Showing papers on "Atomic layer deposition published in 2022"

Advances in SnO2 for Efficient and Stable n–i–p Perovskite Solar Cells

Abstract: Perovskite solar cells (PSCs) based on the regular n–i–p device architecture have reached above 25% certified efficiency with continuously reported improvements in recent years. A key common factor for these recent breakthroughs is the development of SnO2 as an effective electron transport layer in these devices. In this article, the key advances in SnO2 development are reviewed, including various deposition approaches and surface treatment strategies, to enhance the bulk and interface properties of SnO2 for highly efficient and stable n–i–p PSCs. In addition, the general materials chemistry associated with SnO2 along with the corresponding materials challenges and improvement strategies are discussed, focusing on defects, intrinsic properties, and impact on device characteristics. Finally, some SnO2 implementations related to scalable processes and flexible devices are highlighted, and perspectives on the future development of efficient and stable large‐scale perovskite solar modules are also provided.

Scaled indium oxide transistors fabricated using atomic layer deposition

Abstract: In order to continue to improve integrated circuit performance and functionality, scaled transistors with short channel lengths and low thickness are needed. But the further scaling of silicon-based devices and the development of alternative semiconductor channel materials that are compatible with current fabrication processes is challenging. Here we report atomic-layer-deposited indium oxide transistors with channel lengths down to 8 nm, channel thicknesses down to 0.5 nm and equivalent dielectric oxide thickness down to 0.84 nm. Due to the scaled device dimensions and low contact resistance, the devices exhibit high on-state currents of 3.1 A/mm at a drain voltage of 0.5 V and a transconductance of 1.5 S/mm at a drain voltage 1 V. Our devices are a promising alternative channel material for scaled transistors with back-end-of-line processing compatibility.

MoS2/MXene Aerogel with Conformal Heterogeneous Interfaces Tailored by Atomic Layer Deposition for Tunable Microwave Absorption

Abstract: In the design of electromagnetic (EM) wave absorbing materials, it is still a great challenge to optimize the relationship between the attenuation capability and impedance matching synergistically. Herein, a 3D porous MoS2/MXene hybrid aerogel architecture with conformal heterogeneous interface has been built by atomic layer deposition (ALD) based on specific porous templates to optimize the microwave absorption (MA) performance comprehensively. The original porous structure of pristine Ti3C2Tx aerogel used as templates can be preserved well during ALD fabrication, which prolongs the reflection and scattering path and ameliorates the dielectric loss. Meanwhile, plenty of heterointerfaces between MoS2 and Ti3C2Tx have been fabricated based on conformally ALD‐deposited MoS2 with controlled thickness on the porous surfaces of the templates, which can effectively optimize the impedance matching and transform its response to EM waves from shielding into absorbing. Moreover, the interaction between the attenuation capability and impedance matching can also be modulated by the number of ALD cycle in MoS2 fabrication. After optimization, MoS2/MXene hybrid aerogel obtained under 300 ALD cycles shows a minimum reflection loss of −61.65 dB at the thickness of 4.53 mm. In addition, its preferable lightweight, high surface area, mechanical, and hydrophobicity properties will also be conducive to further practical applications.

Zwitterion‐Functionalized SnO2 Substrate Induced Sequential Deposition of Black‐Phase FAPbI3 with Rearranged PbI2 Residue

Abstract: Black‐phase formamidinium lead iodide (FAPbI3) with narrow bandgap and high thermal stability has emerged as the most promising candidate for highly efficient and stable perovskite photovoltaics. In order to overcome the intrinsic difficulty of black‐phase crystallization and to eliminate the lead iodide (PbI2) residue, most sequential deposition methods of FAPbI3‐based perovskite will introduce external ions like methylammonium (MA+), cesium (Cs+), and bromide (Br–) ions to the perovskite structure. Here a zwitterion‐functionalized tin(IV) oxide (SnO2) is introduced as the electron‐transport layer (ETL) to induce the crystallization of high‐quality black‐phase FAPbI3. The SnO2 ETL treated with the zwitterion of formamidine sulfinic acid (FSA) can help rearrange the stack direction, orientation, and distribution of residual PbI2 in the perovskite layer, which reduces the side effect of the residual PbI2. Besides, the FSA functionalization also modifies SnO2 ETL to suppress deep‐level defects at the perovskite/SnO2 interface. As a result, the FSA–FAPbI3‐based perovskite solar cells (PSCs) exhibit an excellent power conversion efficiency of up to 24.1% with 1000 h long‐term operational stability. These findings provide a new interface engineering strategy on the sequential fabrication of black‐phase FAPbI3 PSCs with improved optoelectronic performance.

