Structural analysis of amorphous carbon films by spectroscopic ellipsometry, RBS/ERDA, and NEXAFS

Abstract

The structural analysis of amorphous carbon films is not only the premise of their unique properties applied in the industrial fields but also the indispensable element on their classification. In this letter, we refurbished the classification of amorphous carbon films based on the optical constants in terms of the refractive index (n) and the extinction coefficient (k). In the selected photon energy range, we defined the maximum of n (En-max) and k at a value more than 10−4 (Ek) to explore the relationship between different classification schemes for amorphous carbon films deposited by different techniques. We found that Ek and En-max of the deposited amorphous carbon films have an exponential relationship with the hydrogen contents. Thus, the spectroscopic ellipsometry analysis can also be used as one of the effective methods for the structural evaluation of the amorphous carbon films.

Colorful Diamond‐Like Carbon Films from Different Micro/Nanostructures

“…Due to samples #01–08 and #09–16 were synthesized under the same conditions except for deposition time, only part samples were measured selectively. From the data analysis of pico‐indentation, XRR, RBS/ERDA, NEXAFS, and compare with their optical properties and the previous works, [ 4b,5,6 ] we found samples #01–#08 presented the density, hardness, hydrogen content, sp 3 ratio, n , and k , of ≈1.24 g cm −3 , less than 1.0 GPa (average value is 0.49 GPa), 43 at%, 0.42, 1.65, and 0.01 respectively, should be classified into PLC films; samples #09–#16 presented average value of density, hardness, hydrogen content, sp 3 ratio, n , and k , as ≈1.67 g cm −3 , 3.4 GPa, 26 at%, 0.28, 2.13, and 0.31, respectively, were classified into a‐C:H films. However, due to the various methods and different deposited conditions, samples #17–24, have the density, hardness, hydrogen content, sp 3 ratio, n , and k , distribute in the range of 1.78–3.12 g cm −3 , 12.1–37.2 GPa, 0.2–23 at%, 0.51–0.71, 2.18–2.73, and 0.04–0.74, respectively, they belong to the ta‐C (samples #20 and #21), or ta‐C:H (other samples).…”

“…[ 4b ] Figure 3c shows the typical RBS/ERDA spectrum of DLC film sample #05, the hydrogen content was got from the raw data profile fitting. [ 5,6,14 ] Figure 3d shows the typical carbon k ‐edge NEXAFS spectrum of DLC film sample #21, and curve‐fitting results. The sp 3 /(sp 2 + sp 3 ) ratio (sp 3 ratio) was calculated from the area ratio of blue curve and green curves, which is derived from the π–π* electronic excitation of carbon sp 2 electrons and the σ –σ * electronic excitation of carbon sp 2 and sp 3 electrons, after comparison with the standard materials of highly oriented pyrolytic graphite.…”

“…[ 3 ] Most of the current classification methods are either based on the analysis of the proportion of the above three components of DLC films, [ 1b,3c,4 ] or according to the optical constants. [ 5 ] All these methods have to use large equipment and highly specialized instruments, such as synchrotron based near‐edge X‐ray absorption fine structure (NEXAFS), electrostatic accelerator based Rutherford backscattering/elastic recoil detection analysis (RBS/ERDA), cross‐polarized magic angle spinning solid‐state nuclear magnetic resonance, or spectroscopic ellipsometry (SE), [ 4b,5,6 ] which are difficult to access for small enterprises. Based on these methods DLC films were classified into the following six types: tetrahedral amorphous carbon (ta‐C), hydrogenated tetrahedral amorphous carbon (ta‐C:H), amorphous carbon, hydrogenated amorphous carbon (a‐C:H), graphite‐like carbon, and polymer‐like carbon (PLC) films.…”

Spectroscopic Ellipsometry - Application on the Classification of Diamond-Like Carbon Films

“…In part two, we refurbished the classification of amorphous carbon films based on the optical constants (n and k). In the selected photon energy range, we defined the maximum of n (E n-max ) and k at a value more than 10 −4 (E k ) to explore the relationship between the different classification schemes for amorphous carbon films deposited by different techniques [17].…”

Эллипсометрическое Исследование Тонкопленочных Структур Аморфного Гидрогенизированного Углерода И Наночастиц Золота

“…Для моделирования плазмонных спектров гибридных структур необходимо знать дисперсию показателя преломления и коэффициента экстинкции всех компонент. Метод спектральной эллипсометрии [17] применялся для анализа оптических свойств различных форм аморфного углерода [18]. Красное смещение и уширение поло-сы поверхностного плазмонного резонанса в алмазоподобных пленках с включениями наночастиц серебра анализировались с помощью теории рассеяния Ми и теории эффективной среды Максвелла-Гарнетта [15].…”