Atomic Layer Deposition System Research Articles (Page 1)

High purity aluminum in its bulk form has intrinsicallyhigh reflectancein the far-ultraviolet (FUV) regime and finds utility in astrophysicalinstrumentation applications. However, bulk Al oxidizes rapidly inthe atmosphere, and its native oxide strongly absorbs and severelydegrades the observed FUV properties relative to bare Al. Varioustechniques have been investigated to produce coatings that inhibitaluminum oxide formation and lead to high FUV mirror reflectance.This work examines the development and use of a uniquely modified,hybrid plasma-enhanced atomic layer deposition (PEALD) system to passivatealuminum mirrors with metal fluoride films. This system combines twoplasma sources in a commercial atomic layer deposition (ALD) reactor.The first is a conventional inductively coupled plasma (ICP) sourceoperated as a remote plasma, and the second is an electron beam (e-beam)driven plasma near the mirror surface. To establish the operatingconditions for the in situ e-beam plasma source, the effects of samplegrounding, SF6/Ar flow, and sample temperature on resultingAlF3 films were investigated. Optimal operating conditionsproduced mirrors with excellent FUV reflectivity, 92% at 121 nm and42% at 103 nm wavelengths, which is comparable to state-of-the-artAlF3-based passivation coatings and matches that of previouslyreported ex situ e-beam plasma-processed mirrors. This optimized insitu e-beam process, along with XeF2 passivation, is thenexplored to produce a clean seed layer (unoxidized Al surface) forsubsequent PEALD of AlF3. Both approaches are demonstratedas valid pretreatments before PEALD of AlF3, showing apromising pathway for the deposition of other fluoride-based layers,such as MgF2 or LiF, with ALD or PEALD.

Plasmonic metal nanoparticles, when combined with semiconductors such as titanium dioxide (TiO2) and transition metal dichalcogenides (TMDs), open new avenues for enhancing photocatalytic efficiency. The localized surface plasmon resonance (LSPR) of metal nanoparticles enables efficient light absorption and energy conversion processes, providing a powerful platform for driving photocatalytic reactions under light irradiation. In this study, we investigate the interaction between plasmonic nanoparticles and semiconductor materials to elucidate the underlying mechanisms contributing to high-efficiency photocatalytic reactions. Utilizing a sub-picosecond transient absorption spectroscopy system, we directly probe the dynamics of carrier generation and their impact on reaction yields. This approach offers valuable insights into the fundamental processes that govern photocatalytic performance, paving the way for the rational design of advanced photocatalytic materials.TiO2 thin films (30 nm) were deposited on glass substrates using an atomic layer deposition system. Gold (3 nm) was then deposited onto the TiO2 surface using a vacuum evaporation system, followed by annealing at 400°C to fabricate gold (Au) nanoparticles via the Ostwald ripening method. Molybdenum disulfide (MoS2) was synthesized on SiO2/Si substrates via chemical vapor deposition (CVD) and transferred onto glass substrates using a transfer method. Au nanoparticles were separately prepared on glass substrates via Ostwald ripening and subsequently transferred onto the MoS2-coated glass substrates. For photocatalytic reaction evaluations in liquid-phase systems, MoS2 was synthesized through hydrothermal methods and mixed with Au nanoparticles for loading. The hot carrier generation and relaxation dynamics, as well as the reaction quantum yield for methylene blue decomposition, were analyzed using a sub-picosecond transient absorption spectroscopy system.Photoelectrochemical measurements of Au nanoparticle/TiO2 photoelectrodes under visible light irradiation revealed an anodic photocurrent. Incident photon-to-current efficiency (IPCE) spectra showed photocurrent generation corresponding to the interband transitions of Au and its plasmon resonance wavelength. Transient absorption spectroscopy indicated ground-state bleaching (GSB) at the plasmon resonance wavelength and excited-state absorption (ESA) in the near-infrared region. The ESA signal corresponds to hot carrier populations injected into the conduction band of TiO2. Notably, in the presence of triethanolamine as an electron donor, the relaxation rate of hot carriers (back electron transfer) was suppressed. Similarly, in MoS2 systems, the generation of excitons and hot carriers was enhanced in the presence of Au nanoparticles. This enhancement corresponded to an increase in the reaction quantum yield of methylene blue photoreduction, driven by plasmon resonance. These results highlight the role of plasmonic effects in improving hot carrier generations and photocatalytic efficiency.

