Identification of Dimeric Methylalumina Surface Species during Atomic Layer Deposition Using Operando Surface-Enhanced Raman Spectroscopy

Abstract

Operando surface-enhanced Raman spectroscopy (SERS) was used to successfully identify hitherto unknown dimeric methylalumina surface species during atomic layer deposition (ALD) on a silver surface. Vibrational modes associated with the bridging moieties of both trimethylaluminum (TMA) and dimethylaluminum chloride (DMACl) surface species were found during ALD. The appropriate monomer vibrational modes were found to be absent as a result of the selective nature of SERS. Density functional theory (DFT) calculations were also performed to locate and identify the expected vibrational modes. An operando localized surface plasmon resonance (LSPR) spectrometer was utilized to account for changes in SER signal as a function of the number of ALD cycles. DMACl surface species were unable to be measured after multiple ALD cycles as a result of a loss in SERS enhancement and shift in LSPR. This work highlights how operando optical spectroscopy by SERS and LSPR scattering are useful for probing the identity and structure of the surface species involved in ALD and, ultimately, catalytic reactions on these support materials.

First‐Principles Simulation of Raman Spectra of Adsorbates on Metal Surfaces

“…Moreover, previous studies show that the relative height of the Raman peak, which we refer to as the relative intensity, provides sufficient information of surface species to both identify them out of the mixture and probe the molecular orientation of the adsorbate on the surface . Notably, the relative Raman intensities have been also successfully employed to characterize graphene layers and graphitic materials through the relative intensity of D, G, and 2 D peaks .…”

“…Notably, the relative Raman intensities have been also successfully employed to characterize graphene layers and graphitic materials through the relative intensity of D, G, and 2 D peaks . Furthermore, contrary to absolute values of the Raman intensities, the relative height of the intensities of different Raman active modes, or relative intensity, are less sensitive to the change of working conditions, including temperature and external electronic or magnetic fields . In particular, the relative intensity is less sensitive to the size of metal particles that contain more than 20 atoms .…”

Frequency Shifts in Surface-Enhanced Raman Spectroscopy-Based Immunoassays: Mechanistic Insights and Application in Protein Carbonylation Detection

“…Surface-enhanced Raman spectroscopy (SERS) has been proved to be a powerful tool for chemical analysis, material science, and biomedicine in recent years. − As a novel readout method with excellent spectral reproducibility, SERS frequency shifts have been applied into immunoassays since 2012 . Recent years, the fast growing research field allows widespread applications in the detection of cancer biomarkers, , DNA, miRNA, and protein self-assemblies .…”

A Graphene–Silver Nanoparticle–Silicon Sandwich SERS Chip for Quantitative Detection of Molecules and Capture, Discrimination, and Inactivation of Bacteria

“…Since its discovery in 1974, surface-enhanced Raman scattering (SERS) has attracted extensive attention in various fields because of its extraordinary features. , Remarkably, it can boost inherently feeble Raman signals by several orders of magnitude when molecules are located at “hot spots”, holding great promise for myriad ultrasensitive sensing and analysis applications. , Nevertheless, as it suffers from the relatively poor reproducibility and stability of SERS signals, it is challenging to achieve reliable quantitative SERS analysis. , To date, tremendous efforts have been made to improve SERS quantitative capability, particularly focusing on three aspects: (1) introduction of an internal standard (IS); (2) fabrication of highly ordered SERS substrates; (3) introduction of inert shell shielded SERS substrates from external interferences (e.g., oxidation and corrosion). With regard to the first aspect, IS species share similar SERS enhancement as the analytes, and thus, the ratiometric signal of analyte intensity to IS intensity can be employed for calibrating inhomogeneous electromagnetic enhancement. − However, IS species employed in most current SERS systems still suffer from the disturbances originating from the reactions between naked metal nanoparticles and contacted IS species, including chemical adsorption, charge transfer, photoinduced damage, and metal-assisted catalysis .…”

“…S ince its discovery in 1974, surface-enhanced Raman scattering (SERS) has attracted extensive attention in various fields because of its extraordinary features. 1,2 Remarkably, it can boost inherently feeble Raman signals by several orders of magnitude when molecules are located at "hot spots", holding great promise for myriad ultrasensitive sensing and analysis applications. 3,4 Nevertheless, as it suffers from the relatively poor reproducibility and stability of SERS signals, it is challenging to achieve reliable quantitative SERS analysis.…”