Combined ellipsometry and X-ray related techniques for studies of ultrathin organic nanocomposite films

Krämer, M.; Roodenko, Katy; Pollakowski, B.; Hinrichs, Karsten; Rappich, Jörg; Esser, N.; Bohlen, Alex von; Hergenröder, Roland

doi:10.1016/j.tsf.2010.04.033

Cited by 6 publications

(6 citation statements)

References 37 publications

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“…[28][29][30] A combination of XSW and IRSE measurements was recently published. 31 XSW studies of liquid samples have been performed since 1988, including analyses of membranes, electric double layers, metal ion adsorption on mineral surfaces, and biofilms. [32][33][34][35] The main advantages of XSW measurements are the independence from vacuum conditions (indispensable for surface analysis techniques as XPS), making it compatible with liquid samples, and the subnanometer resolution, allowing spatially resolved measurements on molecular scale.…”

Section: Methodsmentioning

confidence: 99%

“…Experiments based on the generation of a standing waves interference pattern produced by total X-ray reflection have found a wide range of applications. The main advantages of this technique are the low detection limit of the analyte, made possible by a greatly reduced spectral background compared to conventional X-ray fluorescence analysis, and the subnanometer wavelength of X-rays, enabling the in-depth characterization of the sample with high vertical resolution. − A combination of XSW and IRSE measurements was recently published …”

Section: Methodsmentioning

confidence: 99%

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In Situ Studies on the Switching Behavior of Ultrathin Poly(acrylic acid) Polyelectrolyte Brushes in Different Aqueous Environments

et al. 2010

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The pH-dependent switching of a poly(acrylic acid) (PAA) polyelectrolyte brush was investigated in situ using infrared spectroscopic ellipsometry (IRSE). The brush was synthesized by a "grafting to" procedure on silicon substrate with a native oxide layer. The overall thickness of the PAA brush in the dry state was approximately 5 nm. Reversible switching of the polymer brush was studied at titration from pH 2 to 10 and back in steps of 1 pH unit. The switching process was observed by monitoring the characteristic vibrational bands of the carboxylic groups of the PAA molecules. Decreasing of the C=O vibrational band amplitude and arising of a COO(-) vibrational band proved the chemical changes in the molecular structure of the brushes due to changes of the pH value in the aqueous solution. Due to the strong absorption of these bands in the IR region, the switching process could be monitored clearly. Switching the brush in several cycles with increasing and decreasing pH value showed a hysteresis-like behavior. For the first time, such hysteresis is observed in titration experiments of polyelectrolyte brushes. This behavior is attributed to the complex mechanisms of the ion's mobility in the brush layer which is explained with a suggested simplifying model describing the influence of ions inside the brush layer. In addition to the IRSE measurements, X-ray standing waves (XSW), in situ visible ellipsometry, and contact angle measurements have been performed and were in good agreement with the results from IRSE. Repetition of the in situ measurement cycles proved the good reversibility of the switching process which is highly important for practical applications of polymer brushes.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

In Situ Studies on the Switching Behavior of Ultrathin Poly(acrylic acid) Polyelectrolyte Brushes in Different Aqueous Environments

et al. 2010

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“…Infrared spectroscopic ellipsometry (IRSE), X-ray reflectivity (XRR) and X-ray standing waves (XSW) have also been used to investigate the structure of the layers. 430 In addition to these methods, a number of papers have reported the observation of reversible redox couples on the cyclic voltammogram of electrografted electrodes. 227,[431][432][433][434] The results range from the complete disappearance of the redox couple-indicating a completely blocking layer-to a slower electron transfer rate that translates in an increased DE p -the potential difference between the cathodic and anodic peaks-and to an unchanged voltammogram of the redox couple.…”

Section: Diazoniums Saltsmentioning

confidence: 99%

Electrografting: a powerful method for surface modification

2011

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Electrografting refers to the electrochemical reaction that permits organic layers to be attached to solid conducting substrates. This definition can be extended to reactions involving an electron transfer between the substrate to be modified and the reagent, but also to examples where a reducing or oxidizing reagent is added to produce the reactive species. These methods are interesting as they provide a real bond between the surface and the organic layer. Electrografting applies to a variety of substrates including carbon, metals and their oxides, but also dielectrics such as polymers. Since the 1980s several methods have been developed, either by reduction or oxidation, and some of them have reached an industrial stage. This critical review describes the methods that are used for electrografting, their mechanism, the formation and growth of the layers as well as their applications (742 references).

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“…However, in the realm of smooth films of high lateral uniformity (e.g., optical coatings and semiconductor structures) XRR has become an invaluable tool. Both visible light characterization methods (such as optical reflectometry and ellipsometry [6]) and XRR can provide users with thickness and roughness information. However, the index of refraction of materials in the visible wavelength region often varies dramatically between materials.…”

Section: Introductionmentioning

confidence: 99%

Determining sample alignment in x-ray reflectometry using thickness and density from GaAs/AlAs multilayer certified reference materials

Gil¹,

Azuma²,

Fujimoto³

2014

Meas. Sci. Technol.

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Abstract.9 X-ray reflectometry (XRR) provides researchers and manufacturers with a non-10 destructive way to determine thickness, roughness, and density of thin films 11 deposited on smooth substrates. Due to the nested nature of equations modeling 12 this phenomenon, the inter-relation between instrument alignment and parameter 13 estimation accuracy is somewhat opaque. In this study, we intentionally shift incident 14 angle information from a high-quality XRR data set and refine a series of shifted data 15 sets using an identical structural model to assess the effect this angle misalignment 16 has on parameter estimation. We develop a series of calibration curves relating angle 17 misalignment to variation in layer thickness and density for a multilayer GaAs/AlAs 18Certified Reference Material on a GaAs substrate. We then test the validity and 19 robustness of several approaches of using known thickness and density parameters 20 from this structure to calibrate instrument alignment. We find the highest sensitivity 21 to, and linearity with, measurement misalignment from buried AlAs and GaAs layers, 22 in contrast to the surface layers, which show the most variability. This is a fortuitous 23 result, as buried AlAs and GaAs exhibit the highest long-term stability in thickness.24 Therefore, it is indeed possible to use reference thickness estimates to validate XRR 25 angle alignment accuracy. Buried layer mass density information also shows promise as 26 a robust calibration approach. This is surprising, as electron density of buried layers is 27 both a highly-correlated phenomenon, and a subtle component within the XRR model.

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Combined ellipsometry and X-ray related techniques for studies of ultrathin organic nanocomposite films

Cited by 6 publications

References 37 publications

In Situ Studies on the Switching Behavior of Ultrathin Poly(acrylic acid) Polyelectrolyte Brushes in Different Aqueous Environments

In Situ Studies on the Switching Behavior of Ultrathin Poly(acrylic acid) Polyelectrolyte Brushes in Different Aqueous Environments

Electrografting: a powerful method for surface modification

Determining sample alignment in x-ray reflectometry using thickness and density from GaAs/AlAs multilayer certified reference materials

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