Control Of Crystal Orientation Research Articles

A Review of the Fabrication of Pinhole-Free Thin Films Based on Electrodeposition Technology: Theory, Methods and Progress

Pinhole defects in thin films can significantly degrade their physical and chemical properties and act as sites for electrochemical corrosion. Therefore, the development of methods for the preparation of pinhole-free films is crucial. Electrodeposition, recognised for its efficiency and cost-effectiveness, shows great potential for applications in electrochemistry, biosensors, solar cells and electronic device fabrication. This review aims to elucidate the role of nucleation and growth models in understanding and optimising the electrodeposition process. Key parameters, such as crystal structure, orientation, surface morphology and defect control, are highlighted. In addition, the causes of pinhole defects, the effects of impurities and the potential and electrolyte composition on the deposited films are discussed. In particular, methods for minimising pinhole defects and two exemplary cases for a compact layer in relatively large-scale perovskite solar cells and nano-scale ultramicroelectrodes are discussed, exploring the influence of surface morphology, thickness and fabrication size under current common film preparation experiments. Finally, the critical aspects of controlled preparation, theoretical and technological advances, and the ongoing challenges in the field are provided.

Enhancing Photoelectrocatalytic Efficiency of BiVO4 Photoanodes by Crystal Orientation Control

Enhancing Photoelectrocatalytic Efficiency of BiVO4 Photoanodes by Crystal Orientation Control

Crystal orientation control in angstrom-scale channel membranes for significantly enhanced blue energy harvesting

Achieving high-performance blue energy harvesting from the interface between seawater and river water remains challenging, because the current ion-selective membrane suffers from a trade-off between ion permeability and selectivity. Here, we tackle this issue by manipulating the crystal orientations within metal–organic framework (MOF) MIL-178 membranes, including one with the a-axis perpendicular to the substrate, and the other with the b-axis similarly configured. We show that the MIL-178-a-oriented membrane exhibited over one order of magnitude faster ion transport than the MIL-178-b-oriented membrane, and one-dimensional angstrom-scale (∼3.2 Å) channels endow the former with ultrahigh ion selectivity. Consequently, the MIL-178-a-oriented membrane achieves an ultrahigh power density of ∼9.64 W/m2, with an unprecedented energy conversion efficiency of ∼38.5 % approaching the theoretical upper limit of 50 %, when simulated seawater and river water are mixed, surpassing all the reported non-oriented MOF-based membranes. This study presents a method for finely tuning preferred orientations within polycrystalline MOF membranes, enabling precise engineering of ultrahigh-performance osmotic energy conversion.

Magnetic Switching of Second-Harmonic Generation from Single Cerium-Based Coordination Polymer Microcrystals.

Conventional access and modulation of second-harmonic generation (SHG) require precise control of crystal orientation, which faces great mechanical challenges in the case of micro/nanocrystals. Here, we demonstrate the magnetic-field-tunable SHG performance of lanthanide coordination polymer (Ce-BTC CP) microcrystals through field-aligned orientations. The coordination of Ce ions and organic ligands constructs a noncentrosymmetric structure, which not only contributes to a favorable powder SHG efficiency 3.2 times larger than that of the benchmark KH2PO4 (KDP) but also endows the microcrystals with strong magnetic anisotropy. The SHG efficiency (∼0 to 10 × KDP) depends on the orientation of the crystallographic c-axis, whereas magnetic anisotropy always aligns the c-axis with the magnetic field at a specific angle. Accordingly, the SHG can be magnetically switched by field-induced alignments. The adsorption of dyes by Ce-BTC CPs further facilitates the magnetic switching of multicolor fluorescence that can be excited by the SHG. Our work provides a new pathway for achieving SHG modulation at the microscopic level.

Research on the epitaxial direction control and mechanism of polycrystalline diamond grains

The control of diamond film growth is crucial for the application of diamond films. In this article, different diamond film samples were prepared by adding nitrogen and oxygen in different proportions during the growth process. The key conditions for controlling the growth of diamond film with preferred orientation were obtained using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy characterizations. During the growth process, the growth of the diamond film with (100) preferred orientation could be achieved by adjusting nitrogen content. It was necessary to introduce nitrogen and oxygen in the growth process, and precisely regulate the ratio of the two to obtain the (111) preferred orientation of the diamond film. When only oxygen was introduced during growth, the preferred orientation of the diamond could not be achieved, leading to a smaller grain size and poorer crystal quality. From the perspective of grain morphology to film morphology evolution, this study obtained the crystal orientation control conditions during the diamond film growth, which has important guiding significance for the application of the diamond film. This study seeks to drive progress in the large-scale growth of readily machinable diamond and the evolution of diamond-grain optical fiber sensing through comprehensive investigations into the correlation between the preferred orientation in polycrystalline diamonds and reaction conditions.