Atomic Layer Deposition of Rh/ZnO Nanostructures for Anti-humidity Detection of Trimethylamine

Abstract: The design of metal/semiconductor hybrid nanostructures is an important strategy for the development of efficient chemical gas sensors. In this paper, a highly sensitive gas-sensing material for trimethylamine (TMA) detection was designed by atomic layer deposition (ALD) of Rh onto ZnO flower-like nanostructures. The ZnO nanostructures consisted of porous nanosheets prepared by a hydrothermal method, and then functionalized with Rh catalysts to explore the sensing properties to TMA. The gas sensing investigations show that the loading of Rh has a remarkable influence on the performance of the sensors. The Rh/ZnO sensor with 10 cycles of Rh ALD showed the best response to TMA at 180 °C. A very high response of 11.3 was recorded when exposed to 10 ppm TMA, which is 3-times higher than that of pristine ZnO. Furthermore, the sensor also has a fast response-recovery and an excellent humidity resistance, as well as a low detection limit of 55 ppb, which suggest high potential for reliable detection of sub-ppm TMA.

Tunable TiO2-BN-Pd nanofibers by combining electrospinning and atomic layer deposition to enhance photodegradation of acetaminophen.

Abstract: The demand for fresh and clean water sources is increasing globally, and there is a need to develop novel routes to eliminate micropollutants and other harmful species from water. Photocatalysis is a promising alternative green technology that has shown great performance in the degradation of persistent pollutants. Titanium dioxide is the most used catalyst owing to its attractive physico-chemical properties, but this semiconductor presents limitations in the photocatalysis process due to the high band gap and the fast recombination of the photogenerated carriers. Herein, a novel photocatalyst has been developed, based on titanium dioxide nanofibers (TiO2 NFs) synthesized by electrospinning. The TiO2 NFs were coated by atomic layer deposition (ALD) to grow boron nitride (BN) and palladium (Pd) on their surface. The UV-Vis spectroscopy measurements confirmed the increase of the band gap and the extension of the spectral response to the visible range. The obtained TiO2/BN/Pd nanofibers were then tested for photocatalysis, and showed a drastic increase of acetaminophen (ACT) degradation (>90%), compared to only 20% degradation obtained with pure TiO2 after 4 h of visible light irradiation. The high photocatalytic activity was attributed to the good dispersion of Pd NPs on TiO2-BN nanofibers, leading to a higher transfer of photoexcited hole carriers and a decrease of photogenerated electron-charge recombination. To confirm its reusability, recycling tests on the hybrid photocatalyst TiO2/BN/Pd have been performed, showing a good stability over 5 cycles under UV and visible light. In addition, toxicity tests as well as quenching tests were carried out to check the toxicity of the byproducts formed and to determine active species responsible for the degradation. The results presented in this work demonstrate the potential of TiO2/BN/Pd nanomaterials, and open new prospects for the preparation of tunable photocatalysts.

Selectively Coupling Ru Single Atoms to PtNi Concavities for High Performance Methanol Oxidation via d-Band Center Regulation.

Abstract: Single atom tailored metal nanoparticles represent a new type of catalysts. Herein, we demonstrate a single atom-cavity coupling strategy to regulate performance of single atom tailored nano-catalysts. Selective atomic layer deposition (ALD) was conducted to deposit Ru single atoms on the surface concavities of PtNi nanoparticles (Ru-ca-PtNi). Ru-ca-PtNi exhibits a record-high activity for methanol oxidation reaction (MOR) with 2.01 A mg -1 Pt . Also, Ru-ca-PtNi showcases a significant durability with only 16% activity loss. Operando electrochemical Fourier transform infrared spectroscopy (FTIR) and theoretical calculations demonstrate Ru single atoms coupled to cavities accelerate the CO removal by regulating d -band centre position. Further, the high diffusion barrier of Ru single atoms in concavities accounts for excellent stability. The developed Ru-ca-PtNi via single atom-cavity coupling opens an encouraging pathway to design highly efficient single atom-based (electro)catalysts.

