (PDTs) are frequently employed to enhance the crystallinity of chalcogenide-based solar cells. This study examined the influence of the post-deposition heat treatment procedure on thermally evaporated SnS thin film. The post-deposition annealing process, as determined by XRD and AFM studies, supplies the necessary thermal energy for re-crystallization, potentially resulting in a modification of crystallite dimensions. The occurrence of Sn-S polytypes was examined using Raman and XPS studies. Annealing causes changes in the optical properties, as observed through optical analysis, which can be attributed to the improvement in crystallinity. Subjecting the material to annealing at temperature of 300 °C greatly improves both mobility and conductivity, while also causing a change in conduction type. The observed variations in conduction type are attributed to the differing ratios between the amounts of Sn2+ and Sn4+. This strategy offers a novel route for the fabrication of thin-film photovoltaic cells by using a p-type buffer layer.

Crystalline as-deposited TiO 2 anatase thin films grown from TDMAT and water using thermal atomic layer deposition with in situ layer-by-layer air annealing

We report a new thermal atomic layer deposition (thermal-ALD) process including an air exposure as a third precursor to deposit crystalline TiO2 anatase thin films from tetrakis(dimethylamido)titanium(IV) (TDMAT) and water at deposition temperatures as low as 180 °C and film thicknesses as low as 10 nm. This ALD process enables TiO2-antase crystal growth during the deposition at low temperatures (< 220 °C). This additional oxidant pulse is used to fully oxidize the Ti to a 4+ state in the amorphous film, lowering the barrier to crystalline anatase formation. This new approach is informed by preliminary studies of post-deposition annealing (PDA) of thermal ALD films in both nitrogen and air atmospheres, which demonstrate the importance of having an oxidizing atmosphere to achieve the nucleation of the crystalline anatase phase. This oxidizing atmosphere is subsequently introduced into the ALD cycle as a third precursor and is shown to be more effective and efficient in promoting the crystalline transformation than even by post-deposition annealing. The crystalline anatase phase is verified by Raman spectroscopy and grazing incidence X-ray diffraction (GIXRD). The mechanism for crystallization during the TDMAT/H2O/air ALD cycle is probed by chemical state analysis via X-ray photoelectron spectroscopy (XPS). We propose that sub-oxidation in TiO2 thin films deposited by the thermal-ALD process inhibits crystallization during ALD from TDMAT/H2O chemistry. Scanning electron microscopy (SEM) is used to investigate the microstructure of these TiO2 thin films as a function of thickness (5 nm to 50 nm) and deposition temperature (180 °C to 220 °C). The reported layer-by-layer air anneal process is found to crystallize entire films in shorter total process times than thermal-ALD with ex situ post deposition annealing at identical temperatures, presumably due to the improved surface diffusion kinetics accessed during the deposition process.

Metal-organic decomposed lanthanum cerium oxide thin films: A study of chemical and surface properties

Lanthanum cerium oxide thin films have been deposited on n-type (100) silicon wafers using the spin coating technique. The post-deposition annealing was performed over spin-coated films. The compositional studies were conducted by performing Fourier transform infrared spectroscopy, Energy dispersive X-ray spectroscopy, and X-ray diffraction. Ellipsometry was used to determine the thickness and atomic force microscopy was performed to understand the surface morphology of the deposited thin films. The effect of rapid thermal annealing at different temperatures over the structural and chemical properties of the LaCeO2 thin films was observed. The FTIR spectra show the formation of silicates at the interface of the oxide and semiconductor, while XRD results show that the films become crystalline with increased annealing temperature. The refractive index was observed to be reduced with an increase in the annealing temperature and a minor reduction in the physical thickness as per the sample standard deviation of 0.2981[Formula: see text]nm.

Effects of Postdeposition Annealing on the Electrical Properties of Cu2O/4H–SiC PiN Diodes

Copper oxide (Cu2O) is a promising p‐type material owing to its high absorption coefficient, suitable bandgap width, chemical stability, nontoxicity, and abundance. In this study, the effect of postdeposition annealing (PDA) on the electrical properties of Cu2O thin films deposited on silicon carbide (SiC) substrates is investigated. The films are subjected to PDA using radio‐frequency sputtering at various temperatures in air. During PDA, the Cu2O films are maintained at <300 °C and transitioned to cupric oxide (CuO) at 400 °C. The as‐deposited Cu2O film exhibits a low oxidation peak (Cu2+), whereas the phase‐transformed CuO films exhibit a higher binding energy with the emergence of satellite peaks. The rectification ratios of the Cu2O device annealed at 300 °C and CuO device annealed at 400 °C are determined as 2.02 × 107 and 1.01 × 105, respectively, denoting the substantial enhancement of approximately 55.04 for the Cu2O/SiC device and degradation of approximately 0.28 for the CuO/SiC device relative to their non‐annealed counterparts. Therefore, in this study, the significant improvement in the performance of Cu2O thin films with the meticulous deposition control of potential p‐type materials, such as Cu2O and CuO, for high‐throughput and low‐cost electronic applications is demonstrated.

