Film Growth Research Articles

Efficient gradient heating-up approach for rapid growth of high-quality amorphous ZrO2 dielectric films

High-k oxide dielectric films are indispensable for low-power-consumption oxide thin-film transistors (TFTs) applied in advanced and portable electronics. However, high-quality oxide dielectric films prepared by solution process typically require sophisticated processes and long thermal annealing time, severely limiting both the throughput manufacturing and cost-effectiveness. In this study, the influence of different heating-up methods on the surface morphology and dielectric properties was systematically investigated. Gradient heating-up method could not only substantially improve the surface morphology and quality of high-k ZrO2 films but also efficiently shorten the annealing time. The gradient heating-up process was further designed on the basis of thermal behavior of the xerogel-like precursor, which successfully realize the preparation of high-quality ZrO2 films with an annealing time of 5 min (i.e. the efficiency of thermal treatment increased by about 89%). The ZrO2 film presented excellent dielectric properties, including a low leakage current density of ∼10−8 A cm−2 (at 2 MV cm−1 ), a large areal capacitance of 169 nF cm−2 and a high dielectric constant of 20.41 (1 MHz). Furthermore, InSnZnO TFT based on the ZrO2 gate dielectrics shows an acceptable device performances, such as a high carrier mobility of 2.82 cm2 V−1 s, a high on/off current ratio of ∼105 and a low subthreshold swing of 0.19 V decade −1 at a low operation voltage of 5 V. This work provide a highly promising approach to fabricate high-quality solution-processed high-k oxide dielectric films employed for large-scale and low-power-consumption electronics.

Quasi-Homoepitaxial Growth of Highly Strained Alkali-Metal Ultrathin Films on Kagome Superconductors.

Applying lattice strain to thin films, a critical factor to tailor their properties such as stabilizing a structural phase unstable at ambient pressure, generally necessitates heteroepitaxial growth to control the lattice mismatch with substrate. Therefore, while homoepitaxy, the growth of thin film on a substrate made of the same material, is a useful method to fabricate high-quality thin films, its application to studying strain-induced structural phases is limited. Contrary to this general belief, here the quasi-homoepitaxial growth of Cs and Rb thin films is reported with substantial in-plane compressive strain. This is achieved by utilizing the alkali-metal layer existing in bulk crystal of kagome metals AV3Sb5 (A=Cs and Rb) as a structural template. The angle-resolved photoemission spectroscopy measurements reveal the formation of metallic quantum well states and notable thickness-dependent quasiparticle lifetime. Comparison with density functional theory calculations suggests that the obtained thin films crystalize in the face-centered cubic structure, which is typically stable only under high pressure in bulk crystals. These findings provide a useful approach for synthesizing highly strained thin films by quasi-homoepitaxy, and pave the way for investigating many-body interactions in Fermi liquids with tunable dimensionality.

Effects of magnetic fields on the formation of passive films on the surface of 5083 aluminum alloy

This research explores the effect of the magnetic fields on the passive film of 5083 aluminum alloy. After the application of a 0.3 T magnetic field, 5083 aluminum alloy exhibits an improvement in passivation performance. These improvements manifest as a reduction in passivation current density and an increase in impedance, passive film thickness, and carrier concentration. Additionally, there is an augmentation in the content of the Al2O3 phase within the passive film. The magnetic field facilitates the movement of metal ions during the corrosion process of 5083 aluminum alloy through microscale magnetohydrodynamics, facilitating passive film growth and improving corrosion resistance.

Sputtering Growth of Nitrogen-doped Ga2O3 Films and Applications of Photodetectors

Sputtering Growth of Nitrogen-doped Ga2O3 Films and Applications of Photodetectors

Chemical Environment and Structural Variations in High Entropy Oxide Thin Film Probed with Electron Microscopy.