Here, we report a large-scale wafer microfabrication process and in-depth electrical analysis of atomic layer deposition (ALD) grown bilayer (i.e., HfO2/Ta2O5) memristive devices. The fabricated bilayer devices initially require an electroforming event and show stable bipolar resistive switching responses with some variations in the device switching voltages. These variations are covered in the 15.7%–22.7% range corresponding to the maximum switching voltage of the tested devices. Moreover, time series analysis (TSA) is employed by considering the device switching voltages (VSET and VRESET) to predict the device performance and the obtained outcomes are well matched to the experimental data. Furthermore, the least values of coefficient of variability (CV) in the device switching voltages are 6.09% (VSET) and 3.22% (VRESET) in the case of device-to-device (D2D) while 1.76% (VSET) and 2.14% (VRESET) in the case of cycle-to-cycle (C2C). Furthermore, the fabricated devices efficiently perform the synaptic functionalities in terms of potentiation (P) and depression (D), paired-pulse facilitation (PPF), and paired-pulse depression (PPD), with a least value of nonlinearity (NL) factor of 0.43 in synaptic response, which is close to the ideal value of NL in biological synapses. Therefore, the present work shows that the single ALD system can be an efficient deposition method to deposit high-k oxide materials for memristive arrays over large-scale wafers.

Abstract Uniform deposition of metal oxides on 2D materials, while preserving their structural integrity, is a crucial step to realize the integration of 2D materials in practical devices. In this study, we demonstrate the rapid nucleation of ZnO using atmospheric-pressure spatial chemical vapor deposition (AP-SCVD) on 2D transition metal dichalcogenides MoS2 and WS2. The high precursor partial pressure and uniform precursor delivery afforded by the AP-SCVD process, as compared to conventional atomic layer deposition (ALD), led to rapid ZnO nucleation on both CVD-grown MoS2 and WS2 in as little as 5 AP-SCVD oscillations and complete film closure was achieved on CVD-grown WS2 flakes in less than 60 AP-SCVD oscillations. The ZnO nuclei formed larger interconnected clusters on MoS2, whereas more-isolated islands were formed on the WS2. Raman and photoluminescence (PL) spectroscopy revealed that AP-SCVD is a benign process that does not damage the underlying 2D materials and rather helps to passivate defects via oxygen/water adsorption from the air, when performed in an appropriate temperature window. Deposition of the ZnO was found to impact the optical and structural properties of CVD-grown MoS2 and WS2 differently. For the MoS2–ZnO heterostructure, electron doping and strain dominate, resulting in a reduction in the PL of MoS2, whereas for the WS2–ZnO, strain and dielectric screening have a larger impact, resulting in an enhanced PL.

Magnesium oxide, MgO, has excellent physical properties and a wide range of practical applications. It is an alkaline metal oxide, meaning that it is susceptible to reactions with any acidic functional groups. This work examines the modification of the MgO film surface with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hfacH). This investigation addresses the changes in hydrophobicity of the MgO surface upon hfacH modification by gas-phase exposure and evaluates the effect of this modification on a model atomic layer deposition system using tetrakis(dimethylamido)titanium (TDMAT) and water producing a MgO/TiO2 interface.

Aluminum oxynitride (AlOxNy) films with nitrogen content ranging from 2.51% to 6.38% were employed as gate dielectrics in GaN-based metal–insulator–semiconductor (MIS) structures. These films were deposited using a plasma-enhanced atomic layer deposition system through alternating cycles of AlN and Al2O3. X-ray photoelectron spectroscopy analysis of the Al 2p and N 1s peaks shows that the AlOxNy films contain Al–N, Al–O, and N–Al–O bonds, suggesting the appearance of ternary compound AlOxNy. Capacitance–voltage (C–V) measurements reveal that both fixed charge density (Nfix) and the interface trap density (Dit) in all AlOxNy samples are significantly lower than those in Al2O3 samples. Especially, with the increasing nitrogen compositions, the 6.38 N% AlON sample exhibits an exceptionally low Dit of ∼1011 cm−2eV−1. These results provide an effective approach to realizing more reliable and stable GaN-based MIS-high-electron-mobility transistors.