Improvement of Adhesion and Wettability at PEEK-Resin/TiO<sub>2</sub> Interface by Use of Crystal-Orientation Control

Improvement of Adhesion and Wettability at PEEK-Resin/TiO<sub>2</sub> Interface by Use of Crystal-Orientation Control

Oriented Growth for Efficient and Scalable Perovskite Solar Cells by Vapor–Solid Reaction

AbstractThe precise control and understanding of crystal orientation in perovskite polycrystalline films are crucial for the development of efficient and stable devices. However, achieving this control remains a significant challenge. Herein, a PbI2 oriented growth strategy is developed, combined with in situ vapor–solid reaction transformations, to achieve oriented growth of full‐vacuum perovskite films. Grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) analysis revealed the general pattern of PbI2 oriented vapor growth and in situ vapor–solid reaction transformation in this two‐step process. The resulting preferred orientation has effectively reduced trap state density, optimizing the carrier dynamics. As a result, champion efficiencies of 22.11% (0.148 cm2), 20.60% (1 cm2), and 19.41% (5 × 5 cm2 mini‐modules) are achieved, which are the highest value for perovskite based on vapor–solid reaction. Additionally, the oriented growth method is applicable to a variety of guide layers and is extended to 30 × 30 cm2 film, demonstrating the universality and scalability of the method.

Crystal orientation control of HFCVD diamond spherical film tools and tribological behavior on steel

(111)-oriented micron-crystalline diamond (111MCD), (110)-oriented micron-crystalline diamond (110MCD) and (110)-oriented nano-crystalline diamond (110NCD) spherical films were prepared on the surface of spherical WC-Co polishing tools by hot filament chemical vapor deposition technology. The microstructure, molecular structure, crystal orientation and surface roughness of spherical films were characterized by SEM, XRD, EBSD and White-light interferometer. The friction performance and material removal mechanisms were studied by friction experiments on steel. The results showed that both crystal orientation and grain size variation significantly influenced the tool properties. The roughness and friction coefficient of 111MCD, 110MCD, and 110NCD films decreased successively. During the friction process, the transformation of diamond to graphite reduced the friction coefficient but accelerated film delamination. 111MCD has the fastest material removal rate, but the graphitization rate and wear rate of the film are the highest, and there are a lot of abrasive chips in the friction interface. Diamond of (110) orientation can improve the wear resistance of the film and reduce the abrasive wear of the workpiece. Compared to 111MCD, 110NCD exhibited a 29.3 % reduction in friction coefficient, a 90 % improvement in wear resistance, a 49.4 % increase in surface smoothness of the processed workpiece, and the highest ID/IG value of 1.45 after film wear, demonstrating superior polishing performance and anti-graphitization properties. These results indicate that 110NCD tool is a highly efficient polishing tool with great potential.

Recent Advances and Prospects of Solution‐Processed Efficient Sb2S3 Solar Cells

AbstractSolar cells comprising earth‐abundant and non‐toxic elements with applicable bandgaps and high absorption coefficients have attracted considerable interest over the past several decades and are important devices for addressing the future demand for clean and renewable energy. Antimony sulfide (Sb2S3) crystal material effectively meets these requirements owing to its suitable bandgap, high absorption coefficient, high electron and hole mobilities, earth abundance, and excellent stability. Solution‐processed Sb2S3 films are essential to facilitate the fabrication of low‐cost, large‐scale, and high‐efficiency photovoltaic devices, but suffer from several shortcomings of large intrinsic defects, high interfacial barrier, and atomic mismatch, uncontrollable film thickness, and crystal orientation. In this review, a systematic overview of the fundamental properties of solution‐processed Sb2S3 materials is presented, and then interface engineering, defect passivation and control strategies, crystal orientation and modulation methods, device structure, and the performance of Sb2S3 solar cells are focused, highlighting the primary advancements and major challenges based on this technology. Finally, several creative perspectives and constructive innovation strategies for future research on Sb2S3 photovoltaic devices are provided, indicating a roadmap for the practical application of other inorganic semiconductor heterojunction thin film solar cells.