Hindrances and solutions on the path towards adjoined barium titanate–hydroxyapatite ceramics with uncompromised piezoelectric and biological responses

The synergistic piezoelectric and osteoconductive properties of barium titanate (BT) and hydroxyapatite (HA) could stir the development of a new generation of synthetic bone graft substitutes, with capability for rapid and safe osseointegration. The research focused on two concurrent approaches for coupling the BT and HA materials: (i) conventional sintering of BT-HA powder mixtures; and (ii) functionalization of pre-sintered BT with HA coatings using magnetron sputtering (MS). Irrespective of the BT/HA ratios ranging from 95/5 to 80/20 wt%, nanocrystalline or highly-crystallized nature of the powders, sub-micron- or micron-sized particle dimensions, and sintering temperature, it was observed that the BT-HA reactivity cannot be prevented above 800 °C. At higher temperatures in the range of 1000–1300 °C, HA undergoes decomposition and extensively reacts with BT, leading to the formation of several secondary phases such as CaTiO3, Ba2Ca(PO4)2, BaCa6(PO4)4O, BaCa(PO3)4, and β-Ca2P2O7. As a consequence, the cytocompatibility assessed in fibroblast and osteoblast cell cultures, as well as the piezoelectric response, were significantly altered.Applying HA coatings by MS to the sintered BT ceramics successfully preserved their piezoelectric properties, while also providing an unaltered cytocompatible and osteogenic-prone surface. The HA coatings were fully crystallized at post-deposition annealing temperatures of 550 and 700 °C, achieving crystalline qualities comparable to HA powders sintered at 1100 and 1200 °C, respectively. No reactivity events between BT and HA were observed. Partial reactivity was only noticeable upon annealing at 1000 °C. Therefore, it is suggested that the HA coating of BT is effective in seamlessly coupling the piezoelectric and osteogenic properties of the two constituents without compromise.

Influence of Nb substrate morphology and atomic structure on Sn nucleation and early Nb3Sn growth

The enhanced accelerating performance of Nb3Sn-coated Nb superconducting radio frequency (SRF) cavities is severely limited by quenching sites at material defects formed during the Nb3Sn film growth procedure. In this work, we aimed to understand the complex surface-mediated interactions that drive initial Nb3Sn formation during the Sn vapor deposition procedure used to fabricate Nb3Sn coated SRF cavities. Nb substrates were modified, coated with Sn, and then characterized using an ultra-high vacuum (UHV) chamber equipped with metal deposition and in situ surface analysis capabilities. The atomic structure of the Nb oxide surface was modified to assess how the Nb surface defect density and crystallographic orientation impact the size of nucleated Sn islands and relative Nb3Sn growth rates. Formed Nb3Sn/Nb surfaces were visualized using ex situ scanning electron microscopy (SEM) and post-deposition annealing revealed Sn desorption and Nb3Sn degradation pathways. Finally, we showed that the Sn deposition conditions can be modified to overcome the growth barriers that are imposed by the Nb morphology. This study provides a unique bridge between fundamental growth studies in pristine conditions with observed phenomena of Nb3Sn grown on realistic cavity surfaces.

Low temperature crystallization of atomic-layer-deposited SrTiO3 films with an extremely low equivalent oxide thickness of sub-0.4 nm

Despite SrTiO3(STO) possessing a high dielectric constant, its application as a capacitor dielectric in dynamic random-access memory(DRAM) capacitors faces challenges due to the high-temperature annealing for crystallization, its compositional inhomogeneity, and the high leakage currents of STO films. To address these issues, we employ atomic layer deposition(ALD) of STO films onto Pt substrates at elevated temperatures(340–380 °C). The use of low-reactivity Pt electrodes effectively mitigates the initial growth of excess Sr, ensuring enhanced compositional uniformity along the film growth direction. Coupled with ALD at high temperatures, this approach facilitates the crystallization of STO films in the as-grown state, further enhancing the crystallinity with increasing film thickness. Subsequent low-temperature post-deposition annealing (PDA) at 400 and 500 °C achieves full crystallization. This process results in a remarkable increase in the dielectric constant, reaching approximately 150. Furthermore, the absence of microcracks after PDA, attributed to the formation of adequately dense films, contributes to substantially improved dielectric properties. Consequently, these STO films exhibit an exceptionally low equivalent oxide thickness of 0.34 nm coupled with an ultralow leakage current of 3.7 × 10−8 A/cm2 at an operation voltage of 0.8 V, promising for advancing DRAM capacitors. This study presents a pathway for the sustainable scaling of DRAMs, addressing challenges in ALD-grown STO films.

