The success of Graphene has triggered the research interest in other stable, single and few-atom-thick layers of van der Waals materials, which can possess attractive and technologically useful ...properties. Other complex structures, such as boron nitride, MXenes and metal chalcogenides have been successfully synthesized as layered materials showing advanced properties.
Here, after an introduction briefing novel 2D materials, we focus on 2D AlN and present a review covering theoretical considerations on the stability of an infinite hexagonal AlN (h-AlN) sheet, differences that occur in the electronic structure between bulk AlN and single layer and discuss possible methods of tuning their electronic and magnetic properties by manipulating the surface and strain using DFT (density functional theory) computations. We address potential applications of 2D-AlN with an emphasis on gas sensing for CO2, CO, H2, O2, NO and NO2 in the presence of NH3.
Further, we discuss some growth strategies of AlN single layer and few layers on different substrates. 2D AlN layers and nanotubes with ultrawide bandgap (9.20–9.60 eV) which shows a great potential to support innovative and front-end development of deep-ultraviolet optoelectronic devices are illustrated.
•DFT (density functional theory) computations on the stability of 2D-AlN.•DFT analysis of optical properties of 2D-AlN.•DFT computations of electronic and magnetic properties of 2D-AlN.•DFT analysis for potential applications of 2D-AlN on gas sensing.•Growth strategies of 2D-AlN.
Understanding the interaction between noble metals (NMs) and epitaxial graphene is essential for the design and fabrication of novel devices. Within this framework, a combined experimental and ...theoretical investigation of the effect of vapor‐deposited NM (silver Ag and gold Au) nanostructures on the vibrational and electronic properties of monolayer epitaxial graphene (MLG) on 4H‐SiC is presented. Large sets of Raman scattering data are analyzed using supervised classification and statistical methods. This analysis enables identification of the specific Raman fingerprints of Au‐ and Ag‐decorated MLG originating from different dispersion interactions and charge transfer at the metal nanostructure/MLG interface. It is found that Raman scattering spectra of Au‐decorated MLG feature a set of allowed phonon modes similar to those in pristine MLG, whereas the stronger Ag physisorption triggers an activation of defect‐related phonon modes and electron doping of MLG. A principal component analysis (PCA) and linear discriminant analysis (LDA) are leveraged to highlight the features in phonon dispersion of MLG that emanate from the NM deposition process and to robustly classify large‐scale Raman spectra of metal‐decorated graphene. The present results can be advantageous for designing highly selective sensor arrays on MLG patches decorated with different metals.
A comparative study on the interaction between noble metals (NMs) and epitaxial graphene is presented. Combined Raman studies, DFT calculations, and supervised classification methods provide better understanding on the nature of NMs effect on phonon dispersion of graphene. A robust model to classify Raman data of metal‐decorated epitaxial graphene is developed based on principal component analysis and linear discrimination analysis.
Atomic Layer Deposition of AlN on Graphene Beshkova, Milena; Deminskyi, Petro; Hsu, Chih‐Wei ...
Physica status solidi. A, Applications and materials science,
September 2021, Letnik:
218, Številka:
17
Journal Article
Recenzirano
Odprti dostop
Graphene is a material with great promise for several applications within electronics. However, using graphene in any such application requires its integration in a stack of thin layers of materials. ...The ideal structure of graphene has a fully saturated surface without any binding sites for chemisorption of growth species, making film growth on graphene highly challenging. Herein, an attempt to deposit very thin layers of AlN using an atomic layer deposition approach is reported. It is demonstrated using X‐ray photoelectron spectroscopy that Al–N are formed in the films deposited on graphene and shown by scanning electron microscopy and atomic force microscopy that the films have an island morphology. These results may be considered promising toward the development of a growth protocol for AlN on graphene and possibly also for 2D AlN fabrication.
A comparative study on elemental surface composition (X‐ray photoelectron spectroscopy (XPS)) and surface morphology (scanning electron microscopy (SEM)) of AlN thin layers using atomic layer deposition (ALD) approach on graphene and on the 4H‐SiC substrate is presented. XPS and SEM show that deposition on graphene results in a lower surface coverage, highlighting the challenge for growth of 2D AlN.