ZnO thin films with controllable morphologies and crystal orientation fabricated by the mist spin spray method

ZnO thin films with controllable morphologies and crystal orientation fabricated by the mist spin spray method

Vacuum Deposited Perovskites with a Controllable Crystal Orientation.

The preferential orientation of the perovskite (PVK) is typically accomplished by manipulation of the mixed cation/halide composition of the solution used for wet processing. However, for PVKs grown by thermal evaporation, this has been rarely addressed. It is unclear how variation in crystal orientation affects the optoelectronic properties of thermally evaporated films, including the charge carrier mobility, lifetime, and trap densities. In this study, we use different intermediate annealing temperatures Tinter between two sequential evaporation cycles to control the Cs0.15FA0.85PbI2.85Br0.15 orientation of the final PVK layer. XRD and 2D-XRD measurements reveal that when using no intermediate annealing primarily the (110) orientation is obtained, while when using Tinter = 100 °C a nearly isotropic orientation is found. Most interestingly for Tinter > 130 °C a highly oriented PVK (100) is formed. We found that although bulk electronic properties like photoconductivity are independent of the preferential orientation, surface related properties differ substantially. The highly oriented PVK (100) exhibits improved photoluminescence in terms of yield and lifetime. In addition, high spatial resolution mappings of the contact potential difference (CPD) as measured by KPFM for the highly oriented PVK show a more homogeneous surface potential distribution than those of the nonoriented PVK. These observations suggest that a highly oriented growth of thermally evaporated PVK is preferred to improve the charge extraction at the device level.

Surface-Controlled CdS/Ti3C2 MXene Schottky Junction for Highly Selective and Active Photocatalytic Dehydrogenation-Reductive Amination​.

Photocatalytic valorization and selective transformation of biomass-derived platform compounds offer great opportunities for efficient utilization of renewable resources under mild conditions. Here, the novel three-dimensional hierarchical flower-like CdS/Ti3C2 Schottky junction (MCdS) composed of surface-controlled CdS and pretreated Ti3C2 MXene is created for photocatalytic dehydrogenation-reductive amination of biomass-derived amino acid production under ambient temperature with unprecedented activity and selectivity. Schottky junction efficiently promotes photoexcited charge migration and separation and inhibits photogenerated electron-hole recombination, which results in a super-high activity. Meanwhile, CdS with the reduced surface energy supplies sufficient hydrogen sources for imine reduction and induces the preferential orientation of alanine, thus contributing superior selectivity. Moreover, a wide range of hydroxyl acids are successfully converted into corresponding amino acids and even one-pot conversion of glucose to alanine is easily achieved over MCdS. This work illustrates the mechanism of crystal orientation control and heterojunction construction in controlling catalytic behavior of photocatalytic nanoreactor, providing a paradigm for construction of MXene-based heterostructure.

Surface‐Controlled CdS/Ti3C2 MXene Schottky Junction for Highly Selective and Active Photocatalytic Dehydrogenation‐Reductive Amination

AbstractPhotocatalytic valorization and selective transformation of biomass‐derived platform compounds offer great opportunities for efficient utilization of renewable resources under mild conditions. Here, the novel three‐dimensional hierarchical flower‐like CdS/Ti3C2 Schottky junction (MCdS) composed of surface‐controlled CdS and pretreated Ti3C2 MXene is created for photocatalytic dehydrogenation‐reductive amination of biomass‐derived amino acid production under ambient temperature with unprecedented activity and selectivity. Schottky junction efficiently promotes photoexcited charge migration and separation and inhibits photogenerated electron‐hole recombination, which results in a super‐high activity. Meanwhile, CdS with the reduced surface energy supplies sufficient hydrogen sources for imine reduction and induces the preferential orientation of alanine, thus contributing superior selectivity. Moreover, a wide range of hydroxyl acids are successfully converted into corresponding amino acids and even one‐pot conversion of glucose to alanine is easily achieved over MCdS. This work illustrates the mechanism of crystal orientation control and heterojunction construction in controlling catalytic behavior of photocatalytic nanoreactor, providing a paradigm for construction of MXene‐based heterostructure.