We employ analytical transmission electron microscopy (TEM) to correlate the structural and chemical environment variations within a stacked epitaxial thin film of the high entropy oxide (HEO) Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O (J14), with two layers grown at different substrate temperatures (500 and 200 °C) using pulsed laser deposition (PLD). Electron diffraction and atomically resolved STEM imaging reveal the difference in out-of-plane lattice parameters in the stacked thin film, which is further quantified on a larger scale using four-dimensional STEM (4D-STEM). In the layer deposited at a lower temperature, electron energy loss spectroscopy (EELS) mapping indicates drastic changes in the oxidation states and bonding environment for Co ions, and energy-dispersive X-ray spectroscopy (EDX) mapping detects more significant cation deficiency. Ab initio density functional theory (DFT) calculations validate that vacancies on the cation sublattice of J14 result in significant electronic and structural changes. The experimental and computational analyses indicate that low temperatures during film growth result in cation deficiency, an altered chemical environment, and reduced lattice parameters while maintaining a single phase. Our results demonstrate that the complex correlation of configurational entropy, kinetics, and thermodynamics can be utilized for accessing a range of metastable configurations in HEO materials without altering cation proportions, enabling further engineering of functional properties of HEO materials.

Molten glass-mediated conditional CVD growth of MoS2 monolayers and effect of surface treatment on their optical properties

In the rapidly developing field of optoelectronics, the utilization of transition-metal dichalcogenides with adjustable band gaps holds great promise. MoS2, in particular, has garnered considerable attention owing to its versatility. However, a persistent challenge is to establish a simple, reliable and scalable method for large-scale synthesis of continuous monolayer films. In this study, we report the growth of continuous large-area monolayer MoS2 films using a glass-assisted chemical vapor deposition (CVD) process. High-quality monolayer films were achieved by precisely controlling carrier gas flow and sulfur vaporization with a customized CVD system. Additionally, we explored the impact of chemical treatment using lithium bistrifluoromethylsulfonylamine (Li-TFSI) salt on the optical properties of monolayer MoS2 crystals. To investigate the evolution of excitonic characteristics, we conditionally grew monolayer MoS2 flakes by controlling sulfur evaporation. We reported two scenarios on MoS2 films and flakes based on substrate-related strain and defect density. Our findings revealed that high-quality monolayer MoS2 films exhibited lower treatment efficiency due to substrate-induced surface strain. whereas defective monolayer MoS2 flakes demonstrated a higher treatment sensitivity due to the p-doping effect. The Li-TFSI-induced changes in exciton density were elucidated through photoluminescence, Raman, and x-ray photoelectron spectroscopy results. Furthermore, we demonstrated treatment-related healing in flakes under variable laser excitation power. The advancements highlighted in our study carry significant implications for the scalable fabrication of diverse optoelectronic devices, potentially paving the way for widespread real-world applications.

Effects ofAs8structure formation on the surface morphology and internal microstructure of GaAs thin films.

Gallium arsenide (GaAs) materials have the advantages of high electron mobility, electron saturation drift rate, and other irreplaceable semiconducting properties. They play an important role in the electronics, solar and other fields. However, during GaAs film sedimentary growth, As atoms can undergo segregation to formAs8clusters because of the influence of external factors, which affect the surface morphology and internal structure of these films. In this study, a series of investigations on the deposition and growth of GaAs crystal films were performed. Additionally, the deposition and growth of GaAs thin films were simulated using molecular dynamics. The influence of As8clusters on the surface morphology and internal structure of GaAs films at different incidence angles, velocities and substrate temperatures was studied by using 'defect analysis technology' and 'diamond structure identification' in open source software, along with surface roughness and radial distribution function. Results show that with increasing incident angle, the number ofAs8clusters decreases and film density increases. Increasing incident velocity increases the irregular movement ofAs8clusters in air, and their deposition on the film surface affects the morphology of the film, and the surface roughness increases first and then decreases. Additionally, we investigated the effect of different substrate temperatures on the film surface. Results show that at a substrate temperature of 1173 K, the number ofAs8clusters in the film decreases or the As8clusters disappear, heterogeneous nucleation occurs in the film, and the crystallization rate increases. Although the dislocation line associated with nucleation may affect the mechanical and optical properties of the film, it considerably reduces the annealing effort after the deposition and growth.

