Abstract:A combined theoretical and experimental study of the assembly of triphenylboroxines on Au(111) reveals the charge delocalization properties of the interface.
“…S3. Absorption transitions from 1s to only σ* anti-bonding states 44,45 are observed instead of the transition from 1s to π* anti-bonding states after the annealing, in agreement with the result of Raman spectra.Figure 4Comparison of NEXAFS ( a ) B K-edge and ( b ) N K-edge spectra of the h-BN films before and after the post-annealing. NEXAFS was measured at X-ray incident angle of 30° for the h-BN films.…”
Remarkable improvements in both structural and optical properties of wafer-scale hexagonal boron nitride (h-BN) films grown by metal-organic chemical vapor deposition (MOCVD) enabled by high-temperature post-growth annealing is presented. The enhanced crystallinity and homogeneity of the MOCVD-grown h-BN films grown at 1050 °C is attributed to the solid-state atomic rearrangement during the thermal annealing at 1600 °C. In addition, the appearance of the photoluminescence by excitonic transitions as well as enlarged optical band gap were observed for the post-annealed h-BN films as direct consequences of the microstructural improvement. The post-growth annealing is a very promising strategy to overcome limited crystallinity of h-BN films grown by typical MOCVD systems while maintaining their advantage of multiple wafer scalability for practical applications towards two-dimensional electronics and optoelectronics.
“…S3. Absorption transitions from 1s to only σ* anti-bonding states 44,45 are observed instead of the transition from 1s to π* anti-bonding states after the annealing, in agreement with the result of Raman spectra.Figure 4Comparison of NEXAFS ( a ) B K-edge and ( b ) N K-edge spectra of the h-BN films before and after the post-annealing. NEXAFS was measured at X-ray incident angle of 30° for the h-BN films.…”
Remarkable improvements in both structural and optical properties of wafer-scale hexagonal boron nitride (h-BN) films grown by metal-organic chemical vapor deposition (MOCVD) enabled by high-temperature post-growth annealing is presented. The enhanced crystallinity and homogeneity of the MOCVD-grown h-BN films grown at 1050 °C is attributed to the solid-state atomic rearrangement during the thermal annealing at 1600 °C. In addition, the appearance of the photoluminescence by excitonic transitions as well as enlarged optical band gap were observed for the post-annealed h-BN films as direct consequences of the microstructural improvement. The post-growth annealing is a very promising strategy to overcome limited crystallinity of h-BN films grown by typical MOCVD systems while maintaining their advantage of multiple wafer scalability for practical applications towards two-dimensional electronics and optoelectronics.
“…S3. Absorption transitions from 1s to only σ* anti-bonding states 44,45 are observed instead of the transition from 1s to π* anti-bonding states after the annealing, in agreement with the result of Raman spectra.…”
In this work, a monochromator (iHR 320, HORIBA) equipped with a diffraction grating of 1800 lines/mm and slit size of 1 × 1 mm 2 and a photomultiplier tube (PMT, Hamamatsu R943-02) were used for the PL measurement. The entrance and exit slit widths were set at 300 and 5,000 μm, respectively. transfer method. After spin coating of PMMA on the h-BN film on sapphire, and the PMMA-coated h-BN sample was immersed into diluted hydrofluoric acid solution (HF:H 2 O = 1:9) at room temperature. After few seconds, the h-BN film completely delaminated from the sapphire substrate. Floating PMMA/h-BN film was moved onto the distilled water for cleaning, and finally it was fished by a target substrate such as silicon substrate. The transferred film was allowed to dry in air and then immersed into acetone to remove the PMMA on the h-BN film. Vacuum annealing at temperature of approximately 320 °C and pressure below 5 × 10 −6 Torr was performed right before the characterization in order to remove residual hydrocarbon on the surface.
“…On the other hand, on‐surface synthesis can generate unique molecules or extended molecular architectures that have been rationally formed via alternative synthetic routes to those available through solution‐based chemistry . These surface‐stabilized species can lead to compounds that are difficult or impossible to obtain via conventional synthetic procedures …”
On-surface synthesis is an emerging approach to obtain, in asingle step,precisely defined chemical species that cannot be obtained by other synthetic routes.The control of the electronic structure of organic/metal interfaces is crucial for defining the performance of many optoelectronic devices.A facile on-surface chemistry route has now been used to synthesize the strong electron-acceptor organic molecule quinoneazine directly on aC u(110) surface,v ia thermally activated covalent coupling of para-aminophenol precursors. The mechanism is described using ac ombination of in situ surface characterization techniques and theoretical methods. Owing to astrong surface-molecule interaction, the quinoneazine molecule accommodates 1.2 electrons at its carbonyl ends, inducing an intramolecular charge redistribution and leading to partial conjugation of the rings,conferring azo-character at the nitrogen sites.Organicheterostructuresbasedonelectronacceptor-donor organic molecules on surfaces have become strategic materials owing to their huge technological impact in fields such as organic light-emitting diodes (OLEDs), organic field effect transistors (OFETs), or solar cell devices,amongst others.In electronic devices,o rganic layers are placed on metallic surfaces for electrical contact, and the structure of the metalorganic interface enormously affects the performance.[1] In particular,s ome molecules promote charge transfer at the interface with metal electrodes owing to their donor (acceptor) nature,which may induce energy level realignment that can be exploited to tune the transport properties of the system. [1][2][3][4][5] Despite the potential impact of this approach, only af ew molecules have been shown to efficiently donate (or accept) significant charge,t his quality being related to the presence of donor (acceptor) moieties in their structures.[6] A typical example is tetracyano-p-quinodimethane (TCNQ), as trong acceptor molecule that when deposited on Cu(100) accommodates around 1.6 electrons whereby almost one electron aromatizes the central hexagonal ring and the remaining fraction of the charge is accommodated in one of the peripheral nitrogen atoms of the cyano groups.[3]On the other hand, on-surface synthesis can generate unique molecules or extended molecular architectures that have been rationally formed via alternative synthetic routes to those available through solution-based chemistry. [7,8] These surface-stabilized species can lead to compounds that are difficult or impossible to obtain via conventional synthetic procedures. [9][10][11][12] Herein, we combine both of the aforementioned features. We show that the on-surface coupling reaction of two simple and inexpensive para-aminophenol (p-Ap) molecules can be employed to form aq uinonoid-like derivative,q uinoneazine (QAz). This molecule has been theoretically proposed for organic electrodes owing to their extreme redox voltages,and it can also be employed as an intermediate in the preparation of several chemically and biologically active ...
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