Room temperature-grown highly oriented p-type nanocrystalline tellurium thin-films transistors for large-scale CMOS circuits

Although facile fabrication of high-performance thin-film transistor (TFT)-based complementary metal oxide–semiconductor (CMOS) circuits over a large area has generated significant interest, the lack of reliable and uniform p-type TFTs is hindering it. In this study, we prepared high-performance CMOS circuits using room temperature deposited nanocrystalline tellurium (nc-Te) and sputtered amorphous-indium gallium zinc oxide (a-IGZO) TFTs. The facile polyethyleneimine (PEI) surface treatment enabled Te atom anchoring and crystal orientation control along with continuous surface coverage, resulting in a high-performance TFT with an average mobility of 21.1 cm2V−1s−1 and an Ion/Ioff ratio of 104. By introducing monolithic integration of nc-Te and a-IGZO TFTs, various CMOS circuits including inverter, NAND, and NOR circuits were fabricated and operated quite logically. Moreover, seven-stage ring oscillators comprising 14 cross-wired TFTs validated the cascading of multiple stages and device uniformity of the complementary system, achieving an oscillation frequency up to 392.16 kHz at VDD of 20 V. nc-Te on a PEI-treated surface offers a general route to producing high-performance and stable p-type semiconductors while ensuring compatibility with standard CMOS processing and large-scale on-chip device applications.

Highly piezoelectric, biodegradable, and flexible amino acid nanofibers for medical applications.

Amino acid crystals are an attractive piezoelectric material as they have an ultrahigh piezoelectric coefficient and have an appealing safety profile for medical implant applications. Unfortunately, solvent-cast films made from glycine crystals are brittle, quickly dissolve in body fluid, and lack crystal orientation control, reducing the overall piezoelectric effect. Here, we present a material processing strategy to create biodegradable, flexible, and piezoelectric nanofibers of glycine crystals embedded inside polycaprolactone (PCL). The glycine-PCL nanofiber film exhibits stable piezoelectric performance with a high ultrasound output of 334 kPa [under 0.15 voltage root-mean-square (Vrms)], which outperforms the state-of-the-art biodegradable transducers. We use this material to fabricate a biodegradable ultrasound transducer for facilitating the delivery of chemotherapeutic drug to the brain. The device remarkably enhances the animal survival time (twofold) in mice-bearing orthotopic glioblastoma models. The piezoelectric glycine-PCL presented here could offer an excellent platform not only for glioblastoma therapy but also for developing medical implantation fields.

In Situ Observing and Tuning the Crystal Orientation of Two-Dimensional Layered Perovskite via the Chlorine Additive.

Precise control of crystal orientation in two-dimensional (2D) layered perovskites (LPs) is vital for their optoelectronic applications due to the structure-induced anisotropy in optical and electrical properties. Herein, we directly observe and control the crystal orientation of the butylammonium-based 2D LP films. Employing the synchrotron-based in situ grazing-incidence X-ray diffraction technique, we reveal the orientation modulation mechanism of the Cl additive by following the crystallization dynamics and chemical conversion pathways during film formation. Two new Cl-related intermediates are identified which serve as templates directing the orientational growth of the 2D LP films. We fine-tune the crystal orientation of 2D LP films through the Cl additive and incorporate the films with the requisite crystal orientations in solar cells and photodetectors. The optoelectronic performances of the devices show a strong correlation with the crystal orientation of the 2D LP films.

Interfacial Engineering towards Enhanced Photovoltaic Performance of Sb2Se3 Solar Cell

AbstractAntimony selenide (Sb2Se3) is a kind of emerging candidate for the application in low‐cost and high‐efficiency thin film solar cells owing to its non‐toxicity, earth‐abundance, and unique quasi‐1D crystal structure. In this photovoltaic material, quasi‐vertically oriented Sb2Se3 thin films can transfer photocarriers efficiently along the [hk1]‐orientation. However, the crystal orientation control in thin films is still the main obstacle to improve the efficiency of Sb2Se3 solar cells. Herein, an interfacial engineering method is developed by antimony chloride (SbCl3) on CdS films with post‐annealing treatment to improve the quality of both interface and absorber thin film. It is found that the SbCl3 treatment resulted in 1) transformation of the CdS/Sb2Se3 interface from “cliff” to “spike” like energy band alignments; 2) improved surface morphology of CdS surface, and 3) suppressed cubic structure of CdS structure and thus generating improved [hk1]‐oriented Sb2Se3 film on the high‐purity hexagonal CdS. As a result, the Sb2Se3 solar cell treated with SbCl3 achieves a top efficiency of 6.89% in superstrate planar heterojunction Sb2Se3 solar cell. This study provides a new interfacial post‐treatment method for the preparation of high‐performance Sb2Se3 planar heterojunction solar cells.