3C-SiC layers have been grown by using sublimation epitaxy at a source temperature of 2000 °C, under vacuum conditions (<10−5 mbar) on well oriented (on-axis) 6H-SiC (0001) substrates. Close space ...sublimation growth geometry has been used in a RF-heated furnace employing high-purity graphite crucible with a possibility to change the growth environment from Si vapor-rich to C vapor-rich. The optical microscopy in transmission mode reveals continuous 3C-domains for 3C-SiC with less than 0.4% 6H-inclusions for the layer grown at Si-rich conditions, and separate 3C-SiC domains for the layer grown at C-rich conditions. The type of 6H-inclusions for layers with continuous domain structure investigated by Atomic Force Microscopy (AFM) is discussed. 2Theta-omega scan shows 0006 and 111 peaks coming from the substrate and the layer, respectively with a higher intensity of the 111 peak for 3C-SiC grown at Si-rich conditions which is related with the continuous character of the 3C-SiC domains.
► Sublimation epitaxy of 3C-SiC grown at Si- and C-rich conditions. ► Continuous 3C-SiC domains for the layer grown at Si-rich conditions. ► Hill and pit nature of 6H-SiC inclusions investigated by AFM. ► Higher intensity of the 3C-SiC 111 peak for 3C-SiC grown at Si-rich conditions.
Thin films of cerium dioxide were deposited on silicon (100) substrates using e‐beam evaporation. The influence of different technological parameters, such as the substrate temperature, the oxygen ...pressure and the beam power on the crystallographic orientation of the films was explored. By optimizing these parameters, CeO2 thin films with a strongly preferred (200) orientation could be deposited on Si(100) substrates.
XRD patterns of the CeO2 thin films deposited at various temperatures.
Abstract
Summary:
Thin films of cerium dioxide were deposited on silicon (100) substrates using e‐beam evaporation. The influence of different technological parameters, such as the substrate ...temperature, the oxygen pressure and the beam power on the crystallographic orientation of the films was explored. By optimizing these parameters, CeO
2
thin films with a strongly preferred (200) orientation could be deposited on Si(100) substrates.
XRD patterns of the CeO
2
thin films deposited at various temperatures.
image
XRD patterns of the CeO
2
thin films deposited at various temperatures.
Epitaxial layers of aluminum nitride less than or equal to335 mum thick have been grown attemperatures of 1900 and 2100degreesC on 10 x 10 mm(2) (0001)-oriented alpha(4H) silicon carbide (SiC), with ...growth times of 1 and 4h, via sublimation-recondensation in a RF-heated graphite furnace. The source material was polycrystalline AIN. The sublimation process was performed in three types of graphite (C) crucible: C-1, C-2 with inner diameters of 35 and 51 mm, respectively, and C-3 with the same inner diameter as C-1, but coated with a layer of TaC. The surface morphology reflects the hexagonal symmetry of the substrate, suggesting an epitaxial growth for samples grown in C-1 and C-3 crucibles for all growth conditions. The same symmetry is observed for AIN layers grown in the C-2 crucible, but only at 2100degreesC. X-ray diffraction analyses confirm the epitaxial growth of AIN samples with the expected hexagonal symmetry. A high-resolution X-ray diffractometer was used to assess the quality of the single crystals. A full width at half maximum of 242 arcsec was achieved for an AIN layer grown in the crucible coated with TaC. (C) 2003 Kluwer Academic Publishers.
Epitaxial layers of aluminum nitride have been grown at temperatures 1900–2400°C on 10×10mm2 4H–SiC substrate via sublimation recondensation in an RF heated graphite furnace. The source material was ...polycrystalline sintered AlN. A maximum growth rate of about 100μm/h was achieved at 2400°C and seed to source distance of 1mm.
The surface morphology reflects the hexagonal symmetry of the seed suggesting an epitaxial growth. This was confirmed by X-ray diffraction (XRD). The spectra showed very strong and well-defined (0002) reflection position at around 36.04° in symmetric Θ–2Θscans for all samples. Micro-Raman spectroscopy reveals that the films have a wurtzite structure. It is evidenced by the appearance of the A1 (TO) (at 601cm−1) and E2(2) (at 651cm−1) lines in the spectra.
Secondary-ion mass spectroscopy (SIMS) results showed a low concentration of carbon incorporation in the AlN films.
A correlation between the growth conditions and properties of the AlN layers was established.
PDF
