Spectrally Resolving Coherent TERS Spectroscopy of Electrically Biased Carbon-Coated Fibers

Abstract

Tip-enhanced Raman scattering (TERS) represents an advanced spectroscopic tool that enables probing a specimen on scales far beyond the diffraction limit. An investigation of two-dimensional systems reveals a striking feature of TERS, when the near-field intensity is governed by the 8th and 10th power of the tip−sample distance for the coherent and incoherent scattering cases, respectively. Physically, the coherent TERS response can be observed when the excitation spot size does not exceed the phonon coherence length. In this paper, we demonstrate spectrally resolving capabilities of coherent TERS spectroscopy when studying electrically biased amorphous carbon films. Local electro-annealing at hot spots was found to activate temperaturedependent molecular transformations such as an expansion of the defect-free sp 2 domains network at temperatures above 400 °C. Electro-assisted TERS allows one to directly visualize the presence of water-decorated carboxyl/hydroxyl groups at the edge carbon atoms.

Water-Anchored Edge Defects in Amorphous Carbon Probed with Thermal- and Electroassisted Raman Spectroscopy and Nanoscopy

“…38,39 Local electro-annealing at the hot spots enables the activation of the temperature-dependent chemical reactions, for example, the sp 2 domain expansion of graphiticlike crystals at temperatures of above 400 °C. 40 By exposure to the deep subwavelength incident light, a coherent TERS response becomes possible, and thus, the broad first-order Dfamily bands can be spectrally resolved due to the increased phonon coherence length. Figure 5a displays TERS spectra of the 31 nm a-C at different applied voltages.…”

“…This effect is ideally recognized with electroassisted TERS spectroscopy and nanoscopy. It was previously established that the near-field intensity is proportional to the eighth power of the tip–sample distance, whereas the incoherent case meets the 10th power dependence. , Local electro-annealing at the hot spots enables the activation of the temperature-dependent chemical reactions, for example, the sp 2 domain expansion of graphitic-like crystals at temperatures of above 400 °C . By exposure to the deep subwavelength incident light, a coherent TERS response becomes possible, and thus, the broad first-order D-family bands can be spectrally resolved due to the increased phonon coherence length.…”

Progress of tip-enhanced Raman scattering for the last two decades and its challenges in very recent years

“…118 Moreover, ultra-thin amorphous carbon film, which was coated on a silica fiber, was annealed via an electric bias or a heater and investigated in terms of the D-family bands by TERS. 119,120 The D band originates from not only defects, but also edges on which C atoms are arranged in an armchair configuration. 121 Using noncontact AFM-TERS, 114,122 the D band was observed at the edge of epitaxial graphene ribbons without the buffer layer on the Si-face of the SiC substrate (Fig.…”

Исследование Параметров Герметичных Углеродных Покрытий Оптических Волокон, Использующихся В Агрессивных Средах

“…Далее мы приводим результаты двух независимых исследований, проведенных совместно компанией OFS Рис. 1 [18] , , поверхности скола волокна с помощью конфокальной оптической микроскопии и КР-микроскопии в дальнем поле (рис. 6б, в).…”

“…(d) D 1 / D 4 и D 1 / D 3 (для рассчетов использовались интегральные интенсивности компонент. Исследовались образцы двух типов: изготовленные без и с полимерным покрытием[18]…”