Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userTextured organic ferroelectric films from physical vapor deposition and amorphous-to-crystalline transition
100
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Crystallization is a key for ferroelectricity which is a collective behavior of microscopic electric dipoles. On the other hand, uncontrolled crystallization leads to uneven morphology and random crystal orientations, which undermines the application potential of ferroelectric thin films. In this work, we introduce a film fabrication method of low-temperature physical vapor deposition followed by restrained crystallization, with electrical properties monitored in real-time by in situ measurements. This method was adopted to fabricate films of 2-methylbenzimidazole (MBI), whose molecule crystals are proton-transfer type biaxial ferroelectrics and tend to grow into a hedgehog-shaped spherulites morphology. The in situ measurements confirm that the crystallization, corresponding to a clear transition of physical properties, occurs dominantly during post-deposition warming. This enables the fabrication of micron-thick films in disk-shaped morphology with one polarization axis aligned along the out-of-plane direction, while the measured spontaneous polarization and coercive field are comparable to the single-crystal values. These results mark an important advancement of film growth that is expected to benefit widely the fabrication of molecular materials films whose functional properties hinge on crystallization to achieve desirable morphology and crystallinity.
rate research
Read More
We report on the production of nanodiamonds (NDs) with 70-80 nm size via bead assisted sonic disintegration (BASD) of a polycrystalline chemical vapor deposition (CVD) film. The NDs display high crystalline quality as well as intense narrowband (7 nm) room temperature luminescence at 738 nm due to in situ incorporated silicon vacancy (SiV) centers. The fluorescence properties at room and cryogenic temperatures indicate that the NDs are, depending on preparation, applicable as single photon sources or as fluorescence labels.
Recently, monolayer SnS, a two-dimensional group IV monochalcogenide, was grown on a mica substrate at the micrometer-size scale by the simple physical vapor deposition (PVD), resulting in the successful demonstration of its in-plane room temperature ferroelectricity. However, the reason behind the monolayer growth remains unclear because it had been considered that the SnS growth inevitably results in a multilayer thickness due to the strong interlayer interaction arising from lone pair electrons. Here, we investigate the PVD growth of monolayer SnS from two different feed powders, highly purified SnS and commercial phase-impure SnS. Contrary to expectations, it is suggested that the mica substrate surface is modified by sulfur evaporated from the Sn2S3 contaminant in the as-purchased powder and the lateral growth of monolayer SnS is facilitated due to the enhanced surface diffusion of SnS precursor molecules, unlike the growth from the highly purified powder. This insight provides a guide to identify further controllable growth conditions.
Two-dimensional (2D) transition metal dichalcogenides (TMDs), especially MoS2 and WS2 recently attract extensive attentions due to their rich physics and great potential applications. Superior to graphene, MS2 (M = Mo/W) monolayers have a native direct energy gap in visible frequency range. This promises great future of MS2 for optoelectronics. To exploit properties and further develop more applications, producing large-scale single crystals of MS2 by a facile method is highly demanded. Here, we report the synthesis of large-scale triangular single crystals of WS2 monolayer from a chemical vapor deposition process and systematic optical studies of such WS2 monolayers. The observations of high yield of light emission and valley-selective circular dichroism experimentally evidence the high optical quality of the WS2 monolayers. This work paves the road to fabricate large-scale single crystalline 2D semiconductors and study their fundamentals. It must be very meaningful for exploiting great potentials of WS2 for future optoelectronics.
Transition metal dichalcogenides (TMDs) have recently attracted attention due to their interesting electronic and optical properties. Fabrication of these materials in a reliable and facile method is important for future applications, as are methods to characterize material quality. Here we present the chemical vapor deposition of MoSe2 monolayer and few layer crystals. These results show the practicality of using chemical vapor deposition to reliably fabricate these materials. Low frequency Raman spectra and mapping of shear and layer breathing modes of MoSe2 are presented for the first time. We correlate the behavior of these modes with layer number in the materials. The usefulness of low frequency Raman mapping to probe the symmetry, quality, and monolayer presence in CVD grown 2D materials is emphasized.
A Kinetic Monte Carlo model that simulates the growth of thin films under conditions typically encountered in plasma enhanced chemical vapor deposition experiments is presented. The model is intended to reproduce the growth of two different types of materials (amorphous nanocolumnar and anisotropic-polycrystalline) in a coarse-grained fashion. In order to show the advantages and limitations of the model, the microstructure, texture, and scaling properties of TiO2 and ZnO thin-film growth are obtained under several growth conditions and compared with available experimental data obtained by X-Ray Diffraction, analysis of texture coefficients, Atomic Force Microscopy and Scanning Electron Microscopy.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