Influence of precursor aging and condensation progression on silica thin films grown by electrochemically induced sol-gel deposition

Electrochemically induced sol-gel enables the fast synthesis of functional oxide coatings. In the case of silica, the condensation reaction can be catalysed by electrogenerated hydroxides. Using this technique, highly organized nanostructured thin films can be deposited onto conductive substrates by combining structure-directing templates with the electrochemically induced silica sol-gel process that occurs locally at the electrode surface. This specific template-directed process, called electrochemically assisted self-assembly (EASA), utilizes a sol-gel precursor solution optimized for a minimal spontaneous condensation (and gelation) rate in the absence of an electrochemical trigger. Despite the slow kinetics of the condensation reaction, the solution remains unstable and some incipient condensation reactions will still occur over time, continuously modifying the Si(IV) precursor solution. In this work, we discuss how precursor's aging affects the deposition rate and the properties of the deposited coatings. Two distinct aging effects are observed: an aging effect which occurs over time and an aging effect which occurs through electrochemical activation during preceding depositions. Both these aging effects result in accelerated film growth rates, up to 200 × faster than the deposition rate from a fresh precursor solution. Additionally, it was observed that time aging yields less resistive, weaker films, while electrochemical aging leads to films which retain similar properties as films grown using fresh precursor solutions. The time aging effect could be inhibited by storing the precursor solution at -35 °C. These observations are explained based on the different condensation pathways during acidic and alkaline condensation, which is known to yield inherently different silica oligomer products. The results and insights described here contribute to upscaling the electrochemical sol-gel process for mesoporous silica films and provides further fundamental insights into the underlying silica condensation reactions.

Bandgap modulations and promoted carrier separation in crystalline g-C3N4 thin films via chemical vapor deposition

The preparation of high-quality graphite-like phase carbon nitride (g-C3N4) films is challenging, which limits the potential optoelectronic and photocatalytic applications. Here, we report the growth of crystalline g-C3N4 films with thicknesses of approximately 100–200 nm on the indium tin oxide substrates by chemical vapor deposition. The films show high crystalline quality and uniformity as suggested by the appearance of interference fringes in the transmission spectra and the existence of exciton peak. The optimized growth conditions for high-quality g-C3N4 films deposition have been obtained through combined optical characterizations and detailed electronic structure analyses using x-ray spectroscopies. The as-grown g-C3N4 films exhibit a bandgap value of 3.05 eV as well as an enhanced fluorescence lifetime of ∼12.43 ns. By adding thiourea to the melamine precursors, N vacancies have been formed in the main heptazine structure, achieving the modulation of the bandgap and the promoted carrier separation. This work provides guidelines for understanding the property–structure relationships during g-C3N4 film deposition. The deposition of high crystallinity g-C3N4 films therein further extends the applications in the fields of optoelectronic and photocatalytic devices.

High-temperature oxidation behavior of Mar-M247 and Mar-M247LC for aero-engines at 800–950 °C in air

The isothermal oxidation behavior of Mar-M247 and Mar-M247LC was investigated in air at 800–950 °C for 500 h. The oxidation activation energies of 327.7 kJ/mol and 281.4 kJ/mol were obtained, respectively. The oxidation kinetics and oxide layer evolution indicated that the Cr3+ outward diffusion dominated the oxide film growth. Firstly, NiO replaced Cr2O3 as the outer layer above 900 °C. Next, the formation of the internal Al2O3 was closely related to the γ' phase dissolution. The size of the γ' and the γ/γ' interfacial area may be one of the possible reasons for the minor differences in the Mar-M247 and Mar-M247LC oxidation properties. And finally, it is speculated that the oxide pegs in the oxide layer enhance the adherence of the oxide film to the substrate.

Preparation of vertical graphene by PECVD with different plasma conditions

Vertical growth of graphene thin films was achieved on Si (100) substrate employing the sputtering technique. Physical-chemical properties of graphene thin films were examined at annealing temperatures from 500 to 780 °C and flowrate ratios of Ar and C2H2 working gases. The effect of temperature on the growth of graphene thin film, surface morphology, microstructure properties, and chemical state were investigated systematically. The formed graphene thin films were characterized and analyzed using different techniques such as Raman spectroscopy, field emission- and cross-sectional-scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The graphene thin films on the Si substrate exhibited the better growth at the 700 °C and 30:15 (Ar:C2H2) flowrate ratio. Results of Raman spectroscopy showed that the graphene thin films have graphitic structure with crystallite size in the range of 10 to 23 nm. Surface morphology exhibited a wall-like structure with a sheet shape. The CS-SEM images indicated columnar growth of films perpendicular to the film plane. Analysis of the chemical states of C 1 s and O 1 s indicated chemical defects in the graphene thin films, evidenced by the presence of lattice oxygen and non-lattice oxygen ions.