Progress and Challenges of SnO2 Electron Transport Layer for Perovskite Solar Cells: A Critical Review

Abstract: Organic inorganic halide perovskites have drawn great attention in the past decade, due to their superior photovoltaic performance with an efficiency over 25%. For planar heterojunction structure perovskite solar cells (PSCs) tin oxide based electron transport layers (ETLs) have become one of the most suitable candidates to replace titanium oxide to make flexible devices because of their low‐temperature processing. The deposition techniques of SnO2 can be categorized into chemical deposition, such as sol‐gel, chemical bathing or atomic layer deposition, and physical deposition, such as thermal evaporation or sputtering. Depending on the deposition technique, defects, and morphology in the SnO2 layer may vary drastically, leading to poor performance of PSCs. In this review, we have provided a comprehensive picture of the recent progress and challenges of different SnO2 ETL deposition techniques and the performance of PSC devices. The additional modifications on SnO2 mentioned in this article are also effective ways to eliminate the intrinsic defects in the film. The drawbacks and benefits of SnO2 ETLs and the corresponding actions for this are also discussed. We hope this review will help with the comprehensive understanding of the relationship between the property of SnO2 and its structure of ETLs to enhance PSCs' performance.

Pt Atom on the Wall of Atomic Layer Deposition (ALD)-Made MoS2 Nanotubes for Efficient Hydrogen Evolution.

Abstract: Single-atom catalysts (SACs) can achieve excellent catalytic efficiency at ultralow catalyst consumptions. Herein, platinum (Pt) atoms are fixed on the wall of atomic layer deposition (ALD)-made molybdenum disulfide nanotube arrays (MoS2 -NTA) for efficient hydrogen evolution reaction (HER). More concretely, MoS2 -NTA with different nanotube diameters and wall thicknesses are fabricated by a sacrificial strategy of anodic aluminum oxide (AAO) template via ALD; then Pt atoms are fixed on the wall of Ti3 C2 -supported MoS2 -NTA as a catalytic system. The MoS2 -NTA/Ti3 C2 decorated with 0.13 wt.% of Pt results in a low overpotential of 32 mV to deliver a current density of 10 mA cm-2 , which is superior to 20 wt.% commercial Pt/C (41 mV). Ordered MoS2 -NTA instead of 2D MoS2 prevents Pt atoms from aggregating and then exerts catalytic activities. The density functional theory calculations suggest that the Pt atoms are more likely to occupy the sites on the tubular MoS2 than the planar MoS2 , and the Pt atoms accumulated at the Mo site of MoS2 -NT have a moderate Gibbs free energy (close to zero).

Atomic/Molecular Layer Deposition for Designer's Functional Metal–Organic Materials

Abstract: Atomic layer deposition (ALD) for high‐quality conformal inorganic thin films is one of the cornerstones of modern microelectronics, while molecular layer deposition (MLD) is its less‐exploited counterpart for purely organic thin films. Currently, the hybrid of these two techniques, i.e., ALD/MLD, is strongly emerging as a state‐of‐the‐art gas‐phase route for designer's metal–organic thin films, e.g., for the next‐generation energy technologies. The ALD/MLD literature comprises nearly 300 original journal papers covering most of the alkali and alkaline earth metals, 3d transition metals, and lanthanides as the metal component and a variety of aliphatic, aromatic, and natural organic components. Some of these ALD/MLD processes yield in situ crystalline coordination‐polymer‐ or metal–organic‐framework‐like structures. Another attractive aspect is that many of the metal–organics realized through ALD/MLD are fundamentally new materials, and even unaccessible through conventional synthesis. Here, the current state of research in the field is presented, by i) providing a comprehensive account of the ALD/MLD processes so far developed, ii) addressing the constraints/possibilities for growing in situ crystalline metal–organic films, iii) highlighting some intriguing ALD/MLD materials and their application potential, and iv) making a brief outlook to the future perspectives and challenges in the field.