Deposition time dependent structural and optical properties of polycrystalline [formula omitted] films

Sputtering-derived InGaZnO4 (IGZO) thin films were grown on quartz substrates and undergone post-deposition annealing at 700 °C for 2hr in N2 ambient. The influence of deposition time or film thickness on the morphological, structural and optical properties of polycrystalline IGZO thin films has been systematically investigated by means of characterization from field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), high resolution X-ray diffraction (HRXRD) and ultraviolet–visible–near infrared (UV–Vis–NIR) spectrophotometer. Results of AFM have shown that the root-mean-square (RMS) surface roughness of the IGZO films increases from 0.888 to 2.640 nm as the deposition time is extended from 50 to 250min. Analysis of XRD indicates that all the films are in polycrystalline phase, with crystallites growing into larger size accordingly to increasing deposition time. Appealingly and scarcely ever reported, the XRD diffraction planes can be separated into three domains, such as (0 0 l), (1 0 l) and (1 1 l) with different growth thicknesses. Optical measurement suggests that the optical bandgap have redshifted from 3.55 to 3.31eV at longer deposition time. Related mechanics about the change in physical properties against deposition time have been elaborated in detail. The validity of Swanepoel method, 1983 in deriving the refractive index of thick IGZO films has also been discussed.

Novel strategies for low-voltage NAND flash memory with negative capacitance effect

Here, we present a novel approach to employing a negative capacitance (NC) phenomenon in the blocking oxide of charge trap flash (CTF) memory. To achieve this, we developed an inversible mono-domain like ferroelectric (IMFE) film through high-pressure post-deposition annealing in a forming gas at 200 atm (FG-HPPDA). The FG-HPPDA process enables to form a uniform alignment of domains and facilitates invertible domain switching behavior in ferroelectrics, generating an internal field by the flexo-electric effect as well as interface-pinned polarization by chemical reaction. Subsequently, to stabilize the NC effect, we fabricated the IMFE/Al2O3 heterostructure, which exhibits an outstanding capacitance-boosting feature. Finally, we successfully demonstrate unprecedented CTF memory with the NC effect in a blocking oxide. Our unique CTF device shows the improved performance (maximum incremental-step-pulse-programming (ISPP) slope ∼1.05) and a large MW (>8 V), attributed to the capacitance boosting by NC phenomenon.

Growth of Atomic layer-deposited Monoclinic Molybdenum Dioxide Films Stabilized by Tin Oxide Doping for DRAM Capacitor Electrode Applications.

Dynamic random-access memory (DRAM) capacitor electrodes, exemplified by TiN, face performance limitations owing to their relatively low work functions in addition to the formation of a low-k interfacial layer caused by their insufficient chemical stability. With recent advances in device scaling, these issues have become increasingly problematic, prompting the exploration of alternative electrode materials to replace TiN. Molybdenum dioxide (MoO2) has emerged as a promising candidate for this application, outperforming TiN due to its low resistivity, high work function (>5 eV), and excellent chemical stability. Moreover, monoclinic MoO2 exhibits a distorted rutile structure, enabling the in situ growth of high-k rutile TiO2 on MoO2 at low deposition temperatures. However, MoO2 deposition poses challenges because of its metastable nature compared to the more stable molybdenum oxide (MoOx) phases, such as MoO3 and Mo4O11. In this work, we successfully fabricated Sn-doped MoOx (TMO) films by atomic layer deposition (ALD) at 300 °C. A stabilized monoclinic MoO2 phase was achieved using ALD by incorporating SnOx into MoOx on both SiO2 and TiN substrates. The ALD TMO process comprised MoOx and SnOx subcycles, and the MoOx:SnOx subcycle ratio was varied from 100:1 to 20:1. High growth rates ranging from 0.19 to 0.34 nm/cycle were achieved for ALD TMO with varying the MoOx:SnOx subcycle ratio from 20:1 to 100:0. After post-deposition annealing at 500 °C, polycrystalline TMO films were obtained with smooth surface morphology. ALD TMO exhibited excellent interface quality with ALD TiO2, possessing a negligible low-k interfacial layer. Moreover, a rutile TiO2 film with a high dielectric constant of 136 was successfully grown on a 20% Sn-TMO electrode. Overall, this study provides a strategy to stabilize metastable MoO2 films using ALD, and it demonstrates the superiority of ALD TMO as a promising DRAM capacitor electrode material.

Surface passivation of silicon substrate by ternary GaxCeyOz layers grown via combination of forming gas and oxygen at different temperatures

A systematic evaluation of deploying GaxCeyOz passivation layer (PL) on Si substrate subjected to postdeposition annealing in forming gas-oxygen-forming gas ambient at different temperatures (600–900 °C) was carried out. The inclusion of hydrogen and/or nitrogen ions, in addition to their attachment to oxygen vacancies and Si dangling bonds, has been reported. The attachment became more prominent at 600 and 700 °C while oppositely, the incoming oxygen ions acquired adequate energy to break the attachment at/beyond 800 °C. Therefore, it is conceivable that the GaxCeyOz PL annealed at/beyond 800 °C have attained a thicker interfacial layer (IL). The acquisition of a higher Nss has been attributed to the de-passivation of Si dangling bonds by the excessive hydrogen ions present at the interface. The potential of utilizing GaxCeyOz PL annealed at 700 °C as a PL for metal-oxide-semiconductor applications was inferred through a thorough electrical analysis conducted in this work.