Preparation of UiO-66 MOF-Bonded Porous-Layer Open-Tubular Columns Using an In Situ Growth Approach for Gas Chromatography.

The thermally stable zirconium-based MOF, UiO-66, was employed for the preparation of bonded porous-layer open-tubular (PLOT) GC columns. The synthesis included the in situ growth of the UiO-66 film on the inner wall of the capillary through a one-step solvothermal procedure. SEM-EDX analysis revealed the formation of a thin, continuous, uniform, and compact layer of UiO-66 polycrystals on the functionalized inner wall of the column. The average polarity (ΔIav = 700) and the McReynolds constants reflected the polar nature of the UiO-66 stationary phase. Several mixtures of small organic compounds and real samples were used to evaluate the separation performance of the fabricated columns. Linear alkanes from n-pentane to n-decane were baseline separated within 1.35 min. Also, a series of six n-alkylbenzenes (C3-C8) were separated within 3 min with a minimum resolution of 3.09, whereas monohalobenzene mixtures were separated at 220 °C within 14s. UiO-66 PLOT columns are ideally suited for the isothermal separation of chlorobenzene structural isomers at 210 °C within 45 s with Rs ≥ 1.37. The prepared column featured outstanding thermal stability (up to 450 °C) without any observed bleeding or significant impact on its performance. This feature enabled the analysis of various petroleum-based samples.

Thickness dependence of the room-temperature ethanol sensor properties of Cu2O polycrystalline films

This study investigates the fabrication process of copper thin films via thermal evaporation, with precise control over film thickness achieved through Z-position adjustment. Analysis of the as-fabricated copper films reveals a discernible relationship between grain size (〈D〉) and Z-position, characterized by a phenomenological equation 〈D〉XRDn(Z)=〈D〉0n1+32rZ2+158rZ4 , which is further supported by a growth exponent (n) of 0.41 obtained from the analysis. This value aligns well with findings in the literature concerning the growth of copper films, thus underlining the validity and reliability of our experimental outcomes. The resulting crystallites, ranging in size from 20 to 26 nm, exhibit a resistivity within the range of 3.3–4.6 μΩ · cm. Upon thermal annealing at 200 °C, cuprite Cu2O thin films are produced, demonstrating crystallite sizes ranging from ∼9 to ∼24 nm with increasing film thickness. The observed monotonic reduction in Cu2O crystallites relative to film thickness is attributed to a recrystallization process, indicating amorphization when oxygen atoms are introduced, followed by the nucleation and growth of newly formed copper oxide phase. Changes in the optical bandgap of the Cu2O films, ranging from 2.31 to 2.07 eV, are attributed mainly to the quantum confinement effect, particularly important in Cu2O with size close than the Bohr exciton diameter (5 nm) of the Cu2O. Additionally, correlations between refractive index and extinction coefficient with film thickness are observed, notably a linear relationship between refractive index and charge carrier density. Electrical measurements confirm the presence of a p-type semiconductor with carrier concentrations of ∼1014 cm−3, showing a slight decrease with film thickness. This phenomenon is likely attributed to escalating film roughness, which introduces supplementary scattering mechanisms for charge carriers, leading to a resistivity increase, especially as the roughness approaches or surpasses the mean free path of charge carriers (8.61 nm). Moreover, ab-initio calculations on the Cu2O crystalline phase to investigate the impact of hydrostatic strain on its electronic and optical properties was conducted. We believe that our findings provide crucial insights that support the elucidation of the experimental results. Notably, thinner cuprite films exhibit heightened sensitivity to ethanol gas at room temperature, indicating potential for highly responsive gas sensors, particularly for ethanol breath testing, with significant implications for portable device applications.