MOSFETs on (110) C–H Diamond: ALD Al₂O₃/Diamond Interface Analysis and High Performance Normally-OFF Operation Realization

Abstract: Hole concentration of 2-D hole gas (2DHG) on (110) diamond is higher than that on other faces, making it the best choice for power device application. Detailed analysis of atomic layer deposition (ALD) Al₂O₃/(110) C–H diamond interface structure is of vital importance. MOSFETs with thin (10 nm) and thick (100 nm) ALD Al₂O₃ layer were made in this study. The microstructure of Al₂O₃ on (110) C–H diamond was analyzed. Abrupt interface of ALD Al₂O₃/C–H diamond was observed through high resolution transmission electron microscope (HRTEM). Cascode structure using diamond MOSFETs and enhancement mode silicon MOSFET is fabricated and its high performance is confirmed.

Scalable Van der Waals Encapsulation by Inorganic Molecular Crystals

Abstract: Encapsulation is critical for devices to guarantee their stability and reliability. It becomes an even more essential requirement for devices based on 2D materials with atomic thinness and far inferior stability compared to their bulk counterparts. Here a general van der Waals (vdW) encapsulation method for 2D materials using Sb2 O3 layer of inorganic molecular crystal fabricated via thermal evaporation deposition is reported. It is demonstrated that such a scalable encapsulation method not only maintains the intrinsic properties of typical air-susceptible 2D materials due to their vdW interactions but also remarkably improves their environmental stability. Specifically, the encapsulated black phosphorus (BP) exhibits greatly enhanced structural stability of over 80 days and more sustaining-electrical properties of 19 days, while the bare BP undergoes degradation within hours. Moreover, the encapsulation layer can be facilely removed by sublimation in vacuum without damaging the underlying materials. This scalable encapsulation method shows a promising pathway to effectively enhance the environmental stability of 2D materials, which may further boost their practical application in novel (opto)electronic devices.

Atomic and Molecular Layer Deposition of Chiral Thin Films Showing up to 99% Spin Selective Transport.

Abstract: Spin electronics is delivering a much desired combination of properties such as high speed, low power, and high device densities for the next generation of memory devices. Utilizing chiral-induced spin selectivity (CISS) effect is a promising path toward efficient and simple spintronic devices. To be compatible with state-of-the-art integrated circuits manufacturing methodologies, vapor phase methodologies for deposition of spin filtering layers are needed. Here, we present vapor phase deposition of hybrid organic-inorganic thin films with embedded chirality. The deposition scheme relies on a combination of atomic and molecular layer deposition (A/MLD) utilizing enantiomeric pure alaninol molecular precursors combined with trimethyl aluminum (TMA) and water. The A/MLD deposition method deliver highly conformal thin films allowing the fabrication of several types of nanometric scale spintronic devices. The devices showed high spin polarization (close to 100%) for 5 nm thick spin filter layer deposited by A/MLD. The procedure is compatible with common device processing methodologies.

A review of atomic layer deposition modelling and simulation methodologies: Density functional theory and molecular dynamics

Abstract: Abstract The use of computational modelling and simulation methodologies has grown in recent years as researchers try to understand the atomic layer deposition (ALD) process and create new microstructures and nanostructures. This review article explains and simplifies two simulation methodologies, molecular dynamics and the density functional theory (DFT), in solving atomic layer deposition problems computationally. We believe that these simulation methodologies are powerful tools that can be utilised in atomic layer deposition. DFT is used to solve problems in surface science and catalysis (predicting surface energy, adsorption energy, charge transfer, etc.), semiconductors (band structure, defect bands, band gap, etc.), superconductors (electron–phonon coupling, critical transition temperature), and molecular electronics (conductance, current–voltage characteristics). Molecular dynamics (MD) is used to predict the kinetic and thermodynamic properties of a material. Of interest in this article is a review where different material problems emanating from atomic layer deposition from these fields have been addressed by DFT and MD. Selected publications are discussed where DFT and MD have been successfully applied in atomic layer deposition (and related processes in some instances). The applications of DFT stretch from binding energy calculations of molecules and the solid band structure in chemistry and physics, respectively, computing the electron density up to determining the properties of a many-electron system. Also highlighted in this review study are the challenges that DFT and MD simulations must overcome.