The defect-controlled charge transfer mechanism in insulators is crucial for advanced electronic devices. In this study, metal/insulator/metal devices with a multilayer stacked structure are developed in which the off-state current value is reduced by 1 order of magnitude compared to a single-layer structure by modulating the deposition conditions of the atomic layer deposition system. The results of x-ray photoelectron spectroscopy suggest that the pressure modulation of the atomic layer deposition system drives the formation of hydroxyl groups. The different band structures formed by such an oxide layer with more hydroxyl groups further affected the current transport. The possible pathways for carrier transport are presented in detail through electrical analysis and provide the potential for different energy band multilayer stacked structures as advanced electronic devices.

Study of antibacterial functional moisture barrier film based on Zn–Si composite oxide deposited by Plasma-Enhanced Atomic Layer Deposition system

Spatial atomic layer deposition (SALD) is a powerful thin-film deposition technique to control surfaces and interfaces at the nanoscale. To further develop SALD technology, there is need to deepen our understanding of the effects that process parameters have on the deposited film uniformity. In this study, a 3D computational model that incorporates laminar-flow fluid mechanics and transport of diluted species is developed to provide insight into the velocity streamlines and partial-pressure distributions within the process region of a close-proximity atmospheric-pressure spatial atomic layer deposition (AP-SALD) system. The outputs of this transport model are used as the inputs to a surface reaction model that simulates the self-limiting chemical reactions. These coupled models allow for prediction of the film thickness profiles as they evolve in time, based on a relative depositor/substrate motion path. Experimental validation and model parameterization are performed using a mechatronic AP-SALD system, which enable the direct comparison of the simulated and experimentally measured geometry of deposited TiO2 films. Characteristic features in the film geometry are identified, and the model is used to reveal their physical and chemical origins. The influence of custom motion paths on the film geometry is also experimentally and computationally investigated. In the future, this digital twin will allow for the capability to rapidly simulate and predict SALD behavior, enabling a quantitative evaluation of the manufacturing trade-offs between film quality, throughput, cost, and sustainability for close-proximity AP-SALD systems.

Nickel-rich Li(NixCoyMn1-x-y)O2 (NCM) is considered one of the most promising cathode materials for next-generation high-energy lithium-ion batteries (LIBs). However, nickel-rich NCM suffers from short battery lifespan, poor rate performance, and structural instability during cycling due to side reactions between the cathode material and the electrolyte. To overcome the aforementioned problems, coating the surface of nickel-rich NCM powders is an efficient and straightforward strategy. In recent years, atomic layer deposition (ALD) has been gaining attention for its utility in preparing LIB electrode materials. Compared to traditional coating methods, ALD can form uniform and ultrathin coating layers, which protect the cathode from reactions with the electrolyte while maintaining electrical conductivity and fast electron transport. More importantly, this process is energy-efficient, rapid (taking only a few minutes), and does not damage the electrode. Nevertheless, attempts to directly deposit ALD coatings onto nickel-rich NCM composite electrodes to enhance the electrochemical performance of NCM have not been widely reported.This study provides an efficient technique based on ALD to enhance the electrochemical performance of Ni-rich NCM cathode materials. The surface of the Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) composite electrode was directly coated with a high-quality ultrathin layer of aluminum oxide (Al2O3). The thickness of the coating layer was precisely controlled at the sub-nanometer scale by the number of ALD cycles. It could protect the surface of the active NCM811 powder and maintain interparticle electron pathways, thereby enhancing electrochemical performance. The optimal thickness of the Al2O3 coating for maximizing the electrochemical performance of NCM811 was grown via 10 ALD cycles. The ALD-based ultrathin Al2O3 coating on the NCM811 was performed using a rotary ALD system. The morphology of the samples was confirmed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Energy-dispersive X-ray spectroscopy (EDS) elemental mapping was collected in scanning transmission electron microscopy (STEM) mode. X-ray diffraction (XRD) patterns were collected using X-ray powder diffraction equipment. The chemical composition of the coating was analyzed using X-ray photoelectron spectroscopy (XPS) with Al Kα radiation. Cell testing was conducted using a coin-type half-cell with lithium metal as the anode.