Long-lasting BDD/Si3N4–TiN electrodes for sustainable water remediation

Boron-doped diamond (BDD) thin films have the potential to revolutionize water remediation through electrochemical oxidation, converting persistent pollutants into CO2 and water. However, a significant challenge in implementing BDDs on a large scale is the choice of substrate material. Electrode failure typically occurs due to BDD delamination from the substrate. We propose using a ceramic composite of silicon nitride (Si3N4) and titanium nitride (TiN) as a substrate to address this issue. This electroconductive composite combines Si3N4's high wear resistance, chemical stability, and high affinity for diamond film growth with the TiN's metal-like conductivity. In this work, BDD films were grown by Hot Filament Chemical Vapor Deposition (HF-CVD) over Si3N4–TiN substrates containing 30%vol. TiN. The resulting BDD/Si3N4–TiN electrodes were analyzed concerning their microstructure, diamond quality, conductivity, adhesion strength, service life, and electrochemical properties. Phenol was used as a model to test the electrode's ability to oxidize pollutants. We found that the BDD/Si3N4–TiN electrode could eliminate phenol entirely and up to 98.8 % of the model solution's Chemical Oxygen Demand (COD) after 5 h of direct anodic oxidation, with an Average Current Efficiency (ACE) of 14 % and an energy consumption of 138 kW h kgCOD−1. Furthermore, the BDD/Si3N4–TiN electrode could withstand more than 2016 h of accelerated life test without film delamination. Overall, the results demonstrate that BDD/Si3N4–TiN electrodes are a potential long-lasting solution for large-scale water treatment by electrochemical advanced oxidation processes (EAOPs) in a sustainable manner, especially if combined with renewable energy sources.

Interlayer-Confined Alloying Dissolution–Precipitation Growth and Electronic Transport Modulation of Large-Area Coastline-like Fractal Bismuthene Films with Statistic Self-Similarity

Interlayer-Confined Alloying Dissolution–Precipitation Growth and Electronic Transport Modulation of Large-Area Coastline-like Fractal Bismuthene Films with Statistic Self-Similarity

Segmented Control of Selenization Environment for High-Quality Cu2ZnSn(S,Se)4 Films Toward Efficient Kesterite Solar Cells.

High-crystalline-quality absorbers with fewer defects are crucial for further improvement of open-circuit voltage (VOC) and efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. However, the preparation of high-quality CZTSSe absorbers remains challenging due to the uncontrollability of the selenization reaction and the complexity of the required selenization environment for film growth. Herein, a novel segmented control strategy for the selenization environment, specifically targeting the evaporation area of Se, to regulate the selenization reactions and improve the absorber quality is proposed. The large evaporation area of Se in the initial stage of the selenization provides a great evaporation and diffusion flux for Se, which facilitates rapid phase transition reactions and enables the attainment of a single-layer thin film. The reduced evaporation area of Se in the later stage creates a soft-selenization environment for grain growth, effectively suppressing the loss of Sn and promoting element homogenization. Consequently, the mitigation of Sn-related deep-level defects on the surface and in the bulk induced by element imbalance is simultaneously achieved. This leads to a significant improvement in nonradiative recombination suppression and carrier collection enhancement, thereby enhancing the VOC. As a result, the CZTSSe device delivers an impressive efficiency of 13.77% with a low VOC deficit.

Cluster-Assisted Mesoplasma Chemical Vapor Deposition for Fast Epitaxial Growth of SiGe/Si Heterostructures: A Molecular Dynamics Simulation Study.

Co-condensation of mixed SiGe nanoclusters and impingement of SiGe nanoclusters on a Si substrate were applied using molecular dynamics (MD) simulation in this study to mimic the fast epitaxial growth of SiGe/Si heterostructures under mesoplasma chemical vapor deposition (CVD) conditions. The condensation dynamics and properties of the SiGe nanoclusters during the simulations were investigated first, and then the impingement of transient SiGe nanoclusters on both Si smooth and trench substrate surfaces under varying conditions was studied theoretically. The results show that the mixed nanoclusters as precursors demonstrate potential for enhancing epitaxial SiGe film growth at a high growth rate, owing to their loosely bound atomic structures and high mobility on the substrate surface. By varying cluster sizes and substrate temperatures, this study also reveals that smaller clusters and higher substrate temperatures contribute to faster structural ordering and smoother surface morphologies. Furthermore, the formed layers display a consistent SiGe composition, closely aligning with nominal values, and the cluster-assisted deposition method achieves the epitaxial bridging of heterostructures during cluster impingement, highlighting its additional distinctive characteristics. The implications of this work make it clear that the mechanism of fast alloyed epitaxial film growth by cluster-assisted mesoplasma CVD is critical for extending it as a versatile platform for synthesizing various epitaxial films.