Slip-Line-Guided Growth of Graphene.

Manipulating the crystal orientation of emerging 2D materials via chemical vapor deposition (CVD) is a key premise for obtaining single-crystalline films and designing specific grain-boundary (GB) structures. Herein, the controllable crystal orientation of graphene during the CVD process is demonstrated on a single-crystal metal surface with preexisting atomic-scale stair steps resulting from dislocation slip lines. The slip-line-guided growth principle is established to explain and predict the crystal orientation distribution of graphene on a variety of metal facets, especially for the multidirectional growth cases on Cu(hk0) and Cu(hkl) substrates. Not only large-area single-crystal graphene, but also bicrystal graphene with controllable GB misorientations, are successfully synthesized by rationally employing tailored metal substrate facets. As a demonstration, bicrystal graphenes with misorientations of ≈21° and ≈11° are constructed on Cu(410) and Cu(430) foils, respectively. This guideline builds a bridge linking the crystal orientation of graphene and the substrate facet, thereby opening a new avenue for constructing bicrystals with the desired GB structures or manipulating 2D superlattice twist angles in a bottom-up manner.

Research progress on microstructure and property regulation of ultra-high temperature oxide eutectic ceramics by high gradient directional solidification technology

With the rapid development of aerospace and other high-tech fields, a new generation of high perfor-mance, high efficiency ultrahigh temperature structural materials and their preparation technologies increasingly becomes the focus of the development of aerospace strategy in the world. Ultrahigh temperature alumina based eutectic ceramics have excellent intrinsic oxidation resistance, corrosion resistance, creep resistance, high strength and other excellent properties. Therefore, they have outstanding advantages and great development prospect in extreme environment such as ultrahigh temperature above 1 400℃, water and oxygen corrosion circumstances. In this paper, the current development status has been firstly introduced for the ultrahigh temperature oxide eutectic ceramics prepared by high gradient directional solidification technologies. Then, the formation mechanism and control method of the defects during the high gradient directional solidification process of the alumina based ultrahigh temperature eutectic ceramics have been summarized. Furthermore, the microstructure characteristics and homogenization control methods, crystal orientation and texture control methods, mechanical properties and strengthening-toughening control methods of oxide eutectic ceramics have been reviewed. Finally, the development trend and breakthrough point have been comprehensively prospected for the preparation of oxide eutectic ceramics with high performance and large size by high gradient directional solidification technologies.

Precise Control of Crystal Orientation of Conjugated Molecule Enables Anisotropic Charge Transport Properties

AbstractThe crystal orientation of small molecules is one of the key parameters for developing high‐performance small molecule based organic field‐effect transistors. However, achieving a high degree of backbone alignment still remains a challenge, due to the sensitive nature of small molecules to processing conditions. Herein, the thin films of three conjugated small molecules, named as ZR1, ZR2‐C3, and Y6 are prepared by epitaxial‐crystallization on a highly oriented polyethylene (PE) substrate, resulting in the significant enhancement in charge transport properties. The maximum mobilities for aligned edge‐on molecules in the films enhance by up to 9.91 × 10−2 and 8.97 × 10−2 cm2 V−1s−1 for ZR1 and ZR2‐C3 films with conducting channel along small molecule backbones, which are 35‐ and 37‐fold that of the values evaluated in perpendicular to molecular backbones and nearly 23‐and 19‐fold beyond the values measured from unaligned films. Furthermore, the electron and hole mobilities of the small molecule Y6 with face‐on nature increase by nearly fourfold the values measured in perpendicular to the backbone direction and from unaligned films. This work demonstrates the epitaxial crystallization of thin films on oriented PE, offers a critical understanding of small molecules with different orientations and an effective approach for tuning charge transport toward high‐performance organic electronic applications.