We report the design, fabrication, and testing of an atomic layer deposition (ALD) system that is capable of reflection high energy electron diffraction (RHEED) in a single chamber. The details and specifications of the system are described and include capabilities of RHEED at varied accelerating voltages, sample rotation (azimuthal) control, sample height control, sample heating up to set temperatures of 1050 °C, and either single- or dual-differential pumping designs. Thermal and flow simulations were used to justify selected system dimensions as well as carrier gas/precursor mass flow rates. Temperature calibration was conducted to determine actual sample temperatures that are necessary for meaningful analysis of thermally induced transitions in ALD thin films. Several demonstrations of RHEED in the system are described. Calibration of the camera length was conducted using a gold thin film by analyzing RHEED images. Finally, RHEED conducted at a series of increasing temperatures was used to monitor the crystallization of an ALD HfO2 thin film. The crystallization temperature and the ring pattern were consistent with the monoclinic structure as determined by separate x-ray diffraction-based measurements.

Abstract In this paper, a ZnO photodiode in a p-n heterojunction configuration is fabricated on a p-type Si substrate focusing specifically on ZnO/p-Si heterojunction photosensitive devices and photodiodes (PDs) using Al contacts. Through an experimental and theoretical analysis approach aims to evaluate the effects of important parameters, including ZnO layer thickness, defect density, and contact materials, on PD’s efficiency. Numerical analysis simulations comparatively examine the experimentally fabricated device performance at a 5 nm ZnO layer thickness by balancing photon absorption and carrier formation while minimizing carrier transport limitations. Experimentally process, an Atomic Layer Deposition (ALD) system was used to grow ZnO interlayers on one side of the polished Si wafer. Then, Al metallic contacts were created on the ZnO layers using a hole array mask. The PDs were then subjected to electrical characterization using I-V and I-t measurements under various illumination densities. Al/ZnO/p-Si PD’s device with active performance has been produced and analyzed with electrical parameters such as barrier height, photocurrent, spectral response, ideality factor and EQE were derived, analyzed and studied. In conclusion, this work provides a comprehensive understanding of the performance of Al/ZnO/p-Si PD at varying illumination intensities and offering a detailed analysis of key parameters influencing device efficiency for future optoelectronics applications.

Ni-rich Li(NixCoyMnz)O2 (x ≥ 0.8)-layered oxide materials are highly promising as cathode materials for high-energy-density lithium-ion batteries in electric and hybrid vehicles. However, their tendency to undergo side reactions with electrolytes and their structural instability during cyclic lithiation/delithiation impairs their electrochemical cycling performance, posing challenges for large-scale applications. This paper explores the application of an Al2O3 coating using an atomic layer deposition (ALD) system on Ni-enriched Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) cathode material. Characterization techniques, including X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, were used to assess the impact of alumina coating on the morphology and crystal structure of NCM811. The results confirmed that an ultrathin Al2O3 coating was achieved without altering the microstructure and lattice structure of NCM811. The alumina-coated NCM811 exhibited improved cycling stability and capacity retention in the voltage range of 2.8-4.5 V at a 1 C rate. Specifically, the capacity retention of the modified NCM811 was 5%, 9.11%, and 11.28% higher than the pristine material at operating voltages of 4.3, 4.4, and 4.5 V, respectively. This enhanced performance is attributed to reduced electrode-electrolyte interaction, leading to fewer side reactions and improved structural stability. Thus, NCM811@Al2O3 with this coating process emerges as a highly attractive candidate for high-capacity lithium-ion battery cathode materials.

In this study, the internal and external stabilities of a p–i–n methylammonium lead iodide perovskite solar cell (PSC) are improved. Polystyrene (PS) is introduced into the perovskite layer to form a cross‐linked polymer–perovskite network, which enhances the nucleation and growth of the perovskite grains. Moreover, for the first time, 60 nm thick ZnO/AlOx nanolaminate (NL) thin‐film encapsulation (TFE) is deposited directly on the PSC using an atmospheric‐pressure (AP) spatial atomic layer deposition system operated in AP spatial chemical vapor deposition (AP–SCVD) mode. The rapid nature of AP–SCVD enables encapsulation of the PSCs in open air at 130 °C without damaging the perovskite. The PS additive improves the performance and internal stability of the PSCs by reducing ion migration. Both the PS additive and the ZnO/AlOx NL TFEs improve the external stability under standard test conditions (dark, 65 °C, 85% relative humidity [RH]) by preventing water ingress. The number and thickness of the ZnO/AlOx NL layers are optimized, resulting in a water–vapor transmission rate as low as 5.1 × 10−5 g m−2 day−1 at 65 °C and 85% RH. A 14‐fold increase in PSC lifetime is demonstrated; notably, this is achieved using PS, a commodity‐scale polymer, and AP–SCVD, a scalable, open‐air encapsulation method.