Improving quality of AlN films on GaAs substrate via in-situ plasma pre-treatment in plasma enhanced atomic layer deposition

Using plasma-enhanced atomic layer deposition (PEALD), we achieved the low-temperature growth of aluminum nitride (AlN) films on GaAs substrate. The effect of in-situ plasma pre-treatment on AlN films growth has been thoroughly investigated in detail. After in-situ plasma pre-treatment, the surface roughness closely matched that of the substrate, the interfaces between AlN films and GaAs substrate were extremely sharp, and the film density increased from 3.05 g/cm3 to 3.15 g/cm3. Additionally, the oxygen content in the AlN films decreased from 35.5 % to 18.8 %. This indicates that in-situ plasma pre-treatment is an effective method for reducing impurity content and improving film quality.

High-performance Ga2O3 solar-blind UV photodetectors via film growth regulation and surface state engineering

Gallium oxide (Ga2O3) with a wide bandgap is emerging as one of the most promising candidates for solar-blind photodetectors (SBPDs). However, the practical application of Ga2O3-based SBPDs is impeded by substantial defects-related leakage currents, sluggish response speed, and high-cost, making their practical applications face great challenges. Here, we proposed strategic films growth regulation and surface state engineering to grow high-quality yet economical β-Ga2O3 films, thereby achieving high-performance SBPDs. High-resolution transmission electron microscopy revealed the presence of high-quality films with an extremely regular arrangement of β-Ga2O3 (2‾01) planes. The full width at half maximum and root mean square roughness values are 0.07° and 0.716 nm, respectively. The β-Ga2O3 films demonstrated a significant reduction in VO concentrations after O2/N2 plasma treatment. This process can effectively minimize thermal damage to the sample surface while retaining highly reactive free radicals. The photocurrents of devices can be further enhanced, leading to a larger PDCRs of 8.6 × 107, through N2 plasma treatment. Moreover, the films effectually suppress the persistent photoconductivity effect with τr and τd values of 5.31/0.97 s and 0.49/0.87 s before and after N2 plasma treatment, respectively. We have demonstrated the influence mechanism of O2/N2 plasma treatment on photoelectronic performance. This study provides a practical approach to growing high-quality β-Ga2O3 films and preparing high-performance but low-cost Ga2O3-based SBPDs.

Improvement of X-ray Photoelectric Conversion Performance of MAPbI3 Perovskite Crystals by Ionic Liquid Treatment

Although perovskite has great potential in optoelectronic devices, the simultaneous satisfaction of material stability and high performance is still an issue that needs to be solved. Most perovskite optoelectronic devices use quantum dot spin coating or the gas-phase growth of perovskite thin films as the photoelectric conversion layer. Due to stability limitations, these materials often experience a significant decrease in photoelectric conversion efficiency when encountering liquid reagents. The self-assembled growth of hybrid perovskite crystals determines superior lattice ordering and stability. There are three types of ionic liquids—[Emim]BF4, EMIMNTF2, and HMITFSI—that can effectively enhance the X-ray photoelectric conversion performance of hybrid perovskite crystal CH3NH3PbI3 (MAPbI3), and the enhancement in the photocurrent leads to an improvement in the sensitivity of X-ray detectors. We soak the perovskite crystals in an ionic liquid and perform two treatment methods: electrification and dilution with ETOH solution. It is interesting to find that MAPbI3 perovskite single crystal materials choose the same optimized ionic liquid species in X-ray detection and photovoltaic power generation applications, and the effect is quite the opposite. Compared with untreated MAPbI3 crystals, the average photocurrent density of Electrify-HMITFSI MAPbI3 increased by 826.85% under X-ray excitation and the sensitivity of X-ray detectors made from these treated MAPbI3 crystals significantly increased by 72.6%, but the intensity of the PL spectrum decreased to 90% of the untreated intensity.