A special micro LED whose light emitting area is laid out in a U-like shape is fabricated and integrated with colloidal quantum dots (CQDs). An inkjet-type machine directly dispenses the CQD layer to the central courtyard-like area of this U-shape micro LED. The blue photons emitted by the U-shape mesa with InGaN/GaN quantum wells can excite the CQDs at the central courtyard area and be converted into green or red ones. The U-shape micro LEDs are coated with Al2O3 by an atomic layer deposition system and exhibit moderate external quantum efficiency (6.51% max.) and high surface recombination because of their long peripheries. Low-temperature measurement also confirms the recovery of the external quantum efficiency due to lower non-radiative recombination from the exposed surfaces. The color conversion efficiency brought by the CQD layer can be as high as 33.90%. A further continuous CQD aging test, which was evaluated by the strength of the CQD emission, under current densities of 100 A/cm2 and 200 A/cm2 injected into the micro LED, showed a lifetime extension of the unprotected CQD emission up to 1321 min in the U-shape device compared to a 39 min lifetime in the traditional case, where the same CQD layer was placed on the top surface of a squared LED.

Spatial atomic layer deposition of nitrogen-doped alumina thin films for high-performance perovskite solar cell encapsulation

Abstract A customized atmospheric‐pressure spatial atomic layer deposition (AP‐SALD) system is designed and implemented, which enables mechatronic control of key process parameters, including gap size and parallel alignment. A showerhead depositor delivers precursors to the substrate while linear actuators and capacitance probe sensors actively maintain gap size and parallel alignment through multiple‐axis tilt and closed‐loop feedback control. Digital control of geometric process variables with active monitoring is facilitated with a custom software control package and user interface. AP‐SALD of TiO2 is performed to validate self‐limiting deposition with the system. A novel multi‐axis printing methodology is introduced using x‐y position control to define a customized motion path, which enables an improvement in the thickness uniformity by reducing variations from 8% to 2%. In the future, this mechatronic system will enable experimental tuning of parameters that can inform multi‐physics modeling to gain a deeper understanding of AP‐SALD process tolerances, enabling new pathways for non‐traditional SALD processing that can push the technology towards large‐scale manufacturing.

Rapid thermal processing induced interfacial diffusion and solid reaction in the Al2O3/ZnO nano-laminates films

In this study, we have deposited lanthanum oxide (La2O[Formula: see text] ultrathin films onto Si substrate with pre-deposited SiO2 (SiO2/Si substrate) by indigenously developed plasma-enhanced atomic layer deposition (PEALD) system at a low RF power of 30[Formula: see text]W. An in-situ nitrogen plasma (N[Formula: see text] treatment was performed to minimize the defects at interface. Thickness of deposited La2O3 film is estimated to be of 2.1[Formula: see text]nm for 50 cycles as per the growth rate of 0.42A/cycle. The deposited La2O3/SiO2/Si stack underwent post-deposition annealing (PDA) at temperatures of 400∘C, 500∘C, and 600∘C. These films were analyzed using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results showed that the La2O3 ultra thin films on SiO2/Si substrates are amorphous in nature. The atomic force microscopy (AFM) micrograph revealed minimal roughness.

Particle atomic layer deposition (ALD) is an emerging method for engineering 3D materials, such as powders, for energy applications. In our study, we employ a commercially available and scalable particle ALD system to synthesize Pt/C electrocatalysts for fuel cells. Our method yields Pt/C catalysts characterized by highly dispersed platinum nanoparticles with a narrow particle size distribution of 2.2 ± 0.5 nm for 30 wt% Pt and 2.6 ± 0.6 nm for 40 wt% Pt, as verified through transmission electron microscopy and X-ray diffraction analysis. The performance of the ALD-synthesized catalysts is benchmarked against a state-of-the-art catalyst (TEC10V50E), with both catalysts exhibiting similar beginning-of-test performance (1.6 A cm-2 at 0.65 V) under application-relevant operation conditions (80 °C, 50% relative humidity). After 30 000 voltage cycles, conducted in accordance with the U.S. Department of Energy's accelerated catalyst degradation test, the ALD catalysts demonstrate up to 64% greater electrochemical active surface areas and superior retention of cell performance, with a 34% higher current density at 0.65 V, compared to the reference. Given the scalability of the commercial particle ALD system, these promising results encourage the use of particle ALD as a novel synthesis approach for fuel cell catalyst materials in the industry.